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1268 lines
47 KiB
1268 lines
47 KiB
//===- InstCombineSelect.cpp ----------------------------------------------===//
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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 implements the visitSelect function.
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//
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//===----------------------------------------------------------------------===//
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#include "InstCombineInternal.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/PatternMatch.h"
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using namespace llvm;
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using namespace PatternMatch;
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#define DEBUG_TYPE "instcombine"
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static SelectPatternFlavor
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getInverseMinMaxSelectPattern(SelectPatternFlavor SPF) {
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switch (SPF) {
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default:
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llvm_unreachable("unhandled!");
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case SPF_SMIN:
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return SPF_SMAX;
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case SPF_UMIN:
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return SPF_UMAX;
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case SPF_SMAX:
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return SPF_SMIN;
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case SPF_UMAX:
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return SPF_UMIN;
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}
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}
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static CmpInst::Predicate getCmpPredicateForMinMax(SelectPatternFlavor SPF,
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bool Ordered=false) {
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switch (SPF) {
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default:
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llvm_unreachable("unhandled!");
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case SPF_SMIN:
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return ICmpInst::ICMP_SLT;
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case SPF_UMIN:
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return ICmpInst::ICMP_ULT;
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case SPF_SMAX:
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return ICmpInst::ICMP_SGT;
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case SPF_UMAX:
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return ICmpInst::ICMP_UGT;
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case SPF_FMINNUM:
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return Ordered ? FCmpInst::FCMP_OLT : FCmpInst::FCMP_ULT;
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case SPF_FMAXNUM:
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return Ordered ? FCmpInst::FCMP_OGT : FCmpInst::FCMP_UGT;
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}
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}
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static Value *generateMinMaxSelectPattern(InstCombiner::BuilderTy *Builder,
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SelectPatternFlavor SPF, Value *A,
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Value *B) {
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CmpInst::Predicate Pred = getCmpPredicateForMinMax(SPF);
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assert(CmpInst::isIntPredicate(Pred));
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return Builder->CreateSelect(Builder->CreateICmp(Pred, A, B), A, B);
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}
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/// We want to turn code that looks like this:
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/// %C = or %A, %B
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/// %D = select %cond, %C, %A
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/// into:
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/// %C = select %cond, %B, 0
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/// %D = or %A, %C
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///
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/// Assuming that the specified instruction is an operand to the select, return
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/// a bitmask indicating which operands of this instruction are foldable if they
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/// equal the other incoming value of the select.
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///
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static unsigned GetSelectFoldableOperands(Instruction *I) {
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switch (I->getOpcode()) {
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case Instruction::Add:
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case Instruction::Mul:
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor:
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return 3; // Can fold through either operand.
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case Instruction::Sub: // Can only fold on the amount subtracted.
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case Instruction::Shl: // Can only fold on the shift amount.
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case Instruction::LShr:
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case Instruction::AShr:
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return 1;
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default:
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return 0; // Cannot fold
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}
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}
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/// For the same transformation as the previous function, return the identity
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/// constant that goes into the select.
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static Constant *GetSelectFoldableConstant(Instruction *I) {
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switch (I->getOpcode()) {
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default: llvm_unreachable("This cannot happen!");
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case Instruction::Add:
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case Instruction::Sub:
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case Instruction::Or:
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case Instruction::Xor:
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case Instruction::Shl:
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case Instruction::LShr:
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case Instruction::AShr:
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return Constant::getNullValue(I->getType());
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case Instruction::And:
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return Constant::getAllOnesValue(I->getType());
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case Instruction::Mul:
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return ConstantInt::get(I->getType(), 1);
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}
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}
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/// We have (select c, TI, FI), and we know that TI and FI have the same opcode.
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Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
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Instruction *FI) {
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// If this is a cast from the same type, merge.
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if (TI->getNumOperands() == 1 && TI->isCast()) {
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Type *FIOpndTy = FI->getOperand(0)->getType();
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if (TI->getOperand(0)->getType() != FIOpndTy)
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return nullptr;
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// The select condition may be a vector. We may only change the operand
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// type if the vector width remains the same (and matches the condition).
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Type *CondTy = SI.getCondition()->getType();
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if (CondTy->isVectorTy()) {
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if (!FIOpndTy->isVectorTy())
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return nullptr;
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if (CondTy->getVectorNumElements() != FIOpndTy->getVectorNumElements())
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return nullptr;
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// TODO: If the backend knew how to deal with casts better, we could
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// remove this limitation. For now, there's too much potential to create
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// worse codegen by promoting the select ahead of size-altering casts
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// (PR28160).
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//
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// Note that ValueTracking's matchSelectPattern() looks through casts
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// without checking 'hasOneUse' when it matches min/max patterns, so this
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// transform may end up happening anyway.
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if (TI->getOpcode() != Instruction::BitCast &&
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(!TI->hasOneUse() || !FI->hasOneUse()))
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return nullptr;
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} else if (!TI->hasOneUse() || !FI->hasOneUse()) {
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// TODO: The one-use restrictions for a scalar select could be eased if
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// the fold of a select in visitLoadInst() was enhanced to match a pattern
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// that includes a cast.
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return nullptr;
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}
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// Fold this by inserting a select from the input values.
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Value *NewSI = Builder->CreateSelect(SI.getCondition(), TI->getOperand(0),
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FI->getOperand(0), SI.getName()+".v");
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return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
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TI->getType());
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}
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// TODO: This function ends awkwardly in unreachable - fix to be more normal.
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// Only handle binary operators with one-use here. As with the cast case
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// above, it may be possible to relax the one-use constraint, but that needs
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// be examined carefully since it may not reduce the total number of
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// instructions.
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if (!isa<BinaryOperator>(TI) || !TI->hasOneUse() || !FI->hasOneUse())
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return nullptr;
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// Figure out if the operations have any operands in common.
