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[WebAssembly] Optimize convert_iKxN_u into convert_iKxN_s #149609

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Merged
merged 1 commit into from
Jul 21, 2025
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[WebAssembly] Optimize convert_iKxN_u into convert_iKxN_s #149609

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22 changes: 22 additions & 0 deletions llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2934,6 +2934,25 @@ performVectorExtendToFPCombine(SDNode *N,
return DAG.getNode(N->getOpcode(), SDLoc(N), ResVT, Conv);
}

static SDValue
performVectorNonNegToFPCombine(SDNode *N,
TargetLowering::DAGCombinerInfo &DCI) {
auto &DAG = DCI.DAG;

SDNodeFlags Flags = N->getFlags();
SDValue Op0 = N->getOperand(0);
EVT VT = N->getValueType(0);

// Optimize uitofp to sitofp when the sign bit is known to be zero.
// Depending on the target (runtime) backend, this might be performance
// neutral (e.g. AArch64) or a significant improvement (e.g. x86_64).
if (VT.isVector() && (Flags.hasNonNeg() || DAG.SignBitIsZero(Op0))) {
return DAG.getNode(ISD::SINT_TO_FP, SDLoc(N), VT, Op0);
}

return SDValue();
}

static SDValue
performVectorExtendCombine(SDNode *N, TargetLowering::DAGCombinerInfo &DCI) {
auto &DAG = DCI.DAG;
Expand Down Expand Up @@ -3515,6 +3534,9 @@ WebAssemblyTargetLowering::PerformDAGCombine(SDNode *N,
case ISD::ZERO_EXTEND:
return performVectorExtendCombine(N, DCI);
case ISD::UINT_TO_FP:
if (auto ExtCombine = performVectorExtendToFPCombine(N, DCI))
return ExtCombine;
return performVectorNonNegToFPCombine(N, DCI);
case ISD::SINT_TO_FP:
return performVectorExtendToFPCombine(N, DCI);
case ISD::FP_TO_SINT_SAT:
Expand Down
28 changes: 28 additions & 0 deletions llvm/test/CodeGen/WebAssembly/simd-conversions.ll
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Expand Up @@ -441,3 +441,31 @@ define <2 x double> @promote_mixed_v2f64(<4 x float> %x, <4 x float> %y) {
%a = fpext <2 x float> %v to <2 x double>
ret <2 x double> %a
}

define <4 x float> @convert_u_v4f32_maybeneg(<4 x i32> %x) {
; CHECK-LABEL: convert_u_v4f32_maybeneg:
; CHECK: .functype convert_u_v4f32_maybeneg (v128) -> (v128)
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: i32.const 1
; CHECK-NEXT: i32x4.shr_s
; CHECK-NEXT: f32x4.convert_i32x4_u
; CHECK-NEXT: # fallthrough-return
%a = ashr <4 x i32> %x, <i32 1, i32 1, i32 1, i32 1>
%b = uitofp <4 x i32> %a to <4 x float>
ret <4 x float> %b
}

define <4 x float> @convert_u_v4f32_nonneg(<4 x i32> %x) {
; CHECK-LABEL: convert_u_v4f32_nonneg:
; CHECK: .functype convert_u_v4f32_nonneg (v128) -> (v128)
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: i32.const 1
; CHECK-NEXT: i32x4.shr_u
; CHECK-NEXT: f32x4.convert_i32x4_s
; CHECK-NEXT: # fallthrough-return
%a = lshr <4 x i32> %x, <i32 1, i32 1, i32 1, i32 1>
%b = uitofp <4 x i32> %a to <4 x float>
ret <4 x float> %b
}
10 changes: 5 additions & 5 deletions llvm/test/CodeGen/WebAssembly/simd-extending-convert.ll
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Expand Up @@ -12,7 +12,7 @@ define <4 x float> @extend_to_float_low_i16x8_u(<8 x i16> %x) {
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: i32x4.extend_low_i16x8_u
; CHECK-NEXT: f32x4.convert_i32x4_u
; CHECK-NEXT: f32x4.convert_i32x4_s
; CHECK-NEXT: # fallthrough-return
%low = shufflevector <8 x i16> %x, <8 x i16> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
%extended = uitofp <4 x i16> %low to <4 x float>
Expand All @@ -25,7 +25,7 @@ define <4 x float> @extend_to_float_high_i16x8_u(<8 x i16> %x) {
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: i32x4.extend_high_i16x8_u
; CHECK-NEXT: f32x4.convert_i32x4_u
; CHECK-NEXT: f32x4.convert_i32x4_s
; CHECK-NEXT: # fallthrough-return
%high = shufflevector <8 x i16> %x, <8 x i16> undef, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
%extended = uitofp <4 x i16> %high to <4 x float>
Expand All @@ -39,7 +39,7 @@ define <4 x float> @extend_to_float_low_i8x16_u(<8 x i8> %x) {
; CHECK-NEXT: local.get 0
; CHECK-NEXT: i16x8.extend_low_i8x16_u
; CHECK-NEXT: i32x4.extend_low_i16x8_u
; CHECK-NEXT: f32x4.convert_i32x4_u
; CHECK-NEXT: f32x4.convert_i32x4_s
; CHECK-NEXT: # fallthrough-return
%low = shufflevector <8 x i8> %x, <8 x i8> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
%extended = uitofp <4 x i8> %low to <4 x float>
Expand All @@ -55,7 +55,7 @@ define <4 x float> @extend_to_float_high_i8x16_u(<8 x i8> %x) {
; CHECK-NEXT: i8x16.shuffle 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
; CHECK-NEXT: i16x8.extend_low_i8x16_u
; CHECK-NEXT: i32x4.extend_low_i16x8_u
; CHECK-NEXT: f32x4.convert_i32x4_u
; CHECK-NEXT: f32x4.convert_i32x4_s
; CHECK-NEXT: # fallthrough-return
%high = shufflevector <8 x i8> %x, <8 x i8> undef, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
%extended = uitofp <4 x i8> %high to <4 x float>
Expand Down Expand Up @@ -136,7 +136,7 @@ define <2 x double> @extend_to_double_low_i16x4_u(<4 x i16> %x) {
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: i32x4.extend_low_i16x8_u
; CHECK-NEXT: f64x2.convert_low_i32x4_u
; CHECK-NEXT: f64x2.convert_low_i32x4_s
; CHECK-NEXT: # fallthrough-return
%low = shufflevector <4 x i16> %x, <4 x i16> undef, <2 x i32> <i32 0, i32 1>
%extended = uitofp <2 x i16> %low to <2 x double>
Expand Down