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784 lines
30 KiB
784 lines
30 KiB
//===-- Lint.cpp - Check for common errors in LLVM IR ---------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass statically checks for common and easily-identified constructs
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// which produce undefined or likely unintended behavior in LLVM IR.
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//
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// It is not a guarantee of correctness, in two ways. First, it isn't
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// comprehensive. There are checks which could be done statically which are
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// not yet implemented. Some of these are indicated by TODO comments, but
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// those aren't comprehensive either. Second, many conditions cannot be
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// checked statically. This pass does no dynamic instrumentation, so it
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// can't check for all possible problems.
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//
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// Another limitation is that it assumes all code will be executed. A store
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// through a null pointer in a basic block which is never reached is harmless,
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// but this pass will warn about it anyway. This is the main reason why most
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// of these checks live here instead of in the Verifier pass.
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//
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// Optimization passes may make conditions that this pass checks for more or
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// less obvious. If an optimization pass appears to be introducing a warning,
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// it may be that the optimization pass is merely exposing an existing
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// condition in the code.
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//
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// This code may be run before instcombine. In many cases, instcombine checks
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// for the same kinds of things and turns instructions with undefined behavior
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// into unreachable (or equivalent). Because of this, this pass makes some
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// effort to look through bitcasts and so on.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Lint.h"
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#include "llvm/ADT/APInt.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/Analysis/AliasAnalysis.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/InstructionSimplify.h"
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#include "llvm/Analysis/Loads.h"
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#include "llvm/Analysis/MemoryLocation.h"
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#include "llvm/Analysis/Passes.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/Argument.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Constant.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/DerivedTypes.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/InstVisitor.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/Instruction.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/LegacyPassManager.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/Type.h"
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#include "llvm/IR/Value.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/KnownBits.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cassert>
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#include <cstdint>
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#include <iterator>
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#include <string>
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using namespace llvm;
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namespace {
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namespace MemRef {
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static const unsigned Read = 1;
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static const unsigned Write = 2;
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static const unsigned Callee = 4;
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static const unsigned Branchee = 8;
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} // end namespace MemRef
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class Lint : public InstVisitor<Lint> {
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friend class InstVisitor<Lint>;
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void visitFunction(Function &F);
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void visitCallBase(CallBase &CB);
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void visitMemoryReference(Instruction &I, const MemoryLocation &Loc,
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MaybeAlign Alignment, Type *Ty, unsigned Flags);
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void visitEHBeginCatch(IntrinsicInst *II);
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void visitEHEndCatch(IntrinsicInst *II);
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void visitReturnInst(ReturnInst &I);
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void visitLoadInst(LoadInst &I);
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void visitStoreInst(StoreInst &I);
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void visitXor(BinaryOperator &I);
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void visitSub(BinaryOperator &I);
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void visitLShr(BinaryOperator &I);
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void visitAShr(BinaryOperator &I);
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void visitShl(BinaryOperator &I);
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void visitSDiv(BinaryOperator &I);
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void visitUDiv(BinaryOperator &I);
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void visitSRem(BinaryOperator &I);
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void visitURem(BinaryOperator &I);
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void visitAllocaInst(AllocaInst &I);
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void visitVAArgInst(VAArgInst &I);
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void visitIndirectBrInst(IndirectBrInst &I);
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void visitExtractElementInst(ExtractElementInst &I);
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void visitInsertElementInst(InsertElementInst &I);
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void visitUnreachableInst(UnreachableInst &I);
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Value *findValue(Value *V, bool OffsetOk) const;
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Value *findValueImpl(Value *V, bool OffsetOk,
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SmallPtrSetImpl<Value *> &Visited) const;
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public:
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Module *Mod;
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const DataLayout *DL;
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AliasAnalysis *AA;
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AssumptionCache *AC;
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DominatorTree *DT;
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TargetLibraryInfo *TLI;
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std::string Messages;
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raw_string_ostream MessagesStr;
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Lint(Module *Mod, const DataLayout *DL, AliasAnalysis *AA,
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AssumptionCache *AC, DominatorTree *DT, TargetLibraryInfo *TLI)
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: Mod(Mod), DL(DL), AA(AA), AC(AC), DT(DT), TLI(TLI),
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MessagesStr(Messages) {}
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void WriteValues(ArrayRef<const Value *> Vs) {
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for (const Value *V : Vs) {
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if (!V)
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continue;
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if (isa<Instruction>(V)) {
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MessagesStr << *V << '\n';
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} else {
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V->printAsOperand(MessagesStr, true, Mod);
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MessagesStr << '\n';
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}
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}
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}
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/// A check failed, so printout out the condition and the message.