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Value *MatchOp, *OtherOpT, *OtherOpF;
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bool MatchIsOpZero;
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if (TI->getOperand(0) == FI->getOperand(0)) {
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MatchOp = TI->getOperand(0);
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OtherOpT = TI->getOperand(1);
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OtherOpF = FI->getOperand(1);
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MatchIsOpZero = true;
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} else if (TI->getOperand(1) == FI->getOperand(1)) {
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MatchOp = TI->getOperand(1);
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OtherOpT = TI->getOperand(0);
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OtherOpF = FI->getOperand(0);
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MatchIsOpZero = false;
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} else if (!TI->isCommutative()) {
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return nullptr;
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} else if (TI->getOperand(0) == FI->getOperand(1)) {
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MatchOp = TI->getOperand(0);
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OtherOpT = TI->getOperand(1);
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OtherOpF = FI->getOperand(0);
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MatchIsOpZero = true;
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} else if (TI->getOperand(1) == FI->getOperand(0)) {
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MatchOp = TI->getOperand(1);
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OtherOpT = TI->getOperand(0);
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OtherOpF = FI->getOperand(1);
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MatchIsOpZero = true;
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} else {
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return nullptr;
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}
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// If we reach here, they do have operations in common.
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Value *NewSI = Builder->CreateSelect(SI.getCondition(), OtherOpT,
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OtherOpF, SI.getName()+".v");
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if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
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if (MatchIsOpZero)
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return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
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else
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return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
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}
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llvm_unreachable("Shouldn't get here");
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}
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static bool isSelect01(Constant *C1, Constant *C2) {
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ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
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if (!C1I)
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return false;
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ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
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if (!C2I)
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return false;
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if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
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return false;
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return C1I->isOne() || C1I->isAllOnesValue() ||
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C2I->isOne() || C2I->isAllOnesValue();
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}
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/// Try to fold the select into one of the operands to allow further
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/// optimization.
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Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
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Value *FalseVal) {
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// See the comment above GetSelectFoldableOperands for a description of the
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// transformation we are doing here.
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if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
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if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
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!isa<Constant>(FalseVal)) {
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if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
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unsigned OpToFold = 0;
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if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
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OpToFold = 1;
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} else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
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OpToFold = 2;
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}
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if (OpToFold) {
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Constant *C = GetSelectFoldableConstant(TVI);
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Value *OOp = TVI->getOperand(2-OpToFold);
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// Avoid creating select between 2 constants unless it's selecting
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// between 0, 1 and -1.
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if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
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Value *NewSel = Builder->CreateSelect(SI.getCondition(), OOp, C);
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NewSel->takeName(TVI);
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BinaryOperator *TVI_BO = cast<BinaryOperator>(TVI);
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BinaryOperator *BO = BinaryOperator::Create(TVI_BO->getOpcode(),
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FalseVal, NewSel);
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BO->copyIRFlags(TVI_BO);
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return BO;
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}
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}
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}
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}
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}
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if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
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if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
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!isa<Constant>(TrueVal)) {
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if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
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unsigned OpToFold = 0;
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if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
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OpToFold = 1;
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} else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
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OpToFold = 2;
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}
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if (OpToFold) {
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Constant *C = GetSelectFoldableConstant(FVI);
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Value *OOp = FVI->getOperand(2-OpToFold);
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// Avoid creating select between 2 constants unless it's selecting
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// between 0, 1 and -1.
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if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
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Value *NewSel = Builder->CreateSelect(SI.getCondition(), C, OOp);
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NewSel->takeName(FVI);
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BinaryOperator *FVI_BO = cast<BinaryOperator>(FVI);
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BinaryOperator *BO = BinaryOperator::Create(FVI_BO->getOpcode(),
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TrueVal, NewSel);
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BO->copyIRFlags(FVI_BO);
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return BO;
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}
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}
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}
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}
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}
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return nullptr;
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}
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/// We want to turn:
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/// (select (icmp eq (and X, C1), 0), Y, (or Y, C2))
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/// into:
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/// (or (shl (and X, C1), C3), y)
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/// iff:
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/// C1 and C2 are both powers of 2
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/// where:
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/// C3 = Log(C2) - Log(C1)
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///
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/// This transform handles cases where:
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/// 1. The icmp predicate is inverted
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/// 2. The select operands are reversed
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/// 3. The magnitude of C2 and C1 are flipped
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static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
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Value *FalseVal,
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InstCombiner::BuilderTy *Builder) {
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const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
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if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
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return nullptr;
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Value *CmpLHS = IC->getOperand(0);
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Value *CmpRHS = IC->getOperand(1);
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if (!match(CmpRHS, m_Zero()))
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return nullptr;
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Value *X;
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const APInt *C1;
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if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1))))
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return nullptr;
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const APInt *C2;
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bool OrOnTrueVal = false;
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bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
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if (!OrOnFalseVal)
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OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2)));
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if (!OrOnFalseVal && !OrOnTrueVal)
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return nullptr;
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Value *V = CmpLHS;
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Value *Y = OrOnFalseVal ? TrueVal : FalseVal;
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unsigned C1Log = C1->logBase2();
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unsigned C2Log = C2->logBase2();
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if (C2Log > C1Log) {
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V = Builder->CreateZExtOrTrunc(V, Y->getType());
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V = Builder->CreateShl(V, C2Log - C1Log);
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} else if (C1Log > C2Log) {
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V = Builder->CreateLShr(V, C1Log - C2Log);
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V = Builder->CreateZExtOrTrunc(V, Y->getType());
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} else
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V = Builder->CreateZExtOrTrunc(V, Y->getType());
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ICmpInst::Predicate Pred = IC->getPredicate();
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if ((Pred == ICmpInst::ICMP_NE && OrOnFalseVal) ||
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(Pred == ICmpInst::ICMP_EQ && OrOnTrueVal))
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V = Builder->CreateXor(V, *C2);
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return Builder->CreateOr(V, Y);
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}
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/// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single
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/// call to cttz/ctlz with flag 'is_zero_undef' cleared.
