[IR] Let ConstantVector::getSplat use poison instead of undef

This patch updates ConstantVector::getSplat to use poison instead
of undef when using insertelement/shufflevector to splat.

This follows on from D93793.

Differential Revision: https://reviews.llvm.org/D107751

Author: david-arm

llvm/lib/IR/Constants.cpp

@@ -1430,12 +1430,12 @@ Constant *ConstantVector::getSplat(ElementCount EC, Constant *V) {
   Type *I32Ty = Type::getInt32Ty(VTy->getContext());
 
   // Move scalar into vector.
-  Constant *UndefV = UndefValue::get(VTy);
-  V = ConstantExpr::getInsertElement(UndefV, V, ConstantInt::get(I32Ty, 0));
+  Constant *PoisonV = PoisonValue::get(VTy);
+  V = ConstantExpr::getInsertElement(PoisonV, V, ConstantInt::get(I32Ty, 0));
   // Build shuffle mask to perform the splat.
   SmallVector<int, 8> Zeros(EC.getKnownMinValue(), 0);
   // Splat.
-  return ConstantExpr::getShuffleVector(V, UndefV, Zeros);
+  return ConstantExpr::getShuffleVector(V, PoisonV, Zeros);
 }
 
 ConstantTokenNone *ConstantTokenNone::get(LLVMContext &Context) {

llvm/test/Transforms/CodeGenPrepare/AArch64/gather-scatter-opt-inseltpoison.ll

@@ -73,7 +73,7 @@ define <vscale x 4 x i32> @test_global_array(<vscale x 4 x i64> %indxs, <vscale
 
 define <vscale x 4 x i32> @global_struct_splat(<vscale x 4 x i1> %mask) #0 {
 ; CHECK-LABEL: @global_struct_splat(
-; CHECK-NEXT:    [[TMP1:%.*]] = call <vscale x 4 x i32> @llvm.masked.gather.nxv4i32.nxv4p0i32(<vscale x 4 x i32*> shufflevector (<vscale x 4 x i32*> insertelement (<vscale x 4 x i32*> undef, i32* getelementptr inbounds (%struct.a, %struct.a* @c, i64 0, i32 1), i32 0), <vscale x 4 x i32*> undef, <vscale x 4 x i32> zeroinitializer), i32 4, <vscale x 4 x i1> [[MASK:%.*]], <vscale x 4 x i32> undef)
+; CHECK-NEXT:    [[TMP1:%.*]] = call <vscale x 4 x i32> @llvm.masked.gather.nxv4i32.nxv4p0i32(<vscale x 4 x i32*> shufflevector (<vscale x 4 x i32*> insertelement (<vscale x 4 x i32*> poison, i32* getelementptr inbounds ([[STRUCT_A:%.*]], %struct.a* @c, i64 0, i32 1), i32 0), <vscale x 4 x i32*> poison, <vscale x 4 x i32> zeroinitializer), i32 4, <vscale x 4 x i1> [[MASK:%.*]], <vscale x 4 x i32> undef)
 ; CHECK-NEXT:    ret <vscale x 4 x i32> [[TMP1]]
 ;
   %1 = insertelement <vscale x 4 x %struct.a*> poison, %struct.a* @c, i32 0

llvm/test/Transforms/CodeGenPrepare/AArch64/gather-scatter-opt.ll

@@ -73,7 +73,7 @@ define <vscale x 4 x i32> @test_global_array(<vscale x 4 x i64> %indxs, <vscale
 