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///
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/// This provides a nice place to put a breakpoint if you want to see why
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/// something is not correct.
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void CheckFailed(const Twine &Message) { MessagesStr << Message << '\n'; }
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/// A check failed (with values to print).
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///
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/// This calls the Message-only version so that the above is easier to set
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/// a breakpoint on.
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template <typename T1, typename... Ts>
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void CheckFailed(const Twine &Message, const T1 &V1, const Ts &... Vs) {
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CheckFailed(Message);
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WriteValues({V1, Vs...});
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}
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};
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} // end anonymous namespace
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// Assert - We know that cond should be true, if not print an error message.
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#define Assert(C, ...) \
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do { \
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if (!(C)) { \
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CheckFailed(__VA_ARGS__); \
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return; \
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} \
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} while (false)
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void Lint::visitFunction(Function &F) {
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// This isn't undefined behavior, it's just a little unusual, and it's a
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// fairly common mistake to neglect to name a function.
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Assert(F.hasName() || F.hasLocalLinkage(),
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"Unusual: Unnamed function with non-local linkage", &F);
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// TODO: Check for irreducible control flow.
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}
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void Lint::visitCallBase(CallBase &I) {
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Value *Callee = I.getCalledOperand();
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visitMemoryReference(I, MemoryLocation::getAfter(Callee), None, nullptr,
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MemRef::Callee);
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if (Function *F = dyn_cast<Function>(findValue(Callee,
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/*OffsetOk=*/false))) {
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Assert(I.getCallingConv() == F->getCallingConv(),
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"Undefined behavior: Caller and callee calling convention differ",
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&I);
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FunctionType *FT = F->getFunctionType();
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unsigned NumActualArgs = I.arg_size();
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Assert(FT->isVarArg() ? FT->getNumParams() <= NumActualArgs
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: FT->getNumParams() == NumActualArgs,
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"Undefined behavior: Call argument count mismatches callee "
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"argument count",
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&I);
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Assert(FT->getReturnType() == I.getType(),
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"Undefined behavior: Call return type mismatches "
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"callee return type",
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&I);
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// Check argument types (in case the callee was casted) and attributes.
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// TODO: Verify that caller and callee attributes are compatible.
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Function::arg_iterator PI = F->arg_begin(), PE = F->arg_end();
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auto AI = I.arg_begin(), AE = I.arg_end();
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for (; AI != AE; ++AI) {
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Value *Actual = *AI;
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if (PI != PE) {
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Argument *Formal = &*PI++;
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Assert(Formal->getType() == Actual->getType(),
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"Undefined behavior: Call argument type mismatches "
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"callee parameter type",
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&I);
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// Check that noalias arguments don't alias other arguments. This is
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// not fully precise because we don't know the sizes of the dereferenced
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// memory regions.
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if (Formal->hasNoAliasAttr() && Actual->getType()->isPointerTy()) {
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AttributeList PAL = I.getAttributes();
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unsigned ArgNo = 0;
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for (auto BI = I.arg_begin(); BI != AE; ++BI, ++ArgNo) {
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// Skip ByVal arguments since they will be memcpy'd to the callee's
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// stack so we're not really passing the pointer anyway.
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if (PAL.hasParamAttribute(ArgNo, Attribute::ByVal))
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continue;
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// If both arguments are readonly, they have no dependence.
