[CodeGen] Add support for widening INSERT_SUBVECTOR operands

[david-arm]

Summary

When attempting to return something like a <vscale x 1 x i32>
type from a function we end up trying to widen the vector by
inserting a <vscale x 1 x i32> subvector into an undefined
<vscale x 4 x i32> vector. However, during legalisation we
then attempt to widen the INSERT_SUBVECTOR operands and hit
an error in WidenVectorOperand.

This patch adds a new WidenVecOp_INSERT_SUBVECTOR function
that currently only supports inserting subvectors into undefined
vectors.

[frasercrmck]

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

4839

The index operand is required to be a constant. Perhaps we can be stricter here?

[david-arm]

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

4839

Ah ok, you mean we can simply use cast<ConstantSDNode> here?

[frasercrmck]

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

4839

Yeah, then even simplified to N->getConstantOperandVal(2) == 0. There's precedent for that elsewhere so it sounds reasonable to me.

[david-arm]

• Changed WidenVecOp_INSERT_SUBVECTOR to use getConstantOperandVal

[sdesmalen]

llvm/test/CodeGen/AArch64/sve-calling-convention-mixed.ll

190 ↗

(On Diff #346156)

Why is this test in sve-calling-convention-mixed.ll?

[david-arm]

llvm/test/CodeGen/AArch64/sve-calling-convention-mixed.ll

190 ↗

(On Diff #346156)

Ah, mainly because I wasn't sure where else to put it is the honest answer. :) Although I do see now that we only deal with scalar arguments and return types in this file so I can try to find somewhere else. I just wanted to avoid creating a new file for this one test that's all.

[david-arm]

• Moved a test to sve-vector-splat.ll

[sdesmalen]

LGTM, thanks!

llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h

private:
   SDValue WidenVecRes_InregOp(SDNode *N);
 
   // Widen Vector Operand.
   bool WidenVectorOperand(SDNode *N, unsigned OpNo);
   SDValue WidenVecOp_BITCAST(SDNode *N);
   SDValue WidenVecOp_CONCAT_VECTORS(SDNode *N);
   SDValue WidenVecOp_EXTEND(SDNode *N);
   SDValue WidenVecOp_EXTRACT_VECTOR_ELT(SDNode *N);
+  SDValue WidenVecOp_INSERT_SUBVECTOR(SDNode *N);
   SDValue WidenVecOp_EXTRACT_SUBVECTOR(SDNode *N);
   SDValue WidenVecOp_STORE(SDNode* N);
   SDValue WidenVecOp_MSTORE(SDNode* N, unsigned OpNo);
   SDValue WidenVecOp_MGATHER(SDNode* N, unsigned OpNo);
   SDValue WidenVecOp_MSCATTER(SDNode* N, unsigned OpNo);
   SDValue WidenVecOp_SETCC(SDNode* N);
   SDValue WidenVecOp_STRICT_FSETCC(SDNode* N);
   SDValue WidenVecOp_VSELECT(SDNode *N);

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

#ifndef NDEBUG
     dbgs() << "WidenVectorOperand op #" << OpNo << ": ";
     N->dump(&DAG);
     dbgs() << "\n";
 #endif
     llvm_unreachable("Do not know how to widen this operator's operand!");
 
   case ISD::BITCAST:            Res = WidenVecOp_BITCAST(N); break;
   case ISD::CONCAT_VECTORS:     Res = WidenVecOp_CONCAT_VECTORS(N); break;
+  case ISD::INSERT_SUBVECTOR:   Res = WidenVecOp_INSERT_SUBVECTOR(N); break;
   case ISD::EXTRACT_SUBVECTOR:  Res = WidenVecOp_EXTRACT_SUBVECTOR(N); break;
   case ISD::EXTRACT_VECTOR_ELT: Res = WidenVecOp_EXTRACT_VECTOR_ELT(N); break;
   case ISD::STORE:              Res = WidenVecOp_STORE(N); break;
   case ISD::MSTORE:             Res = WidenVecOp_MSTORE(N, OpNo); break;
   case ISD::MGATHER:            Res = WidenVecOp_MGATHER(N, OpNo); break;
   case ISD::MSCATTER:           Res = WidenVecOp_MSCATTER(N, OpNo); break;
   case ISD::SETCC:              Res = WidenVecOp_SETCC(N); break;
   case ISD::STRICT_FSETCC:
for (unsigned i=0; i < NumOperands; ++i) {
     InOp = GetWidenedVector(InOp);
     for (unsigned j = 0; j < NumInElts; ++j)
       Ops[Idx++] = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, EltVT, InOp,
                                DAG.getVectorIdxConstant(j, dl));
   }
   return DAG.getBuildVector(VT, dl, Ops);
 }
 
+SDValue DAGTypeLegalizer::WidenVecOp_INSERT_SUBVECTOR(SDNode *N) {
+  SDValue SubVec = N->getOperand(1);
+  SDValue InVec = N->getOperand(0);
+
+  if (getTypeAction(InVec.getValueType()) == TargetLowering::TypeWidenVector)
+    InVec = GetWidenedVector(InVec);
+
+  if (getTypeAction(SubVec.getValueType()) == TargetLowering::TypeWidenVector)
+    SubVec = GetWidenedVector(SubVec);
+
+  if (SubVec.getValueType() == InVec.getValueType() && InVec.isUndef() &&
+      N->getConstantOperandVal(2) == 0)
+    return SubVec;
+
+  report_fatal_error("Don't know how to widen the operands for "
+                     "INSERT_SUBVECTOR");
+}
+
 SDValue DAGTypeLegalizer::WidenVecOp_EXTRACT_SUBVECTOR(SDNode *N) {
   SDValue InOp = GetWidenedVector(N->getOperand(0));
   return DAG.getNode(ISD::EXTRACT_SUBVECTOR, SDLoc(N),
                      N->getValueType(0), InOp, N->getOperand(1));
 }
 
