[llvm-commits] [llvm] r114097 - in /llvm/trunk: lib/Analysis/InstructionSimplify.cpp test/Transforms/CorrelatedValuePropagation/crash.ll

[Chris Lattner]

On Sep 16, 2010, at 10:42 AM, Owen Anderson wrote:

> Author: resistor
> Date: Thu Sep 16 12:42:36 2010
> New Revision: 114097
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=114097&view=rev
> Log:
> Fix PR8161, in which an unreachable loop causes recursive instruction simplification to try
> to replace an instruction with itself.  Add a predicate to the simplifier to prevent this case.

Why is CVP doing simplifications in unreachable blocks?  Why not do a quick DFS of the CFG to find the reachable blocks?

-Chris

> 
> Added:
>    llvm/trunk/test/Transforms/CorrelatedValuePropagation/crash.ll
> Modified:
>    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
> 
> Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=114097&r1=114096&r2=114097&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
> +++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Thu Sep 16 12:42:36 2010
> @@ -423,31 +423,44 @@
> /// SimplifyInstruction - See if we can compute a simplified version of this
> /// instruction.  If not, this returns null.
> Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
> +  Value *Ret = 0;
>   switch (I->getOpcode()) {
>   default:
>     return ConstantFoldInstruction(I, TD);
>   case Instruction::Add:
> -    return SimplifyAddInst(I->getOperand(0), I->getOperand(1),
> -                           cast<BinaryOperator>(I)->hasNoSignedWrap(),
> -                           cast<BinaryOperator>(I)->hasNoUnsignedWrap(), TD);
> +    Ret = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
> +                          cast<BinaryOperator>(I)->hasNoSignedWrap(),
> +                          cast<BinaryOperator>(I)->hasNoUnsignedWrap(), TD);
> +    break; 
>   case Instruction::And:
> -    return SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD);
> +    Ret =  SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD);
> +    break;
>   case Instruction::Or:
> -    return SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD);
> +    Ret = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD);
> +    break;
>   case Instruction::ICmp:
> -    return SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
> -                            I->getOperand(0), I->getOperand(1), TD);
> +    Ret = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
> +                           I->getOperand(0), I->getOperand(1), TD);
> +    break;
>   case Instruction::FCmp:
> -    return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
> -                            I->getOperand(0), I->getOperand(1), TD);
> +    Ret = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
> +                           I->getOperand(0), I->getOperand(1), TD);
> +    break;
>   case Instruction::Select:
> -    return SimplifySelectInst(I->getOperand(0), I->getOperand(1),
> +    Ret = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
>                               I->getOperand(2), TD);
> +    break;
>   case Instruction::GetElementPtr: {
>     SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
> -    return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
> +    Ret = SimplifyGEPInst(&Ops[0], Ops.size(), TD);
> +    break;
>   }
>   }
> +  
> +  // It is possible, in situations involving unreachable loops, to
> +  // have a replacement that, through recursive simplification, ends up
> +  // simplifying to itself.
> +  return Ret != I ? Ret : 0;
> }
> 
> /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
> 
> Added: llvm/trunk/test/Transforms/CorrelatedValuePropagation/crash.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CorrelatedValuePropagation/crash.ll?rev=114097&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/CorrelatedValuePropagation/crash.ll (added)
> +++ llvm/trunk/test/Transforms/CorrelatedValuePropagation/crash.ll Thu Sep 16 12:42:36 2010
> @@ -0,0 +1,20 @@
> +; RUN: opt < %s -correlated-propagation
> +
> +; PR8161
> +define void @test1() nounwind ssp {
> +entry:
> +  br label %for.end
> +
> +for.cond.us.us:                                   ; preds = %for.cond.us.us
> +  %cmp6.i.us.us = icmp sgt i32 1, 0
> +  %lor.ext.i.us.us = zext i1 %cmp6.i.us.us to i32
> +  %lor.ext.add.i.us.us = select i1 %cmp6.i.us.us, i32 %lor.ext.i.us.us, i32 undef
> +  %conv.i.us.us = trunc i32 %lor.ext.add.i.us.us to i16
> +  %sext.us.us = shl i16 %conv.i.us.us, 8
> +  %conv6.us.us = ashr i16 %sext.us.us, 8
> +  %and.us.us = and i16 %conv6.us.us, %and.us.us
> +  br i1 false, label %for.end, label %for.cond.us.us
> +
> +for.end:                                          ; preds = %for.cond.us, %for.cond.us.us, %entry
> +  ret void
> +}
> 
> 
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