mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232388 91177308-0d34-0410-b5e6-96231b3b80d8
918 lines
35 KiB
C++
918 lines
35 KiB
C++
//===-- Lint.cpp - Check for common errors in LLVM IR ---------------------===//
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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 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/STLExtras.h"
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#include "llvm/ADT/SmallSet.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/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/CallSite.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstVisitor.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/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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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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}
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class Lint : public FunctionPass, public InstVisitor<Lint> {
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friend class InstVisitor<Lint>;
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void visitFunction(Function &F);
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void visitCallSite(CallSite CS);
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void visitMemoryReference(Instruction &I, Value *Ptr,
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uint64_t Size, unsigned Align,
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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 visitCallInst(CallInst &I);
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void visitInvokeInst(InvokeInst &I);
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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, const DataLayout &DL, bool OffsetOk) const;
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Value *findValueImpl(Value *V, const DataLayout &DL, 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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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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static char ID; // Pass identification, replacement for typeid
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Lint() : FunctionPass(ID), MessagesStr(Messages) {
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initializeLintPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesAll();
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AU.addRequired<AliasAnalysis>();
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AU.addRequired<AssumptionCacheTracker>();
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AU.addRequired<TargetLibraryInfoWrapperPass>();
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AU.addRequired<DominatorTreeWrapperPass>();
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}
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void print(raw_ostream &O, const Module *M) const override {}
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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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/// \brief 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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/// \brief 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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}
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char Lint::ID = 0;
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INITIALIZE_PASS_BEGIN(Lint, "lint", "Statically lint-checks LLVM IR",
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false, true)
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INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
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INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
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INITIALIZE_PASS_END(Lint, "lint", "Statically lint-checks LLVM IR",
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false, true)
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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 { if (!(C)) { CheckFailed(__VA_ARGS__); return; } } while (0)
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// Lint::run - This is the main Analysis entry point for a
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// function.
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//
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bool Lint::runOnFunction(Function &F) {
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Mod = F.getParent();
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AA = &getAnalysis<AliasAnalysis>();
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AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
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DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
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TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
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visit(F);
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dbgs() << MessagesStr.str();
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Messages.clear();
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return false;
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}
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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::visitCallSite(CallSite CS) {
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Instruction &I = *CS.getInstruction();
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Value *Callee = CS.getCalledValue();
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const DataLayout &DL = CS->getModule()->getDataLayout();
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visitMemoryReference(I, Callee, AliasAnalysis::UnknownSize,
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0, nullptr, MemRef::Callee);
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if (Function *F = dyn_cast<Function>(findValue(Callee, DL,
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/*OffsetOk=*/false))) {
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Assert(CS.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 = CS.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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CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.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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for (CallSite::arg_iterator BI = CS.arg_begin(); BI != AE; ++BI)
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if (AI != BI && (*BI)->getType()->isPointerTy()) {
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AliasAnalysis::AliasResult Result = AA->alias(*AI, *BI);
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Assert(Result != AliasAnalysis::MustAlias &&
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Result != AliasAnalysis::PartialAlias,
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"Unusual: noalias argument aliases another argument", &I);
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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 =
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cast<PointerType>(Formal->getType())->getElementType();
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visitMemoryReference(I, Actual, AA->getTypeStoreSize(Ty),
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DL.getABITypeAlignment(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 (CS.isCall() && cast<CallInst>(CS.getInstruction())->isTailCall())
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for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
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AI != AE; ++AI) {
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Value *Obj = findValue(*AI, DL, /*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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if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I))
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switch (II->getIntrinsicID()) {
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default: 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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// TODO: If the size is known, use it.
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visitMemoryReference(I, MCI->getDest(), AliasAnalysis::UnknownSize,
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MCI->getAlignment(), nullptr,
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MemRef::Write);
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visitMemoryReference(I, MCI->getSource(), AliasAnalysis::UnknownSize,
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MCI->getAlignment(), nullptr,
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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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uint64_t Size = 0;
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if (const ConstantInt *Len =
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dyn_cast<ConstantInt>(findValue(MCI->getLength(), DL,
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/*OffsetOk=*/false)))
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if (Len->getValue().isIntN(32))
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Size = Len->getValue().getZExtValue();
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Assert(AA->alias(MCI->getSource(), Size, MCI->getDest(), Size) !=
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AliasAnalysis::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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// TODO: If the size is known, use it.