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///
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/// For example, we can fold the following code sequence:
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/// \code
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/// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
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/// %1 = icmp ne i32 %x, 0
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/// %2 = select i1 %1, i32 %0, i32 32
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/// \code
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///
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/// into:
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/// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
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static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal,
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InstCombiner::BuilderTy *Builder) {
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ICmpInst::Predicate Pred = ICI->getPredicate();
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Value *CmpLHS = ICI->getOperand(0);
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Value *CmpRHS = ICI->getOperand(1);
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// Check if the condition value compares a value for equality against zero.
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if (!ICI->isEquality() || !match(CmpRHS, m_Zero()))
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return nullptr;
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Value *Count = FalseVal;
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Value *ValueOnZero = TrueVal;
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if (Pred == ICmpInst::ICMP_NE)
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std::swap(Count, ValueOnZero);
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// Skip zero extend/truncate.
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Value *V = nullptr;
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if (match(Count, m_ZExt(m_Value(V))) ||
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match(Count, m_Trunc(m_Value(V))))
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Count = V;
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// Check if the value propagated on zero is a constant number equal to the
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// sizeof in bits of 'Count'.
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unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits();
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if (!match(ValueOnZero, m_SpecificInt(SizeOfInBits)))
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return nullptr;
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// Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the
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// input to the cttz/ctlz is used as LHS for the compare instruction.
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if (match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) ||
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match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) {
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IntrinsicInst *II = cast<IntrinsicInst>(Count);
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IRBuilder<> Builder(II);
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// Explicitly clear the 'undef_on_zero' flag.
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IntrinsicInst *NewI = cast<IntrinsicInst>(II->clone());
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Type *Ty = NewI->getArgOperand(1)->getType();
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NewI->setArgOperand(1, Constant::getNullValue(Ty));
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Builder.Insert(NewI);
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return Builder.CreateZExtOrTrunc(NewI, ValueOnZero->getType());
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}
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return nullptr;
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}
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/// Visit a SelectInst that has an ICmpInst as its first operand.
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Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
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ICmpInst *ICI) {
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bool Changed = false;
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ICmpInst::Predicate Pred = ICI->getPredicate();
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Value *CmpLHS = ICI->getOperand(0);
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Value *CmpRHS = ICI->getOperand(1);
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Value *TrueVal = SI.getTrueValue();
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Value *FalseVal = SI.getFalseValue();
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// Check cases where the comparison is with a constant that
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// can be adjusted to fit the min/max idiom. We may move or edit ICI
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// here, so make sure the select is the only user.
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if (ICI->hasOneUse())
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if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
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switch (Pred) {
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default: break;
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case ICmpInst::ICMP_ULT:
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case ICmpInst::ICMP_SLT:
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case ICmpInst::ICMP_UGT:
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case ICmpInst::ICMP_SGT: {
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// These transformations only work for selects over integers.
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IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType());
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if (!SelectTy)
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break;
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Constant *AdjustedRHS;
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if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT)
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AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1);
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else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
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AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
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// X > C ? X : C+1 --> X < C+1 ? C+1 : X
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// X < C ? X : C-1 --> X > C-1 ? C-1 : X
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if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
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(CmpLHS == FalseVal && AdjustedRHS == TrueVal))
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; // Nothing to do here. Values match without any sign/zero extension.
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// Types do not match. Instead of calculating this with mixed types
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// promote all to the larger type. This enables scalar evolution to
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// analyze this expression.
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|
else if (CmpRHS->getType()->getScalarSizeInBits()
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< SelectTy->getBitWidth()) {
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Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy);
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|
|
// X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
|
|
// X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
|
|
// X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
|
|
// X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
|
|
if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) &&
|
|
sextRHS == FalseVal) {
|
|
CmpLHS = TrueVal;
|
|
AdjustedRHS = sextRHS;
|
|
} else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) &&
|
|
sextRHS == TrueVal) {
|
|
CmpLHS = FalseVal;
|
|
AdjustedRHS = sextRHS;
|
|
} else if (ICI->isUnsigned()) {
|
|
Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy);
|
|
// X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
|
|
// X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
|
|
// zext + signed compare cannot be changed:
|
|
// 0xff <s 0x00, but 0x00ff >s 0x0000
|
|
if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) &&
|
|
zextRHS == FalseVal) {
|
|
CmpLHS = TrueVal;
|
|
AdjustedRHS = zextRHS;
|
|
} else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) &&
|
|
zextRHS == TrueVal) {
|
|
CmpLHS = FalseVal;
|
|
AdjustedRHS = zextRHS;
|
|
} else
|
|
break;
|
|
} else
|
|
break;
|
|
} else
|
|
break;
|
|
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
CmpRHS = AdjustedRHS;
|
|
std::swap(FalseVal, TrueVal);
|
|
ICI->setPredicate(Pred);
|
|
ICI->setOperand(0, CmpLHS);
|
|
ICI->setOperand(1, CmpRHS);
|
|
SI.setOperand(1, TrueVal);
|
|
SI.setOperand(2, FalseVal);
|
|
|
|
// Move ICI instruction right before the select instruction. Otherwise
|
|
// the sext/zext value may be defined after the ICI instruction uses it.
|
|
ICI->moveBefore(&SI);
|
|
|
|
Changed = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
|
|
// and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
|
|
// FIXME: Type and constness constraints could be lifted, but we have to
|
|
// watch code size carefully. We should consider xor instead of
|
|
// sub/add when we decide to do that.
|
|
if (IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
|
|
if (TrueVal->getType() == Ty) {
|
|
if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
|
|
ConstantInt *C1 = nullptr, *C2 = nullptr;
|
|
if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
|
|
C1 = dyn_cast<ConstantInt>(TrueVal);
|
|
C2 = dyn_cast<ConstantInt>(FalseVal);
|
|
} else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
|
|
C1 = dyn_cast<ConstantInt>(FalseVal);
|
|
C2 = dyn_cast<ConstantInt>(TrueVal);
|
|
}
|
|
if (C1 && C2) {
|
|
// This shift results in either -1 or 0.
|
|
Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
|
|
|
|
// Check if we can express the operation with a single or.