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if (Formal->onlyReadsMemory() && I.onlyReadsMemory(ArgNo))
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continue;
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if (AI != BI && (*BI)->getType()->isPointerTy()) {
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AliasResult Result = AA->alias(*AI, *BI);
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Assert(Result != MustAlias && Result != PartialAlias,
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"Unusual: noalias argument aliases another argument", &I);
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}
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}
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}
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// Check that an sret argument points to valid memory.
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if (Formal->hasStructRetAttr() && Actual->getType()->isPointerTy()) {
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Type *Ty = Formal->getParamStructRetType();
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MemoryLocation Loc(
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Actual, LocationSize::precise(DL->getTypeStoreSize(Ty)));
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visitMemoryReference(I, Loc, DL->getABITypeAlign(Ty), Ty,
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MemRef::Read | MemRef::Write);
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}
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}
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}
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}
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if (const auto *CI = dyn_cast<CallInst>(&I)) {
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if (CI->isTailCall()) {
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const AttributeList &PAL = CI->getAttributes();
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unsigned ArgNo = 0;
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for (Value *Arg : I.args()) {
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// Skip ByVal arguments since they will be memcpy'd to the callee's
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// stack anyway.
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if (PAL.hasParamAttribute(ArgNo++, Attribute::ByVal))
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continue;
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Value *Obj = findValue(Arg, /*OffsetOk=*/true);
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Assert(!isa<AllocaInst>(Obj),
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"Undefined behavior: Call with \"tail\" keyword references "
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"alloca",
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&I);
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}
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}
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}
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if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I))
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switch (II->getIntrinsicID()) {
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default:
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break;
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// TODO: Check more intrinsics
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case Intrinsic::memcpy: {
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MemCpyInst *MCI = cast<MemCpyInst>(&I);
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visitMemoryReference(I, MemoryLocation::getForDest(MCI),
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MCI->getDestAlign(), nullptr, MemRef::Write);
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visitMemoryReference(I, MemoryLocation::getForSource(MCI),
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MCI->getSourceAlign(), nullptr, MemRef::Read);
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// Check that the memcpy arguments don't overlap. The AliasAnalysis API
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// isn't expressive enough for what we really want to do. Known partial
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// overlap is not distinguished from the case where nothing is known.
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auto Size = LocationSize::afterPointer();
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if (const ConstantInt *Len =
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dyn_cast<ConstantInt>(findValue(MCI->getLength(),
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/*OffsetOk=*/false)))
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if (Len->getValue().isIntN(32))
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Size = LocationSize::precise(Len->getValue().getZExtValue());
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Assert(AA->alias(MCI->getSource(), Size, MCI->getDest(), Size) !=
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MustAlias,
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"Undefined behavior: memcpy source and destination overlap", &I);
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break;
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}
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case Intrinsic::memcpy_inline: {
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MemCpyInlineInst *MCII = cast<MemCpyInlineInst>(&I);
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const uint64_t Size = MCII->getLength()->getValue().getLimitedValue();
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visitMemoryReference(I, MemoryLocation::getForDest(MCII),
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MCII->getDestAlign(), nullptr, MemRef::Write);
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visitMemoryReference(I, MemoryLocation::getForSource(MCII),
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MCII->getSourceAlign(), nullptr, MemRef::Read);
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// Check that the memcpy arguments don't overlap. The AliasAnalysis API
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// isn't expressive enough for what we really want to do. Known partial
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// overlap is not distinguished from the case where nothing is known.
