[llvm-commits] [llvm] r162120 - in /llvm/trunk: include/llvm/Analysis/MemoryBuiltins.h lib/Analysis/MemoryBuiltins.cpp test/Transforms/InstCombine/objsize.ll

[Eli Friedman]

On Fri, Aug 17, 2012 at 12:26 PM, Benjamin Kramer
<benny.kra at googlemail.com> wrote:
> Author: d0k
> Date: Fri Aug 17 14:26:41 2012
> New Revision: 162120
>
> URL: http://llvm.org/viewvc/llvm-project?rev=162120&view=rev
> Log:
> MemoryBuiltins: Properly guard ObjectSizeOffsetVisitor against cycles in the IR.
>
> The previous fix only checked for simple cycles, use a set to catch longer
> cycles too.
>
> Drop the broken check from the ObjectSizeOffsetEvaluator. The BoundsChecking
> pass doesn't have to deal with invalid IR like InstCombine does.
>
> Modified:
>     llvm/trunk/include/llvm/Analysis/MemoryBuiltins.h
>     llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
>     llvm/trunk/test/Transforms/InstCombine/objsize.ll
>
> Modified: llvm/trunk/include/llvm/Analysis/MemoryBuiltins.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/MemoryBuiltins.h?rev=162120&r1=162119&r2=162120&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/MemoryBuiltins.h (original)
> +++ llvm/trunk/include/llvm/Analysis/MemoryBuiltins.h Fri Aug 17 14:26:41 2012
> @@ -146,6 +146,7 @@
>    bool RoundToAlign;
>    unsigned IntTyBits;
>    APInt Zero;
> +  SmallPtrSet<Instruction *, 8> SeenInsts;
>
>    APInt align(APInt Size, uint64_t Align);
>
> @@ -203,7 +204,6 @@
>    const TargetData *TD;
>    LLVMContext &Context;
>    BuilderTy Builder;
> -  ObjectSizeOffsetVisitor Visitor;
>    IntegerType *IntTy;
>    Value *Zero;
>    CacheMapTy CacheMap;
>
> Modified: llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryBuiltins.cpp?rev=162120&r1=162119&r2=162120&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/MemoryBuiltins.cpp (original)
> +++ llvm/trunk/lib/Analysis/MemoryBuiltins.cpp Fri Aug 17 14:26:41 2012
> @@ -358,11 +358,16 @@
>
>  SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
>    V = V->stripPointerCasts();
> +  if (Instruction *I = dyn_cast<Instruction>(V)) {
> +    // If we have already seen this instruction, bail out. Cycles can happen in
> +    // unreachable code after constant propagation.
> +    if (!SeenInsts.insert(I))
> +      return unknown();
>
> -  if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
> -    return visitGEPOperator(*GEP);
> -  if (Instruction *I = dyn_cast<Instruction>(V))
> +    if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
> +      return visitGEPOperator(*GEP);
>      return visit(*I);
> +  }
>    if (Argument *A = dyn_cast<Argument>(V))
>      return visitArgument(*A);
>    if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
> @@ -371,9 +376,12 @@
>      return visitGlobalVariable(*GV);
>    if (UndefValue *UV = dyn_cast<UndefValue>(V))
>      return visitUndefValue(*UV);
> -  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
> +  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
>      if (CE->getOpcode() == Instruction::IntToPtr)
>        return unknown(); // clueless
> +    if (CE->getOpcode() == Instruction::GetElementPtr)
> +      return visitGEPOperator(cast<GEPOperator>(*CE));
> +  }
>
>    DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
>          << '\n');
> @@ -473,10 +481,6 @@
>  }
>
>  SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
> -  // Ignore self-referencing GEPs, they can occur in unreachable code.
> -  if (&GEP == GEP.getPointerOperand())
> -    return unknown();
> -
>    SizeOffsetType PtrData = compute(GEP.getPointerOperand());
>    if (!bothKnown(PtrData) || !GEP.hasAllConstantIndices())
>      return unknown();
> @@ -510,10 +514,6 @@
>  }
>
>  SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
> -  // ignore malformed self-looping selects
> -  if (I.getTrueValue() == &I || I.getFalseValue() == &I)
> -    return unknown();
> -
>    SizeOffsetType TrueSide  = compute(I.getTrueValue());
>    SizeOffsetType FalseSide = compute(I.getFalseValue());
>    if (bothKnown(TrueSide) && bothKnown(FalseSide) && TrueSide == FalseSide)
> @@ -533,8 +533,7 @@
>
>  ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(const TargetData *TD,
>                                                       LLVMContext &Context)
> -: TD(TD), Context(Context), Builder(Context, TargetFolder(TD)),
> -Visitor(TD, Context) {
> +: TD(TD), Context(Context), Builder(Context, TargetFolder(TD)) {
>    IntTy = TD->getIntPtrType(Context);
>    Zero = ConstantInt::get(IntTy, 0);
>  }
> @@ -559,6 +558,7 @@
>  }
>
>  SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
> +  ObjectSizeOffsetVisitor Visitor(TD, Context);
>    SizeOffsetType Const = Visitor.compute(V);
>    if (Visitor.bothKnown(Const))
>      return std::make_pair(ConstantInt::get(Context, Const.first),
> @@ -719,10 +719,6 @@
>  }
>
>  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
> -  // ignore malformed self-looping selects
> -  if (I.getTrueValue() == &I || I.getFalseValue() == &I)
> -    return unknown();
> -
>    SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
>    SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
>
>
> Modified: llvm/trunk/test/Transforms/InstCombine/objsize.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/objsize.ll?rev=162120&r1=162119&r2=162120&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/objsize.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/objsize.ll Fri Aug 17 14:26:41 2012
> @@ -247,7 +247,8 @@
>
>  ; technically reachable, but this malformed IR may appear as a result of constant propagation
>  xpto:
> -  %gep = getelementptr i8* %gep, i32 1
> +  %gep2 = getelementptr i8* %gep, i32 1
> +  %gep = getelementptr i8* %gep2, i32 1
>    %o = call i32 @llvm.objectsize.i32(i8* %gep, i1 true)
>  ; CHECK: ret i32 undef
>    ret i32 %o

Err, wait a sec: this testcase isn't valid!  The verifier should catch it.

-Eli