|
|
if (C2->isAllOnesValue())
|
|
return replaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
|
|
|
|
Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
|
|
return replaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// NOTE: if we wanted to, this is where to detect integer MIN/MAX
|
|
|
|
if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) {
|
|
if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) {
|
|
// Transform (X == C) ? X : Y -> (X == C) ? C : Y
|
|
SI.setOperand(1, CmpRHS);
|
|
Changed = true;
|
|
} else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) {
|
|
// Transform (X != C) ? Y : X -> (X != C) ? Y : C
|
|
SI.setOperand(2, CmpRHS);
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
{
|
|
unsigned BitWidth = DL.getTypeSizeInBits(TrueVal->getType());
|
|
APInt MinSignedValue = APInt::getSignBit(BitWidth);
|
|
Value *X;
|
|
const APInt *Y, *C;
|
|
bool TrueWhenUnset;
|
|
bool IsBitTest = false;
|
|
if (ICmpInst::isEquality(Pred) &&
|
|
match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
|
|
match(CmpRHS, m_Zero())) {
|
|
IsBitTest = true;
|
|
TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
|
|
} else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
|
|
X = CmpLHS;
|
|
Y = &MinSignedValue;
|
|
IsBitTest = true;
|
|
TrueWhenUnset = false;
|
|
} else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
|
|
X = CmpLHS;
|
|
Y = &MinSignedValue;
|
|
IsBitTest = true;
|
|
TrueWhenUnset = true;
|
|
}
|
|
if (IsBitTest) {
|
|
Value *V = nullptr;
|
|
// (X & Y) == 0 ? X : X ^ Y --> X & ~Y
|
|
if (TrueWhenUnset && TrueVal == X &&
|
|
match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
|
|
V = Builder->CreateAnd(X, ~(*Y));
|
|
// (X & Y) != 0 ? X ^ Y : X --> X & ~Y
|
|
else if (!TrueWhenUnset && FalseVal == X &&
|
|
match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
|
|
V = Builder->CreateAnd(X, ~(*Y));
|
|
// (X & Y) == 0 ? X ^ Y : X --> X | Y
|
|
else if (TrueWhenUnset && FalseVal == X &&
|
|
match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
|
|
V = Builder->CreateOr(X, *Y);
|
|
// (X & Y) != 0 ? X : X ^ Y --> X | Y
|
|
else if (!TrueWhenUnset && TrueVal == X &&
|
|
match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
|
|
V = Builder->CreateOr(X, *Y);
|
|
|
|
if (V)
|
|
return replaceInstUsesWith(SI, V);
|
|
}
|
|
}
|
|
|
|
if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder))
|
|
return replaceInstUsesWith(SI, V);
|
|
|
|
if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder))
|
|
return replaceInstUsesWith(SI, V);
|
|
|
|
return Changed ? &SI : nullptr;
|
|
}
|
|
|
|
|
|
/// SI is a select whose condition is a PHI node (but the two may be in
|
|
/// different blocks). See if the true/false values (V) are live in all of the
|
|
/// predecessor blocks of the PHI. For example, cases like this can't be mapped:
|
|
///
|
|
/// X = phi [ C1, BB1], [C2, BB2]
|
|
/// Y = add
|
|
/// Z = select X, Y, 0
|
|
///
|
|
/// because Y is not live in BB1/BB2.
|
|
///
|
|
static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
|
|
const SelectInst &SI) {
|
|
// If the value is a non-instruction value like a constant or argument, it
|
|
// can always be mapped.
|
|
const Instruction *I = dyn_cast<Instruction>(V);
|
|
if (!I) return true;
|
|
|
|
// If V is a PHI node defined in the same block as the condition PHI, we can
|
|
// map the arguments.
|
|
const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
|
|
|
|
if (const PHINode *VP = dyn_cast<PHINode>(I))
|
|
if (VP->getParent() == CondPHI->getParent())
|
|
return true;
|
|
|
|
// Otherwise, if the PHI and select are defined in the same block and if V is
|
|
// defined in a different block, then we can transform it.
|
|
if (SI.getParent() == CondPHI->getParent() &&
|
|
I->getParent() != CondPHI->getParent())
|
|
return true;
|
|
|
|
// Otherwise we have a 'hard' case and we can't tell without doing more
|
|
// detailed dominator based analysis, punt.
|
|
return false;
|
|
}
|
|
|
|
/// We have an SPF (e.g. a min or max) of an SPF of the form:
|
|
/// SPF2(SPF1(A, B), C)
|
|
Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
|
|
SelectPatternFlavor SPF1,
|
|
Value *A, Value *B,
|
|
Instruction &Outer,
|
|
SelectPatternFlavor SPF2, Value *C) {
|
|
if (Outer.getType() != Inner->getType())
|
|
return nullptr;
|
|
|
|
if (C == A || C == B) {
|
|
// MAX(MAX(A, B), B) -> MAX(A, B)
|
|
// MIN(MIN(a, b), a) -> MIN(a, b)
|
|
if (SPF1 == SPF2)
|
|
return replaceInstUsesWith(Outer, Inner);
|
|
|
|
// MAX(MIN(a, b), a) -> a
|
|
// MIN(MAX(a, b), a) -> a
|
|
if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
|
|
(SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
|
|
(SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
|
|
(SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
|
|
return replaceInstUsesWith(Outer, C);
|
|
}
|
|
|
|
if (SPF1 == SPF2) {
|
|
if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) {
|
|
if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) {
|
|
const APInt &ACB = CB->getValue();
|
|
const APInt &ACC = CC->getValue();
|
|
|
|
// MIN(MIN(A, 23), 97) -> MIN(A, 23)
|
|
// MAX(MAX(A, 97), 23) -> MAX(A, 97)
|
|
if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) ||
|
|
(SPF1 == SPF_SMIN && ACB.sle(ACC)) ||
|
|
(SPF1 == SPF_UMAX && ACB.uge(ACC)) ||
|
|
(SPF1 == SPF_SMAX && ACB.sge(ACC)))
|
|
return replaceInstUsesWith(Outer, Inner);
|
|
|
|
// MIN(MIN(A, 97), 23) -> MIN(A, 23)
|
|
// MAX(MAX(A, 23), 97) -> MAX(A, 97)
|
|
if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) ||
|
|
(SPF1 == SPF_SMIN && ACB.sgt(ACC)) ||
|
|
(SPF1 == SPF_UMAX && ACB.ult(ACC)) ||
|
|
(SPF1 == SPF_SMAX && ACB.slt(ACC))) {
|
|
Outer.replaceUsesOfWith(Inner, A);
|
|
return &Outer;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// ABS(ABS(X)) -> ABS(X)
|
|
// NABS(NABS(X)) -> NABS(X)
|
|
if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) {
|
|
return replaceInstUsesWith(Outer, Inner);
|
|
}
|
|
|
|
// ABS(NABS(X)) -> ABS(X)
|
|
// NABS(ABS(X)) -> NABS(X)
|
|
if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) ||
|
|
(SPF1 == SPF_NABS && SPF2 == SPF_ABS)) {
|
|
SelectInst *SI = cast<SelectInst>(Inner);
|
|
Value *NewSI = Builder->CreateSelect(
|
|
SI->getCondition(), SI->getFalseValue(), SI->getTrueValue());
|
|
return replaceInstUsesWith(Outer, NewSI);
|
|
}
|
|
|
|
auto IsFreeOrProfitableToInvert =
|
|
[&](Value *V, Value *&NotV, bool &ElidesXor) {
|
|
if (match(V, m_Not(m_Value(NotV)))) {
|
|
// If V has at most 2 uses then we can get rid of the xor operation
|
|
// entirely.