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visitMemoryReference(I, MMI->getDest(), AliasAnalysis::UnknownSize,
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MMI->getAlignment(), nullptr,
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MemRef::Write);
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visitMemoryReference(I, MMI->getSource(), AliasAnalysis::UnknownSize,
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MMI->getAlignment(), nullptr,
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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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// TODO: If the size is known, use it.
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visitMemoryReference(I, MSI->getDest(), AliasAnalysis::UnknownSize,
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MSI->getAlignment(), nullptr,
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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, CS.getArgument(0), AliasAnalysis::UnknownSize,
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0, nullptr, MemRef::Read | MemRef::Write);
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break;
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case Intrinsic::vacopy:
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visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
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0, nullptr, MemRef::Write);
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visitMemoryReference(I, CS.getArgument(1), AliasAnalysis::UnknownSize,
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0, nullptr, MemRef::Read);
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break;
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case Intrinsic::vaend:
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visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
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0, 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, CS.getArgument(0), AliasAnalysis::UnknownSize,
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0, nullptr, MemRef::Read | MemRef::Write);
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break;
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case Intrinsic::eh_begincatch:
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visitEHBeginCatch(II);
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break;
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case Intrinsic::eh_endcatch:
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visitEHEndCatch(II);
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break;
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}
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}
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void Lint::visitCallInst(CallInst &I) {
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return visitCallSite(&I);
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}
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void Lint::visitInvokeInst(InvokeInst &I) {
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return visitCallSite(&I);
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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 =
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findValue(V, F->getParent()->getDataLayout(), /*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,
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Value *Ptr, uint64_t Size, unsigned Align,
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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 (Size == 0)
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return;
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Value *UnderlyingObject =
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findValue(Ptr, I.getModule()->getDataLayout(), /*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)->isAllOnesValue(),
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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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}
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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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auto &DL = I.getModule()->getDataLayout();
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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 = AliasAnalysis::UnknownSize;
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unsigned BaseAlign = 0;
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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->getAlignment();
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if (BaseAlign == 0 && ATy->isSized())
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BaseAlign = DL.getABITypeAlignment(ATy);
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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
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// then don't warn about funky memory accesses.
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if (GV->hasDefinitiveInitializer()) {
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Type *GTy = GV->getType()->getElementType();
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if (GTy->isSized())
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BaseSize = DL.getTypeAllocSize(GTy);
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BaseAlign = GV->getAlignment();
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if (BaseAlign == 0 && GTy->isSized())
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BaseAlign = DL.getABITypeAlignment(GTy);
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}
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}
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// Accesses from before the start or after the end of the object are not
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// defined.
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Assert(Size == AliasAnalysis::UnknownSize ||
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BaseSize == AliasAnalysis::UnknownSize ||
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(Offset >= 0 && Offset + Size <= BaseSize),
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"Undefined behavior: Buffer overflow", &I);
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// Accesses that say that the memory is more aligned than it is are not
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// defined.
|
|
if (Align == 0 && Ty && Ty->isSized())
|
|
Align = DL.getABITypeAlignment(Ty);
|
|
Assert(!BaseAlign || Align <= MinAlign(BaseAlign, Offset),
|
|
"Undefined behavior: Memory reference address is misaligned", &I);
|
|
}
|
|
}
|
|
|
|
void Lint::visitLoadInst(LoadInst &I) {
|
|
visitMemoryReference(I, I.getPointerOperand(),
|
|
AA->getTypeStoreSize(I.getType()), I.getAlignment(),
|
|
I.getType(), MemRef::Read);
|
|
}
|
|
|
|
void Lint::visitStoreInst(StoreInst &I) {
|
|
visitMemoryReference(I, I.getPointerOperand(),
|
|
AA->getTypeStoreSize(I.getOperand(0)->getType()),
|
|
I.getAlignment(),
|
|
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), I.getModule()->getDataLayout(),
|
|
/*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), I.getModule()->getDataLayout(), /*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), I.getModule()->getDataLayout(), /*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
|
|
"Undefined result: Shift count out of range", &I);
|
|
}
|
|
|
|
static bool
|
|
allPredsCameFromLandingPad(BasicBlock *BB,
|
|
SmallSet<BasicBlock *, 4> &VisitedBlocks) {
|
|
VisitedBlocks.insert(BB);
|
|
if (BB->isLandingPad())
|
|
return true;
|
|
// If we find a block with no predecessors, the search failed.
