PR9218: SimplifyDemandedVectorElts can return a non-null value that i…

…s not

the instruction passed in.  Make sure to account for this correctly, instead
of looping infinitely.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126058 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineVectorOps.cpp

@@ -426,8 +426,11 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
   unsigned VWidth = cast<VectorType>(VecOp->getType())->getNumElements();
   APInt UndefElts(VWidth, 0);
   APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
-  if (SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts))
+  if (Value *V = SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts)) {
+    if (V != &IE)
+      return ReplaceInstUsesWith(IE, V);
     return &IE;
+  }
 
   return 0;
 }
@@ -451,7 +454,9 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
 
   APInt UndefElts(VWidth, 0);
   APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
-  if (SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
+  if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
+    if (V != &SVI)
+      return ReplaceInstUsesWith(SVI, V);
     LHS = SVI.getOperand(0);
     RHS = SVI.getOperand(1);
     MadeChange = true;

test/Transforms/InstCombine/2011-02-16-InsertelementHang.ll

@@ -0,0 +1,11 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; PR9218
+
+%vec2x2 = type { <2 x double>, <2 x double> }
+
+define %vec2x2 @split(double) nounwind alwaysinline {
+; CHECK: @split
+; CHECK: ret %vec2x2 undef
+  %vba = insertelement <2 x double> undef, double %0, i32 2
+  ret <2 x double> %vba, <2 x double> %vba
+}