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shader: decode S_FLBIT_I32 and S_FLBIT_I32_I64 with a 4-op signed leading-bit search

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nmzik committed 2026-10-23 19:48:53 +02:00
1 parent 3688412dca
commit ecc30a1f2d
6 files changed
+71 -10
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src/graphics/shader/recompiler/frontend/translate/Integer.cpp
+22 -6
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@@ -221,8 +221,17 @@ void Translator::V_XOR3_B32(const Decoder::Instruction& inst) {
WriteOperand(DestinationOperand(inst), result);
}
void Translator::S_FF_I32_B64(const Decoder::Instruction& inst, bool find_zero, bool from_msb) {
void Translator::S_FF_I32_B64(const Decoder::Instruction& inst, bool find_zero, bool from_msb,
bool sign) {
auto source = ReadU32Pair(inst.src0);
if (sign) {
// A signed source sign-extends a literal; then bits equal to the sign become zero.
if (inst.src0.kind == Decoder::OperandKind::LiteralConstant) {
source[1] = ir.ShiftRightArithmetic(source[0], IR::U32(IR::Value(31u)));
}
const auto mask = ir.ShiftRightArithmetic(source[1], IR::U32(IR::Value(31u)));
source = {ir.BitwiseXor(source[0], mask), ir.BitwiseXor(source[1], mask)};
}
for (auto& word: source) {
word = find_zero ? ir.BitwiseNot(word) : word;
}
@@ -240,12 +249,19 @@ void Translator::S_FF_I32_B64(const Decoder::Instruction& inst, bool find_zero,
void Translator::V_FFBH_32(const Decoder::Instruction& inst, bool sign) {
const auto source = ReadU32(inst.src0);
const auto value = sign ? ir.BitwiseXor(
source, ir.ShiftRightArithmetic(source, IR::U32(IR::Value(31u))))
: source;
const auto msb = IR::U32(ir.Emit(IR::ValueOpcode::FindUMsb32, {value}));
if (sign) {
// Bits equal to the sign become zero; FindILsb of the reversed bits is ~0 when none.
const auto bits =
ir.BitwiseXor(source, ir.ShiftRightArithmetic(source, IR::U32(IR::Value(31u))));
const auto reversed = ir.Emit(IR::ValueOpcode::BitReverse32, {bits});
WriteOperand(DestinationOperand(inst),
IR::U32(ir.Emit(IR::ValueOpcode::FindILsb32, {reversed})));
return;
}
// ResourceTracking matches this 31 - FindUMsb32 form.
const auto msb = IR::U32(ir.Emit(IR::ValueOpcode::FindUMsb32, {source}));
const auto position = ir.ISub(IR::U32(IR::Value(31u)), msb);
const auto result = ir.Select(ir.INotEqual(value, IR::U32(IR::Value(0u))), position,
const auto result = ir.Select(ir.INotEqual(source, IR::U32(IR::Value(0u))), position,
IR::U32(IR::Value(0xffffffffu)));
WriteOperand(DestinationOperand(inst), result);
}