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[WIP] spirv-opt: Fix when ConvertToHalfPass relaxes a image operand #6480

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[WIP] spirv-opt: Fix when ConvertToHalfPass relaxes a image operand #6480

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155 changes: 154 additions & 1 deletion source/opt/convert_to_half_pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,12 +16,15 @@

#include "convert_to_half_pass.h"

#include <cstdint>

#include "source/opt/ir_builder.h"

namespace spvtools {
namespace opt {
namespace {
// Indices of operands in SPIR-V instructions
constexpr int kImageSampleCoordinateIdInIdx = 1;
constexpr int kImageSampleDrefIdInIdx = 2;
} // namespace

Expand Down Expand Up @@ -195,6 +198,118 @@ bool ConvertToHalfPass::MatConvertCleanup(Instruction* inst) {
return true;
}

// Return operand position of Image Operands <ID> or zero if there is none
static constexpr uint32_t GetImageOperandsPosition(spv::Op opcode) {
uint32_t position = 0;
switch (opcode) {
case spv::Op::OpImageWrite:
return 3;
case spv::Op::OpImageSampleImplicitLod:
case spv::Op::OpImageSampleExplicitLod:
case spv::Op::OpImageSampleProjImplicitLod:
case spv::Op::OpImageSampleProjExplicitLod:
case spv::Op::OpImageFetch:
case spv::Op::OpImageRead:
case spv::Op::OpImageSparseSampleImplicitLod:
case spv::Op::OpImageSparseSampleExplicitLod:
case spv::Op::OpImageSparseSampleProjImplicitLod:
case spv::Op::OpImageSparseSampleProjExplicitLod:
case spv::Op::OpImageSparseFetch:
case spv::Op::OpImageSparseRead:
return 4;
case spv::Op::OpImageSampleDrefImplicitLod:
case spv::Op::OpImageSampleDrefExplicitLod:
case spv::Op::OpImageSampleProjDrefImplicitLod:
case spv::Op::OpImageSampleProjDrefExplicitLod:
case spv::Op::OpImageGather:
case spv::Op::OpImageDrefGather:
case spv::Op::OpImageSparseSampleDrefImplicitLod:
case spv::Op::OpImageSparseSampleDrefExplicitLod:
case spv::Op::OpImageSparseSampleProjDrefImplicitLod:
case spv::Op::OpImageSparseSampleProjDrefExplicitLod:
case spv::Op::OpImageSparseGather:
case spv::Op::OpImageSparseDrefGather:
return 5;
case spv::Op::OpImageSampleFootprintNV:
return 6;
default:
break;
}
return position;
}

bool ConvertToHalfPass::ImageOperandCleanup(Instruction* inst) {
if (image_ops_.count(inst->opcode()) == 0) return false;

const uint32_t image_operand_position =
GetImageOperandsPosition(inst->opcode());
// Image operands can be optional, also some things like |SignExtend| don't
// have additonal operands
if (image_operand_position == 0 ||
(image_operand_position + 1) >= inst->NumOperandWords()) {
return false;
}

bool modified = false;
const uint32_t mask = inst->GetSingleWordOperand(image_operand_position);
uint32_t next_operand = image_operand_position + 1;

InstructionBuilder builder(
context(), inst,
IRContext::kAnalysisDefUse | IRContext::kAnalysisInstrToBlockMapping);

uint32_t float32_type =
context()->get_type_mgr()->GetTypeInstruction(FloatScalarType(32));

// All mask after don't have a 32-bit restriction
for (uint32_t i = 1;
i <= static_cast<uint32_t>(spv::ImageOperandsMask::MinLod); i <<= 1) {
if ((mask & i) == 0) {
continue;
}

uint32_t update_operand = next_operand++;
const uint32_t ref_id = inst->GetSingleWordOperand(update_operand);
Instruction* ref_inst = get_def_use_mgr()->GetDef(ref_id);
Instruction* type_inst = get_def_use_mgr()->GetDef(ref_inst->type_id());
assert(type_inst->opcode() == spv::Op::OpTypeFloat);
if (type_inst->GetSingleWordInOperand(0) != 32) {
Instruction* cvt_inst =
builder.AddUnaryOp(float32_type, spv::Op::OpFConvert, ref_id);
if (cvt_inst == nullptr) {
status_ = Status::Failure;
return false;
}
inst->SetOperand(update_operand, {cvt_inst->result_id()});
get_def_use_mgr()->AnalyzeInstUse(inst);
modified = true;
}

// All masks have 1 operand, except grad has two
if (i == static_cast<uint32_t>(spv::ImageOperandsMask::Grad)) {
uint32_t dy_update_operand = next_operand++;
const uint32_t dy_ref_id = inst->GetSingleWordOperand(dy_update_operand);
Instruction* dy_ref_inst = get_def_use_mgr()->GetDef(dy_ref_id);
Instruction* dy_type_inst =
get_def_use_mgr()->GetDef(dy_ref_inst->type_id());
assert(dy_type_inst->opcode() == spv::Op::OpTypeFloat);
if (dy_type_inst->GetSingleWordInOperand(0) != 32) {
Instruction* dy_cvt_inst =
builder.AddUnaryOp(float32_type, spv::Op::OpFConvert, ref_id);
if (dy_cvt_inst == nullptr) {
status_ = Status::Failure;
return false;
}
inst->SetOperand(dy_update_operand, {dy_cvt_inst->result_id()});
get_def_use_mgr()->AnalyzeInstUse(inst);
modified = true;
}
Comment on lines +290 to +306
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@s-perron s-perron Jan 5, 2026

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This seems to repeat a lot of the code above, could it be factored out into a function that modifies the given operand?