|
|
if (pred_empty(BB))
|
|
return false;
|
|
for (BasicBlock *Pred : predecessors(BB)) {
|
|
if (VisitedBlocks.count(Pred))
|
|
continue;
|
|
if (!allPredsCameFromLandingPad(Pred, VisitedBlocks))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static bool
|
|
allSuccessorsReachEndCatch(BasicBlock *BB, BasicBlock::iterator InstBegin,
|
|
IntrinsicInst **SecondBeginCatch,
|
|
SmallSet<BasicBlock *, 4> &VisitedBlocks) {
|
|
VisitedBlocks.insert(BB);
|
|
for (BasicBlock::iterator I = InstBegin, E = BB->end(); I != E; ++I) {
|
|
IntrinsicInst *IC = dyn_cast<IntrinsicInst>(I);
|
|
if (IC && IC->getIntrinsicID() == Intrinsic::eh_endcatch)
|
|
return true;
|
|
// If we find another begincatch while looking for an endcatch,
|
|
// that's also an error.
|
|
if (IC && IC->getIntrinsicID() == Intrinsic::eh_begincatch) {
|
|
*SecondBeginCatch = IC;
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// If we reach a block with no successors while searching, the
|
|
// search has failed.
|
|
if (succ_empty(BB))
|
|
return false;
|
|
// Otherwise, search all of the successors.
|
|
for (BasicBlock *Succ : successors(BB)) {
|
|
if (VisitedBlocks.count(Succ))
|
|
continue;
|
|
if (!allSuccessorsReachEndCatch(Succ, Succ->begin(), SecondBeginCatch,
|
|
VisitedBlocks))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void Lint::visitEHBeginCatch(IntrinsicInst *II) {
|
|
// The checks in this function make a potentially dubious assumption about
|
|
// the CFG, namely that any block involved in a catch is only used for the
|
|
// catch. This will very likely be true of IR generated by a front end,
|
|
// but it may cease to be true, for example, if the IR is run through a
|
|
// pass which combines similar blocks.
|
|
//
|
|
// In general, if we encounter a block the isn't dominated by the catch
|
|
// block while we are searching the catch block's successors for a call
|
|
// to end catch intrinsic, then it is possible that it will be legal for
|
|
// a path through this block to never reach a call to llvm.eh.endcatch.
|
|
// An analogous statement could be made about our search for a landing
|
|
// pad among the catch block's predecessors.
|
|
//
|
|
// What is actually required is that no path is possible at runtime that
|
|
// reaches a call to llvm.eh.begincatch without having previously visited
|
|
// a landingpad instruction and that no path is possible at runtime that
|
|
// calls llvm.eh.begincatch and does not subsequently call llvm.eh.endcatch
|
|
// (mentally adjusting for the fact that in reality these calls will be
|
|
// removed before code generation).
|
|
//
|
|
// Because this is a lint check, we take a pessimistic approach and warn if
|
|
// the control flow is potentially incorrect.
|
|
|
|
SmallSet<BasicBlock *, 4> VisitedBlocks;
|
|
BasicBlock *CatchBB = II->getParent();
|
|
|
|
// The begin catch must occur in a landing pad block or all paths
|
|
// to it must have come from a landing pad.
|
|
Assert(allPredsCameFromLandingPad(CatchBB, VisitedBlocks),
|
|
"llvm.eh.begincatch may be reachable without passing a landingpad",
|
|
II);
|
|
|
|
// Reset the visited block list.
|
|
VisitedBlocks.clear();
|
|
|
|
IntrinsicInst *SecondBeginCatch = nullptr;
|
|
|
|
// This has to be called before it is asserted. Otherwise, the first assert
|
|
// below can never be hit.
