From ce947366ec07ed3e9b017f0f4a07fa668a799119 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Sun, 14 Feb 2010 18:50:49 +0000 Subject: [PATCH] When complicated expressions are broken down into subexpressions with multiplication by constants distributed through, occasionally those subexpressions can include both x and -x. For now, if this condition is discovered within LSR, just prune such cases away, as they won't be profitable. This fixes a "zero allocated in a base register" assertion failure. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96177 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/LoopStrengthReduce.cpp | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp index b6ef718ce16..11f21879347 100644 --- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -2012,8 +2012,14 @@ void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx, F.BaseRegs.push_back(BaseReg); } if (Ops.size() > 1) { - F.BaseRegs.push_back(SE.getAddExpr(Ops)); - (void)InsertFormula(LU, LUIdx, F); + const SCEV *Sum = SE.getAddExpr(Ops); + // TODO: If Sum is zero, it probably means ScalarEvolution missed an + // opportunity to fold something. For now, just ignore such cases + // rather than procede with zero in a register. + if (!Sum->isZero()) { + F.BaseRegs.push_back(Sum); + (void)InsertFormula(LU, LUIdx, F); + } } } -- 2.34.1