shader: clamp V_FRACT_F16/F32/F64 results below one

src/graphics/shader/recompiler/frontend/translate/Float.cpp

@@ -1,6 +1,7 @@
 #include "graphics/shader/recompiler/frontend/translate/Translator.h"
 
 #include <array>
+#include <bit>
 #include <utility>
 
 namespace Libs::Graphics::ShaderRecompiler::Frontend {
@@ -118,6 +119,33 @@ void Translator::FloatUnary(const Decoder::Instruction& inst, IR::ValueOpcode op
 	WriteOperand(DestinationOperand(inst), ir.Emit(opcode, {ReadOperand(inst.src0, type)}));
 }
 
+void Translator::V_FRACT(const Decoder::Instruction& inst, IR::Type type) {
+	// x - floor(x) rounds to 1.0 for a tiny negative x; v_fract returns the largest value below
+	// one instead. The ordered compare lets NaN through.
+	const auto destination = DestinationOperand(inst);
+	if (type == IR::Type::F64) {
+		const auto result    = ir.Emit(IR::ValueOpcode::FPFract64, {ReadOperand(inst.src0, type)});
+		const auto below_one = ir.Emit(IR::ValueOpcode::BitCastF64U64,
+		                               {IR::Value(uint64_t {0x3fefffffffffffff})});
+		const auto above     = ir.Emit(IR::ValueOpcode::FPOrdGreaterThan64, {result, below_one});
+		WriteOperand(destination, ir.Emit(IR::ValueOpcode::SelectF64, {above, below_one, result}));
+		return;
+	}
+	const bool half   = type == IR::Type::F16;
+	const auto source = half ? ReadF16AsF32(inst.src0) : IR::F32(ReadOperand(inst.src0, type));
+	const auto result = IR::F32(ir.Emit(IR::ValueOpcode::FPFract32, {source}));
+	// Clamp in the destination precision: 0x3f7fe000 is the half 0x3bff.
+	const auto below_one =
+	    IR::F32(IR::Value::F32(std::bit_cast<float>(half ? 0x3f7fe000u : 0x3f7fffffu)));
+	const auto above   = IR::U1(ir.Emit(IR::ValueOpcode::FPOrdGreaterThan32, {result, below_one}));
+	const auto clamped = SelectF32(above, below_one, result);
+	if (half) {
+		WriteF16(destination, clamped);
+	} else {
+		WriteOperand(destination, clamped);
+	}
+}
+
 void Translator::FloatBinary(const Decoder::Instruction& inst, IR::ValueOpcode opcode,
                              bool reverse) {
 	std::array<IR::Value, 2> args;