|
|
bool EndCatchFound = allSuccessorsReachEndCatch(
|
|
CatchBB, std::next(static_cast<BasicBlock::iterator>(II)),
|
|
&SecondBeginCatch, VisitedBlocks);
|
|
Assert(
|
|
SecondBeginCatch == nullptr,
|
|
"llvm.eh.begincatch may be called a second time before llvm.eh.endcatch",
|
|
II, SecondBeginCatch);
|
|
Assert(EndCatchFound,
|
|
"Some paths from llvm.eh.begincatch may not reach llvm.eh.endcatch",
|
|
II);
|
|
}
|
|
|
|
static bool allPredCameFromBeginCatch(
|
|
BasicBlock *BB, BasicBlock::reverse_iterator InstRbegin,
|
|
IntrinsicInst **SecondEndCatch, SmallSet<BasicBlock *, 4> &VisitedBlocks) {
|
|
VisitedBlocks.insert(BB);
|
|
// Look for a begincatch in this block.
|
|
for (BasicBlock::reverse_iterator RI = InstRbegin, RE = BB->rend(); RI != RE;
|
|
++RI) {
|
|
IntrinsicInst *IC = dyn_cast<IntrinsicInst>(&*RI);
|
|
if (IC && IC->getIntrinsicID() == Intrinsic::eh_begincatch)
|
|
return true;
|
|
// If we find another end catch before we find a begin catch, that's
|
|
// an error.
|
|
if (IC && IC->getIntrinsicID() == Intrinsic::eh_endcatch) {
|
|
*SecondEndCatch = IC;
|
|
return false;
|
|
}
|
|
// If we encounter a landingpad instruction, the search failed.
|
|
if (isa<LandingPadInst>(*RI))
|
|
return false;
|
|
}
|
|
// If while searching we find a block with no predeccesors,
|
|
// the search failed.
|
|
if (pred_empty(BB))
|
|
return false;
|
|
// Search any predecessors we haven't seen before.
|
|
for (BasicBlock *Pred : predecessors(BB)) {
|
|
if (VisitedBlocks.count(Pred))
|
|
continue;
|
|
if (!allPredCameFromBeginCatch(Pred, Pred->rbegin(), SecondEndCatch,
|
|
VisitedBlocks))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void Lint::visitEHEndCatch(IntrinsicInst *II) {
|
|
// The check in this function makes a potentially dubious assumption about
|
|
// the CFG, namely that any block involved in a catch is only used for the
|
|
// catch. This will very likely be true of IR generated by a front end,
|
|
// but it may cease to be true, for example, if the IR is run through a
|
|
// pass which combines similar blocks.
|
|
//
|
|
// In general, if we encounter a block the isn't post-dominated by the
|
|
// end catch block while we are searching the end catch block's predecessors
|
|
// for a call to the begin catch intrinsic, then it is possible that it will
|
|
// be legal for a path to reach the end catch block without ever having
|
|
// called llvm.eh.begincatch.
|
|
//
|
|
// What is actually required is that no path is possible at runtime that
|
|
// reaches a call to llvm.eh.endcatch without having previously visited
|
|
// a call to llvm.eh.begincatch (mentally adjusting for the fact that in
|
|
// reality these calls will be removed before code generation).
|
|
//
|
|
// Because this is a lint check, we take a pessimistic approach and warn if
|
|
// the control flow is potentially incorrect.
|
|
|
|
BasicBlock *EndCatchBB = II->getParent();
|
|
|
|
// Alls paths to the end catch call must pass through a begin catch call.
|
|
|
|
// If llvm.eh.begincatch wasn't called in the current block, we'll use this
|
|
// lambda to recursively look for it in predecessors.
|
|
SmallSet<BasicBlock *, 4> VisitedBlocks;
|
|
IntrinsicInst *SecondEndCatch = nullptr;
|
|
|
|
// This has to be called before it is asserted. Otherwise, the first assert
|
|
// below can never be hit.
