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1717 lines
61 KiB
1717 lines
61 KiB
//===- LazyValueInfo.cpp - Value constraint analysis ------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the interface for lazy computation of value constraint
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// information.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LazyValueInfo.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/TargetLibraryInfo.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/ConstantRange.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include <map>
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#include <stack>
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using namespace llvm;
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using namespace PatternMatch;
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#define DEBUG_TYPE "lazy-value-info"
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char LazyValueInfoWrapperPass::ID = 0;
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INITIALIZE_PASS_BEGIN(LazyValueInfoWrapperPass, "lazy-value-info",
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"Lazy Value Information Analysis", false, true)
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INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
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INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
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INITIALIZE_PASS_END(LazyValueInfoWrapperPass, "lazy-value-info",
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"Lazy Value Information Analysis", false, true)
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namespace llvm {
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FunctionPass *createLazyValueInfoPass() { return new LazyValueInfoWrapperPass(); }
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}
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char LazyValueAnalysis::PassID;
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//===----------------------------------------------------------------------===//
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// LVILatticeVal
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//===----------------------------------------------------------------------===//
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/// This is the information tracked by LazyValueInfo for each value.
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///
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/// FIXME: This is basically just for bringup, this can be made a lot more rich
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/// in the future.
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///
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namespace {
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class LVILatticeVal {
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enum LatticeValueTy {
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/// This Value has no known value yet. As a result, this implies the
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/// producing instruction is dead. Caution: We use this as the starting
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/// state in our local meet rules. In this usage, it's taken to mean
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/// "nothing known yet".
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undefined,
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/// This Value has a specific constant value. (For integers, constantrange
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/// is used instead.)
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constant,
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/// This Value is known to not have the specified value. (For integers,
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/// constantrange is used instead.)
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notconstant,
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/// The Value falls within this range. (Used only for integer typed values.)
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constantrange,
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/// We can not precisely model the dynamic values this value might take.
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overdefined
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};
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/// Val: This stores the current lattice value along with the Constant* for
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/// the constant if this is a 'constant' or 'notconstant' value.
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LatticeValueTy Tag;
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Constant *Val;
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ConstantRange Range;
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public:
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LVILatticeVal() : Tag(undefined), Val(nullptr), Range(1, true) {}
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static LVILatticeVal get(Constant *C) {
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LVILatticeVal Res;
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if (!isa<UndefValue>(C))
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Res.markConstant(C);
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return Res;
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}
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static LVILatticeVal getNot(Constant *C) {
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LVILatticeVal Res;
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if (!isa<UndefValue>(C))
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Res.markNotConstant(C);
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return Res;
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}
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static LVILatticeVal getRange(ConstantRange CR) {
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LVILatticeVal Res;
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Res.markConstantRange(std::move(CR));
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return Res;
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}
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static LVILatticeVal getOverdefined() {
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LVILatticeVal Res;
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Res.markOverdefined();
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return Res;
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}
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bool isUndefined() const { return Tag == undefined; }
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bool isConstant() const { return Tag == constant; }
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bool isNotConstant() const { return Tag == notconstant; }
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bool isConstantRange() const { return Tag == constantrange; }
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bool isOverdefined() const { return Tag == overdefined; }
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Constant *getConstant() const {
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assert(isConstant() && "Cannot get the constant of a non-constant!");
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return Val;
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}
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Constant *getNotConstant() const {
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assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
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return Val;
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}
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ConstantRange getConstantRange() const {
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assert(isConstantRange() &&
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"Cannot get the constant-range of a non-constant-range!");
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return Range;
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}
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/// Return true if this is a change in status.
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bool markOverdefined() {
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if (isOverdefined())
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return false;
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Tag = overdefined;
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return true;
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}
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/// Return true if this is a change in status.
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bool markConstant(Constant *V) {
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assert(V && "Marking constant with NULL");
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
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return markConstantRange(ConstantRange(CI->getValue()));
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if (isa<UndefValue>(V))
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return false;
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assert((!isConstant() || getConstant() == V) &&
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"Marking constant with different value");
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assert(isUndefined());
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Tag = constant;
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Val = V;
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return true;
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}
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/// Return true if this is a change in status.
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bool markNotConstant(Constant *V) {
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assert(V && "Marking constant with NULL");
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
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return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
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if (isa<UndefValue>(V))
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return false;
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assert((!isConstant() || getConstant() != V) &&
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"Marking constant !constant with same value");
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assert((!isNotConstant() || getNotConstant() == V) &&
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"Marking !constant with different value");
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assert(isUndefined() || isConstant());
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Tag = notconstant;
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Val = V;
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return true;
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}
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/// Return true if this is a change in status.
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bool markConstantRange(ConstantRange NewR) {
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if (isConstantRange()) {
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if (NewR.isEmptySet())
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return markOverdefined();
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bool changed = Range != NewR;
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Range = std::move(NewR);
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return changed;
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}
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assert(isUndefined());
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if (NewR.isEmptySet())
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return markOverdefined();
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Tag = constantrange;
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Range = std::move(NewR);
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return true;
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}
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/// Merge the specified lattice value into this one, updating this
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/// one and returning true if anything changed.
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bool mergeIn(const LVILatticeVal &RHS, const DataLayout &DL) {
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if (RHS.isUndefined() || isOverdefined()) return false;
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if (RHS.isOverdefined()) return markOverdefined();
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if (isUndefined()) {
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Tag = RHS.Tag;
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Val = RHS.Val;
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Range = RHS.Range;
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return true;
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}
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if (isConstant()) {
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if (RHS.isConstant()) {
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if (Val == RHS.Val)
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return false;
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return markOverdefined();
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}
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if (RHS.isNotConstant()) {
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if (Val == RHS.Val)
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return markOverdefined();
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// Unless we can prove that the two Constants are different, we must
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// move to overdefined.
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if (ConstantInt *Res =
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dyn_cast<ConstantInt>(ConstantFoldCompareInstOperands(
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CmpInst::ICMP_NE, getConstant(), RHS.getNotConstant(), DL)))
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if (Res->isOne())
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return markNotConstant(RHS.getNotConstant());
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return markOverdefined();
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}
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return markOverdefined();
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}
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if (isNotConstant()) {
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if (RHS.isConstant()) {
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if (Val == RHS.Val)
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return markOverdefined();
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// Unless we can prove that the two Constants are different, we must
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// move to overdefined.
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if (ConstantInt *Res =
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dyn_cast<ConstantInt>(ConstantFoldCompareInstOperands(
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CmpInst::ICMP_NE, getNotConstant(), RHS.getConstant(), DL)))
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if (Res->isOne())
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return false;
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return markOverdefined();
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}
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if (RHS.isNotConstant()) {
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if (Val == RHS.Val)
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return false;
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return markOverdefined();
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}
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return markOverdefined();
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}
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assert(isConstantRange() && "New LVILattice type?");
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if (!RHS.isConstantRange())
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return markOverdefined();
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ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
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if (NewR.isFullSet())
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return markOverdefined();
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return markConstantRange(NewR);
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}
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};
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} // end anonymous namespace.
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namespace llvm {
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raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val)
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LLVM_ATTRIBUTE_USED;
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raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
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if (Val.isUndefined())
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return OS << "undefined";
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if (Val.isOverdefined())
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return OS << "overdefined";
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if (Val.isNotConstant())
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return OS << "notconstant<" << *Val.getNotConstant() << '>';
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if (Val.isConstantRange())
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return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
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<< Val.getConstantRange().getUpper() << '>';
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return OS << "constant<" << *Val.getConstant() << '>';
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}
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}
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/// Returns true if this lattice value represents at most one possible value.
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/// This is as precise as any lattice value can get while still representing
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/// reachable code.
