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fix(shader): convert f16 bits to f32 without UnpackHalf2x16 #1463

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Merged
oneandonlydean merged 1 commit into from
Oct 11, 2026
Merged

fix(shader): convert f16 bits to f32 without UnpackHalf2x16 #1463

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19 changes: 14 additions & 5 deletions core/shader/recompiler/SpirvBackend/src/SpirvModuleEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -860,11 +860,20 @@ std::uint32_t EmitTrigCycleF32(SpirvEmitterState& state, std::uint32_t src, bool
}

std::uint32_t EmitF16BitsToF32(SpirvEmitterState& state, std::uint32_t bits) {
const auto unpacked = state.module.AllocateId();
const auto result = state.module.AllocateId();
state.module.AddFunction(spv::OpExtInst, TypeF32Vector(state, 2), unpacked, GlslStd450(state), GLSLstd450UnpackHalf2x16, bits);
state.module.AddFunction(spv::OpCompositeExtract, TypeF32(state), result, unpacked, 0u);
return result;
const auto u32 = TypeU32(state);
const auto f32 = TypeF32(state);
const auto op = [&](spv::Op opcode, std::uint32_t lhs, std::uint32_t rhs) { return Binary(state, opcode, u32, lhs, rhs); };
const auto sign = op(spv::OpShiftLeftLogical, op(spv::OpBitwiseAnd, bits, ConstantU32(state, 0x8000u)), ConstantU32(state, 16u));
const auto exponent = op(spv::OpBitwiseAnd, op(spv::OpShiftRightLogical, bits, ConstantU32(state, 10u)), ConstantU32(state, 0x1fu));
const auto mantissa = op(spv::OpBitwiseAnd, bits, ConstantU32(state, 0x3ffu));
const auto mantissa32 = op(spv::OpShiftLeftLogical, mantissa, ConstantU32(state, 13u));
const auto normal = op(spv::OpBitwiseOr, op(spv::OpShiftLeftLogical, op(spv::OpIAdd, exponent, ConstantU32(state, 127u - 15u)), ConstantU32(state, 23u)), mantissa32);
const auto special = op(spv::OpBitwiseOr, ConstantU32(state, 0x7f800000u), mantissa32);
const auto subnormal = Unary(state, spv::OpBitcast, u32, Binary(state, spv::OpFMul, f32, Unary(state, spv::OpConvertUToF, f32, mantissa), ConstantF32Value(state, 0x1p-24f)));
const auto boolean = TypeBool(state);
const auto finite = Select(state, u32, Binary(state, spv::OpIEqual, boolean, exponent, ConstantU32(state, 0u)), subnormal, normal);
const auto magnitude = Select(state, u32, Binary(state, spv::OpIEqual, boolean, exponent, ConstantU32(state, 0x1fu)), special, finite);
return Unary(state, spv::OpBitcast, f32, op(spv::OpBitwiseOr, sign, magnitude));
}

void EmitProgram(SpirvEmitterState& state) {
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