|
|
ElidesXor |= !V->hasNUsesOrMore(3);
|
|
return true;
|
|
}
|
|
|
|
if (IsFreeToInvert(V, !V->hasNUsesOrMore(3))) {
|
|
NotV = nullptr;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
};
|
|
|
|
Value *NotA, *NotB, *NotC;
|
|
bool ElidesXor = false;
|
|
|
|
// MIN(MIN(~A, ~B), ~C) == ~MAX(MAX(A, B), C)
|
|
// MIN(MAX(~A, ~B), ~C) == ~MAX(MIN(A, B), C)
|
|
// MAX(MIN(~A, ~B), ~C) == ~MIN(MAX(A, B), C)
|
|
// MAX(MAX(~A, ~B), ~C) == ~MIN(MIN(A, B), C)
|
|
//
|
|
// This transform is performance neutral if we can elide at least one xor from
|
|
// the set of three operands, since we'll be tacking on an xor at the very
|
|
// end.
|
|
if (IsFreeOrProfitableToInvert(A, NotA, ElidesXor) &&
|
|
IsFreeOrProfitableToInvert(B, NotB, ElidesXor) &&
|
|
IsFreeOrProfitableToInvert(C, NotC, ElidesXor) && ElidesXor) {
|
|
if (!NotA)
|
|
NotA = Builder->CreateNot(A);
|
|
if (!NotB)
|
|
NotB = Builder->CreateNot(B);
|
|
if (!NotC)
|
|
NotC = Builder->CreateNot(C);
|
|
|
|
Value *NewInner = generateMinMaxSelectPattern(
|
|
Builder, getInverseMinMaxSelectPattern(SPF1), NotA, NotB);
|
|
Value *NewOuter = Builder->CreateNot(generateMinMaxSelectPattern(
|
|
Builder, getInverseMinMaxSelectPattern(SPF2), NewInner, NotC));
|
|
return replaceInstUsesWith(Outer, NewOuter);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// If one of the constants is zero (we know they can't both be) and we have an
|
|
/// icmp instruction with zero, and we have an 'and' with the non-constant value
|
|
/// and a power of two we can turn the select into a shift on the result of the
|
|
/// 'and'.
|
|
static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
|
|
ConstantInt *FalseVal,
|
|
InstCombiner::BuilderTy *Builder) {
|
|
const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
|
|
if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
|
|
return nullptr;
|
|
|
|
if (!match(IC->getOperand(1), m_Zero()))
|
|
return nullptr;
|
|
|
|
ConstantInt *AndRHS;
|
|
Value *LHS = IC->getOperand(0);
|
|
if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
|
|
return nullptr;
|
|
|
|
// If both select arms are non-zero see if we have a select of the form
|
|
// 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
|
|
// for 'x ? 2^n : 0' and fix the thing up at the end.
|
|
ConstantInt *Offset = nullptr;
|
|
if (!TrueVal->isZero() && !FalseVal->isZero()) {
|
|
if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
|
|
Offset = FalseVal;
|
|
else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
|
|
Offset = TrueVal;
|
|
else
|
|
return nullptr;
|
|
|
|
// Adjust TrueVal and FalseVal to the offset.
|
|
TrueVal = ConstantInt::get(Builder->getContext(),
|
|
TrueVal->getValue() - Offset->getValue());
|
|
FalseVal = ConstantInt::get(Builder->getContext(),
|
|
FalseVal->getValue() - Offset->getValue());
|
|
}
|
|
|
|
// Make sure the mask in the 'and' and one of the select arms is a power of 2.
|
|
if (!AndRHS->getValue().isPowerOf2() ||
|
|
(!TrueVal->getValue().isPowerOf2() &&
|
|
!FalseVal->getValue().isPowerOf2()))
|
|
return nullptr;
|
|
|
|
// Determine which shift is needed to transform result of the 'and' into the
|
|
// desired result.
|
|
ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
|
|
unsigned ValZeros = ValC->getValue().logBase2();
|
|
unsigned AndZeros = AndRHS->getValue().logBase2();
|
|
|
|
// If types don't match we can still convert the select by introducing a zext
|
|
// or a trunc of the 'and'. The trunc case requires that all of the truncated
|
|
// bits are zero, we can figure that out by looking at the 'and' mask.
|
|
if (AndZeros >= ValC->getBitWidth())
|
|
return nullptr;
|
|
|
|
Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
|
|
if (ValZeros > AndZeros)
|
|
V = Builder->CreateShl(V, ValZeros - AndZeros);
|
|
else if (ValZeros < AndZeros)
|
|
V = Builder->CreateLShr(V, AndZeros - ValZeros);
|
|
|
|
// Okay, now we know that everything is set up, we just don't know whether we
|
|
// have a icmp_ne or icmp_eq and whether the true or false val is the zero.