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const LocationSize LS = LocationSize::precise(Size);
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Assert(AA->alias(MCII->getSource(), LS, MCII->getDest(), LS) != MustAlias,
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"Undefined behavior: memcpy source and destination overlap", &I);
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break;
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}
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case Intrinsic::memmove: {
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MemMoveInst *MMI = cast<MemMoveInst>(&I);
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visitMemoryReference(I, MemoryLocation::getForDest(MMI),
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MMI->getDestAlign(), nullptr, MemRef::Write);
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visitMemoryReference(I, MemoryLocation::getForSource(MMI),
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MMI->getSourceAlign(), nullptr, MemRef::Read);
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break;
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}
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case Intrinsic::memset: {
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MemSetInst *MSI = cast<MemSetInst>(&I);
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visitMemoryReference(I, MemoryLocation::getForDest(MSI),
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MSI->getDestAlign(), nullptr, MemRef::Write);
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break;
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}
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case Intrinsic::vastart:
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Assert(I.getParent()->getParent()->isVarArg(),
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"Undefined behavior: va_start called in a non-varargs function",
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&I);
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visitMemoryReference(I, MemoryLocation::getForArgument(&I, 0, TLI), None,
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nullptr, MemRef::Read | MemRef::Write);
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break;
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case Intrinsic::vacopy:
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visitMemoryReference(I, MemoryLocation::getForArgument(&I, 0, TLI), None,
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nullptr, MemRef::Write);
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visitMemoryReference(I, MemoryLocation::getForArgument(&I, 1, TLI), None,
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nullptr, MemRef::Read);
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break;
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case Intrinsic::vaend:
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visitMemoryReference(I, MemoryLocation::getForArgument(&I, 0, TLI), None,
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nullptr, MemRef::Read | MemRef::Write);
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break;
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case Intrinsic::stackrestore:
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// Stackrestore doesn't read or write memory, but it sets the
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// stack pointer, which the compiler may read from or write to
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// at any time, so check it for both readability and writeability.
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visitMemoryReference(I, MemoryLocation::getForArgument(&I, 0, TLI), None,
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nullptr, MemRef::Read | MemRef::Write);
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break;
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case Intrinsic::get_active_lane_mask:
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if (auto *TripCount = dyn_cast<ConstantInt>(I.getArgOperand(1)))
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Assert(!TripCount->isZero(), "get_active_lane_mask: operand #2 "
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"must be greater than 0", &I);
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break;
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}
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}
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void Lint::visitReturnInst(ReturnInst &I) {
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Function *F = I.getParent()->getParent();
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Assert(!F->doesNotReturn(),
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"Unusual: Return statement in function with noreturn attribute", &I);
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if (Value *V = I.getReturnValue()) {
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Value *Obj = findValue(V, /*OffsetOk=*/true);
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Assert(!isa<AllocaInst>(Obj), "Unusual: Returning alloca value", &I);
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}
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}
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// TODO: Check that the reference is in bounds.
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// TODO: Check readnone/readonly function attributes.
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void Lint::visitMemoryReference(Instruction &I, const MemoryLocation &Loc,
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MaybeAlign Align, Type *Ty, unsigned Flags) {
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// If no memory is being referenced, it doesn't matter if the pointer
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// is valid.
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if (Loc.Size.isZero())
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return;
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Value *Ptr = const_cast<Value *>(Loc.Ptr);
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Value *UnderlyingObject = findValue(Ptr, /*OffsetOk=*/true);
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Assert(!isa<ConstantPointerNull>(UnderlyingObject),
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"Undefined behavior: Null pointer dereference", &I);
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Assert(!isa<UndefValue>(UnderlyingObject),
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"Undefined behavior: Undef pointer dereference", &I);
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Assert(!isa<ConstantInt>(UnderlyingObject) ||
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!cast<ConstantInt>(UnderlyingObject)->isMinusOne(),
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"Unusual: All-ones pointer dereference", &I);
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Assert(!isa<ConstantInt>(UnderlyingObject) ||
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!cast<ConstantInt>(UnderlyingObject)->isOne(),
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"Unusual: Address one pointer dereference", &I);
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if (Flags & MemRef::Write) {
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if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(UnderlyingObject))
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Assert(!GV->isConstant(), "Undefined behavior: Write to read-only memory",
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&I);
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Assert(!isa<Function>(UnderlyingObject) &&
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!isa<BlockAddress>(UnderlyingObject),
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"Undefined behavior: Write to text section", &I);
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}
|
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if (Flags & MemRef::Read) {
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Assert(!isa<Function>(UnderlyingObject), "Unusual: Load from function body",
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&I);
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Assert(!isa<BlockAddress>(UnderlyingObject),
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|
"Undefined behavior: Load from block address", &I);
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}
|
|
if (Flags & MemRef::Callee) {
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Assert(!isa<BlockAddress>(UnderlyingObject),
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|
"Undefined behavior: Call to block address", &I);
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}
|
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if (Flags & MemRef::Branchee) {
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Assert(!isa<Constant>(UnderlyingObject) ||
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isa<BlockAddress>(UnderlyingObject),
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"Undefined behavior: Branch to non-blockaddress", &I);
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|
}
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|
|
|
// Check for buffer overflows and misalignment.