 define <vscale x 4 x i32> @global_struct_splat(<vscale x 4 x i1> %mask) #0 {
 ; CHECK-LABEL: @global_struct_splat(
-; CHECK-NEXT:    [[TMP1:%.*]] = call <vscale x 4 x i32> @llvm.masked.gather.nxv4i32.nxv4p0i32(<vscale x 4 x i32*> shufflevector (<vscale x 4 x i32*> insertelement (<vscale x 4 x i32*> undef, i32* getelementptr inbounds (%struct.a, %struct.a* @c, i64 0, i32 1), i32 0), <vscale x 4 x i32*> undef, <vscale x 4 x i32> zeroinitializer), i32 4, <vscale x 4 x i1> [[MASK:%.*]], <vscale x 4 x i32> undef)
+; CHECK-NEXT:    [[TMP1:%.*]] = call <vscale x 4 x i32> @llvm.masked.gather.nxv4i32.nxv4p0i32(<vscale x 4 x i32*> shufflevector (<vscale x 4 x i32*> insertelement (<vscale x 4 x i32*> poison, i32* getelementptr inbounds ([[STRUCT_A:%.*]], %struct.a* @c, i64 0, i32 1), i32 0), <vscale x 4 x i32*> poison, <vscale x 4 x i32> zeroinitializer), i32 4, <vscale x 4 x i1> [[MASK:%.*]], <vscale x 4 x i32> undef)
 ; CHECK-NEXT:    ret <vscale x 4 x i32> [[TMP1]]
 ;
   %1 = insertelement <vscale x 4 x %struct.a*> undef, %struct.a* @c, i32 0

llvm/test/Transforms/InstCombine/div.ll

@@ -1058,7 +1058,7 @@ define <2 x i8> @sdiv_by_negconst_v2i8(<2 x i8> %x) {
 
 define <vscale x 2 x i8> @sdiv_by_negconst_nxv2i8(<vscale x 2 x i8> %x) {
 ; CHECK-LABEL: @sdiv_by_negconst_nxv2i8(
-; CHECK-NEXT:    [[DIV_NEG:%.*]] = sdiv <vscale x 2 x i8> [[X:%.*]], shufflevector (<vscale x 2 x i8> insertelement (<vscale x 2 x i8> undef, i8 108, i32 0), <vscale x 2 x i8> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[DIV_NEG:%.*]] = sdiv <vscale x 2 x i8> [[X:%.*]], shufflevector (<vscale x 2 x i8> insertelement (<vscale x 2 x i8> poison, i8 108, i32 0), <vscale x 2 x i8> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 2 x i8> [[DIV_NEG]]
 ;
   %div = sdiv <vscale x 2 x i8> %x, shufflevector (<vscale x 2 x i8> insertelement (<vscale x 2 x i8> undef, i8 -108, i32 0), <vscale x 2 x i8> undef, <vscale x 2 x i32> zeroinitializer)

llvm/test/Transforms/InstCombine/fdiv.ll

@@ -87,7 +87,7 @@ define <2 x float> @exact_inverse_splat(<2 x float> %x) {
 
 define <vscale x 2 x float> @exact_inverse_scalable_splat(<vscale x 2 x float> %x) {
 ; CHECK-LABEL: @exact_inverse_scalable_splat(
-; CHECK-NEXT:    [[DIV:%.*]] = fmul <vscale x 2 x float> [[X:%.*]], shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> undef, float 2.500000e-01, i32 0), <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[DIV:%.*]] = fmul <vscale x 2 x float> [[X:%.*]], shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> poison, float 2.500000e-01, i32 0), <vscale x 2 x float> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 2 x float> [[DIV]]
 ;
   %div = fdiv <vscale x 2 x float> %x, shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> undef, float 4.0, i32 0), <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer)

llvm/test/Transforms/InstCombine/fmul.ll

@@ -795,7 +795,7 @@ define <2 x float> @fmul_fadd_distribute_vec(<2 x float> %x) {
 define <vscale x 2 x float> @fmul_fadd_distribute_scalablevec(<vscale x 2 x float> %x) {
 ; CHECK-LABEL: @fmul_fadd_distribute_scalablevec(
 ; CHECK-NEXT:    [[TMP1:%.*]] = fmul reassoc <vscale x 2 x float> [[X:%.*]], shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> undef, float 6.000000e+03, i32 0), <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer)
-; CHECK-NEXT:    [[T3:%.*]] = fadd reassoc <vscale x 2 x float> [[TMP1]], shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> undef, float 1.200000e+07, i32 0), <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[T3:%.*]] = fadd reassoc <vscale x 2 x float> [[TMP1]], shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> poison, float 1.200000e+07, i32 0), <vscale x 2 x float> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 2 x float> [[T3]]
 ;
   %t1 = fadd <vscale x 2 x float> shufflevector (<vscale x 2 x float> insertelement (<vscale x 2 x float> undef, float 2.0e+3, i32 0), <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer), %x

