From 0fd518beb38568e58eeec86876bb597bab06b722 Mon Sep 17 00:00:00 2001 From: Nuno Lopes Date: Tue, 3 Jul 2012 21:15:40 +0000 Subject: [PATCH] PHINode::hasConstantValue(): return undef if the PHI is fully recursive. Thanks Duncan for the idea git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159687 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ValueTracking.cpp | 2 +- lib/VMCore/Instructions.cpp | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index d245783ec65..cea34e16e7b 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -694,7 +694,7 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, // taking conservative care to avoid excessive recursion. if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) { // Skip if every incoming value references to ourself. - if (P->hasConstantValue() == P) + if (dyn_cast_or_null(P->hasConstantValue())) break; KnownZero = APInt::getAllOnesValue(BitWidth); diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp index 5aef4592501..9af98e8a9b3 100644 --- a/lib/VMCore/Instructions.cpp +++ b/lib/VMCore/Instructions.cpp @@ -167,6 +167,8 @@ Value *PHINode::hasConstantValue() const { // The case where the first value is this PHI. ConstantValue = getIncomingValue(i); } + if (ConstantValue == this) + return UndefValue::get(getType()); return ConstantValue; } -- 2.34.1