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|
// Only handles memory references that read/write something simple like an
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// alloca instruction or a global variable.
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|
int64_t Offset = 0;
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if (Value *Base = GetPointerBaseWithConstantOffset(Ptr, Offset, *DL)) {
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// OK, so the access is to a constant offset from Ptr. Check that Ptr is
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|
// something we can handle and if so extract the size of this base object
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// along with its alignment.
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uint64_t BaseSize = MemoryLocation::UnknownSize;
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|
MaybeAlign BaseAlign;
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|
if (AllocaInst *AI = dyn_cast<AllocaInst>(Base)) {
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Type *ATy = AI->getAllocatedType();
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if (!AI->isArrayAllocation() && ATy->isSized())
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BaseSize = DL->getTypeAllocSize(ATy);
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BaseAlign = AI->getAlign();
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} else if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
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|
// If the global may be defined differently in another compilation unit
|
|
// then don't warn about funky memory accesses.
|
|
if (GV->hasDefinitiveInitializer()) {
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Type *GTy = GV->getValueType();
|
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if (GTy->isSized())
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BaseSize = DL->getTypeAllocSize(GTy);
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BaseAlign = GV->getAlign();
|
|
if (!BaseAlign && GTy->isSized())
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BaseAlign = DL->getABITypeAlign(GTy);
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|
}
|
|
}
|
|
|
|
// Accesses from before the start or after the end of the object are not
|
|
// defined.
|
|
Assert(!Loc.Size.hasValue() || BaseSize == MemoryLocation::UnknownSize ||
|
|
(Offset >= 0 && Offset + Loc.Size.getValue() <= BaseSize),
|
|
"Undefined behavior: Buffer overflow", &I);
|
|
|
|
// Accesses that say that the memory is more aligned than it is are not
|
|
// defined.
|
|
if (!Align && Ty && Ty->isSized())
|
|
Align = DL->getABITypeAlign(Ty);
|
|
if (BaseAlign && Align)
|
|
Assert(*Align <= commonAlignment(*BaseAlign, Offset),
|
|
"Undefined behavior: Memory reference address is misaligned", &I);
|
|
}
|
|
}
|
|
|
|
void Lint::visitLoadInst(LoadInst &I) {
|
|
visitMemoryReference(I, MemoryLocation::get(&I), I.getAlign(), I.getType(),
|
|
MemRef::Read);
|
|
}
|
|
|
|
void Lint::visitStoreInst(StoreInst &I) {
|
|
visitMemoryReference(I, MemoryLocation::get(&I), I.getAlign(),
|
|
I.getOperand(0)->getType(), MemRef::Write);
|
|
}
|
|
|
|
void Lint::visitXor(BinaryOperator &I) {
|
|
Assert(!isa<UndefValue>(I.getOperand(0)) || !isa<UndefValue>(I.getOperand(1)),
|
|
"Undefined result: xor(undef, undef)", &I);
|
|
}
|
|
|
|
void Lint::visitSub(BinaryOperator &I) {
|
|
Assert(!isa<UndefValue>(I.getOperand(0)) || !isa<UndefValue>(I.getOperand(1)),
|
|
"Undefined result: sub(undef, undef)", &I);
|
|
}
|
|
|
|
void Lint::visitLShr(BinaryOperator &I) {
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(findValue(I.getOperand(1),
|
|
/*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
|
|
"Undefined result: Shift count out of range", &I);
|
|
}
|
|
|
|
void Lint::visitAShr(BinaryOperator &I) {
|
|
if (ConstantInt *CI =
|
|
dyn_cast<ConstantInt>(findValue(I.getOperand(1), /*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
|
|
"Undefined result: Shift count out of range", &I);
|
|
}
|
|
|
|
void Lint::visitShl(BinaryOperator &I) {
|
|
if (ConstantInt *CI =
|
|
dyn_cast<ConstantInt>(findValue(I.getOperand(1), /*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
|
|
"Undefined result: Shift count out of range", &I);
|
|
}
|
|
|
|
static bool isZero(Value *V, const DataLayout &DL, DominatorTree *DT,
|
|
AssumptionCache *AC) {
|
|
// Assume undef could be zero.