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static bool hasSingleValue(const LVILatticeVal &Val) {
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if (Val.isConstantRange() &&
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Val.getConstantRange().isSingleElement())
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// Integer constants are single element ranges
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return true;
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if (Val.isConstant())
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// Non integer constants
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return true;
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return false;
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}
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/// Combine two sets of facts about the same value into a single set of
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/// facts. Note that this method is not suitable for merging facts along
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/// different paths in a CFG; that's what the mergeIn function is for. This
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/// is for merging facts gathered about the same value at the same location
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/// through two independent means.
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/// Notes:
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/// * This method does not promise to return the most precise possible lattice
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/// value implied by A and B. It is allowed to return any lattice element
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/// which is at least as strong as *either* A or B (unless our facts
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/// conflict, see below).
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/// * Due to unreachable code, the intersection of two lattice values could be
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/// contradictory. If this happens, we return some valid lattice value so as
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/// not confuse the rest of LVI. Ideally, we'd always return Undefined, but
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/// we do not make this guarantee. TODO: This would be a useful enhancement.
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static LVILatticeVal intersect(LVILatticeVal A, LVILatticeVal B) {
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// Undefined is the strongest state. It means the value is known to be along
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// an unreachable path.
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if (A.isUndefined())
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return A;
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if (B.isUndefined())
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return B;
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// If we gave up for one, but got a useable fact from the other, use it.
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if (A.isOverdefined())
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return B;
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if (B.isOverdefined())
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return A;
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// Can't get any more precise than constants.
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if (hasSingleValue(A))
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return A;
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if (hasSingleValue(B))
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return B;
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// Could be either constant range or not constant here.
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if (!A.isConstantRange() || !B.isConstantRange()) {
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// TODO: Arbitrary choice, could be improved
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return A;
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}
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// Intersect two constant ranges
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ConstantRange Range =
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A.getConstantRange().intersectWith(B.getConstantRange());
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// Note: An empty range is implicitly converted to overdefined internally.
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// TODO: We could instead use Undefined here since we've proven a conflict
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// and thus know this path must be unreachable.
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return LVILatticeVal::getRange(std::move(Range));
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}
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//===----------------------------------------------------------------------===//
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// LazyValueInfoCache Decl
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//===----------------------------------------------------------------------===//
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namespace {
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/// A callback value handle updates the cache when values are erased.
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class LazyValueInfoCache;
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struct LVIValueHandle final : public CallbackVH {
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LazyValueInfoCache *Parent;
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LVIValueHandle(Value *V, LazyValueInfoCache *P)
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: CallbackVH(V), Parent(P) { }
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void deleted() override;
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void allUsesReplacedWith(Value *V) override {
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deleted();
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}
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};
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}
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namespace {
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/// This is the cache kept by LazyValueInfo which
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/// maintains information about queries across the clients' queries.
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class LazyValueInfoCache {
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/// This is all of the cached block information for exactly one Value*.
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/// The entries are sorted by the BasicBlock* of the
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/// entries, allowing us to do a lookup with a binary search.
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/// Over-defined lattice values are recorded in OverDefinedCache to reduce
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/// memory overhead.
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typedef SmallDenseMap<AssertingVH<BasicBlock>, LVILatticeVal, 4>
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ValueCacheEntryTy;
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/// This is all of the cached information for all values,
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/// mapped from Value* to key information.
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std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
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/// This tracks, on a per-block basis, the set of values that are
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/// over-defined at the end of that block.
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typedef DenseMap<AssertingVH<BasicBlock>, SmallPtrSet<Value *, 4>>
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OverDefinedCacheTy;
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OverDefinedCacheTy OverDefinedCache;
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/// Keep track of all blocks that we have ever seen, so we
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/// don't spend time removing unused blocks from our caches.
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DenseSet<AssertingVH<BasicBlock> > SeenBlocks;
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/// This stack holds the state of the value solver during a query.
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/// It basically emulates the callstack of the naive
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/// recursive value lookup process.
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std::stack<std::pair<BasicBlock*, Value*> > BlockValueStack;
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/// Keeps track of which block-value pairs are in BlockValueStack.
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DenseSet<std::pair<BasicBlock*, Value*> > BlockValueSet;
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/// Push BV onto BlockValueStack unless it's already in there.
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/// Returns true on success.
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bool pushBlockValue(const std::pair<BasicBlock *, Value *> &BV) {
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if (!BlockValueSet.insert(BV).second)
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return false; // It's already in the stack.
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DEBUG(dbgs() << "PUSH: " << *BV.second << " in " << BV.first->getName()
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<< "\n");
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BlockValueStack.push(BV);
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return true;
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}
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AssumptionCache *AC; ///< A pointer to the cache of @llvm.assume calls.
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const DataLayout &DL; ///< A mandatory DataLayout
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DominatorTree *DT; ///< An optional DT pointer.
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friend struct LVIValueHandle;
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void insertResult(Value *Val, BasicBlock *BB, const LVILatticeVal &Result) {
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SeenBlocks.insert(BB);
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// Insert over-defined values into their own cache to reduce memory
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// overhead.
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if (Result.isOverdefined())
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OverDefinedCache[BB].insert(Val);
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else
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lookup(Val)[BB] = Result;
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}
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LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
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bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
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LVILatticeVal &Result, Instruction *CxtI = nullptr);
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bool hasBlockValue(Value *Val, BasicBlock *BB);
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// These methods process one work item and may add more. A false value
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// returned means that the work item was not completely processed and must
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// be revisited after going through the new items.
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bool solveBlockValue(Value *Val, BasicBlock *BB);
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bool solveBlockValueNonLocal(LVILatticeVal &BBLV, Value *Val, BasicBlock *BB);
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bool solveBlockValuePHINode(LVILatticeVal &BBLV, PHINode *PN, BasicBlock *BB);
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bool solveBlockValueSelect(LVILatticeVal &BBLV, SelectInst *S,
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BasicBlock *BB);
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bool solveBlockValueBinaryOp(LVILatticeVal &BBLV, Instruction *BBI,
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BasicBlock *BB);
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bool solveBlockValueCast(LVILatticeVal &BBLV, Instruction *BBI,
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BasicBlock *BB);
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void intersectAssumeBlockValueConstantRange(Value *Val, LVILatticeVal &BBLV,
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Instruction *BBI);
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void solve();
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ValueCacheEntryTy &lookup(Value *V) {
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return ValueCache[LVIValueHandle(V, this)];
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}
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bool isOverdefined(Value *V, BasicBlock *BB) const {
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auto ODI = OverDefinedCache.find(BB);
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if (ODI == OverDefinedCache.end())
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return false;
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return ODI->second.count(V);
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}
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bool hasCachedValueInfo(Value *V, BasicBlock *BB) {
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if (isOverdefined(V, BB))
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return true;
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LVIValueHandle ValHandle(V, this);
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auto I = ValueCache.find(ValHandle);
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if (I == ValueCache.end())
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return false;
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return I->second.count(BB);
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}
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LVILatticeVal getCachedValueInfo(Value *V, BasicBlock *BB) {
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if (isOverdefined(V, BB))
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return LVILatticeVal::getOverdefined();
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return lookup(V)[BB];
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}
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public:
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/// This is the query interface to determine the lattice
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/// value for the specified Value* at the end of the specified block.
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LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB,
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Instruction *CxtI = nullptr);
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|
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/// This is the query interface to determine the lattice
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/// value for the specified Value* at the specified instruction (generally
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/// from an assume intrinsic).
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LVILatticeVal getValueAt(Value *V, Instruction *CxtI);
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|
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/// This is the query interface to determine the lattice
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/// value for the specified Value* that is true on the specified edge.
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LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB,
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Instruction *CxtI = nullptr);
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/// This is the update interface to inform the cache that an edge from
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/// PredBB to OldSucc has been threaded to be from PredBB to NewSucc.
