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[RISCV] Re-work how VWADD_W_VL and similar _W_VL nodes are handled in combineOp_VLToVWOp_VL. #159205

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Merged
merged 4 commits into from
Sep 19, 2025
Merged

[RISCV] Re-work how VWADD_W_VL and similar _W_VL nodes are handled in combineOp_VLToVWOp_VL. #159205

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9945af0
Pre-commit test
topperc Sep 16, 2025
a156475
[RISCV] Re-work how VWADD_W_VL and similar _W_VL nodes are handled in…
topperc Sep 16, 2025
ef8ff36
fixup! Adjust FIXME.
topperc Sep 17, 2025
1e4fae0
fixup! Fix mistake in comment
topperc Sep 19, 2025
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86 changes: 49 additions & 37 deletions llvm/lib/Target/RISCV/RISCVISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17325,18 +17325,9 @@ struct NodeExtensionHelper {
case RISCVISD::VWSUBU_W_VL:
case RISCVISD::VFWADD_W_VL:
case RISCVISD::VFWSUB_W_VL:
if (OperandIdx == 1) {
SupportsZExt =
Opc == RISCVISD::VWADDU_W_VL || Opc == RISCVISD::VWSUBU_W_VL;
SupportsSExt =
Opc == RISCVISD::VWADD_W_VL || Opc == RISCVISD::VWSUB_W_VL;
SupportsFPExt =
Opc == RISCVISD::VFWADD_W_VL || Opc == RISCVISD::VFWSUB_W_VL;
// There's no existing extension here, so we don't have to worry about
// making sure it gets removed.
EnforceOneUse = false;
// Operand 1 can't be changed.
if (OperandIdx == 1)
break;
}
[[fallthrough]];
default:
fillUpExtensionSupport(Root, DAG, Subtarget);
Expand Down Expand Up @@ -17374,20 +17365,20 @@ struct NodeExtensionHelper {
case RISCVISD::ADD_VL:
case RISCVISD::MUL_VL:
case RISCVISD::OR_VL:
case RISCVISD::VWADD_W_VL:
case RISCVISD::VWADDU_W_VL:
case RISCVISD::FADD_VL:
case RISCVISD::FMUL_VL:
case RISCVISD::VFWADD_W_VL:
case RISCVISD::VFMADD_VL:
case RISCVISD::VFNMSUB_VL:
case RISCVISD::VFNMADD_VL:
case RISCVISD::VFMSUB_VL:
return true;
case RISCVISD::VWADD_W_VL:
case RISCVISD::VWADDU_W_VL:
case ISD::SUB:
case RISCVISD::SUB_VL:
case RISCVISD::VWSUB_W_VL:
case RISCVISD::VWSUBU_W_VL:
case RISCVISD::VFWADD_W_VL:
case RISCVISD::FSUB_VL:
case RISCVISD::VFWSUB_W_VL:
case ISD::SHL:
Expand Down Expand Up @@ -17506,6 +17497,30 @@ canFoldToVWWithSameExtension(SDNode *Root, const NodeExtensionHelper &LHS,
Subtarget);
}

/// Check if \p Root follows a pattern Root(zext(LHS), zext(RHS))
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
/// can be used to apply the pattern.
static std::optional<CombineResult>
canFoldToVWWithSameExtZEXT(SDNode *Root, const NodeExtensionHelper &LHS,
const NodeExtensionHelper &RHS, SelectionDAG &DAG,
const RISCVSubtarget &Subtarget) {
return canFoldToVWWithSameExtensionImpl(Root, LHS, RHS, ExtKind::ZExt, DAG,
Subtarget);
}

/// Check if \p Root follows a pattern Root(bf16ext(LHS), bf16ext(RHS))
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
/// can be used to apply the pattern.
static std::optional<CombineResult>
canFoldToVWWithSameExtBF16(SDNode *Root, const NodeExtensionHelper &LHS,
const NodeExtensionHelper &RHS, SelectionDAG &DAG,
const RISCVSubtarget &Subtarget) {
return canFoldToVWWithSameExtensionImpl(Root, LHS, RHS, ExtKind::BF16Ext, DAG,
Subtarget);
}

/// Check if \p Root follows a pattern Root(LHS, ext(RHS))
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
Expand Down Expand Up @@ -17534,52 +17549,49 @@ canFoldToVW_W(SDNode *Root, const NodeExtensionHelper &LHS,
return std::nullopt;
}

/// Check if \p Root follows a pattern Root(sext(LHS), sext(RHS))
/// Check if \p Root follows a pattern Root(sext(LHS), RHS)
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
/// can be used to apply the pattern.
static std::optional<CombineResult>
canFoldToVWWithSEXT(SDNode *Root, const NodeExtensionHelper &LHS,
const NodeExtensionHelper &RHS, SelectionDAG &DAG,
const RISCVSubtarget &Subtarget) {
return canFoldToVWWithSameExtensionImpl(Root, LHS, RHS, ExtKind::SExt, DAG,
Subtarget);
if (LHS.SupportsSExt)
return CombineResult(NodeExtensionHelper::getSExtOpcode(Root->getOpcode()),
Root, LHS, /*LHSExt=*/{ExtKind::SExt}, RHS,
/*RHSExt=*/std::nullopt);
return std::nullopt;
}

