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[FP16] Implement f16x8.demote_{f64x2, f32x4}_zero. #8580

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[FP16] Implement f16x8.demote_{f64x2, f32x4}_zero. #8580

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2 changes: 2 additions & 0 deletions scripts/gen-s-parser.py
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Expand Up @@ -550,6 +550,8 @@
("f16x8.convert_i16x8_s", "makeUnary(UnaryOp::ConvertSVecI16x8ToVecF16x8)"),
("f16x8.convert_i16x8_u", "makeUnary(UnaryOp::ConvertUVecI16x8ToVecF16x8)"),
("f32x4.promote_low_f16x8", "makeUnary(UnaryOp::PromoteLowVecF16x8ToVecF32x4)"),
("f16x8.demote_f32x4_zero", "makeUnary(UnaryOp::DemoteZeroVecF32x4ToVecF16x8)"),
("f16x8.demote_f64x2_zero", "makeUnary(UnaryOp::DemoteZeroVecF64x2ToVecF16x8)"),
("f16x8.madd", "makeSIMDTernary(SIMDTernaryOp::MaddVecF16x8)"),
("f16x8.nmadd", "makeSIMDTernary(SIMDTernaryOp::NmaddVecF16x8)"),

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32 changes: 27 additions & 5 deletions src/gen-s-parser.inc
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Expand Up @@ -505,12 +505,34 @@ switch (buf[0]) {
default: goto parse_error;
}
}
case 'd':
if (op == "f16x8.div"sv) {
CHECK_ERR(makeBinary(ctx, pos, annotations, BinaryOp::DivVecF16x8));
return Ok{};
case 'd': {
switch (buf[7]) {
case 'e': {
switch (buf[14]) {
case '3':
if (op == "f16x8.demote_f32x4_zero"sv) {
CHECK_ERR(makeUnary(ctx, pos, annotations, UnaryOp::DemoteZeroVecF32x4ToVecF16x8));
return Ok{};
}
goto parse_error;
case '6':
if (op == "f16x8.demote_f64x2_zero"sv) {
CHECK_ERR(makeUnary(ctx, pos, annotations, UnaryOp::DemoteZeroVecF64x2ToVecF16x8));
return Ok{};
}
goto parse_error;
default: goto parse_error;
}
}
case 'i':
if (op == "f16x8.div"sv) {
CHECK_ERR(makeBinary(ctx, pos, annotations, BinaryOp::DivVecF16x8));
return Ok{};
}
goto parse_error;
default: goto parse_error;
}
goto parse_error;
}
case 'e': {
switch (buf[7]) {
case 'q':
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2 changes: 2 additions & 0 deletions src/ir/child-typer.h
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Expand Up @@ -448,6 +448,8 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
case ConvertSVecI16x8ToVecF16x8:
case ConvertUVecI16x8ToVecF16x8:
case PromoteLowVecF16x8ToVecF32x4:
case DemoteZeroVecF32x4ToVecF16x8:
case DemoteZeroVecF64x2ToVecF16x8:
case AnyTrueVec128:
case AllTrueVecI8x16:
case AllTrueVecI16x8:
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2 changes: 2 additions & 0 deletions src/ir/cost.h
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Expand Up @@ -285,6 +285,8 @@ struct CostAnalyzer : public OverriddenVisitor<CostAnalyzer, CostType> {
case ConvertSVecI16x8ToVecF16x8:
case ConvertUVecI16x8ToVecF16x8:
case PromoteLowVecF16x8ToVecF32x4:
case DemoteZeroVecF32x4ToVecF16x8:
case DemoteZeroVecF64x2ToVecF16x8:
ret = 1;
break;
case InvalidUnary:
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2 changes: 2 additions & 0 deletions src/literal.h
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Expand Up @@ -724,6 +724,8 @@ class Literal {
Literal demoteZeroToF32x4() const;
Literal promoteLowToF64x2() const;
Literal promoteLowF16x8ToF32x4() const;
Literal demoteZeroF32x4ToF16x8() const;
Literal demoteZeroF64x2ToF16x8() const;
Literal truncSatToSI16x8() const;
Literal truncSatToUI16x8() const;
Literal convertSToF16x8() const;
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6 changes: 6 additions & 0 deletions src/passes/Print.cpp
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Expand Up @@ -1404,6 +1404,12 @@ struct PrintExpressionContents
case PromoteLowVecF16x8ToVecF32x4:
o << "f32x4.promote_low_f16x8";
break;
case DemoteZeroVecF32x4ToVecF16x8:
o << "f16x8.demote_f32x4_zero";
break;
case DemoteZeroVecF64x2ToVecF16x8:
o << "f16x8.demote_f64x2_zero";
break;
case InvalidUnary:
WASM_UNREACHABLE("unvalid unary operator");
}
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2 changes: 2 additions & 0 deletions src/wasm-binary.h
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Expand Up @@ -1126,6 +1126,8 @@ enum ASTNodes {
I16x8TruncSatF16x8U = 0x146,
F16x8ConvertI16x8S = 0x147,
F16x8ConvertI16x8U = 0x148,
F16x8DemoteF32x4Zero = 0x149,
F16x8DemoteF64x2Zero = 0x14a,
F32x4PromoteLowF16x8 = 0x14b,