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void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
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|
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/// This is part of the update interface to inform the cache
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/// that a block has been deleted.
|
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void eraseBlock(BasicBlock *BB);
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|
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/// clear - Empty the cache.
|
|
void clear() {
|
|
SeenBlocks.clear();
|
|
ValueCache.clear();
|
|
OverDefinedCache.clear();
|
|
}
|
|
|
|
LazyValueInfoCache(AssumptionCache *AC, const DataLayout &DL,
|
|
DominatorTree *DT = nullptr)
|
|
: AC(AC), DL(DL), DT(DT) {}
|
|
};
|
|
} // end anonymous namespace
|
|
|
|
void LVIValueHandle::deleted() {
|
|
SmallVector<AssertingVH<BasicBlock>, 4> ToErase;
|
|
for (auto &I : Parent->OverDefinedCache) {
|
|
SmallPtrSetImpl<Value *> &ValueSet = I.second;
|
|
if (ValueSet.count(getValPtr()))
|
|
ValueSet.erase(getValPtr());
|
|
if (ValueSet.empty())
|
|
ToErase.push_back(I.first);
|
|
}
|
|
for (auto &BB : ToErase)
|
|
Parent->OverDefinedCache.erase(BB);
|
|
|
|
// This erasure deallocates *this, so it MUST happen after we're done
|
|
// using any and all members of *this.
|
|
Parent->ValueCache.erase(*this);
|
|
}
|
|
|
|
void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
|
|
// Shortcut if we have never seen this block.
|
|
DenseSet<AssertingVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
|
|
if (I == SeenBlocks.end())
|
|
return;
|
|
SeenBlocks.erase(I);
|
|
|
|
auto ODI = OverDefinedCache.find(BB);
|
|
if (ODI != OverDefinedCache.end())
|
|
OverDefinedCache.erase(ODI);
|
|
|
|
for (auto &I : ValueCache)
|
|
I.second.erase(BB);
|
|
}
|
|
|
|
void LazyValueInfoCache::solve() {
|
|
while (!BlockValueStack.empty()) {
|
|
std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
|
|
assert(BlockValueSet.count(e) && "Stack value should be in BlockValueSet!");
|
|
|
|
if (solveBlockValue(e.second, e.first)) {
|
|
// The work item was completely processed.
|
|
assert(BlockValueStack.top() == e && "Nothing should have been pushed!");
|
|
assert(hasCachedValueInfo(e.second, e.first) &&
|
|
"Result should be in cache!");
|
|
|
|
DEBUG(dbgs() << "POP " << *e.second << " in " << e.first->getName()
|
|
<< " = " << getCachedValueInfo(e.second, e.first) << "\n");
|
|
|
|
BlockValueStack.pop();
|
|
BlockValueSet.erase(e);
|
|
} else {
|
|
// More work needs to be done before revisiting.
|
|
assert(BlockValueStack.top() != e && "Stack should have been pushed!");
|
|
}
|
|
}
|
|
}
|
|
|
|
bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
|
|
// If already a constant, there is nothing to compute.
|
|
if (isa<Constant>(Val))
|
|
return true;
|
|
|
|
return hasCachedValueInfo(Val, BB);
|
|
}
|
|
|
|
LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
|
|
// If already a constant, there is nothing to compute.
|
|
if (Constant *VC = dyn_cast<Constant>(Val))
|
|
return LVILatticeVal::get(VC);
|
|
|
|
SeenBlocks.insert(BB);
|
|
return getCachedValueInfo(Val, BB);
|
|
}
|
|
|
|
static LVILatticeVal getFromRangeMetadata(Instruction *BBI) {
|
|
switch (BBI->getOpcode()) {
|
|
default: break;
|
|
case Instruction::Load:
|
|
case Instruction::Call:
|
|
case Instruction::Invoke:
|
|
if (MDNode *Ranges = BBI->getMetadata(LLVMContext::MD_range))
|
|
if (isa<IntegerType>(BBI->getType())) {
|
|
return LVILatticeVal::getRange(getConstantRangeFromMetadata(*Ranges));
|
|
}
|
|
break;
|
|
};
|
|
// Nothing known - will be intersected with other facts
|
|
return LVILatticeVal::getOverdefined();
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
|
|
if (isa<Constant>(Val))
|
|
return true;
|
|
|
|
if (hasCachedValueInfo(Val, BB)) {
|
|
// If we have a cached value, use that.
|
|
DEBUG(dbgs() << " reuse BB '" << BB->getName()
|
|
<< "' val=" << getCachedValueInfo(Val, BB) << '\n');
|
|
|
|
// Since we're reusing a cached value, we don't need to update the
|
|
// OverDefinedCache. The cache will have been properly updated whenever the
|
|
// cached value was inserted.
|
|
return true;
|
|
}
|
|
|
|
// Hold off inserting this value into the Cache in case we have to return
|
|
// false and come back later.
|
|
LVILatticeVal Res;
|
|
|
|
Instruction *BBI = dyn_cast<Instruction>(Val);
|
|
if (!BBI || BBI->getParent() != BB) {
|
|
if (!solveBlockValueNonLocal(Res, Val, BB))
|
|
return false;
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
|
|
if (!solveBlockValuePHINode(Res, PN, BB))
|
|
return false;
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
|
|
if (auto *SI = dyn_cast<SelectInst>(BBI)) {
|
|
if (!solveBlockValueSelect(Res, SI, BB))
|
|
return false;
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
|
|
// If this value is a nonnull pointer, record it's range and bailout. Note
|
|
// that for all other pointer typed values, we terminate the search at the
|
|
// definition. We could easily extend this to look through geps, bitcasts,
|
|
// and the like to prove non-nullness, but it's not clear that's worth it
|
|
// compile time wise. The context-insensative value walk done inside
|
|
// isKnownNonNull gets most of the profitable cases at much less expense.
|
|
// This does mean that we have a sensativity to where the defining
|
|
// instruction is placed, even if it could legally be hoisted much higher.
|
|
// That is unfortunate.
|
|
PointerType *PT = dyn_cast<PointerType>(BBI->getType());
|
|
if (PT && isKnownNonNull(BBI)) {
|
|
Res = LVILatticeVal::getNot(ConstantPointerNull::get(PT));
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
if (BBI->getType()->isIntegerTy()) {
|
|
if (isa<CastInst>(BBI)) {
|
|
if (!solveBlockValueCast(Res, BBI, BB))
|
|
return false;
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
|
|
if (BO && isa<ConstantInt>(BO->getOperand(1))) {
|
|
if (!solveBlockValueBinaryOp(Res, BBI, BB))
|
|
return false;
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - unknown inst def found.\n");
|
|
Res = getFromRangeMetadata(BBI);
|
|
insertResult(Val, BB, Res);
|
|
return true;
|
|
}
|
|
|
|
static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
|
|
if (LoadInst *L = dyn_cast<LoadInst>(I)) {
|
|
return L->getPointerAddressSpace() == 0 &&
|
|
GetUnderlyingObject(L->getPointerOperand(),
|
|
L->getModule()->getDataLayout()) == Ptr;
|
|
}
|
|
if (StoreInst *S = dyn_cast<StoreInst>(I)) {
|
|
return S->getPointerAddressSpace() == 0 &&
|
|
GetUnderlyingObject(S->getPointerOperand(),
|
|
S->getModule()->getDataLayout()) == Ptr;
|
|
}
|
|
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
|
|
if (MI->isVolatile()) return false;
|
|
|
|
// FIXME: check whether it has a valuerange that excludes zero?
|
|
ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
|
|
if (!Len || Len->isZero()) return false;
|
|
|
|
if (MI->getDestAddressSpace() == 0)
|
|
if (GetUnderlyingObject(MI->getRawDest(),
|
|
MI->getModule()->getDataLayout()) == Ptr)
|
|
return true;
|
|
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
|
|
if (MTI->getSourceAddressSpace() == 0)
|
|
if (GetUnderlyingObject(MTI->getRawSource(),
|
|
MTI->getModule()->getDataLayout()) == Ptr)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Return true if the allocation associated with Val is ever dereferenced
|
|
/// within the given basic block. This establishes the fact Val is not null,
|
|
/// but does not imply that the memory at Val is dereferenceable. (Val may
|
|
/// point off the end of the dereferenceable part of the object.)
