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spirv: Add a postprocessing pass to fix up uses of OpSampledImage

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SPIR-V requires that any instruction using the result of an
OpSampledImage instruction be in the same block as the OpSampledImage.
This is hard to guarantee in code generation but easy to fix after the
fact, by simply inserting a new OpSampledImage before the user of its
result if needed, with the new instruction having the same operands as
the original OpSampledImage.
This change adds a new pass to spv::Builder::postProcess that does this.
This might leave the original OpSampledImage instructions "orphaned"
with no users of their result ID, but dead code elimination would take
care of those further down the line.
This commit is contained in:
arcady-lunarg 2024-05-20 10:25:55 -07:00 committed by GitHub
parent 2712d643b1
commit 7c3c50ea94
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GPG Key ID: B5690EEEBB952194
6 changed files with 180 additions and 1 deletions
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2
SPIRV/SpvBuilder.h
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@ -855,6 +855,8 @@ public:
void postProcess(Instruction&);
// Hook to visit each non-32-bit sized float/int operation in a block.
void postProcessType(const Instruction&, spv::Id typeId);
// move OpSampledImage instructions to be next to their users.
void postProcessSamplers();
void dump(std::vector<unsigned int>&) const;

53
SPIRV/SpvPostProcess.cpp
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@ -483,6 +483,58 @@ void Builder::postProcessFeatures() {
}
}
// SPIR-V requires that any instruction consuming the result of an OpSampledImage
// be in the same block as the OpSampledImage instruction. This pass goes finds
// uses of OpSampledImage where that is not the case and duplicates the
// OpSampledImage to be immediately before the instruction that consumes it.
// The old OpSampledImage is left in place, potentially with no users.
void Builder::postProcessSamplers()
{
// first, find all OpSampledImage instructions and store them in a map.
std::map<Id, Instruction*> sampledImageInstrs;
for (auto f: module.getFunctions()) {
for (auto b: f->getBlocks()) {
for (auto &i: b->getInstructions()) {
if (i->getOpCode() == spv::OpSampledImage) {
sampledImageInstrs[i->getResultId()] = i.get();
}
}
}
}
// next find all uses of the given ids and rewrite them if needed.
for (auto f: module.getFunctions()) {
for (auto b: f->getBlocks()) {
auto &instrs = b->getInstructions();
for (size_t idx = 0; idx < instrs.size(); idx++) {
Instruction *i = instrs[idx].get();
for (int opnum = 0; opnum < i->getNumOperands(); opnum++) {
// Is this operand of the current instruction the result of an OpSampledImage?
if (i->isIdOperand(opnum) &&
sampledImageInstrs.count(i->getIdOperand(opnum)))
{
Instruction *opSampImg = sampledImageInstrs[i->getIdOperand(opnum)];
if (i->getBlock() != opSampImg->getBlock()) {
Instruction *newInstr = new Instruction(getUniqueId(),
opSampImg->getTypeId(),
spv::OpSampledImage);
newInstr->addIdOperand(opSampImg->getIdOperand(0));
newInstr->addIdOperand(opSampImg->getIdOperand(1));
newInstr->setBlock(b);
// rewrite the user of the OpSampledImage to use the new instruction.
i->setIdOperand(opnum, newInstr->getResultId());
// insert the new OpSampledImage right before the current instruction.
instrs.insert(instrs.begin() + idx,
std::unique_ptr<Instruction>(newInstr));
idx++;
}
}
}
}
}
}
}
// comment in header
void Builder::postProcess(bool compileOnly)
{
@ -491,6 +543,7 @@ void Builder::postProcess(bool compileOnly)
postProcessCFG();
postProcessFeatures();
postProcessSamplers();
}
}; // end spv namespace

10
SPIRV/spvIR.h
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@ -107,6 +107,14 @@ public:
operands.push_back(id);
idOperand.push_back(true);
}
// This method is potentially dangerous as it can break assumptions
// about SSA and lack of forward references.
void setIdOperand(unsigned idx, Id id) {
assert(id);
assert(idOperand[idx]);
operands[idx] = id;
}
void addImmediateOperand(unsigned int immediate) {
operands.push_back(immediate);
idOperand.push_back(false);
@ -238,7 +246,7 @@ public:
void addLocalVariable(std::unique_ptr<Instruction> inst) { localVariables.push_back(std::move(inst)); }
const std::vector<Block*>& getPredecessors() const { return predecessors; }
const std::vector<Block*>& getSuccessors() const { return successors; }
const std::vector<std::unique_ptr<Instruction> >& getInstructions() const {
std::vector<std::unique_ptr<Instruction> >& getInstructions() {
return instructions;
}
const std::vector<std::unique_ptr<Instruction> >& getLocalVariables() const { return localVariables; }