/// Check if \p Root follows a pattern Root(zext(LHS), zext(RHS))
/// Check if \p Root follows a pattern Root(zext(LHS), RHS)
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
/// can be used to apply the pattern.
static std::optional<CombineResult>
canFoldToVWWithZEXT(SDNode *Root, const NodeExtensionHelper &LHS,
const NodeExtensionHelper &RHS, SelectionDAG &DAG,
const RISCVSubtarget &Subtarget) {
return canFoldToVWWithSameExtensionImpl(Root, LHS, RHS, ExtKind::ZExt, DAG,
Subtarget);
if (LHS.SupportsZExt)
return CombineResult(NodeExtensionHelper::getZExtOpcode(Root->getOpcode()),
Root, LHS, /*LHSExt=*/{ExtKind::ZExt}, RHS,
/*RHSExt=*/std::nullopt);
return std::nullopt;
}

/// Check if \p Root follows a pattern Root(fpext(LHS), fpext(RHS))
/// Check if \p Root follows a pattern Root(fpext(LHS), RHS)
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
/// can be used to apply the pattern.
static std::optional<CombineResult>
canFoldToVWWithFPEXT(SDNode *Root, const NodeExtensionHelper &LHS,
const NodeExtensionHelper &RHS, SelectionDAG &DAG,
const RISCVSubtarget &Subtarget) {
return canFoldToVWWithSameExtensionImpl(Root, LHS, RHS, ExtKind::FPExt, DAG,
Subtarget);
}

/// Check if \p Root follows a pattern Root(bf16ext(LHS), bf16ext(RHS))
///
/// \returns std::nullopt if the pattern doesn't match or a CombineResult that
/// can be used to apply the pattern.
static std::optional<CombineResult>
canFoldToVWWithBF16EXT(SDNode *Root, const NodeExtensionHelper &LHS,
const NodeExtensionHelper &RHS, SelectionDAG &DAG,
const RISCVSubtarget &Subtarget) {
return canFoldToVWWithSameExtensionImpl(Root, LHS, RHS, ExtKind::BF16Ext, DAG,
Subtarget);
if (LHS.SupportsFPExt)
return CombineResult(NodeExtensionHelper::getFPExtOpcode(Root->getOpcode()),
Root, LHS, /*LHSExt=*/{ExtKind::FPExt}, RHS,
/*RHSExt=*/std::nullopt);
return std::nullopt;
}

/// Check if \p Root follows a pattern Root(sext(LHS), zext(RHS))
Expand Down Expand Up @@ -17622,7 +17634,7 @@ NodeExtensionHelper::getSupportedFoldings(const SDNode *Root) {
case RISCVISD::VFNMSUB_VL:
Strategies.push_back(canFoldToVWWithSameExtension);
if (Root->getOpcode() == RISCVISD::VFMADD_VL)
Strategies.push_back(canFoldToVWWithBF16EXT);
Strategies.push_back(canFoldToVWWithSameExtBF16);
break;
case ISD::MUL:
case RISCVISD::MUL_VL:
Expand All @@ -17634,7 +17646,7 @@ NodeExtensionHelper::getSupportedFoldings(const SDNode *Root) {
case ISD::SHL:
case RISCVISD::SHL_VL:
// shl -> vwsll
Strategies.push_back(canFoldToVWWithZEXT);
Strategies.push_back(canFoldToVWWithSameExtZEXT);
break;
case RISCVISD::VWADD_W_VL:
case RISCVISD::VWSUB_W_VL:
Expand Down
23 changes: 23 additions & 0 deletions llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vw-web-simplification.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -58,3 +58,26 @@ define <2 x i16> @vwmul_v2i16_multiple_users(ptr %x, ptr %y, ptr %z) {
%i = or <2 x i16> %h, %g
ret <2 x i16> %i
}

; Make sure we have a vsext.vl and a vwaddu.vx.
define <4 x i32> @pr159152(<4 x i8> %x) {
; NO_FOLDING-LABEL: pr159152:
; NO_FOLDING: # %bb.0:
; NO_FOLDING-NEXT: vsetivli zero, 4, e16, mf2, ta, ma
; NO_FOLDING-NEXT: vsext.vf2 v9, v8
; NO_FOLDING-NEXT: li a0, 9
; NO_FOLDING-NEXT: vwaddu.vx v8, v9, a0
; NO_FOLDING-NEXT: ret
;
; FOLDING-LABEL: pr159152:
; FOLDING: # %bb.0:
; FOLDING-NEXT: vsetivli zero, 4, e16, mf2, ta, ma
; FOLDING-NEXT: vsext.vf2 v9, v8
; FOLDING-NEXT: li a0, 9
; FOLDING-NEXT: vwaddu.vx v8, v9, a0
; FOLDING-NEXT: ret
%a = sext <4 x i8> %x to <4 x i16>
%b = zext <4 x i16> %a to <4 x i32>
%c = add <4 x i32> %b, <i32 9, i32 9, i32 9, i32 9>
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The constant vector allows a RISCVISD::VWADDU_W_VL to be formed between LegalizeVectorOps and LegalizeDAG. LegalizeDAG will turn the build_vector into RISCVISD::VMV_V_X_VL. Then we will try to turn the VWADDU_W_VL into VWADD_VL. If we don't use a constant vector we'll go straight to VWADD_VL after LegalizeVectorOps.

ret <4 x i32> %c
}