[SLP][NFC]Add tests for constants/undefs used in insertelements, NFC.

Author: alexey-bataev

llvm/test/Transforms/SLPVectorizer/X86/sitofp.ll

@@ -1096,6 +1096,40 @@ define <4 x double> @sitofp_4xi32_4f64(i32 %a0, i32 %a1, i32 %a2, i32 %a3) #0 {
   ret <4 x double> %res3
 }
 
+define <4 x double> @sitofp_with_const_4xi32_4f64(i32 %a2, i32 %a3) #0 {
+; CHECK-LABEL: @sitofp_with_const_4xi32_4f64(
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x i32> poison, i32 [[A2:%.*]], i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x i32> [[TMP1]], i32 [[A3:%.*]], i32 1
+; CHECK-NEXT:    [[TMP3:%.*]] = sitofp <2 x i32> [[TMP2]] to <2 x double>
+; CHECK-NEXT:    [[RES0:%.*]] = insertelement <4 x double> undef, double 1.000000e+00, i32 3
+; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <2 x double> [[TMP3]], <2 x double> poison, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[RES31:%.*]] = shufflevector <4 x double> [[RES0]], <4 x double> [[TMP4]], <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; CHECK-NEXT:    ret <4 x double> [[RES31]]
+;
+  %cvt2 = sitofp i32 %a2 to double
+  %cvt3 = sitofp i32 %a3 to double
+  %res0 = insertelement <4 x double> undef, double 1.0, i32 3
+  %res2 = insertelement <4 x double> %res0, double %cvt2, i32 0
+  %res3 = insertelement <4 x double> %res2, double %cvt3, i32 1
+  ret <4 x double> %res3
+}
+
+define <4 x double> @sitofp_with_undef_4xi32_4f64(i32 %a2, i32 %a3) #0 {
+; CHECK-LABEL: @sitofp_with_undef_4xi32_4f64(
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x i32> poison, i32 [[A2:%.*]], i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x i32> [[TMP1]], i32 [[A3:%.*]], i32 1
+; CHECK-NEXT:    [[TMP3:%.*]] = sitofp <2 x i32> [[TMP2]] to <2 x double>
+; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <2 x double> [[TMP3]], <2 x double> poison, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[RES31:%.*]] = shufflevector <4 x double> undef, <4 x double> [[TMP4]], <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; CHECK-NEXT:    ret <4 x double> [[RES31]]
+;
+  %cvt2 = sitofp i32 %a2 to double
+  %cvt3 = sitofp i32 %a3 to double
+  %res2 = insertelement <4 x double> undef, double %cvt2, i32 0
+  %res3 = insertelement <4 x double> %res2, double %cvt3, i32 1
+  ret <4 x double> %res3
+}
+
 define <4 x float> @sitofp_4xi32_4f32(i32 %a0, i32 %a1, i32 %a2, i32 %a3) #0 {
 ; CHECK-LABEL: @sitofp_4xi32_4f32(
 ; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <4 x i32> poison, i32 [[A0:%.*]], i32 0