ConstantVector returns arbitrary value for the wrong index.

This fixes PR10813.

llvm-svn: 139006

2 files changed, 33 insertions, 0 deletions

diff --git a/llvm/lib/VMCore/ConstantFold.cpp b/llvm/lib/VMCore/ConstantFold.cpp
index 47c693b0306..458f224575c 100644
--- a/llvm/lib/VMCore/ConstantFold.cpp
+++ b/llvm/lib/VMCore/ConstantFold.cpp
@@ -761,6 +761,10 @@ Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
 
   if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
     if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
+      uint64_t Index = CIdx->getZExtValue();
+      if (Index >= CVal->getNumOperands())
+        // ee({w,x,y,z}, wrong_value) -> w (an arbitrary value).
+        return CVal->getOperand(0);
       return CVal->getOperand(CIdx->getZExtValue());
     } else if (isa<UndefValue>(Idx)) {
       // ee({w,x,y,z}, undef) -> w (an arbitrary value).
diff --git a/llvm/test/Transforms/LoopUnroll/pr10813.ll b/llvm/test/Transforms/LoopUnroll/pr10813.ll
new file mode 100644
index 00000000000..7daefc2f788
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/pr10813.ll
@@ -0,0 +1,29 @@
+; RUN: opt < %s -loop-unroll -disable-output
+
+define void @"f_fu___REFUf[]REFUf[]Uf"() nounwind {
+allocas:
+  br i1 undef, label %cif_mask_all, label %cif_mixed_test_all
+
+cif_mask_all:                                     ; preds = %allocas
+  unreachable
+
+cif_mixed_test_all:                               ; preds = %allocas
+  br label %pl_loop.i964
+
+pl_loop.i964:                                     ; preds = %pl_loopend.i973, %cif_mixed_test_all
+  %0 = phi i32 [ %pl_nextlane.i971, %pl_loopend.i973 ], [ 0, %cif_mixed_test_all ]
+  br i1 undef, label %pl_dolane.i970, label %pl_loopend.i973
+
+pl_dolane.i970:                                   ; preds = %pl_loop.i964
+  %storeval.i.i969 = extractelement <4 x i8> <i8 0, i8 1, i8 2, i8 3>, i32 %0
+  store i8 %storeval.i.i969, i8* undef, align 1
+  br label %pl_loopend.i973
+
+pl_loopend.i973:                                  ; preds = %pl_dolane.i970, %pl_loop.i964
+  %pl_nextlane.i971 = add i32 %0, 1
+  %exitcond5 = icmp ne i32 %pl_nextlane.i971, 5
+  br i1 %exitcond5, label %pl_loop.i964, label %__scatter_base_offsets_i8.exit974
+
+__scatter_base_offsets_i8.exit974:                ; preds = %pl_loopend.i973
+  unreachable
+}