llvm/test/Transforms/InstCombine/select.ll

@@ -99,7 +99,7 @@ define <2 x i1> @test9vec(<2 x i1> %C, <2 x i1> %X) {
 
 define <vscale x 2 x i1> @test9vvec(<vscale x 2 x i1> %C, <vscale x 2 x i1> %X) {
 ; CHECK-LABEL: @test9vvec(
-; CHECK-NEXT:    [[NOT_C:%.*]] = xor <vscale x 2 x i1> [[C:%.*]], shufflevector (<vscale x 2 x i1> insertelement (<vscale x 2 x i1> undef, i1 true, i32 0), <vscale x 2 x i1> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[NOT_C:%.*]] = xor <vscale x 2 x i1> [[C:%.*]], shufflevector (<vscale x 2 x i1> insertelement (<vscale x 2 x i1> poison, i1 true, i32 0), <vscale x 2 x i1> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    [[R:%.*]] = select <vscale x 2 x i1> [[NOT_C]], <vscale x 2 x i1> [[X:%.*]], <vscale x 2 x i1> zeroinitializer
 ; CHECK-NEXT:    ret <vscale x 2 x i1> [[R]]
 ;

llvm/test/Transforms/InstCombine/sub.ll

@@ -841,7 +841,7 @@ define <2 x i32> @test44vec(<2 x i32> %x) {
 
 define <vscale x 2 x i32> @test44scalablevec(<vscale x 2 x i32> %x) {
 ; CHECK-LABEL: @test44scalablevec(
-; CHECK-NEXT:    [[SUB:%.*]] = add nsw <vscale x 2 x i32> [[X:%.*]], shufflevector (<vscale x 2 x i32> insertelement (<vscale x 2 x i32> undef, i32 -32768, i32 0), <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[SUB:%.*]] = add nsw <vscale x 2 x i32> [[X:%.*]], shufflevector (<vscale x 2 x i32> insertelement (<vscale x 2 x i32> poison, i32 -32768, i32 0), <vscale x 2 x i32> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 2 x i32> [[SUB]]
 ;
   %sub = sub nsw <vscale x 2 x i32> %x, shufflevector (<vscale x 2 x i32> insertelement (<vscale x 2 x i32> undef, i32 32768, i32 0), <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer)
@@ -861,7 +861,7 @@ define <2 x i16> @test44vecminval(<2 x i16> %x) {
 ; uses m_ImmConstant which matches Constant but (explicitly) not ConstantExpr.
 define <vscale x 2 x i16> @test44scalablevecminval(<vscale x 2 x i16> %x) {
 ; CHECK-LABEL: @test44scalablevecminval(
-; CHECK-NEXT:    [[SUB:%.*]] = add <vscale x 2 x i16> [[X:%.*]], shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> undef, i16 -32768, i32 0), <vscale x 2 x i16> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[SUB:%.*]] = add <vscale x 2 x i16> [[X:%.*]], shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> poison, i16 -32768, i32 0), <vscale x 2 x i16> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 2 x i16> [[SUB]]
 ;
   %sub = sub nsw <vscale x 2 x i16> %x, shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> undef, i16 -32768, i32 0), <vscale x 2 x i16> undef, <vscale x 2 x i32> zeroinitializer)

