[InstSimplify] add test to demonstrate undef matching differences; NFC

This is a baseline test for D54631.
Patch by:
@nikic (Nikita Popov)

llvm-svn: 347055

llvm/test/Transforms/InstSimplify/shr-scalar-vector-consistency.ll

@@ -0,0 +1,25 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+; This tests checks optimization consistency for scalar and vector code.
+; If m_Zero() is able to match a vector undef, but not a scalar undef,
+; the two cases will simplify differently.
+
+define i32 @test_scalar(i32 %a, i1 %b) {
+; CHECK-LABEL: @test_scalar(
+; CHECK-NEXT:    ret i32 undef
+;
+  %c = sext i1 %b to i32
+  %d = ashr i32 undef, %c
+  ret i32 %d
+}
+
+define <2 x i32> @test_vector(<2 x i32> %a, <2 x i1> %b) {
+; CHECK-LABEL: @test_vector(
+; CHECK-NEXT:    ret <2 x i32> zeroinitializer
+;
+  %c = sext <2 x i1> %b to <2 x i32>
+  %d = ashr <2 x i32> undef, %c
+  ret <2 x i32> %d
+}
+