// bulk memory opcodes
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4 changes: 4 additions & 0 deletions src/wasm-interpreter.h
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Expand Up @@ -1166,6 +1166,10 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
return value.convertUToF16x8();
case PromoteLowVecF16x8ToVecF32x4:
return value.promoteLowF16x8ToF32x4();
case DemoteZeroVecF32x4ToVecF16x8:
return value.demoteZeroF32x4ToF16x8();
case DemoteZeroVecF64x2ToVecF16x8:
return value.demoteZeroF64x2ToF16x8();
case InvalidUnary:
WASM_UNREACHABLE("invalid unary op");
}
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2 changes: 2 additions & 0 deletions src/wasm.h
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Expand Up @@ -252,6 +252,8 @@ enum UnaryOp {
ConvertSVecI16x8ToVecF16x8,
ConvertUVecI16x8ToVecF16x8,
PromoteLowVecF16x8ToVecF32x4,
DemoteZeroVecF32x4ToVecF16x8,
DemoteZeroVecF64x2ToVecF16x8,

InvalidUnary
};
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24 changes: 24 additions & 0 deletions src/wasm/literal.cpp
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Expand Up @@ -2912,6 +2912,30 @@ Literal Literal::truncSatZeroUToI32x4() const {
Literal Literal::demoteZeroToF32x4() const {
return unary_zero<4, &Literal::getLanesF64x2, &Literal::demote>(*this);
}
Literal Literal::demoteZeroF32x4ToF16x8() const {
auto lanes = getLanesF32x4();
LaneArray<8> result;
for (size_t i = 0; i < 4; ++i) {
result[i] = Literal(fp16_ieee_from_fp32_value(lanes[i].getf32()));
}
for (size_t i = 4; i < 8; ++i) {
result[i] = Literal(int32_t(0));
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@stevenfontanella stevenfontanella Apr 7, 2026

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Can we use a constructor instead of a C-style functional cast? Like int32_t{0}. Ditto below

}
return Literal(result);
}

Literal Literal::demoteZeroF64x2ToF16x8() const {
auto lanes = getLanesF64x2();
LaneArray<8> result;
for (size_t i = 0; i < 2; ++i) {
result[i] = Literal(fp16_ieee_from_fp32_value(lanes[i].demote().getf32()));
}
for (size_t i = 2; i < 8; ++i) {
result[i] = Literal(int32_t(0));
}
return Literal(result);
}

