add pre-test

Author: ParkHanbum

llvm/test/Transforms/VectorCombine/X86/select-shuffle.ll

@@ -36,3 +36,20 @@ end:
   %t5 = shufflevector <4 x double> %t3, <4 x double> %t4, <4 x i32> <i32 0, i32 1, i32 6, i32 7>
   ret <4 x double> %t5
 }
+
+define <8 x i16> @shuffle_select_select(<4 x i16> %x, <4 x i16> %y, <4 x i16> %z) {
+; CHECK-LABEL: @shuffle_select_select(
+; CHECK-NEXT:    [[CMP_XY:%.*]] = icmp slt <4 x i16> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[CMP_YZ:%.*]] = icmp slt <4 x i16> [[Y]], [[Z:%.*]]
+; CHECK-NEXT:    [[SELECT_XZ:%.*]] = select <4 x i1> [[CMP_XY]], <4 x i16> [[X]], <4 x i16> [[Z]]
+; CHECK-NEXT:    [[SELECT_YX:%.*]] = select <4 x i1> [[CMP_YZ]], <4 x i16> [[Y]], <4 x i16> [[X]]
+; CHECK-NEXT:    [[RES:%.*]] = shufflevector <4 x i16> [[SELECT_XZ]], <4 x i16> [[SELECT_YX]], <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:    ret <8 x i16> [[RES]]
+;
+  %cmp.xy = icmp slt <4 x i16> %x, %y
+  %cmp.yz = icmp slt <4 x i16> %y, %z
+  %select.xz = select <4 x i1> %cmp.xy, <4 x i16> %x, <4 x i16> %z
+  %select.yx = select <4 x i1> %cmp.yz, <4 x i16> %y, <4 x i16> %x
+  %res = shufflevector <4 x i16> %select.xz, <4 x i16> %select.yx, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  ret <8 x i16> %res
+}