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@spencer-lunarg spencer-lunarg Jan 5, 2026

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debated about it, probably better, especially if a new operand is ever added doing something similar (or worse)

}
}

return modified;
}

bool ConvertToHalfPass::RemoveRelaxedDecoration(uint32_t id) {
return context()->get_decoration_mgr()->RemoveDecorationsFrom(
id, [](const Instruction& dec) {
Expand Down Expand Up @@ -325,7 +440,7 @@ bool ConvertToHalfPass::ProcessConvert(Instruction* inst) {

bool ConvertToHalfPass::ProcessImageRef(Instruction* inst) {
bool modified = false;
// If image reference, only need to convert dref args back to float32
// If image reference, some operands aren't allowed to be non-32 bit floats
if (dref_image_ops_.count(inst->opcode()) != 0) {
uint32_t dref_id = inst->GetSingleWordInOperand(kImageSampleDrefIdInIdx);
if (converted_ids_.count(dref_id) > 0) {
Expand All @@ -338,6 +453,19 @@ bool ConvertToHalfPass::ProcessImageRef(Instruction* inst) {
modified = true;
}
}
if (coordinate_image_ops_.count(inst->opcode()) != 0) {
uint32_t coordinate_id =
inst->GetSingleWordInOperand(kImageSampleCoordinateIdInIdx);
if (converted_ids_.count(coordinate_id) > 0) {
GenConvert(&coordinate_id, 32, inst);
if (status_ == Status::Failure) {
return false;
}
inst->SetInOperand(kImageSampleCoordinateIdInIdx, {coordinate_id});
get_def_use_mgr()->AnalyzeInstUse(inst);
modified = true;
}
}
return modified;
}

Expand Down Expand Up @@ -452,6 +580,7 @@ bool ConvertToHalfPass::ProcessFunction(Function* func) {
}
for (auto ii = bb->begin(); ii != bb->end(); ++ii) {
bool Mmodified = MatConvertCleanup(&*ii);
Mmodified |= ImageOperandCleanup(&*ii);
if (status_ == Status::Failure) {
ok = false;
break;
Expand Down Expand Up @@ -591,6 +720,30 @@ void ConvertToHalfPass::Initialize() {
spv::Op::OpImageSparseSampleProjDrefExplicitLod,
spv::Op::OpImageSparseDrefGather,
};
coordinate_image_ops_ = {
spv::Op::OpImageSampleImplicitLod,
spv::Op::OpImageSampleExplicitLod,
spv::Op::OpImageSampleDrefImplicitLod,
spv::Op::OpImageSampleDrefExplicitLod,
spv::Op::OpImageSampleProjImplicitLod,
spv::Op::OpImageSampleProjExplicitLod,
spv::Op::OpImageSampleProjDrefImplicitLod,
spv::Op::OpImageSampleProjDrefExplicitLod,
spv::Op::OpImageFetch,
spv::Op::OpImageGather,
spv::Op::OpImageDrefGather,
spv::Op::OpImageRead,
spv::Op::OpImageWrite,
spv::Op::OpImageQueryLod,
spv::Op::OpImageSparseSampleImplicitLod,
spv::Op::OpImageSparseSampleExplicitLod,
spv::Op::OpImageSparseSampleDrefImplicitLod,
spv::Op::OpImageSparseSampleDrefExplicitLod,
spv::Op::OpImageSparseFetch,
spv::Op::OpImageSparseGather,
spv::Op::OpImageSparseDrefGather,
spv::Op::OpImageSparseRead,
};
closure_ops_ = {
spv::Op::OpVectorExtractDynamic,
spv::Op::OpVectorInsertDynamic,
Expand Down
7 changes: 7 additions & 0 deletions source/opt/convert_to_half_pass.h
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,10 @@ class ConvertToHalfPass : public Pass {
// invalid so we need to clean them up.
bool MatConvertCleanup(Instruction* inst);

// If |inst| has any image operands, make sure to covert it back to a 32-bit
// float
bool ImageOperandCleanup(Instruction* inst);

// Call GenHalfInst on every instruction in |func|.
// If code is generated for an instruction, replace the instruction
// with the new instructions that are generated.
Expand Down Expand Up @@ -145,6 +149,9 @@ class ConvertToHalfPass : public Pass {
// Set of only dref sample operations
std::unordered_set<spv::Op, hasher> dref_image_ops_;

// Set of only sample operations that have a Coordinate operand
std::unordered_set<spv::Op, hasher> coordinate_image_ops_;

// Set of operations that can be marked as relaxed
std::unordered_set<spv::Op, hasher> closure_ops_;

Expand Down
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