94
Test/baseResults/spv.sampledImageBlock.frag.out Normal file
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@ -0,0 +1,94 @@
spv.sampledImageBlock.frag
// Module Version 10000
// Generated by (magic number): 8000b
// Id's are bound by 55
Capability Shader
1: ExtInstImport "GLSL.std.450"
MemoryModel Logical GLSL450
EntryPoint Fragment 4 "main" 36 45
ExecutionMode 4 OriginUpperLeft
Source GLSL 450
Name 4 "main"
Name 9 "texel"
Name 12 "tex0"
Name 16 "samp0"
Name 21 "ParamBuffer"
MemberName 21(ParamBuffer) 0 "cond"
Name 23 "paramBuffer"
Name 36 "texCoord"
Name 45 "fragColor"
Decorate 12(tex0) DescriptorSet 0
Decorate 12(tex0) Binding 0
Decorate 16(samp0) DescriptorSet 0
Decorate 16(samp0) Binding 1
MemberDecorate 21(ParamBuffer) 0 Offset 0
Decorate 21(ParamBuffer) Block
Decorate 23(paramBuffer) DescriptorSet 0
Decorate 23(paramBuffer) Binding 2
Decorate 36(texCoord) Flat
Decorate 36(texCoord) Location 0
Decorate 45(fragColor) Location 0
2: TypeVoid
3: TypeFunction 2
6: TypeFloat 32
7: TypeVector 6(float) 4
8: TypePointer Function 7(fvec4)
10: TypeImage 6(float) 2D sampled format:Unknown
11: TypePointer UniformConstant 10
12(tex0): 11(ptr) Variable UniformConstant
14: TypeSampler
15: TypePointer UniformConstant 14
16(samp0): 15(ptr) Variable UniformConstant
18: TypeSampledImage 10
20: TypeInt 32 1
21(ParamBuffer): TypeStruct 20(int)
22: TypePointer Uniform 21(ParamBuffer)
23(paramBuffer): 22(ptr) Variable Uniform
24: 20(int) Constant 0
25: TypePointer Uniform 20(int)
28: TypeBool
30: TypeVector 20(int) 2
31: TypePointer Function 30(ivec2)
35: TypePointer Input 30(ivec2)
36(texCoord): 35(ptr) Variable Input
44: TypePointer Output 7(fvec4)
45(fragColor): 44(ptr) Variable Output
46: TypeVector 6(float) 3
49: 6(float) Constant 1065353216
4(main): 2 Function None 3
5: Label
9(texel): 8(ptr) Variable Function
32: 31(ptr) Variable Function
13: 10 Load 12(tex0)
17: 14 Load 16(samp0)
19: 18 SampledImage 13 17
26: 25(ptr) AccessChain 23(paramBuffer) 24
27: 20(int) Load 26
29: 28(bool) IEqual 27 24
SelectionMerge 34 None
BranchConditional 29 33 38
33: Label
37: 30(ivec2) Load 36(texCoord)
Store 32 37
Branch 34
38: Label
39: 30(ivec2) Load 36(texCoord)
40: 30(ivec2) VectorShuffle 39 39 1 0
Store 32 40
Branch 34
34: Label
41: 30(ivec2) Load 32
54: 18 SampledImage 13 17
42: 10 Image 54
43: 7(fvec4) ImageFetch 42 41 Lod 24
Store 9(texel) 43
47: 7(fvec4) Load 9(texel)
48: 46(fvec3) VectorShuffle 47 47 0 1 2
50: 6(float) CompositeExtract 48 0
51: 6(float) CompositeExtract 48 1
52: 6(float) CompositeExtract 48 2
53: 7(fvec4) CompositeConstruct 50 51 52 49
Store 45(fragColor) 53
Return
FunctionEnd

21
Test/spv.sampledImageBlock.frag Normal file
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@ -0,0 +1,21 @@
#version 450
layout(set = 0, binding = 0) uniform texture2D tex0;
layout(set = 0, binding = 1) uniform sampler samp0;
layout(set = 0, binding = 2) uniform ParamBuffer {
int cond;
} paramBuffer;
layout(location = 0) out vec4 fragColor;
layout(location = 0) in flat ivec2 texCoord;
void main() {
// get input
const vec4 texel = texelFetch(sampler2D(tex0, samp0),
paramBuffer.cond == 0 ? texCoord.xy : texCoord.yx,
0);
fragColor = vec4(texel.xyz, 1.0);
}

1
gtests/Spv.FromFile.cpp
View File

@ -551,6 +551,7 @@ INSTANTIATE_TEST_SUITE_P(
"spv.ext.textureShadowLod.error.frag",
"spv.floatFetch.frag",
"spv.atomicRvalue.error.vert",
"spv.sampledImageBlock.frag",
})),
FileNameAsCustomTestSuffix
);