|
|
static bool isObjectDereferencedInBlock(Value *Val, BasicBlock *BB) {
|
|
assert(Val->getType()->isPointerTy());
|
|
|
|
const DataLayout &DL = BB->getModule()->getDataLayout();
|
|
Value *UnderlyingVal = GetUnderlyingObject(Val, DL);
|
|
// If 'GetUnderlyingObject' didn't converge, skip it. It won't converge
|
|
// inside InstructionDereferencesPointer either.
|
|
if (UnderlyingVal == GetUnderlyingObject(UnderlyingVal, DL, 1))
|
|
for (Instruction &I : *BB)
|
|
if (InstructionDereferencesPointer(&I, UnderlyingVal))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
|
|
Value *Val, BasicBlock *BB) {
|
|
LVILatticeVal Result; // Start Undefined.
|
|
|
|
// If this is the entry block, we must be asking about an argument. The
|
|
// value is overdefined.
|
|
if (BB == &BB->getParent()->getEntryBlock()) {
|
|
assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
|
|
// Bofore giving up, see if we can prove the pointer non-null local to
|
|
// this particular block.
|
|
if (Val->getType()->isPointerTy() &&
|
|
(isKnownNonNull(Val) || isObjectDereferencedInBlock(Val, BB))) {
|
|
PointerType *PTy = cast<PointerType>(Val->getType());
|
|
Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
|
|
} else {
|
|
Result.markOverdefined();
|
|
}
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
// Loop over all of our predecessors, merging what we know from them into
|
|
// result.
|
|
bool EdgesMissing = false;
|
|
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
|
|
LVILatticeVal EdgeResult;
|
|
EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
|
|
if (EdgesMissing)
|
|
continue;
|
|
|
|
Result.mergeIn(EdgeResult, DL);
|
|
|
|
// If we hit overdefined, exit early. The BlockVals entry is already set
|
|
// to overdefined.
|
|
if (Result.isOverdefined()) {
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because of pred (non local).\n");
|
|
// Bofore giving up, see if we can prove the pointer non-null local to
|
|
// this particular block.
|
|
if (Val->getType()->isPointerTy() &&
|
|
isObjectDereferencedInBlock(Val, BB)) {
|
|
PointerType *PTy = cast<PointerType>(Val->getType());
|
|
Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
|
|
}
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
}
|
|
if (EdgesMissing)
|
|
return false;
|
|
|
|
// Return the merged value, which is more precise than 'overdefined'.
|
|
assert(!Result.isOverdefined());
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
|
|
PHINode *PN, BasicBlock *BB) {
|
|
LVILatticeVal Result; // Start Undefined.
|
|
|
|
// Loop over all of our predecessors, merging what we know from them into
|
|
// result.
|
|
bool EdgesMissing = false;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
BasicBlock *PhiBB = PN->getIncomingBlock(i);
|
|
Value *PhiVal = PN->getIncomingValue(i);
|
|
LVILatticeVal EdgeResult;
|
|
// Note that we can provide PN as the context value to getEdgeValue, even
|
|
// though the results will be cached, because PN is the value being used as
|
|
// the cache key in the caller.
|
|
EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult, PN);
|
|
if (EdgesMissing)
|
|
continue;
|
|
|
|
Result.mergeIn(EdgeResult, DL);
|
|
|
|
// If we hit overdefined, exit early. The BlockVals entry is already set
|
|
// to overdefined.
|
|
if (Result.isOverdefined()) {
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined because of pred (local).\n");
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
}
|
|
if (EdgesMissing)
|
|
return false;
|
|
|
|
// Return the merged value, which is more precise than 'overdefined'.
|
|
assert(!Result.isOverdefined() && "Possible PHI in entry block?");
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
static bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
|
|
LVILatticeVal &Result,
|
|
bool isTrueDest = true);
|
|
|
|
// If we can determine a constraint on the value given conditions assumed by
|
|
// the program, intersect those constraints with BBLV
|
|
void LazyValueInfoCache::intersectAssumeBlockValueConstantRange(Value *Val,
|
|
LVILatticeVal &BBLV,
|
|
Instruction *BBI) {
|
|
BBI = BBI ? BBI : dyn_cast<Instruction>(Val);
|
|
if (!BBI)
|
|
return;
|
|
|
|
for (auto &AssumeVH : AC->assumptions()) {
|
|
if (!AssumeVH)
|
|
continue;
|
|
auto *I = cast<CallInst>(AssumeVH);
|
|
if (!isValidAssumeForContext(I, BBI, DT))
|
|
continue;
|
|
|
|
Value *C = I->getArgOperand(0);
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(C)) {
|
|
LVILatticeVal Result;
|
|
if (getValueFromFromCondition(Val, ICI, Result))
|
|
BBLV = intersect(BBLV, Result);
|
|
}
|
|
}
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValueSelect(LVILatticeVal &BBLV,
|
|
SelectInst *SI, BasicBlock *BB) {
|
|
|
|
// Recurse on our inputs if needed
|
|
if (!hasBlockValue(SI->getTrueValue(), BB)) {
|
|
if (pushBlockValue(std::make_pair(BB, SI->getTrueValue())))
|
|
return false;
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
LVILatticeVal TrueVal = getBlockValue(SI->getTrueValue(), BB);
|
|
// If we hit overdefined, don't ask more queries. We want to avoid poisoning
|
|
// extra slots in the table if we can.
|
|
if (TrueVal.isOverdefined()) {
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
|
|
if (!hasBlockValue(SI->getFalseValue(), BB)) {
|
|
if (pushBlockValue(std::make_pair(BB, SI->getFalseValue())))
|
|
return false;
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
LVILatticeVal FalseVal = getBlockValue(SI->getFalseValue(), BB);
|
|
// If we hit overdefined, don't ask more queries. We want to avoid poisoning
|
|
// extra slots in the table if we can.
|
|
if (FalseVal.isOverdefined()) {
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
|
|
if (TrueVal.isConstantRange() && FalseVal.isConstantRange()) {
|
|
ConstantRange TrueCR = TrueVal.getConstantRange();
|
|
ConstantRange FalseCR = FalseVal.getConstantRange();
|
|
Value *LHS = nullptr;
|
|
Value *RHS = nullptr;
|
|
SelectPatternResult SPR = matchSelectPattern(SI, LHS, RHS);
|
|
// Is this a min specifically of our two inputs? (Avoid the risk of
|
|
// ValueTracking getting smarter looking back past our immediate inputs.)
|
|
if (SelectPatternResult::isMinOrMax(SPR.Flavor) &&
|
|
LHS == SI->getTrueValue() && RHS == SI->getFalseValue()) {
|
|
switch (SPR.Flavor) {
|
|
default:
|
|
llvm_unreachable("unexpected minmax type!");
|
|
case SPF_SMIN: /// Signed minimum
|
|
BBLV.markConstantRange(TrueCR.smin(FalseCR));
|
|
return true;
|
|
case SPF_UMIN: /// Unsigned minimum
|
|
BBLV.markConstantRange(TrueCR.umin(FalseCR));
|
|
return true;
|
|
case SPF_SMAX: /// Signed maximum
|
|
BBLV.markConstantRange(TrueCR.smax(FalseCR));
|
|
return true;
|
|
case SPF_UMAX: /// Unsigned maximum
|
|
BBLV.markConstantRange(TrueCR.umax(FalseCR));
|
|
return true;
|
|
};
|
|
}
|
|
|
|
// TODO: ABS, NABS from the SelectPatternResult
|
|
}
|
|
|
|
// Can we constrain the facts about the true and false values by using the
|
|
// condition itself? This shows up with idioms like e.g. select(a > 5, a, 5).
|
|
// TODO: We could potentially refine an overdefined true value above.