|
|
bool ShouldNotVal = !TrueVal->isZero();
|
|
ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
|
|
if (ShouldNotVal)
|
|
V = Builder->CreateXor(V, ValC);
|
|
|
|
// Apply an offset if needed.
|
|
if (Offset)
|
|
V = Builder->CreateAdd(V, Offset);
|
|
return V;
|
|
}
|
|
|
|
/// Turn select C, (X + Y), (X - Y) --> (X + (select C, Y, (-Y))).
|
|
/// This is even legal for FP.
|
|
static Instruction *foldAddSubSelect(SelectInst &SI,
|
|
InstCombiner::BuilderTy &Builder) {
|
|
Value *CondVal = SI.getCondition();
|
|
Value *TrueVal = SI.getTrueValue();
|
|
Value *FalseVal = SI.getFalseValue();
|
|
auto *TI = dyn_cast<Instruction>(TrueVal);
|
|
auto *FI = dyn_cast<Instruction>(FalseVal);
|
|
if (!TI || !FI || !TI->hasOneUse() || !FI->hasOneUse())
|
|
return nullptr;
|
|
|
|
Instruction *AddOp = nullptr, *SubOp = nullptr;
|
|
if ((TI->getOpcode() == Instruction::Sub &&
|
|
FI->getOpcode() == Instruction::Add) ||
|
|
(TI->getOpcode() == Instruction::FSub &&
|
|
FI->getOpcode() == Instruction::FAdd)) {
|
|
AddOp = FI;
|
|
SubOp = TI;
|
|
} else if ((FI->getOpcode() == Instruction::Sub &&
|
|
TI->getOpcode() == Instruction::Add) ||
|
|
(FI->getOpcode() == Instruction::FSub &&
|
|
TI->getOpcode() == Instruction::FAdd)) {
|
|
AddOp = TI;
|
|
SubOp = FI;
|
|
}
|
|
|
|
if (AddOp) {
|
|
Value *OtherAddOp = nullptr;
|
|
if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
|
|
OtherAddOp = AddOp->getOperand(1);
|
|
} else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
|
|
OtherAddOp = AddOp->getOperand(0);
|
|
}
|
|
|
|
if (OtherAddOp) {
|
|
// So at this point we know we have (Y -> OtherAddOp):
|
|
// select C, (add X, Y), (sub X, Z)
|
|
Value *NegVal; // Compute -Z
|
|
if (SI.getType()->isFPOrFPVectorTy()) {
|
|
NegVal = Builder.CreateFNeg(SubOp->getOperand(1));
|
|
if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) {
|
|
FastMathFlags Flags = AddOp->getFastMathFlags();
|
|
Flags &= SubOp->getFastMathFlags();
|
|
NegInst->setFastMathFlags(Flags);
|
|
}
|
|
} else {
|
|
NegVal = Builder.CreateNeg(SubOp->getOperand(1));
|
|
}
|
|
|
|
Value *NewTrueOp = OtherAddOp;
|
|
Value *NewFalseOp = NegVal;
|
|
if (AddOp != TI)
|
|
std::swap(NewTrueOp, NewFalseOp);
|
|
Value *NewSel = Builder.CreateSelect(CondVal, NewTrueOp, NewFalseOp,
|
|
SI.getName() + ".p");
|
|
|
|
if (SI.getType()->isFPOrFPVectorTy()) {
|
|
Instruction *RI =
|
|
BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
|
|
|
|
FastMathFlags Flags = AddOp->getFastMathFlags();
|
|
Flags &= SubOp->getFastMathFlags();
|
|
RI->setFastMathFlags(Flags);
|
|
return RI;
|
|
} else
|
|
return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
|
|
Value *CondVal = SI.getCondition();
|
|
Value *TrueVal = SI.getTrueValue();
|
|
Value *FalseVal = SI.getFalseValue();
|
|
Type *SelType = SI.getType();
|
|
|
|
if (Value *V =
|
|
SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC))
|
|
return replaceInstUsesWith(SI, V);
|
|
|
|
if (SelType->getScalarType()->isIntegerTy(1) &&
|
|
TrueVal->getType() == CondVal->getType()) {
|
|
if (match(TrueVal, m_One())) {
|
|
// Change: A = select B, true, C --> A = or B, C
|
|
return BinaryOperator::CreateOr(CondVal, FalseVal);
|
|
}
|
|
if (match(TrueVal, m_Zero())) {
|
|
// Change: A = select B, false, C --> A = and !B, C
|
|
Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName());
|
|
return BinaryOperator::CreateAnd(NotCond, FalseVal);
|
|
}
|
|
if (match(FalseVal, m_Zero())) {
|
|
// Change: A = select B, C, false --> A = and B, C
|
|
return BinaryOperator::CreateAnd(CondVal, TrueVal);
|
|
}
|
|
if (match(FalseVal, m_One())) {
|
|
// Change: A = select B, C, true --> A = or !B, C
|
|
Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName());
|
|
return BinaryOperator::CreateOr(NotCond, TrueVal);
|
|
}
|
|
|
|
// select a, a, b -> a | b
|
|
// select a, b, a -> a & b
|
|
if (CondVal == TrueVal)
|
|
return BinaryOperator::CreateOr(CondVal, FalseVal);
|
|
if (CondVal == FalseVal)
|
|
return BinaryOperator::CreateAnd(CondVal, TrueVal);
|
|
|
|
// select a, ~a, b -> (~a) & b
|
|
// select a, b, ~a -> (~a) | b
|
|
if (match(TrueVal, m_Not(m_Specific(CondVal))))
|
|
return BinaryOperator::CreateAnd(TrueVal, FalseVal);
|
|
if (match(FalseVal, m_Not(m_Specific(CondVal))))
|
|
return BinaryOperator::CreateOr(TrueVal, FalseVal);
|
|
}
|
|
|
|
// Selecting between two integer or vector splat integer constants?