Literal Literal::promoteLowToF64x2() const {
return extendF32<LaneOrder::Low>(*this);
}
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4 changes: 4 additions & 0 deletions src/wasm/wasm-binary.cpp
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Expand Up @@ -4474,6 +4474,10 @@ Result<> WasmBinaryReader::readInst() {
return builder.makeUnary(ConvertSVecI16x8ToVecF16x8);
case BinaryConsts::F16x8ConvertI16x8U:
return builder.makeUnary(ConvertUVecI16x8ToVecF16x8);
case BinaryConsts::F16x8DemoteF32x4Zero:
return builder.makeUnary(DemoteZeroVecF32x4ToVecF16x8);
case BinaryConsts::F16x8DemoteF64x2Zero:
return builder.makeUnary(DemoteZeroVecF64x2ToVecF16x8);
case BinaryConsts::F32x4PromoteLowF16x8:
return builder.makeUnary(PromoteLowVecF16x8ToVecF32x4);
case BinaryConsts::I8x16ExtractLaneS:
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8 changes: 8 additions & 0 deletions src/wasm/wasm-stack.cpp
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Expand Up @@ -1459,6 +1459,14 @@ void BinaryInstWriter::visitUnary(Unary* curr) {
o << static_cast<int8_t>(BinaryConsts::SIMDPrefix)
<< U32LEB(BinaryConsts::F16x8ConvertI16x8U);
break;
case DemoteZeroVecF32x4ToVecF16x8:
o << static_cast<int8_t>(BinaryConsts::SIMDPrefix)
<< U32LEB(BinaryConsts::F16x8DemoteF32x4Zero);
break;
case DemoteZeroVecF64x2ToVecF16x8:
o << static_cast<int8_t>(BinaryConsts::SIMDPrefix)
<< U32LEB(BinaryConsts::F16x8DemoteF64x2Zero);
break;
case PromoteLowVecF16x8ToVecF32x4:
o << static_cast<int8_t>(BinaryConsts::SIMDPrefix)
<< U32LEB(BinaryConsts::F32x4PromoteLowF16x8);
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2 changes: 2 additions & 0 deletions src/wasm/wasm-validator.cpp
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Expand Up @@ -2381,6 +2381,8 @@ void FunctionValidator::visitUnary(Unary* curr) {
case DemoteZeroVecF64x2ToVecF32x4:
case PromoteLowVecF32x4ToVecF64x2:
case PromoteLowVecF16x8ToVecF32x4:
case DemoteZeroVecF32x4ToVecF16x8:
case DemoteZeroVecF64x2ToVecF16x8:
case RelaxedTruncSVecF32x4ToVecI32x4:
case RelaxedTruncUVecF32x4ToVecI32x4:
case RelaxedTruncZeroSVecF64x2ToVecI32x4:
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2 changes: 2 additions & 0 deletions src/wasm/wasm.cpp
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Expand Up @@ -715,6 +715,8 @@ void Unary::finalize() {
case ConvertSVecI16x8ToVecF16x8:
case ConvertUVecI16x8ToVecF16x8:
case PromoteLowVecF16x8ToVecF32x4:
case DemoteZeroVecF32x4ToVecF16x8:
case DemoteZeroVecF64x2ToVecF16x8:
type = Type::v128;
break;
case AnyTrueVec128:
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42 changes: 42 additions & 0 deletions test/lit/basic/f16.wast
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Expand Up @@ -613,6 +613,36 @@
(local.get $0)
)
)
;; CHECK-TEXT: (func $f16x8.demote_f32x4_zero (type $1) (param $0 v128) (result v128)
;; CHECK-TEXT-NEXT: (f16x8.demote_f32x4_zero
;; CHECK-TEXT-NEXT: (local.get $0)
;; CHECK-TEXT-NEXT: )
;; CHECK-TEXT-NEXT: )
;; CHECK-BIN: (func $f16x8.demote_f32x4_zero (type $1) (param $0 v128) (result v128)
;; CHECK-BIN-NEXT: (f16x8.demote_f32x4_zero
;; CHECK-BIN-NEXT: (local.get $0)
;; CHECK-BIN-NEXT: )
;; CHECK-BIN-NEXT: )
(func $f16x8.demote_f32x4_zero (param $0 v128) (result v128)
(f16x8.demote_f32x4_zero
(local.get $0)
)
)
;; CHECK-TEXT: (func $f16x8.demote_f64x2_zero (type $1) (param $0 v128) (result v128)
;; CHECK-TEXT-NEXT: (f16x8.demote_f64x2_zero
;; CHECK-TEXT-NEXT: (local.get $0)
;; CHECK-TEXT-NEXT: )
;; CHECK-TEXT-NEXT: )
;; CHECK-BIN: (func $f16x8.demote_f64x2_zero (type $1) (param $0 v128) (result v128)
;; CHECK-BIN-NEXT: (f16x8.demote_f64x2_zero
;; CHECK-BIN-NEXT: (local.get $0)
;; CHECK-BIN-NEXT: )
;; CHECK-BIN-NEXT: )
(func $f16x8.demote_f64x2_zero (param $0 v128) (result v128)
(f16x8.demote_f64x2_zero
(local.get $0)
)
)
)
;; CHECK-BIN-NODEBUG: (type $0 (func (param v128 v128) (result v128)))

Expand Down Expand Up @@ -849,3 +879,15 @@
;; CHECK-BIN-NODEBUG-NEXT: (local.get $0)
;; CHECK-BIN-NODEBUG-NEXT: )
;; CHECK-BIN-NODEBUG-NEXT: )

;; CHECK-BIN-NODEBUG: (func $33 (type $1) (param $0 v128) (result v128)
;; CHECK-BIN-NODEBUG-NEXT: (f16x8.demote_f32x4_zero
;; CHECK-BIN-NODEBUG-NEXT: (local.get $0)
;; CHECK-BIN-NODEBUG-NEXT: )
;; CHECK-BIN-NODEBUG-NEXT: )