|
|
if (auto *ICI = dyn_cast<ICmpInst>(SI->getCondition())) {
|
|
LVILatticeVal TrueValTaken, FalseValTaken;
|
|
if (!getValueFromFromCondition(SI->getTrueValue(), ICI,
|
|
TrueValTaken, true))
|
|
TrueValTaken.markOverdefined();
|
|
if (!getValueFromFromCondition(SI->getFalseValue(), ICI,
|
|
FalseValTaken, false))
|
|
FalseValTaken.markOverdefined();
|
|
|
|
TrueVal = intersect(TrueVal, TrueValTaken);
|
|
FalseVal = intersect(FalseVal, FalseValTaken);
|
|
|
|
|
|
// Handle clamp idioms such as:
|
|
// %24 = constantrange<0, 17>
|
|
// %39 = icmp eq i32 %24, 0
|
|
// %40 = add i32 %24, -1
|
|
// %siv.next = select i1 %39, i32 16, i32 %40
|
|
// %siv.next = constantrange<0, 17> not <-1, 17>
|
|
// In general, this can handle any clamp idiom which tests the edge
|
|
// condition via an equality or inequality.
|
|
ICmpInst::Predicate Pred = ICI->getPredicate();
|
|
Value *A = ICI->getOperand(0);
|
|
if (ConstantInt *CIBase = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
|
|
auto addConstants = [](ConstantInt *A, ConstantInt *B) {
|
|
assert(A->getType() == B->getType());
|
|
return ConstantInt::get(A->getType(), A->getValue() + B->getValue());
|
|
};
|
|
// See if either input is A + C2, subject to the constraint from the
|
|
// condition that A != C when that input is used. We can assume that
|
|
// that input doesn't include C + C2.
|
|
ConstantInt *CIAdded;
|
|
switch (Pred) {
|
|
default: break;
|
|
case ICmpInst::ICMP_EQ:
|
|
if (match(SI->getFalseValue(), m_Add(m_Specific(A),
|
|
m_ConstantInt(CIAdded)))) {
|
|
auto ResNot = addConstants(CIBase, CIAdded);
|
|
FalseVal = intersect(FalseVal,
|
|
LVILatticeVal::getNot(ResNot));
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_NE:
|
|
if (match(SI->getTrueValue(), m_Add(m_Specific(A),
|
|
m_ConstantInt(CIAdded)))) {
|
|
auto ResNot = addConstants(CIBase, CIAdded);
|
|
TrueVal = intersect(TrueVal,
|
|
LVILatticeVal::getNot(ResNot));
|
|
}
|
|
break;
|
|
};
|
|
}
|
|
}
|
|
|
|
LVILatticeVal Result; // Start Undefined.
|
|
Result.mergeIn(TrueVal, DL);
|
|
Result.mergeIn(FalseVal, DL);
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValueCast(LVILatticeVal &BBLV,
|
|
Instruction *BBI,
|
|
BasicBlock *BB) {
|
|
if (!BBI->getOperand(0)->getType()->isSized()) {
|
|
// Without knowing how wide the input is, we can't analyze it in any useful
|
|
// way.
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
|
|
// Filter out casts we don't know how to reason about before attempting to
|
|
// recurse on our operand. This can cut a long search short if we know we're
|
|
// not going to be able to get any useful information anways.
|
|
switch (BBI->getOpcode()) {
|
|
case Instruction::Trunc:
|
|
case Instruction::SExt:
|
|
case Instruction::ZExt:
|
|
case Instruction::BitCast:
|
|
break;
|
|
default:
|
|
// Unhandled instructions are overdefined.
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined (unknown cast).\n");
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
}
|
|
|
|
// Figure out the range of the LHS. If that fails, we still apply the
|
|
// transfer rule on the full set since we may be able to locally infer
|
|
// interesting facts.
|
|
if (!hasBlockValue(BBI->getOperand(0), BB))
|
|
if (pushBlockValue(std::make_pair(BB, BBI->getOperand(0))))
|
|
// More work to do before applying this transfer rule.
|
|
return false;
|
|
|
|
const unsigned OperandBitWidth =
|
|
DL.getTypeSizeInBits(BBI->getOperand(0)->getType());
|
|
ConstantRange LHSRange = ConstantRange(OperandBitWidth);
|
|
if (hasBlockValue(BBI->getOperand(0), BB)) {
|
|
LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
|
|
intersectAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
|
|
if (LHSVal.isConstantRange())
|
|
LHSRange = LHSVal.getConstantRange();
|
|
}
|
|
|
|
const unsigned ResultBitWidth =
|
|
cast<IntegerType>(BBI->getType())->getBitWidth();
|
|
|
|
// NOTE: We're currently limited by the set of operations that ConstantRange
|
|
// can evaluate symbolically. Enhancing that set will allows us to analyze
|
|
// more definitions.
|
|
LVILatticeVal Result;
|
|
switch (BBI->getOpcode()) {
|
|
case Instruction::Trunc:
|
|
Result.markConstantRange(LHSRange.truncate(ResultBitWidth));
|
|
break;
|
|
case Instruction::SExt:
|
|
Result.markConstantRange(LHSRange.signExtend(ResultBitWidth));
|
|
break;
|
|
case Instruction::ZExt:
|
|
Result.markConstantRange(LHSRange.zeroExtend(ResultBitWidth));
|
|
break;
|
|
case Instruction::BitCast:
|
|
Result.markConstantRange(LHSRange);
|
|
break;
|
|
default:
|
|
// Should be dead if the code above is correct
|
|
llvm_unreachable("inconsistent with above");
|
|
break;
|
|
}
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
bool LazyValueInfoCache::solveBlockValueBinaryOp(LVILatticeVal &BBLV,
|
|
Instruction *BBI,
|
|
BasicBlock *BB) {
|
|
|
|
assert(BBI->getOperand(0)->getType()->isSized() &&
|
|
"all operands to binary operators are sized");
|
|
|
|
// Filter out operators we don't know how to reason about before attempting to
|
|
// recurse on our operand(s). This can cut a long search short if we know
|
|
// we're not going to be able to get any useful information anways.
|
|
switch (BBI->getOpcode()) {
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
case Instruction::Mul:
|
|
case Instruction::UDiv:
|
|
case Instruction::Shl:
|
|
case Instruction::LShr:
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
// continue into the code below
|
|
break;
|
|
default:
|
|
// Unhandled instructions are overdefined.
|
|
DEBUG(dbgs() << " compute BB '" << BB->getName()
|
|
<< "' - overdefined (unknown binary operator).\n");
|
|
BBLV.markOverdefined();
|
|
return true;
|
|
};
|
|
|
|
// Figure out the range of the LHS. If that fails, use a conservative range,
|
|
// but apply the transfer rule anyways. This lets us pick up facts from
|
|
// expressions like "and i32 (call i32 @foo()), 32"
|
|
if (!hasBlockValue(BBI->getOperand(0), BB))
|
|
if (pushBlockValue(std::make_pair(BB, BBI->getOperand(0))))
|
|
// More work to do before applying this transfer rule.
|
|
return false;
|
|
|
|
const unsigned OperandBitWidth =
|
|
DL.getTypeSizeInBits(BBI->getOperand(0)->getType());
|
|
ConstantRange LHSRange = ConstantRange(OperandBitWidth);
|
|
if (hasBlockValue(BBI->getOperand(0), BB)) {
|
|
LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
|
|
intersectAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
|
|
if (LHSVal.isConstantRange())
|
|
LHSRange = LHSVal.getConstantRange();
|
|
}
|
|
|
|
ConstantInt *RHS = cast<ConstantInt>(BBI->getOperand(1));
|
|
ConstantRange RHSRange = ConstantRange(RHS->getValue());
|
|
|
|
// NOTE: We're currently limited by the set of operations that ConstantRange
|
|
// can evaluate symbolically. Enhancing that set will allows us to analyze
|
|
// more definitions.