llvm/test/Transforms/InstCombine/zext-ctlz-trunc-to-ctlz-add.ll

@@ -42,7 +42,7 @@ define <2 x i8> @trunc_ctlz_zext_v2i8_v2i33(<2 x i8> %x) {
 define <vscale x 2 x i16> @trunc_ctlz_zext_nxv2i16_nxv2i64(<vscale x 2 x i16> %x) {
 ; CHECK-LABEL: @trunc_ctlz_zext_nxv2i16_nxv2i64(
 ; CHECK-NEXT:    [[TMP1:%.*]] = call <vscale x 2 x i16> @llvm.ctlz.nxv2i16(<vscale x 2 x i16> [[X:%.*]], i1 false)
-; CHECK-NEXT:    [[ZZ:%.*]] = add nuw nsw <vscale x 2 x i16> [[TMP1]], shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> undef, i16 48, i32 0), <vscale x 2 x i16> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[ZZ:%.*]] = add nuw nsw <vscale x 2 x i16> [[TMP1]], shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> poison, i16 48, i32 0), <vscale x 2 x i16> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 2 x i16> [[ZZ]]
 ;
   %z = zext <vscale x 2 x i16> %x to <vscale x 2 x i64>
@@ -74,7 +74,7 @@ define <vscale x 2 x i16> @trunc_ctlz_zext_nxv2i16_nxv2i63_multiple_uses(<vscale
 ; CHECK-LABEL: @trunc_ctlz_zext_nxv2i16_nxv2i63_multiple_uses(
 ; CHECK-NEXT:    [[Z:%.*]] = zext <vscale x 2 x i16> [[X:%.*]] to <vscale x 2 x i63>
 ; CHECK-NEXT:    [[TMP1:%.*]] = call <vscale x 2 x i16> @llvm.ctlz.nxv2i16(<vscale x 2 x i16> [[X]], i1 true)
-; CHECK-NEXT:    [[ZZ:%.*]] = add nuw nsw <vscale x 2 x i16> [[TMP1]], shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> undef, i16 47, i32 0), <vscale x 2 x i16> undef, <vscale x 2 x i32> zeroinitializer)
+; CHECK-NEXT:    [[ZZ:%.*]] = add nuw nsw <vscale x 2 x i16> [[TMP1]], shufflevector (<vscale x 2 x i16> insertelement (<vscale x 2 x i16> poison, i16 47, i32 0), <vscale x 2 x i16> poison, <vscale x 2 x i32> zeroinitializer)
 ; CHECK-NEXT:    call void @use1(<vscale x 2 x i63> [[Z]])
 ; CHECK-NEXT:    ret <vscale x 2 x i16> [[ZZ]]
 ;

llvm/test/Transforms/InstSimplify/ConstProp/vscale-inseltpoison.ll

@@ -43,7 +43,7 @@ define <vscale x 4 x i32> @sub() {
 
 define <vscale x 4 x i32> @sub_splat() {
 ; CHECK-LABEL: @sub_splat(
-; CHECK-NEXT:    ret <vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 -16, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    ret <vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> poison, i32 -16, i32 0), <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer)
 ;
   %r = sub <vscale x 4 x i32> zeroinitializer, shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 16, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer)
   ret <vscale x 4 x i32> %r
@@ -262,15 +262,15 @@ define <vscale x 4 x i1> @icmp_undef() {
 
 define <vscale x 4 x i1> @icmp_zero() {
 ; CHECK-LABEL: @icmp_zero(
-; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> undef, i1 true, i32 0), <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i32 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer)
 ;
   %r = icmp eq <vscale x 4 x i32> zeroinitializer, zeroinitializer
   ret <vscale x 4 x i1> %r
 }
 
 define <vscale x 4 x i1> @fcmp_true() {
 ; CHECK-LABEL: @fcmp_true(
-; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> undef, i1 true, i32 0), <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i32 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer)
 ;
   %r = fcmp true <vscale x 4 x float> undef, undef
   ret <vscale x 4 x i1> %r
@@ -294,7 +294,7 @@ define <vscale x 4 x i1> @fcmp_undef() {
 
 define <vscale x 4 x i1> @fcmp_not_equality() {
 ; CHECK-LABEL: @fcmp_not_equality(
-; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> undef, i1 true, i32 0), <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i32 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer)
 ;
   %r = icmp ule <vscale x 4 x i32> undef, zeroinitializer
   ret <vscale x 4 x i1> %r