From ff666bd962a4446d80955fe75619201c29795501 Mon Sep 17 00:00:00 2001 From: Hal Finkel Date: Tue, 9 Jul 2013 18:16:16 +0000 Subject: Don't crash in SE dealing with ashr x, -1 ScalarEvolution::getSignedRange uses ComputeNumSignBits from ValueTracking on ashr instructions. ComputeNumSignBits can return zero, but this case was not handled correctly by the code in getSignedRange which was calling: APInt::getSignedMinValue(BitWidth).ashr(NS - 1) with NS = 0, resulting in an assertion failure in APInt::ashr. Now, we just return the conservative result (as with NS == 1). Another bug found by llvm-stress. llvm-svn: 185955 --- llvm/lib/Analysis/ScalarEvolution.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'llvm/lib/Analysis/ScalarEvolution.cpp') diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 0bff21e7c3e..af5051650ee 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -3589,7 +3589,7 @@ ScalarEvolution::getSignedRange(const SCEV *S) { if (!U->getValue()->getType()->isIntegerTy() && !TD) return setSignedRange(U, ConservativeResult); unsigned NS = ComputeNumSignBits(U->getValue(), TD); - if (NS == 1) + if (NS <= 1) return setSignedRange(U, ConservativeResult); return setSignedRange(U, ConservativeResult.intersectWith( ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1), -- cgit v1.2.3