|
|
LVILatticeVal Result;
|
|
switch (BBI->getOpcode()) {
|
|
case Instruction::Add:
|
|
Result.markConstantRange(LHSRange.add(RHSRange));
|
|
break;
|
|
case Instruction::Sub:
|
|
Result.markConstantRange(LHSRange.sub(RHSRange));
|
|
break;
|
|
case Instruction::Mul:
|
|
Result.markConstantRange(LHSRange.multiply(RHSRange));
|
|
break;
|
|
case Instruction::UDiv:
|
|
Result.markConstantRange(LHSRange.udiv(RHSRange));
|
|
break;
|
|
case Instruction::Shl:
|
|
Result.markConstantRange(LHSRange.shl(RHSRange));
|
|
break;
|
|
case Instruction::LShr:
|
|
Result.markConstantRange(LHSRange.lshr(RHSRange));
|
|
break;
|
|
case Instruction::And:
|
|
Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
|
|
break;
|
|
case Instruction::Or:
|
|
Result.markConstantRange(LHSRange.binaryOr(RHSRange));
|
|
break;
|
|
default:
|
|
// Should be dead if the code above is correct
|
|
llvm_unreachable("inconsistent with above");
|
|
break;
|
|
}
|
|
|
|
BBLV = Result;
|
|
return true;
|
|
}
|
|
|
|
bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
|
|
LVILatticeVal &Result, bool isTrueDest) {
|
|
assert(ICI && "precondition");
|
|
if (isa<Constant>(ICI->getOperand(1))) {
|
|
if (ICI->isEquality() && ICI->getOperand(0) == Val) {
|
|
// We know that V has the RHS constant if this is a true SETEQ or
|
|
// false SETNE.
|
|
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
|
|
Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
|
|
else
|
|
Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
|
|
return true;
|
|
}
|
|
|
|
// Recognize the range checking idiom that InstCombine produces.
|
|
// (X-C1) u< C2 --> [C1, C1+C2)
|
|
ConstantInt *NegOffset = nullptr;
|
|
if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
|
|
match(ICI->getOperand(0), m_Add(m_Specific(Val),
|
|
m_ConstantInt(NegOffset)));
|
|
|
|
ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
|
|
if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
|
|
// Calculate the range of values that are allowed by the comparison
|
|
ConstantRange CmpRange(CI->getValue());
|
|
ConstantRange TrueValues =
|
|
ConstantRange::makeAllowedICmpRegion(ICI->getPredicate(), CmpRange);
|
|
|
|
if (NegOffset) // Apply the offset from above.
|
|
TrueValues = TrueValues.subtract(NegOffset->getValue());
|
|
|
|
// If we're interested in the false dest, invert the condition.
|
|
if (!isTrueDest) TrueValues = TrueValues.inverse();
|
|
|
|
Result = LVILatticeVal::getRange(std::move(TrueValues));
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
|
|
/// Val is not constrained on the edge. Result is unspecified if return value
|
|
/// is false.
|
|
static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
|
|
BasicBlock *BBTo, LVILatticeVal &Result) {
|
|
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
|
|
// know that v != 0.
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
|
|
// If this is a conditional branch and only one successor goes to BBTo, then
|
|
// we may be able to infer something from the condition.
|
|
if (BI->isConditional() &&
|
|
BI->getSuccessor(0) != BI->getSuccessor(1)) {
|
|
bool isTrueDest = BI->getSuccessor(0) == BBTo;
|
|
assert(BI->getSuccessor(!isTrueDest) == BBTo &&
|
|
"BBTo isn't a successor of BBFrom");
|
|
|
|
// If V is the condition of the branch itself, then we know exactly what
|
|
// it is.
|
|
if (BI->getCondition() == Val) {
|
|
Result = LVILatticeVal::get(ConstantInt::get(
|
|
Type::getInt1Ty(Val->getContext()), isTrueDest));
|
|
return true;
|
|
}
|
|
|
|
// If the condition of the branch is an equality comparison, we may be
|
|
// able to infer the value.
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
|
|
if (getValueFromFromCondition(Val, ICI, Result, isTrueDest))
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// If the edge was formed by a switch on the value, then we may know exactly
|
|
// what it is.
|
|
if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
|
|
if (SI->getCondition() != Val)
|
|
return false;
|
|
|
|
bool DefaultCase = SI->getDefaultDest() == BBTo;
|
|
unsigned BitWidth = Val->getType()->getIntegerBitWidth();
|
|
ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
|
|
|
|
for (SwitchInst::CaseIt i : SI->cases()) {
|
|
ConstantRange EdgeVal(i.getCaseValue()->getValue());
|
|
if (DefaultCase) {
|
|
// It is possible that the default destination is the destination of
|
|
// some cases. There is no need to perform difference for those cases.
|
|
if (i.getCaseSuccessor() != BBTo)
|
|
EdgesVals = EdgesVals.difference(EdgeVal);
|
|
} else if (i.getCaseSuccessor() == BBTo)
|
|
EdgesVals = EdgesVals.unionWith(EdgeVal);
|
|
}
|
|
Result = LVILatticeVal::getRange(std::move(EdgesVals));
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// \brief Compute the value of Val on the edge BBFrom -> BBTo or the value at
|
|
/// the basic block if the edge does not constrain Val.
|
|
bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
|
|
BasicBlock *BBTo, LVILatticeVal &Result,
|
|
Instruction *CxtI) {
|
|
// If already a constant, there is nothing to compute.
|
|
if (Constant *VC = dyn_cast<Constant>(Val)) {
|
|
Result = LVILatticeVal::get(VC);
|
|
return true;
|
|
}
|
|
|
|
LVILatticeVal LocalResult;
|
|
if (!getEdgeValueLocal(Val, BBFrom, BBTo, LocalResult))
|
|
// If we couldn't constrain the value on the edge, LocalResult doesn't
|
|
// provide any information.
|
|
LocalResult.markOverdefined();
|
|
|
|
if (hasSingleValue(LocalResult)) {
|
|
// Can't get any more precise here
|
|
Result = LocalResult;
|
|
return true;
|
|
}
|
|
|
|
if (!hasBlockValue(Val, BBFrom)) {
|
|
if (pushBlockValue(std::make_pair(BBFrom, Val)))
|
|
return false;
|
|
// No new information.
|
|
Result = LocalResult;
|
|
return true;
|
|
}
|
|
|
|
// Try to intersect ranges of the BB and the constraint on the edge.
|
|
LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
|
|
intersectAssumeBlockValueConstantRange(Val, InBlock, BBFrom->getTerminator());
|
|
// We can use the context instruction (generically the ultimate instruction
|
|
// the calling pass is trying to simplify) here, even though the result of
|
|
// this function is generally cached when called from the solve* functions
|
|
// (and that cached result might be used with queries using a different
|
|
// context instruction), because when this function is called from the solve*
|
|
// functions, the context instruction is not provided. When called from
|
|
// LazyValueInfoCache::getValueOnEdge, the context instruction is provided,
|
|
// but then the result is not cached.
|
|
intersectAssumeBlockValueConstantRange(Val, InBlock, CxtI);
|
|
|
|
Result = intersect(LocalResult, InBlock);
|
|
return true;
|
|
}
|
|
|
|
LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB,
|
|
Instruction *CxtI) {
|
|
DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
|
|
<< BB->getName() << "'\n");
|
|
|
|
assert(BlockValueStack.empty() && BlockValueSet.empty());
|
|
if (!hasBlockValue(V, BB)) {
|
|
pushBlockValue(std::make_pair(BB, V));
|
|
solve();
|
|
}
|
|
LVILatticeVal Result = getBlockValue(V, BB);
|
|
intersectAssumeBlockValueConstantRange(V, Result, CxtI);
|
|
|
|
DEBUG(dbgs() << " Result = " << Result << "\n");
|
|
return Result;
|
|
}
|
|
|
|
LVILatticeVal LazyValueInfoCache::getValueAt(Value *V, Instruction *CxtI) {
|
|
DEBUG(dbgs() << "LVI Getting value " << *V << " at '"
|
|
<< CxtI->getName() << "'\n");
|
|
|
|
if (auto *C = dyn_cast<Constant>(V))
|
|
return LVILatticeVal::get(C);
|
|
|
|
LVILatticeVal Result = LVILatticeVal::getOverdefined();
|
|
if (auto *I = dyn_cast<Instruction>(V))
|
|
Result = getFromRangeMetadata(I);
|
|
intersectAssumeBlockValueConstantRange(V, Result, CxtI);
|
|
|
|
DEBUG(dbgs() << " Result = " << Result << "\n");
|
|
return Result;
|
|
}
|
|
|
|
LVILatticeVal LazyValueInfoCache::
|
|
getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,
|
|
Instruction *CxtI) {
|
|
DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
|
|
<< FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
|
|
|
|
LVILatticeVal Result;
|
|
if (!getEdgeValue(V, FromBB, ToBB, Result, CxtI)) {
|
|
solve();
|
|
bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result, CxtI);
|
|
(void)WasFastQuery;
|
|
assert(WasFastQuery && "More work to do after problem solved?");
|
|
}
|
|
|
|
DEBUG(dbgs() << " Result = " << Result << "\n");
|
|
return Result;
|
|
}
|
|
|
|
void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
|
|
BasicBlock *NewSucc) {
|
|
// When an edge in the graph has been threaded, values that we could not
|
|
// determine a value for before (i.e. were marked overdefined) may be
|
|
// possible to solve now. We do NOT try to proactively update these values.