|
|
if (isa<UndefValue>(V))
|
|
return true;
|
|
|
|
VectorType *VecTy = dyn_cast<VectorType>(V->getType());
|
|
if (!VecTy) {
|
|
KnownBits Known =
|
|
computeKnownBits(V, DL, 0, AC, dyn_cast<Instruction>(V), DT);
|
|
return Known.isZero();
|
|
}
|
|
|
|
// Per-component check doesn't work with zeroinitializer
|
|
Constant *C = dyn_cast<Constant>(V);
|
|
if (!C)
|
|
return false;
|
|
|
|
if (C->isZeroValue())
|
|
return true;
|
|
|
|
// For a vector, KnownZero will only be true if all values are zero, so check
|
|
// this per component
|
|
for (unsigned I = 0, N = cast<FixedVectorType>(VecTy)->getNumElements();
|
|
I != N; ++I) {
|
|
Constant *Elem = C->getAggregateElement(I);
|
|
if (isa<UndefValue>(Elem))
|
|
return true;
|
|
|
|
KnownBits Known = computeKnownBits(Elem, DL);
|
|
if (Known.isZero())
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
void Lint::visitSDiv(BinaryOperator &I) {
|
|
Assert(!isZero(I.getOperand(1), I.getModule()->getDataLayout(), DT, AC),
|
|
"Undefined behavior: Division by zero", &I);
|
|
}
|
|
|
|
void Lint::visitUDiv(BinaryOperator &I) {
|
|
Assert(!isZero(I.getOperand(1), I.getModule()->getDataLayout(), DT, AC),
|
|
"Undefined behavior: Division by zero", &I);
|
|
}
|
|
|
|
void Lint::visitSRem(BinaryOperator &I) {
|
|
Assert(!isZero(I.getOperand(1), I.getModule()->getDataLayout(), DT, AC),
|
|
"Undefined behavior: Division by zero", &I);
|
|
}
|
|
|
|
void Lint::visitURem(BinaryOperator &I) {
|
|
Assert(!isZero(I.getOperand(1), I.getModule()->getDataLayout(), DT, AC),
|
|
"Undefined behavior: Division by zero", &I);
|
|
}
|
|
|
|
void Lint::visitAllocaInst(AllocaInst &I) {
|
|
if (isa<ConstantInt>(I.getArraySize()))
|
|
// This isn't undefined behavior, it's just an obvious pessimization.
|
|
Assert(&I.getParent()->getParent()->getEntryBlock() == I.getParent(),
|
|
"Pessimization: Static alloca outside of entry block", &I);
|
|
|
|
// TODO: Check for an unusual size (MSB set?)
|
|
}
|
|
|
|
void Lint::visitVAArgInst(VAArgInst &I) {
|
|
visitMemoryReference(I, MemoryLocation::get(&I), None, nullptr,
|
|
MemRef::Read | MemRef::Write);
|
|
}
|
|
|
|
void Lint::visitIndirectBrInst(IndirectBrInst &I) {
|
|
visitMemoryReference(I, MemoryLocation::getAfter(I.getAddress()), None,
|
|
nullptr, MemRef::Branchee);
|
|
|
|
Assert(I.getNumDestinations() != 0,
|
|
"Undefined behavior: indirectbr with no destinations", &I);
|
|
}
|
|
|
|
void Lint::visitExtractElementInst(ExtractElementInst &I) {
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(findValue(I.getIndexOperand(),
|
|
/*OffsetOk=*/false)))
|
|
Assert(
|
|
CI->getValue().ult(
|
|
cast<FixedVectorType>(I.getVectorOperandType())->getNumElements()),
|
|
"Undefined result: extractelement index out of range", &I);
|
|
}
|
|
|
|
void Lint::visitInsertElementInst(InsertElementInst &I) {
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(findValue(I.getOperand(2),
|
|
/*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(
|
|
cast<FixedVectorType>(I.getType())->getNumElements()),
|
|
"Undefined result: insertelement index out of range", &I);
|
|
}
|
|
|
|
void Lint::visitUnreachableInst(UnreachableInst &I) {
|
|
// This isn't undefined behavior, it's merely suspicious.