 SDValue DAGTypeLegalizer::WidenVecOp_EXTRACT_VECTOR_ELT(SDNode *N) {
   SDValue InOp = GetWidenedVector(N->getOperand(0));

llvm/test/CodeGen/AArch64/sve-insert-vector.ll

 ; CHECK-NEXT:    ret
   %sv = load <2 x i64>, <2 x i64>* %psv
   %v = call <vscale x 16 x i64> @llvm.experimental.vector.insert.v2i64.nxv16i64(<vscale x 16 x i64> undef, <2 x i64> %sv, i64 2)
   store <vscale x 16 x i64> %v, <vscale x 16 x i64>* %out
   ret void
 }
 
 
+; Insert subvectors that need widening
+
+define <vscale x 4 x i32> @insert_nxv1i32_nxv4i32_undef() nounwind {
+; CHECK-LABEL: insert_nxv1i32_nxv4i32_undef:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    mov z0.s, #1 // =0x1
+; CHECK-NEXT:    ret
+entry:
+  %0 = insertelement <vscale x 1 x i32> undef, i32 1, i32 0
+  %subvec = shufflevector <vscale x 1 x i32> %0, <vscale x 1 x i32> undef, <vscale x 1 x i32> zeroinitializer
+  %retval = call <vscale x 4 x i32> @llvm.experimental.vector.insert.nxv4i32.nxv1i32(<vscale x 4 x i32> undef, <vscale x 1 x i32> %subvec, i64 0)
+  ret <vscale x 4 x i32> %retval
+}
+
+define <vscale x 6 x i16> @insert_nxv1i16_nxv6i16_undef() nounwind {
+; CHECK-LABEL: insert_nxv1i16_nxv6i16_undef:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    mov z0.h, #1 // =0x1
+; CHECK-NEXT:    ret
+entry:
+  %0 = insertelement <vscale x 1 x i16> undef, i16 1, i32 0
+  %subvec = shufflevector <vscale x 1 x i16> %0, <vscale x 1 x i16> undef, <vscale x 1 x i32> zeroinitializer
+  %retval = call <vscale x 6 x i16> @llvm.experimental.vector.insert.nxv6i16.nxv1i16(<vscale x 6 x i16> undef, <vscale x 1 x i16> %subvec, i64 0)
+  ret <vscale x 6 x i16> %retval
+}
+
+
 declare <vscale x 2 x i64> @llvm.experimental.vector.insert.nxv2i64.v2i64(<vscale x 2 x i64>, <2 x i64>, i64)
 declare <vscale x 4 x i32> @llvm.experimental.vector.insert.nxv4i32.v4i32(<vscale x 4 x i32>, <4 x i32>, i64)
 declare <vscale x 8 x i16> @llvm.experimental.vector.insert.nxv8i16.v8i16(<vscale x 8 x i16>, <8 x i16>, i64)
 declare <vscale x 16 x i8> @llvm.experimental.vector.insert.nxv16i8.v16i8(<vscale x 16 x i8>, <16 x i8>, i64)
 
 declare <vscale x 16 x i64> @llvm.experimental.vector.insert.nxv8i64.nxv16i64(<vscale x 16 x i64>, <vscale x 8 x i64>, i64)
 declare <vscale x 16 x i64> @llvm.experimental.vector.insert.v2i64.nxv16i64(<vscale x 16 x i64>, <2 x i64>, i64)
+declare <vscale x 4 x i32> @llvm.experimental.vector.insert.nxv4i32.nxv1i32(<vscale x 4 x i32>, <vscale x 1 x i32>, i64)
+declare <vscale x 6 x i16> @llvm.experimental.vector.insert.nxv6i16.nxv1i16(<vscale x 6 x i16>, <vscale x 1 x i16>, i64)

llvm/test/CodeGen/AArch64/sve-vector-splat.ll

 ; CHECK-NEXT: ret
   %ins = insertelement <vscale x 2 x i32> undef, i32 %val, i32 0
   %splat = shufflevector <vscale x 2 x i32> %ins, <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer
   ret <vscale x 2 x i32> %splat
 }
 
 ;; Widen/split splats of wide vector types.
 
+define <vscale x 1 x i32> @sve_splat_1xi32(i32 %val) {
+; CHECK-LABEL: sve_splat_1xi32:
+; CHECK:       mov z0.s, w0
+; CHECK-NEXT:  ret
+entry:
+  %ins = insertelement <vscale x 1 x i32> undef, i32 %val, i32 0
+  %splat = shufflevector <vscale x 1 x i32> %ins, <vscale x 1 x i32> undef, <vscale x 1 x i32> zeroinitializer
+  ret <vscale x 1 x i32> %splat
+}
+
 define <vscale x 12 x i32> @sve_splat_12xi32(i32 %val) {
 ; CHECK-LABEL: @sve_splat_12xi32
 ; CHECK: mov z0.s, w0
 ; CHECK-NEXT: mov z1.d, z0.d
 ; CHECK-NEXT: mov z2.d, z0.d
 ; CHECK-NEXT: ret
   %ins = insertelement <vscale x 12 x i32> undef, i32 %val, i32 0
   %splat = shufflevector <vscale x 12 x i32> %ins, <vscale x 12 x i32> undef, <vscale x 12 x i32> zeroinitializer