|
|
// Instead, we clear their entries from the cache, and allow lazy updating to
|
|
// recompute them when needed.
|
|
|
|
// The updating process is fairly simple: we need to drop cached info
|
|
// for all values that were marked overdefined in OldSucc, and for those same
|
|
// values in any successor of OldSucc (except NewSucc) in which they were
|
|
// also marked overdefined.
|
|
std::vector<BasicBlock*> worklist;
|
|
worklist.push_back(OldSucc);
|
|
|
|
auto I = OverDefinedCache.find(OldSucc);
|
|
if (I == OverDefinedCache.end())
|
|
return; // Nothing to process here.
|
|
SmallVector<Value *, 4> ValsToClear(I->second.begin(), I->second.end());
|
|
|
|
// Use a worklist to perform a depth-first search of OldSucc's successors.
|
|
// NOTE: We do not need a visited list since any blocks we have already
|
|
// visited will have had their overdefined markers cleared already, and we
|
|
// thus won't loop to their successors.
|
|
while (!worklist.empty()) {
|
|
BasicBlock *ToUpdate = worklist.back();
|
|
worklist.pop_back();
|
|
|
|
// Skip blocks only accessible through NewSucc.
|
|
if (ToUpdate == NewSucc) continue;
|
|
|
|
bool changed = false;
|
|
for (Value *V : ValsToClear) {
|
|
// If a value was marked overdefined in OldSucc, and is here too...
|
|
auto OI = OverDefinedCache.find(ToUpdate);
|
|
if (OI == OverDefinedCache.end())
|
|
continue;
|
|
SmallPtrSetImpl<Value *> &ValueSet = OI->second;
|
|
if (!ValueSet.count(V))
|
|
continue;
|
|
|
|
ValueSet.erase(V);
|
|
if (ValueSet.empty())
|
|
OverDefinedCache.erase(OI);
|
|
|
|
// If we removed anything, then we potentially need to update
|
|
// blocks successors too.
|
|
changed = true;
|
|
}
|
|
|
|
if (!changed) continue;
|
|
|
|
worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
|
|
}
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// LazyValueInfo Impl
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// This lazily constructs the LazyValueInfoCache.
|
|
static LazyValueInfoCache &getCache(void *&PImpl, AssumptionCache *AC,
|
|
const DataLayout *DL,
|
|
DominatorTree *DT = nullptr) {
|
|
if (!PImpl) {
|
|
assert(DL && "getCache() called with a null DataLayout");
|
|
PImpl = new LazyValueInfoCache(AC, *DL, DT);
|
|
}
|
|
return *static_cast<LazyValueInfoCache*>(PImpl);
|
|
}
|
|
|
|
bool LazyValueInfoWrapperPass::runOnFunction(Function &F) {
|
|
Info.AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
|
|
const DataLayout &DL = F.getParent()->getDataLayout();
|
|
|
|
DominatorTreeWrapperPass *DTWP =
|
|
getAnalysisIfAvailable<DominatorTreeWrapperPass>();
|
|
Info.DT = DTWP ? &DTWP->getDomTree() : nullptr;
|
|
Info.TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
|
|
|
|
if (Info.PImpl)
|
|
getCache(Info.PImpl, Info.AC, &DL, Info.DT).clear();
|
|
|
|
// Fully lazy.
|
|
return false;
|
|
}
|
|
|
|
void LazyValueInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesAll();
|
|
AU.addRequired<AssumptionCacheTracker>();
|
|
AU.addRequired<TargetLibraryInfoWrapperPass>();
|
|
}
|
|
|
|
LazyValueInfo &LazyValueInfoWrapperPass::getLVI() { return Info; }
|
|
|
|
LazyValueInfo::~LazyValueInfo() { releaseMemory(); }
|
|
|
|
void LazyValueInfo::releaseMemory() {
|
|
// If the cache was allocated, free it.
|
|
if (PImpl) {
|
|
delete &getCache(PImpl, AC, nullptr);
|
|
PImpl = nullptr;
|
|
}
|
|
}
|
|
|
|
void LazyValueInfoWrapperPass::releaseMemory() { Info.releaseMemory(); }
|
|
|
|
LazyValueInfo LazyValueAnalysis::run(Function &F, FunctionAnalysisManager &FAM) {
|
|
auto &AC = FAM.getResult<AssumptionAnalysis>(F);
|
|
auto &TLI = FAM.getResult<TargetLibraryAnalysis>(F);
|
|
auto *DT = FAM.getCachedResult<DominatorTreeAnalysis>(F);
|
|
|
|
return LazyValueInfo(&AC, &TLI, DT);
|
|
}
|
|
|
|
Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
|
|
Instruction *CxtI) {
|
|
const DataLayout &DL = BB->getModule()->getDataLayout();
|
|
LVILatticeVal Result =
|
|
getCache(PImpl, AC, &DL, DT).getValueInBlock(V, BB, CxtI);
|
|
|
|
if (Result.isConstant())
|
|
return Result.getConstant();
|
|
if (Result.isConstantRange()) {
|
|
ConstantRange CR = Result.getConstantRange();
|
|
if (const APInt *SingleVal = CR.getSingleElement())
|
|
return ConstantInt::get(V->getContext(), *SingleVal);
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
ConstantRange LazyValueInfo::getConstantRange(Value *V, BasicBlock *BB,
|
|
Instruction *CxtI) {
|
|
assert(V->getType()->isIntegerTy());
|
|
unsigned Width = V->getType()->getIntegerBitWidth();
|
|
const DataLayout &DL = BB->getModule()->getDataLayout();
|
|
LVILatticeVal Result =
|
|
getCache(PImpl, AC, &DL, DT).getValueInBlock(V, BB, CxtI);
|
|
assert(!Result.isConstant());
|
|
if (Result.isUndefined())
|
|
return ConstantRange(Width, /*isFullSet=*/false);
|
|
if (Result.isConstantRange())
|
|
return Result.getConstantRange();
|
|
return ConstantRange(Width, /*isFullSet=*/true);
|
|
}
|
|
|
|
/// Determine whether the specified value is known to be a
|
|
/// constant on the specified edge. Return null if not.
|
|
Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
|
|
BasicBlock *ToBB,
|
|
Instruction *CxtI) {
|
|
const DataLayout &DL = FromBB->getModule()->getDataLayout();
|
|
LVILatticeVal Result =
|
|
getCache(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
|
|
|
|
if (Result.isConstant())
|
|
return Result.getConstant();
|
|
if (Result.isConstantRange()) {
|
|
ConstantRange CR = Result.getConstantRange();
|
|
if (const APInt *SingleVal = CR.getSingleElement())
|
|
return ConstantInt::get(V->getContext(), *SingleVal);
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
static LazyValueInfo::Tristate getPredicateResult(unsigned Pred, Constant *C,
|
|
LVILatticeVal &Result,
|
|
const DataLayout &DL,
|
|
TargetLibraryInfo *TLI) {
|
|
|
|
// If we know the value is a constant, evaluate the conditional.
