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[Vulkan] Clamp scalar maxas/maxasf address register to [0, 255]

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Matches DXBC.

Co-authored-by: Herman S. <429230+has207@users.noreply.github.com>
This commit is contained in:
goldislead
2026-08-04 16:00:00 -07:00
committed by Radosław Gliński
parent 3ff230d23b
commit 4aeb518c9c
1 changed files with 5 additions and 3 deletions
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8
src/xenia/gpu/spirv_shader_translator_alu.cc
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@@ -1051,8 +1051,10 @@ spv::Id SpirvShaderTranslator::ProcessScalarAluOperation(
GetOperandScalarXY(operand_storage[0], instr.scalar_operands[0], a, b);
if (instr.scalar_opcode == ucode::AluScalarOpcode::kMaxAs ||
instr.scalar_opcode == ucode::AluScalarOpcode::kMaxAsf) {
// maxas: a0 = (int)clamp(floor(src0.a + 0.5), -256.0, 255.0)
// maxasf: a0 = (int)clamp(floor(src0.a), -256.0, 255.0)
// Scalar maxas/maxasf clamp a0 to [0, 255] (non-negative), unlike the
// vector maxa which allows [-256, 255]. Matches DxbcShaderTranslator.
// maxas: a0 = (int)clamp(floor(src0.a + 0.5), 0.0, 255.0)
// maxasf: a0 = (int)clamp(floor(src0.a), 0.0, 255.0)
spv::Id maxa_address;
if (instr.scalar_opcode == ucode::AluScalarOpcode::kMaxAs) {
maxa_address = builder_->createNoContractionBinOp(
@@ -1068,7 +1070,7 @@ spv::Id SpirvShaderTranslator::ProcessScalarAluOperation(
builder_->createUnaryBuiltinCall(
type_float_, ext_inst_glsl_std_450_, GLSLstd450Floor,
maxa_address),
builder_->makeFloatConstant(-256.0f),
builder_->makeFloatConstant(0.0f),
builder_->makeFloatConstant(255.0f))),
var_main_address_register_);
}