InstCombine: Don't assume that m_ZExt matches an Instruction

m_ZExt might bind against a ConstantExpr instead of an Instruction.
Assuming this, using cast<Instruction>, results in InstCombine crashing.

Instead, introduce ZExtOperator to bridge both Instruction and
ConstantExpr ZExts.

This fixes PR21445.

llvm-svn: 221069

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/overflow-mul.ll b/llvm/test/Transforms/InstCombine/overflow-mul.ll
index cbb2f5f9500..6d8d40bcac3 100644
--- a/llvm/test/Transforms/InstCombine/overflow-mul.ll
+++ b/llvm/test/Transforms/InstCombine/overflow-mul.ll
@@ -173,3 +173,16 @@ define <4 x i32> @pr20113(<4 x i16> %a, <4 x i16> %b) {
   %vcgez.i = sext <4 x i1> %tmp to <4 x i32>
   ret <4 x i32> %vcgez.i
 }
+
+@pr21445_data = external global i32
+define i1 @pr21445(i8 %a) {
+; CHECK-LABEL: @pr21445(
+; CHECK-NEXT:  %[[umul:.*]] = call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 ptrtoint (i32* @pr21445_data to i8))
+; CHECK-NEXT:  %[[cmp:.*]] = extractvalue { i8, i1 } %[[umul]], 1
+; CHECK-NEXT:  ret i1 %[[cmp]]
+  %ext = zext i8 %a to i32
+  %mul = mul i32 %ext, zext (i8 ptrtoint (i32* @pr21445_data to i8) to i32)
+  %and = and i32 %mul, 255
+  %cmp = icmp ne i32 %mul, %and
+  ret i1 %cmp
+}