|
|
//
|
|
// Note that we don't handle a scalar select of vectors:
|
|
// select i1 %c, <2 x i8> <1, 1>, <2 x i8> <0, 0>
|
|
// because that may need 3 instructions to splat the condition value:
|
|
// extend, insertelement, shufflevector.
|
|
if (CondVal->getType()->isVectorTy() == SelType->isVectorTy()) {
|
|
// select C, 1, 0 -> zext C to int
|
|
if (match(TrueVal, m_One()) && match(FalseVal, m_Zero()))
|
|
return new ZExtInst(CondVal, SelType);
|
|
|
|
// select C, -1, 0 -> sext C to int
|
|
if (match(TrueVal, m_AllOnes()) && match(FalseVal, m_Zero()))
|
|
return new SExtInst(CondVal, SelType);
|
|
|
|
// select C, 0, 1 -> zext !C to int
|
|
if (match(TrueVal, m_Zero()) && match(FalseVal, m_One())) {
|
|
Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName());
|
|
return new ZExtInst(NotCond, SelType);
|
|
}
|
|
|
|
// select C, 0, -1 -> sext !C to int
|
|
if (match(TrueVal, m_Zero()) && match(FalseVal, m_AllOnes())) {
|
|
Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName());
|
|
return new SExtInst(NotCond, SelType);
|
|
}
|
|
}
|
|
|
|
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
|
|
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal))
|
|
if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
|
|
return replaceInstUsesWith(SI, V);
|
|
|
|
// See if we are selecting two values based on a comparison of the two values.
|
|
if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
|
|
if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
|
|
// Transform (X == Y) ? X : Y -> Y
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return replaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
// Transform (X une Y) ? X : Y -> X
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return replaceInstUsesWith(SI, TrueVal);
|
|
}
|
|
|
|
// Canonicalize to use ordered comparisons by swapping the select
|
|
// operands.
|
|
//
|
|
// e.g.
|
|
// (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
|
|
if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
|
|
FCmpInst::Predicate InvPred = FCI->getInversePredicate();
|
|
IRBuilder<>::FastMathFlagGuard FMFG(*Builder);
|
|
Builder->setFastMathFlags(FCI->getFastMathFlags());
|
|
Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal,
|
|
FCI->getName() + ".inv");
|
|
|
|
return SelectInst::Create(NewCond, FalseVal, TrueVal,
|
|
SI.getName() + ".p");
|
|
}
|
|
|
|
// NOTE: if we wanted to, this is where to detect MIN/MAX
|
|
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
|
|
// Transform (X == Y) ? Y : X -> X
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return replaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
// Transform (X une Y) ? Y : X -> Y
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return replaceInstUsesWith(SI, TrueVal);
|
|
}
|
|
|
|
// Canonicalize to use ordered comparisons by swapping the select
|
|
// operands.
|
|
//
|
|
// e.g.
|
|
// (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
|
|
if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
|
|
FCmpInst::Predicate InvPred = FCI->getInversePredicate();
|
|
IRBuilder<>::FastMathFlagGuard FMFG(*Builder);
|
|
Builder->setFastMathFlags(FCI->getFastMathFlags());
|
|
Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal,
|
|
FCI->getName() + ".inv");
|
|
|
|
return SelectInst::Create(NewCond, FalseVal, TrueVal,
|
|
SI.getName() + ".p");
|
|
}
|
|
|
|
// NOTE: if we wanted to, this is where to detect MIN/MAX
|
|
}
|
|
// NOTE: if we wanted to, this is where to detect ABS
|
|
}
|
|
|
|
// See if we are selecting two values based on a comparison of the two values.
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
|
|
if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
|
|
return Result;
|
|
|
|
if (Instruction *Add = foldAddSubSelect(SI, *Builder))
|
|
return Add;
|
|
|
|
// Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
|
|
auto *TI = dyn_cast<Instruction>(TrueVal);
|
|
auto *FI = dyn_cast<Instruction>(FalseVal);
|
|
if (TI && FI && TI->getOpcode() == FI->getOpcode())
|
|
if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
|
|
return IV;
|
|
|
|
// See if we can fold the select into one of our operands.
|
|
if (SelType->isIntOrIntVectorTy() || SelType->isFPOrFPVectorTy()) {
|
|
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
|
|
return FoldI;
|
|
|
|
Value *LHS, *RHS, *LHS2, *RHS2;
|
|
Instruction::CastOps CastOp;
|
|
SelectPatternResult SPR = matchSelectPattern(&SI, LHS, RHS, &CastOp);
|
|
auto SPF = SPR.Flavor;
|
|
|
|
if (SelectPatternResult::isMinOrMax(SPF)) {
|
|
// Canonicalize so that type casts are outside select patterns.