|
|
Assert(&I == &I.getParent()->front() ||
|
|
std::prev(I.getIterator())->mayHaveSideEffects(),
|
|
"Unusual: unreachable immediately preceded by instruction without "
|
|
"side effects",
|
|
&I);
|
|
}
|
|
|
|
/// findValue - Look through bitcasts and simple memory reference patterns
|
|
/// to identify an equivalent, but more informative, value. If OffsetOk
|
|
/// is true, look through getelementptrs with non-zero offsets too.
|
|
///
|
|
/// Most analysis passes don't require this logic, because instcombine
|
|
/// will simplify most of these kinds of things away. But it's a goal of
|
|
/// this Lint pass to be useful even on non-optimized IR.
|
|
Value *Lint::findValue(Value *V, bool OffsetOk) const {
|
|
SmallPtrSet<Value *, 4> Visited;
|
|
return findValueImpl(V, OffsetOk, Visited);
|
|
}
|
|
|
|
/// findValueImpl - Implementation helper for findValue.
|
|
Value *Lint::findValueImpl(Value *V, bool OffsetOk,
|
|
SmallPtrSetImpl<Value *> &Visited) const {
|
|
// Detect self-referential values.
|
|
if (!Visited.insert(V).second)
|
|
return UndefValue::get(V->getType());
|
|
|
|
// TODO: Look through sext or zext cast, when the result is known to
|
|
// be interpreted as signed or unsigned, respectively.
|
|
// TODO: Look through eliminable cast pairs.
|
|
// TODO: Look through calls with unique return values.
|
|
// TODO: Look through vector insert/extract/shuffle.
|
|
V = OffsetOk ? getUnderlyingObject(V) : V->stripPointerCasts();
|
|
if (LoadInst *L = dyn_cast<LoadInst>(V)) {
|
|
BasicBlock::iterator BBI = L->getIterator();
|
|
BasicBlock *BB = L->getParent();
|
|
SmallPtrSet<BasicBlock *, 4> VisitedBlocks;
|
|
for (;;) {
|
|
if (!VisitedBlocks.insert(BB).second)
|
|
break;
|
|
if (Value *U =
|
|
FindAvailableLoadedValue(L, BB, BBI, DefMaxInstsToScan, AA))
|
|
return findValueImpl(U, OffsetOk, Visited);
|
|
if (BBI != BB->begin())
|
|
break;
|
|
BB = BB->getUniquePredecessor();
|
|
if (!BB)
|
|
break;
|
|
BBI = BB->end();
|
|
}
|
|
} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
|
|
if (Value *W = PN->hasConstantValue())
|
|
return findValueImpl(W, OffsetOk, Visited);
|
|
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
|
|
if (CI->isNoopCast(*DL))
|
|
return findValueImpl(CI->getOperand(0), OffsetOk, Visited);
|
|
} else if (ExtractValueInst *Ex = dyn_cast<ExtractValueInst>(V)) {
|
|
if (Value *W =
|
|
FindInsertedValue(Ex->getAggregateOperand(), Ex->getIndices()))
|
|
if (W != V)
|
|
return findValueImpl(W, OffsetOk, Visited);
|
|
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
|
|
// Same as above, but for ConstantExpr instead of Instruction.
