[PIX] Attribute library accesses to reaching entry points by damyanp · Pull Request #8849 · microsoft/DirectXShaderCompiler

Damyan Pepper (damyanp) · 2026-08-27T23:41:29Z

Part 8 of 14 in the PIX instrumentation stack. It targets users/damyanp/pix-fixes-07, which supplies the bind-point test support.

The pass either skips a helper function in a library or gives its access the Library shader kind. Library is the kind of the module. It does not identify the pipeline stage that reaches the access. PIX cannot tell whether a record comes from a ray generation, closest-hit, or miss shader.

The access record holds the instruction number in a field of 24 bits. A larger number overflows into the adjacent fields of the record.

PIX receives records for helper functions, and each record carries a pipeline stage. A tool that filtered out records with the Library kind will see more data.

Assisted-by: Copilot

This changes only the PIX instrumentation, so it needs no release note.

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Copilot

Pull request overview

Attributes PIX resource-access records in library helpers to their reaching shader entry-point kind and prevents instruction ordinals from corrupting adjacent record fields.

Changes:

Resolves shader kinds through the library call graph.
Masks instruction ordinals to 24 bits.
Adds library-helper and bindless-access tests.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
`lib/DxilPIXPasses/DxilShaderAccessTracking.cpp`	Adds shader-kind propagation and safe record encoding.
`tools/clang/test/HLSLFileCheck/pix/AccessTrackingLibHelperShaderKind.hlsl`	Verifies ray-generation encoding in a helper.
`tools/clang/unittests/HLSL/PixTest.cpp`	Adds instrumentation and validation tests.

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+      auto emplaced =
+          functionToShaderKind.emplace(reached, entryPointShaderKind);
+      if (!emplaced.second && emplaced.first->second != entryPointShaderKind) {
+        emplaced.first->second = ambiguousShaderKind;
+      }


+      uint32_t value =
+          static_cast<uint32_t>(strtoul(line.c_str() + position, &end, 10));


+      constexpr uint32_t InstructionOrdinalMask = 0x00FF'FFFF;
+      uint32_t EncodedInstructionNumber =
+          (InstructionNumber & InstructionOrdinalMask) |


Copilot

Copilot review overview

🟡 Changes recommended

Core overflow and multi-stage ambiguity behaviors need direct regression coverage.

Review effort: Balanced
Findings: 2 · 2

Open (4)

The 24-bit truncation has no boundary regression test: both new tests use ordinary…
No test exercises this ambiguity path. Please add a library where differently typed entry points…
Use explicit ConstantInt pointer type · New
This introduces strtoul without directly including its declaring standard header. Add <cstdlib>…

+      auto *EncodedShaderKindConstant = cast<ConstantInt>(
+          m_FunctionToEncodedAccess.at(Builder.GetInsertBlock()->getParent())
+              .at(ResourceAccessStyle::None));


Copilot

Copilot review overview

🟡 Changes recommended

The call-graph traversal has scalability concerns and key boundary and ambiguity behavior lacks regression coverage.

Review effort: Balanced
Findings: 3 · 4

Open (7)

Avoid rescanning shared helper subtrees per shader export · New
The 24-bit truncation has no boundary regression test: both new tests use ordinary…
No test exercises this ambiguity path. Please add a library where differently typed entry points…
Spell out CallInst pointer type · New
Spell out string loop element type · New
Use explicit ConstantInt pointer type
This introduces strtoul without directly including its declaring standard header. Add <cstdlib>…

+  for (llvm::Function *entryPoint : entryPoints) {
+    if (entryPoint == nullptr || entryPoint->isDeclaration()) {
+      continue;
+    }
+
+    const DXIL::ShaderKind entryPointShaderKind =
+        PIXPassHelpers::GetFunctionShaderKind(DM, entryPoint);
+
+    std::vector<llvm::Function *> pending{entryPoint};
+    std::set<llvm::Function *> visited;
+    while (!pending.empty()) {


+
+      for (llvm::BasicBlock &block : reached->getBasicBlockList()) {
+        for (llvm::Instruction &instruction : block.getInstList()) {
+          auto *call = llvm::dyn_cast<llvm::CallInst>(&instruction);


+static bool
+HasBufferStoreValueMatchingMask(std::vector<std::string> const &lines,
+                                uint32_t mask, uint32_t maskedValue) {
+  for (auto const &line : lines) {


Copilot

Copilot review overview

🟡 Changes recommended

The multi-stage ambiguity path needs regression coverage, and several declarations violate the explicit-type convention.

Review effort: Balanced
Findings: 3 · 5

Open (8)

Avoid rescanning shared helper subtrees per shader export
The 24-bit truncation has no boundary regression test: both new tests use ordinary…
No test exercises this ambiguity path. Please add a library where differently typed entry points…
Use explicit function-pointer vector return type · New
Spell out string loop element type
Spell out CallInst pointer type
Use explicit ConstantInt pointer type
This introduces strtoul without directly including its declaring standard header. Add <cstdlib>…

    auto instrumentableFunctions =
        PIXPassHelpers::GetAllInstrumentableFunctions(DM);


Copilot

Copilot review overview

🟡 Changes recommended

Library hull patch-constant functions are omitted as traversal roots and remain incorrectly attributed as Library.