|
|
Constant *Res = nullptr;
|
|
if (Result.isConstant()) {
|
|
Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL,
|
|
TLI);
|
|
if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
|
|
return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True;
|
|
return LazyValueInfo::Unknown;
|
|
}
|
|
|
|
if (Result.isConstantRange()) {
|
|
ConstantInt *CI = dyn_cast<ConstantInt>(C);
|
|
if (!CI) return LazyValueInfo::Unknown;
|
|
|
|
ConstantRange CR = Result.getConstantRange();
|
|
if (Pred == ICmpInst::ICMP_EQ) {
|
|
if (!CR.contains(CI->getValue()))
|
|
return LazyValueInfo::False;
|
|
|
|
if (CR.isSingleElement() && CR.contains(CI->getValue()))
|
|
return LazyValueInfo::True;
|
|
} else if (Pred == ICmpInst::ICMP_NE) {
|
|
if (!CR.contains(CI->getValue()))
|
|
return LazyValueInfo::True;
|
|
|
|
if (CR.isSingleElement() && CR.contains(CI->getValue()))
|
|
return LazyValueInfo::False;
|
|
}
|
|
|
|
// Handle more complex predicates.
|
|
ConstantRange TrueValues =
|
|
ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
|
|
if (TrueValues.contains(CR))
|
|
return LazyValueInfo::True;
|
|
if (TrueValues.inverse().contains(CR))
|
|
return LazyValueInfo::False;
|
|
return LazyValueInfo::Unknown;
|
|
}
|
|
|
|
if (Result.isNotConstant()) {
|
|
// If this is an equality comparison, we can try to fold it knowing that
|
|
// "V != C1".
|
|
if (Pred == ICmpInst::ICMP_EQ) {
|
|
// !C1 == C -> false iff C1 == C.
|
|
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
|
|
Result.getNotConstant(), C, DL,
|
|
TLI);
|
|
if (Res->isNullValue())
|
|
return LazyValueInfo::False;
|
|
} else if (Pred == ICmpInst::ICMP_NE) {
|
|
// !C1 != C -> true iff C1 == C.
|
|
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
|
|
Result.getNotConstant(), C, DL,
|
|
TLI);
|
|
if (Res->isNullValue())
|
|
return LazyValueInfo::True;
|
|
}
|
|
return LazyValueInfo::Unknown;
|
|
}
|
|
|
|
return LazyValueInfo::Unknown;
|
|
}
|
|
|
|
/// Determine whether the specified value comparison with a constant is known to
|
|
/// be true or false on the specified CFG edge. Pred is a CmpInst predicate.
|
|
LazyValueInfo::Tristate
|
|
LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
|
|
BasicBlock *FromBB, BasicBlock *ToBB,
|
|
Instruction *CxtI) {
|
|
const DataLayout &DL = FromBB->getModule()->getDataLayout();
|
|
LVILatticeVal Result =
|
|
getCache(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
|
|
|
|
return getPredicateResult(Pred, C, Result, DL, TLI);
|
|
}
|
|
|
|
LazyValueInfo::Tristate
|
|
LazyValueInfo::getPredicateAt(unsigned Pred, Value *V, Constant *C,
|
|
Instruction *CxtI) {
|
|
const DataLayout &DL = CxtI->getModule()->getDataLayout();
|
|
LVILatticeVal Result = getCache(PImpl, AC, &DL, DT).getValueAt(V, CxtI);
|
|
Tristate Ret = getPredicateResult(Pred, C, Result, DL, TLI);
|
|
if (Ret != Unknown)
|
|
return Ret;
|
|
|
|
// Note: The following bit of code is somewhat distinct from the rest of LVI;
|
|
// LVI as a whole tries to compute a lattice value which is conservatively
|
|
// correct at a given location. In this case, we have a predicate which we
|
|
// weren't able to prove about the merged result, and we're pushing that
|
|
// predicate back along each incoming edge to see if we can prove it
|
|
// separately for each input. As a motivating example, consider:
|
|
// bb1:
|
|
// %v1 = ... ; constantrange<1, 5>
|
|
// br label %merge
|
|
// bb2:
|
|
// %v2 = ... ; constantrange<10, 20>
|
|
// br label %merge
|
|
// merge:
|
|
// %phi = phi [%v1, %v2] ; constantrange<1,20>
|
|
// %pred = icmp eq i32 %phi, 8
|
|
// We can't tell from the lattice value for '%phi' that '%pred' is false
|
|
// along each path, but by checking the predicate over each input separately,
|
|
// we can.
|
|
// We limit the search to one step backwards from the current BB and value.
|
|
// We could consider extending this to search further backwards through the
|
|
// CFG and/or value graph, but there are non-obvious compile time vs quality
|
|
// tradeoffs.
|
|
if (CxtI) {
|
|
BasicBlock *BB = CxtI->getParent();
|
|
|
|
// Function entry or an unreachable block. Bail to avoid confusing
|
|
// analysis below.
|
|
pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
|
|
if (PI == PE)
|
|
return Unknown;
|
|
|
|
// If V is a PHI node in the same block as the context, we need to ask
|
|
// questions about the predicate as applied to the incoming value along
|
|
// each edge. This is useful for eliminating cases where the predicate is
|
|
// known along all incoming edges.
|
|
if (auto *PHI = dyn_cast<PHINode>(V))
|
|
if (PHI->getParent() == BB) {
|
|
Tristate Baseline = Unknown;
|
|
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i < e; i++) {
|
|
Value *Incoming = PHI->getIncomingValue(i);
|
|
BasicBlock *PredBB = PHI->getIncomingBlock(i);
|
|
// Note that PredBB may be BB itself.
|
|
Tristate Result = getPredicateOnEdge(Pred, Incoming, C, PredBB, BB,
|
|
CxtI);
|
|
|
|
// Keep going as long as we've seen a consistent known result for
|
|
// all inputs.
|
|
Baseline = (i == 0) ? Result /* First iteration */
|
|
: (Baseline == Result ? Baseline : Unknown); /* All others */
|
|
if (Baseline == Unknown)
|
|
break;
|
|
}
|
|
if (Baseline != Unknown)
|
|
return Baseline;
|
|
}
|
|
|
|
// For a comparison where the V is outside this block, it's possible
|
|
// that we've branched on it before. Look to see if the value is known
|
|
// on all incoming edges.
|
|
if (!isa<Instruction>(V) ||
|
|
cast<Instruction>(V)->getParent() != BB) {
|
|
// For predecessor edge, determine if the comparison is true or false
|
|
// on that edge. If they're all true or all false, we can conclude
|
|
// the value of the comparison in this block.
|
|
Tristate Baseline = getPredicateOnEdge(Pred, V, C, *PI, BB, CxtI);
|
|
if (Baseline != Unknown) {
|
|
// Check that all remaining incoming values match the first one.
|
|
while (++PI != PE) {
|
|
Tristate Ret = getPredicateOnEdge(Pred, V, C, *PI, BB, CxtI);
|
|
if (Ret != Baseline) break;
|
|
}
|
|
// If we terminated early, then one of the values didn't match.
|
|
if (PI == PE) {
|
|
return Baseline;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return Unknown;
|
|
}
|
|
|
|
void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
|
|
BasicBlock *NewSucc) {
|
|
if (PImpl) {
|
|
const DataLayout &DL = PredBB->getModule()->getDataLayout();
|
|
getCache(PImpl, AC, &DL, DT).threadEdge(PredBB, OldSucc, NewSucc);
|
|
}
|
|
}
|
|
|
|
void LazyValueInfo::eraseBlock(BasicBlock *BB) {
|
|
if (PImpl) {
|
|
const DataLayout &DL = BB->getModule()->getDataLayout();
|
|
getCache(PImpl, AC, &DL, DT).eraseBlock(BB);
|
|
}
|
|
}
|