|
|
if (LHS->getType()->getPrimitiveSizeInBits() !=
|
|
SelType->getPrimitiveSizeInBits()) {
|
|
CmpInst::Predicate Pred = getCmpPredicateForMinMax(SPF, SPR.Ordered);
|
|
|
|
Value *Cmp;
|
|
if (CmpInst::isIntPredicate(Pred)) {
|
|
Cmp = Builder->CreateICmp(Pred, LHS, RHS);
|
|
} else {
|
|
IRBuilder<>::FastMathFlagGuard FMFG(*Builder);
|
|
auto FMF = cast<FPMathOperator>(SI.getCondition())->getFastMathFlags();
|
|
Builder->setFastMathFlags(FMF);
|
|
Cmp = Builder->CreateFCmp(Pred, LHS, RHS);
|
|
}
|
|
|
|
Value *NewSI = Builder->CreateCast(CastOp,
|
|
Builder->CreateSelect(Cmp, LHS, RHS),
|
|
SelType);
|
|
return replaceInstUsesWith(SI, NewSI);
|
|
}
|
|
}
|
|
|
|
if (SPF) {
|
|
// MAX(MAX(a, b), a) -> MAX(a, b)
|
|
// MIN(MIN(a, b), a) -> MIN(a, b)
|
|
// MAX(MIN(a, b), a) -> a
|
|
// MIN(MAX(a, b), a) -> a
|
|
// ABS(ABS(a)) -> ABS(a)
|
|
// NABS(NABS(a)) -> NABS(a)
|
|
if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor)
|
|
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
|
|
SI, SPF, RHS))
|
|
return R;
|
|
if (SelectPatternFlavor SPF2 = matchSelectPattern(RHS, LHS2, RHS2).Flavor)
|
|
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
|
|
SI, SPF, LHS))
|
|
return R;
|
|
}
|
|
|
|
// MAX(~a, ~b) -> ~MIN(a, b)
|
|
if (SPF == SPF_SMAX || SPF == SPF_UMAX) {
|
|
if (IsFreeToInvert(LHS, LHS->hasNUses(2)) &&
|
|
IsFreeToInvert(RHS, RHS->hasNUses(2))) {
|
|
|
|
// This transform adds a xor operation and that extra cost needs to be
|
|
// justified. We look for simplifications that will result from
|
|
// applying this rule:
|
|
|
|
bool Profitable =
|
|
(LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) ||
|
|
(RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) ||
|
|
(SI.hasOneUse() && match(*SI.user_begin(), m_Not(m_Value())));
|
|
|
|
if (Profitable) {
|
|
Value *NewLHS = Builder->CreateNot(LHS);
|
|
Value *NewRHS = Builder->CreateNot(RHS);
|
|
Value *NewCmp = SPF == SPF_SMAX
|
|
? Builder->CreateICmpSLT(NewLHS, NewRHS)
|
|
: Builder->CreateICmpULT(NewLHS, NewRHS);
|
|
Value *NewSI =
|
|
Builder->CreateNot(Builder->CreateSelect(NewCmp, NewLHS, NewRHS));
|
|
return replaceInstUsesWith(SI, NewSI);
|
|
}
|
|
}
|
|
}
|
|
|
|
// TODO.
|
|
// ABS(-X) -> ABS(X)
|
|
}
|
|
|
|
// See if we can fold the select into a phi node if the condition is a select.
|
|
if (isa<PHINode>(SI.getCondition()))
|
|
// The true/false values have to be live in the PHI predecessor's blocks.
|
|
if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
|
|
CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
|
|
if (Instruction *NV = FoldOpIntoPhi(SI))
|
|
return NV;
|
|
|
|
if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
|
|
if (TrueSI->getCondition()->getType() == CondVal->getType()) {
|
|
// select(C, select(C, a, b), c) -> select(C, a, c)
|
|
if (TrueSI->getCondition() == CondVal) {
|
|
if (SI.getTrueValue() == TrueSI->getTrueValue())
|
|
return nullptr;
|
|
SI.setOperand(1, TrueSI->getTrueValue());
|
|
return &SI;
|
|
}
|
|
// select(C0, select(C1, a, b), b) -> select(C0&C1, a, b)
|
|
// We choose this as normal form to enable folding on the And and shortening
|
|
// paths for the values (this helps GetUnderlyingObjects() for example).
|
|
if (TrueSI->getFalseValue() == FalseVal && TrueSI->hasOneUse()) {
|
|
Value *And = Builder->CreateAnd(CondVal, TrueSI->getCondition());
|
|
SI.setOperand(0, And);
|
|
SI.setOperand(1, TrueSI->getTrueValue());
|
|
return &SI;
|
|
}
|
|
}
|
|
}
|
|
if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
|
|
if (FalseSI->getCondition()->getType() == CondVal->getType()) {
|
|
// select(C, a, select(C, b, c)) -> select(C, a, c)
|
|
if (FalseSI->getCondition() == CondVal) {
|
|
if (SI.getFalseValue() == FalseSI->getFalseValue())
|
|
return nullptr;
|
|
SI.setOperand(2, FalseSI->getFalseValue());
|
|
return &SI;
|
|
}
|
|
// select(C0, a, select(C1, a, b)) -> select(C0|C1, a, b)
|
|
if (FalseSI->getTrueValue() == TrueVal && FalseSI->hasOneUse()) {
|
|
Value *Or = Builder->CreateOr(CondVal, FalseSI->getCondition());
|
|
SI.setOperand(0, Or);
|
|
SI.setOperand(2, FalseSI->getFalseValue());
|
|
return &SI;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (BinaryOperator::isNot(CondVal)) {
|
|
SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
|
|
SI.setOperand(1, FalseVal);
|
|
SI.setOperand(2, TrueVal);
|
|
return &SI;
|
|
}
|
|
|
|
if (VectorType* VecTy = dyn_cast<VectorType>(SelType)) {
|
|
unsigned VWidth = VecTy->getNumElements();
|
|
APInt UndefElts(VWidth, 0);
|
|
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
|
|
if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) {
|
|
if (V != &SI)
|
|
return replaceInstUsesWith(SI, V);
|
|
return &SI;
|
|
}
|
|
|
|
if (isa<ConstantAggregateZero>(CondVal)) {
|
|
return replaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
}
|
|
|
|
// See if we can determine the result of this select based on a dominating
|
|
// condition.
|
|
BasicBlock *Parent = SI.getParent();
|
|
if (BasicBlock *Dom = Parent->getSinglePredecessor()) {
|
|
auto *PBI = dyn_cast_or_null<BranchInst>(Dom->getTerminator());
|
|
if (PBI && PBI->isConditional() &&
|
|
PBI->getSuccessor(0) != PBI->getSuccessor(1) &&
|
|
(PBI->getSuccessor(0) == Parent || PBI->getSuccessor(1) == Parent)) {
|
|
bool CondIsFalse = PBI->getSuccessor(1) == Parent;
|
|
Optional<bool> Implication = isImpliedCondition(
|
|
PBI->getCondition(), SI.getCondition(), DL, CondIsFalse);
|
|
if (Implication) {
|
|
Value *V = *Implication ? TrueVal : FalseVal;
|
|
return replaceInstUsesWith(SI, V);
|
|
}
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|