From 40f59e4466762ddcbe19da63e9434cbf50ba98dd Mon Sep 17 00:00:00 2001 From: Andrea Di Biagio Date: Tue, 6 Oct 2015 10:34:53 +0000 Subject: [InstCombine] Teach SimplifyDemandedVectorElts how to handle ConstantVector select masks with ConstantExpr elements (PR24922) If the mask of a select instruction is a ConstantVector, method SimplifyDemandedVectorElts iterates over the mask elements to identify which values are selected from the select inputs. Before this patch, method SimplifyDemandedVectorElts always used method Constant::isNullValue() to check if a value in the mask was zero. Unfortunately that method always returns false when called on a ConstantExpr. This patch fixes the problem in SimplifyDemandedVectorElts by adding an explicit check for ConstantExpr values. Now, if a value in the mask is a ConstantExpr, we avoid calling isNullValue() on it. Fixes PR24922. Differential Revision: http://reviews.llvm.org/D13219 llvm-svn: 249390 --- llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index a1fbda7..743d514 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -1057,7 +1057,13 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts); if (ConstantVector* CV = dyn_cast(I->getOperand(0))) { for (unsigned i = 0; i < VWidth; i++) { - if (CV->getAggregateElement(i)->isNullValue()) + Constant *CElt = CV->getAggregateElement(i); + // Method isNullValue always returns false when called on a + // ConstantExpr. If CElt is a ConstantExpr then skip it in order to + // to avoid propagating incorrect information. + if (isa(CElt)) + continue; + if (CElt->isNullValue()) LeftDemanded.clearBit(i); else RightDemanded.clearBit(i); -- cgit v1.1