[InstCombine] Add pre-commit tests. NFC.

Author: dtcxzyw

llvm/test/Transforms/InstCombine/vector-udiv.ll

@@ -97,3 +97,15 @@ define <4 x i32> @test_v4i32_zext_shl_const_pow2(<4 x i32> %a0, <4 x i16> %a1) {
   %3 = udiv <4 x i32> %a0, %2
   ret <4 x i32> %3
 }
+
+; Make sure we do not simplify udiv <i32 42, i32 -7>, <i32 0, i32 1> to
+; poison when threading udiv over selects
+
+define <2 x i32> @vec_select_udiv_poison(<2 x i1> %x) {
+; CHECK-LABEL: @vec_select_udiv_poison(
+; CHECK-NEXT:    ret <2 x i32> zeroinitializer
+;
+  %sel = select <2 x i1> %x, <2 x i32> <i32 -1, i32 -1>, <2 x i32> <i32 0, i32 1>
+  %div = udiv <2 x i32> <i32 42, i32 -7>, %sel
+  ret <2 x i32> %div
+}