|
|
if (Instruction::isCast(CE->getOpcode())) {
|
|
if (CastInst::isNoopCast(Instruction::CastOps(CE->getOpcode()),
|
|
CE->getOperand(0)->getType(), CE->getType(),
|
|
*DL))
|
|
return findValueImpl(CE->getOperand(0), OffsetOk, Visited);
|
|
} else if (CE->getOpcode() == Instruction::ExtractValue) {
|
|
ArrayRef<unsigned> Indices = CE->getIndices();
|
|
if (Value *W = FindInsertedValue(CE->getOperand(0), Indices))
|
|
if (W != V)
|
|
return findValueImpl(W, OffsetOk, Visited);
|
|
}
|
|
}
|
|
|
|
// As a last resort, try SimplifyInstruction or constant folding.
|
|
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
|
|
if (Value *W = SimplifyInstruction(Inst, {*DL, TLI, DT, AC}))
|
|
return findValueImpl(W, OffsetOk, Visited);
|
|
} else if (auto *C = dyn_cast<Constant>(V)) {
|
|
Value *W = ConstantFoldConstant(C, *DL, TLI);
|
|
if (W != V)
|
|
return findValueImpl(W, OffsetOk, Visited);
|
|
}
|
|
|
|
return V;
|
|
}
|
|
|
|
PreservedAnalyses LintPass::run(Function &F, FunctionAnalysisManager &AM) {
|
|
auto *Mod = F.getParent();
|
|
auto *DL = &F.getParent()->getDataLayout();
|
|
auto *AA = &AM.getResult<AAManager>(F);
|
|
auto *AC = &AM.getResult<AssumptionAnalysis>(F);
|
|
auto *DT = &AM.getResult<DominatorTreeAnalysis>(F);
|
|
auto *TLI = &AM.getResult<TargetLibraryAnalysis>(F);
|
|
Lint L(Mod, DL, AA, AC, DT, TLI);
|
|
L.visit(F);
|
|
dbgs() << L.MessagesStr.str();
|
|
return PreservedAnalyses::all();
|
|
}
|
|
|
|
class LintLegacyPass : public FunctionPass {
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
LintLegacyPass() : FunctionPass(ID) {
|
|
initializeLintLegacyPassPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &F) override;
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.setPreservesAll();
|
|
AU.addRequired<AAResultsWrapperPass>();
|
|
AU.addRequired<AssumptionCacheTracker>();
|
|
AU.addRequired<TargetLibraryInfoWrapperPass>();
|
|
AU.addRequired<DominatorTreeWrapperPass>();
|
|
}
|
|
void print(raw_ostream &O, const Module *M) const override {}
|
|
};
|
|
|
|
char LintLegacyPass::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(LintLegacyPass, "lint", "Statically lint-checks LLVM IR",
|
|
false, true)
|
|
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
|
|
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
|
|
INITIALIZE_PASS_END(LintLegacyPass, "lint", "Statically lint-checks LLVM IR",
|
|
false, true)
|
|
|
|
bool LintLegacyPass::runOnFunction(Function &F) {
|
|
auto *Mod = F.getParent();
|
|
auto *DL = &F.getParent()->getDataLayout();
|
|
auto *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
|
|
auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
|
|
auto *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
|
auto *TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
|
|
Lint L(Mod, DL, AA, AC, DT, TLI);
|
|
L.visit(F);
|
|
dbgs() << L.MessagesStr.str();
|
|
return false;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Implement the public interfaces to this file...
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
FunctionPass *llvm::createLintLegacyPassPass() { return new LintLegacyPass(); }
|
|
|
|
/// lintFunction - Check a function for errors, printing messages on stderr.
|
|
///
|
|
void llvm::lintFunction(const Function &f) {
|
|
Function &F = const_cast<Function &>(f);
|
|
assert(!F.isDeclaration() && "Cannot lint external functions");
|
|
|
|
legacy::FunctionPassManager FPM(F.getParent());
|
|
auto *V = new LintLegacyPass();
|
|
FPM.add(V);
|
|
FPM.run(F);
|
|
}
|
|
|
|
/// lintModule - Check a module for errors, printing messages on stderr.
|
|
///
|
|
void llvm::lintModule(const Module &M) {
|
|
legacy::PassManager PM;
|
|
auto *V = new LintLegacyPass();
|
|
PM.add(V);
|
|
PM.run(const_cast<Module &>(M));
|
|
}
|