Review effort: Balanced
Findings: 4 · 6

Open (10)

Include hull patch-constant functions in exported function traversal · New
Avoid rescanning shared helper subtrees per shader export
The 24-bit truncation has no boundary regression test: both new tests use ordinary…
No test exercises this ambiguity path. Please add a library where differently typed entry points…
Use the short explicit result type · New
Use explicit function-pointer vector return type
Spell out string loop element type
Spell out CallInst pointer type
Use explicit ConstantInt pointer type
This introduces strtoul without directly including its declaring standard header. Add <cstdlib>…

+  std::map<llvm::Function *, DXIL::ShaderKind> functionToShaderKind;
+
+  const DXIL::ShaderKind ambiguousShaderKind = DM.GetShaderModel()->GetKind();
+  auto entryPoints = DM.GetExportedFunctions();


+      auto *EncodedShaderKindConstant = cast<ConstantInt>(
+          m_FunctionToEncodedAccess.at(Builder.GetInsertBlock()->getParent())
+              .at(ResourceAccessStyle::None));


Attribute accesses in library helper functions to the pipeline stage of the entry points that reach them instead of the Library kind, and keep instruction numbers from overflowing the 24-bit record field. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 40dc9de3-617e-4caf-ab0d-fba0a033ed93

Copilot

Copilot review overview

🟡 Changes recommended

Library hull patch-constant functions remain incorrectly attributed to the Library shader kind.

Review effort: Balanced
Findings: 4 · 8

Open (12)

Include hull patch-constant functions in exported function traversal
Avoid rescanning shared helper subtrees per shader export
The 24-bit truncation has no boundary regression test: both new tests use ordinary…
No test exercises this ambiguity path. Please add a library where differently typed entry points…
Use explicit map type instead of auto · New
Use explicit types instead of auto in test helpers · New
Use the short explicit result type
Use explicit function-pointer vector return type
Spell out string loop element type
Spell out CallInst pointer type
Use explicit ConstantInt pointer type
This introduces strtoul without directly including its declaring standard header. Add <cstdlib>…

    auto instrumentableFunctions =
        PIXPassHelpers::GetAllInstrumentableFunctions(DM);

+    auto functionToShaderKind = ResolveShaderKindByReachingEntryPoint(DM);


+  auto compiled = Compile(m_dllSupport, hlsl, L"lib_6_6", {L"-Od"});
+  auto output = RunShaderAccessTrackingPass(compiled, L".0;0;0.");
+  auto lines = Split(Disassemble(output.blob), '\n');


github-project-automation Bot added this to HLSL Roadmap Aug 27, 2026

github-project-automation Bot moved this to New in HLSL Roadmap Aug 27, 2026

Damyan Pepper (damyanp) requested a review from Austin Kinross (austinkinross) August 27, 2026 23:41

Damyan Pepper (damyanp) marked this pull request as ready for review August 27, 2026 23:42

Copilot AI balanced review requested due to automatic review settings August 27, 2026 23:42

Copilot started reviewing on behalf of Damyan Pepper (damyanp) August 27, 2026 23:43 View session

Austin Kinross (austinkinross) approved these changes Aug 27, 2026

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Copilot AI reviewed Aug 27, 2026

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Copilot AI review requested due to automatic review settings September 29, 2026 02:56

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 29, 2026 02:57 View session

Copilot AI reviewed Sep 29, 2026

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Comment thread lib/DxilPIXPasses/DxilShaderAccessTracking.cpp

Comment on lines +551 to +553

auto *EncodedShaderKindConstant = cast<ConstantInt>(

m_FunctionToEncodedAccess.at(Builder.GetInsertBlock()->getParent())

.at(ResourceAccessStyle::None));

Copilot AI review requested due to automatic review settings September 29, 2026 16:29

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 29, 2026 16:30 View session

Copilot AI reviewed Sep 29, 2026

View reviewed changes

Copilot AI balanced review requested due to automatic review settings September 30, 2026 00:06

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 30, 2026 00:07 View session

Copilot AI reviewed Sep 30, 2026

View reviewed changes

Comment thread lib/DxilPIXPasses/DxilShaderAccessTracking.cpp

Comment on lines 910 to 911

auto instrumentableFunctions =

PIXPassHelpers::GetAllInstrumentableFunctions(DM);

Copilot AI balanced review requested due to automatic review settings October 1, 2026 22:00

Damyan Pepper (damyanp) force-pushed the users/damyanp/pix-fixes-08 branch from 9370fe9 to 7acdd2b Compare October 1, 2026 22:00

Copilot started reviewing on behalf of Damyan Pepper (damyanp) October 1, 2026 22:01 View session

Copilot AI reviewed Oct 1, 2026

View reviewed changes

Copilot AI balanced review requested due to automatic review settings October 1, 2026 23:11

Damyan Pepper (damyanp) force-pushed the users/damyanp/pix-fixes-08 branch from 7acdd2b to 379abfc Compare October 1, 2026 23:11

Copilot started reviewing on behalf of Damyan Pepper (damyanp) October 1, 2026 23:11 View session

Copilot AI reviewed Oct 1, 2026

View reviewed changes

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[PIX] Attribute library accesses to reaching entry points - #8849

[PIX] Attribute library accesses to reaching entry points#8849
Damyan Pepper (damyanp) wants to merge 1 commit into
users/damyanp/pix-fixes-07from
users/damyanp/pix-fixes-08

Damyan Pepper (damyanp) commented Aug 27, 2026 •

edited

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		uint32_t value =
		static_cast<uint32_t>(strtoul(line.c_str() + position, &end, 10));

		auto instrumentableFunctions =
		PIXPassHelpers::GetAllInstrumentableFunctions(DM);

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Damyan Pepper (damyanp) commented Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Damyan Pepper (damyanp) commented Aug 27, 2026 •

edited

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