;; CHECK-BIN-NODEBUG: (func $34 (type $1) (param $0 v128) (result v128)
;; CHECK-BIN-NODEBUG-NEXT: (f16x8.demote_f64x2_zero
;; CHECK-BIN-NODEBUG-NEXT: (local.get $0)
;; CHECK-BIN-NODEBUG-NEXT: )
;; CHECK-BIN-NODEBUG-NEXT: )
54 changes: 54 additions & 0 deletions test/spec/f16.wast
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Expand Up @@ -39,6 +39,8 @@
(func (export "f16x8.convert_i16x8_s") (param $0 v128) (result v128) (f16x8.convert_i16x8_s (local.get $0)))
(func (export "f16x8.convert_i16x8_u") (param $0 v128) (result v128) (f16x8.convert_i16x8_u (local.get $0)))
(func (export "f32x4.promote_low_f16x8") (param $0 v128) (result v128) (f32x4.promote_low_f16x8 (local.get $0)))
(func (export "f16x8.demote_f32x4_zero") (param $0 v128) (result v128) (f16x8.demote_f32x4_zero (local.get $0)))
(func (export "f16x8.demote_f64x2_zero") (param $0 v128) (result v128) (f16x8.demote_f64x2_zero (local.get $0)))
;; Multiple operation tests:
(func (export "splat_replace") (result v128) (f16x8.replace_lane 0 (f16x8.splat (f32.const 1)) (f32.const 99))
)
Expand Down Expand Up @@ -268,3 +270,55 @@
(v128.const i16x8 0x0001 0 0 0 0 0 0 0))
;; 2^-24
(v128.const i32x4 0x33800000 0 0 0))

(assert_return (invoke "f16x8.demote_f32x4_zero"
;; 1.0 2.0 3.0 4.0
(v128.const i32x4 0x3f800000 0x40000000 0x40400000 0x40800000))
;; 1.0 2.0 3.0 4.0 0 0 0 0
(v128.const i16x8 0x3c00 0x4000 0x4200 0x4400 0 0 0 0))

(assert_return (invoke "f16x8.demote_f64x2_zero"
;; 1.0 2.0
(v128.const i64x2 0x3ff0000000000000 0x4000000000000000))
;; 1.0 2.0 0 0 0 0 0 0
(v128.const i16x8 0x3c00 0x4000 0 0 0 0 0 0))

;; Edge cases: Infinities, NaNs, Zeros
(assert_return (invoke "f16x8.demote_f32x4_zero"
;; inf -inf nan -0.0
(v128.const i32x4 0x7f800000 0xff800000 0x7fc00000 0x80000000))
;; inf -inf nan -0.0 0 0 0 0
(v128.const i16x8 0x7c00 0xfc00 0x7e00 0x8000 0 0 0 0))

;; Edge cases: Overflow
(assert_return (invoke "f16x8.demote_f32x4_zero"
;; 1e5 -1e5 65504 -65504
(v128.const i32x4 0x47c35000 0xc7c35000 0x477fe000 0xc77fe000))
;; inf -inf 65504 -65504 0 0 0 0
(v128.const i16x8 0x7c00 0xfc00 0x7bff 0xfbff 0 0 0 0))

;; Edge cases: Infinities, NaNs, Zeros
(assert_return (invoke "f16x8.demote_f64x2_zero"
;; inf -inf
(v128.const i64x2 0x7ff0000000000000 0xfff0000000000000))
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@stevenfontanella stevenfontanella Apr 7, 2026

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It looks like this NaN and the one below are canonical, can we have a case covering a non-canonical NaN?

;; inf -inf 0 0 0 0 0 0
(v128.const i16x8 0x7c00 0xfc00 0 0 0 0 0 0))

(assert_return (invoke "f16x8.demote_f64x2_zero"
;; nan -0.0
(v128.const i64x2 0x7ff8000000000000 0x8000000000000000))
;; nan -0.0 0 0 0 0 0 0
(v128.const i16x8 0x7e00 0x8000 0 0 0 0 0 0))

;; Edge cases: Overflow
(assert_return (invoke "f16x8.demote_f64x2_zero"
;; 1e5 -1e5
(v128.const i64x2 0x40f86a0000000000 0xc0f86a0000000000))
;; inf -inf 0 0 0 0 0 0
(v128.const i16x8 0x7c00 0xfc00 0 0 0 0 0 0))

(assert_return (invoke "f16x8.demote_f64x2_zero"
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@stevenfontanella stevenfontanella Apr 7, 2026

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Should we include a case that loses precision (besides overflow)?

;; 65504 -65504
(v128.const i64x2 0x40effc0000000000 0xc0effc0000000000))
;; 65504 -65504 0 0 0 0 0 0
(v128.const i16x8 0x7bff 0xfbff 0 0 0 0 0 0))
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