|
|
bool BeginCatchFound =
|
|
allPredCameFromBeginCatch(EndCatchBB, BasicBlock::reverse_iterator(II),
|
|
&SecondEndCatch, VisitedBlocks);
|
|
Assert(
|
|
SecondEndCatch == nullptr,
|
|
"llvm.eh.endcatch may be called a second time after llvm.eh.begincatch",
|
|
II, SecondEndCatch);
|
|
Assert(BeginCatchFound,
|
|
"llvm.eh.endcatch may be reachable without passing llvm.eh.begincatch",
|
|
II);
|
|
}
|
|
|
|
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) {
|
|
unsigned BitWidth = V->getType()->getIntegerBitWidth();
|
|
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
|
|
computeKnownBits(V, KnownZero, KnownOne, DL, 0, AC,
|
|
dyn_cast<Instruction>(V), DT);
|
|
return KnownZero.isAllOnesValue();
|
|
}
|
|
|
|
// 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
|
|
unsigned BitWidth = VecTy->getElementType()->getIntegerBitWidth();
|
|
for (unsigned I = 0, N = VecTy->getNumElements(); I != N; ++I) {
|
|
Constant *Elem = C->getAggregateElement(I);
|
|
if (isa<UndefValue>(Elem))
|
|
return true;
|
|
|
|
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
|
|
computeKnownBits(Elem, KnownZero, KnownOne, DL);
|
|
if (KnownZero.isAllOnesValue())
|
|
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, I.getOperand(0), AliasAnalysis::UnknownSize, 0,
|
|
nullptr, MemRef::Read | MemRef::Write);
|
|
}
|
|
|
|
void Lint::visitIndirectBrInst(IndirectBrInst &I) {
|
|
visitMemoryReference(I, I.getAddress(), AliasAnalysis::UnknownSize, 0,
|
|
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(), I.getModule()->getDataLayout(),
|
|
/*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(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), I.getModule()->getDataLayout(),
|
|
/*OffsetOk=*/false)))
|
|
Assert(CI->getValue().ult(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()->begin() ||
|
|
std::prev(BasicBlock::iterator(&I))->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, const DataLayout &DL, bool OffsetOk) const {
|
|
SmallPtrSet<Value *, 4> Visited;
|
|
return findValueImpl(V, DL, OffsetOk, Visited);
|
|
}
|
|
|
|
/// findValueImpl - Implementation helper for findValue.
|
|
Value *Lint::findValueImpl(Value *V, const DataLayout &DL, 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, DL) : V->stripPointerCasts();
|
|
if (LoadInst *L = dyn_cast<LoadInst>(V)) {
|
|
BasicBlock::iterator BBI = L;
|
|
BasicBlock *BB = L->getParent();
|
|
SmallPtrSet<BasicBlock *, 4> VisitedBlocks;
|
|
for (;;) {
|
|
if (!VisitedBlocks.insert(BB).second)
|
|
break;
|
|
if (Value *U = FindAvailableLoadedValue(L->getPointerOperand(),
|
|
BB, BBI, 6, AA))
|
|
return findValueImpl(U, DL, 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())
|
|
if (W != V)
|
|
return findValueImpl(W, DL, OffsetOk, Visited);
|
|
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
|
|
if (CI->isNoopCast(DL))
|
|
return findValueImpl(CI->getOperand(0), DL, OffsetOk, Visited);
|
|
} else if (ExtractValueInst *Ex = dyn_cast<ExtractValueInst>(V)) {
|
|
if (Value *W = FindInsertedValue(Ex->getAggregateOperand(),
|
|
Ex->getIndices()))
|
|
if (W != V)
|
|
return findValueImpl(W, DL, 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.getIntPtrType(V->getType())))
|
|
return findValueImpl(CE->getOperand(0), DL, 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, DL, 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, DL, OffsetOk, Visited);
|
|
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
|
|
if (Value *W = ConstantFoldConstantExpression(CE, DL, TLI))
|
|
if (W != V)
|
|
return findValueImpl(W, DL, OffsetOk, Visited);
|
|
}
|
|
|
|
return V;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Implement the public interfaces to this file...
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
FunctionPass *llvm::createLintPass() {
|
|
return new Lint();
|
|
}
|
|
|
|
/// 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());
|
|
Lint *V = new Lint();
|
|
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;
|
|
Lint *V = new Lint();
|
|
PM.add(V);
|
|
PM.run(const_cast<Module&>(M));
|
|
}
|