[PIX] Inline helper functions before shader debugging by damyanp · Pull Request #8853 · microsoft/DirectXShaderCompiler

Damyan Pepper (damyanp) · 2026-08-28T03:56:37Z

Part 12 of 14 in the PIX instrumentation stack. It targets users/damyanp/pix-fixes-11. Its content depends on PR 10 for the textual-IR test support, and on PR 2.

PIX maps one shader invocation to one record stream in the debug UAV, and one stream to exactly one function. A [noinline] helper instrumented as its own function looks like a second invocation of a thread that runs once. PIX discards those records, and you cannot step into the helper.

The debug instrumentation always emits RawBufferStore. That operation is legal only from shader model 6.2, so shader models 6.0 and 6.1 get an invalid module.

The pass creates the tools UAV before it knows whether there is anything to instrument. A library that contains only helpers therefore gains a UAV although the pass reports that it changed nothing.

Inlining happens before the pass numbers instructions or creates shadow storage. Every prepass does it, so the debug, non-uniform-resource-index, and debug-break pipelines all see the same module shape. A library module is left alone, because each exported function is its own invocation. The runtime invokes the patch-constant function of a hull shader directly. That function therefore survives inlining, and the pass instruments it. The pass selects an invocation of it by primitive alone, because OutputControlPointID is valid only in the control point phase.

A function that survives inlining is named in the pass report as UninlinedFunction:, so PIX does not offer a range with no records. The pass reports it and continues, instead of stopping the process.

Assisted-by: Copilot

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

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Copilot

Pull request overview

Updates PIX instrumentation to inline helper functions, support older shader models, and avoid unnecessary debug UAVs.

Changes:

Inlines non-entry helpers before PIX prepasses and reports survivors.
Instruments hull patch-constant functions.
Uses BufferStore before shader model 6.2 and adds regression coverage.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`tools/clang/unittests/HLSL/PixTest.cpp`	Adds PIX regression tests and helpers.
`tools/clang/test/HLSLFileCheck/pix/NonUniformResourceIndexInHelperFunction.hlsl`	Tests resource indexing after helper inlining.
`tools/clang/test/HLSLFileCheck/pix/DebugStoreOpcodeByShaderModel.hlsl`	Tests store opcode selection.
`tools/clang/test/HLSLFileCheck/pix/DebugNoInlineHelperFunction.hlsl`	Tests debug information after inlining.
`tools/clang/test/HLSLFileCheck/pix/DebugHullPatchConstantFunction.hlsl`	Tests hull patch-constant instrumentation.
`tools/clang/test/HLSLFileCheck/pix/DebugBreakInstrumentationInHelperFunction.hlsl`	Tests debug-break helper inlining.
`lib/DxilPIXPasses/PixPassHelpers.h`	Declares the inlining helper.
`lib/DxilPIXPasses/PixPassHelpers.cpp`	Implements helper inlining and survivor collection.
`lib/DxilPIXPasses/DxilDebugInstrumentation.cpp`	Updates instrumentation targets and store operations.
`lib/DxilPIXPasses/DxilDbgValueToDbgDeclare.cpp`	Runs inlining before shadow-storage generation.
`lib/DxilPIXPasses/DxilAnnotateWithVirtualRegister.cpp`	Runs inlining before annotation and reports survivors.

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+  if (M.HasDxilModule() ||
+      M.getNamedMetadata(hlsl::DxilMDHelper::kDxilVersionMDName) != nullptr) {
+    PIXPassHelpers::InlineNonEntryFunctions(M.GetOrCreateDxilModule());
+  }
+
  auto GlobalEmbeddedArrayStorage = GatherGlobalEmbeddedArrayStorage(M);

  bool Changed = false;


+      // llvm::InlineFunction is the mechanical inliner and ignores inlining
+      // attributes. Clear the attribute so the module carries no claim that
+      // contradicts its own shape.
+      function->removeFnAttr(llvm::Attribute::NoInline);


+  llvm::SmallVector<llvm::Function *, 4> UninlinedFunctions;
+  PIXPassHelpers::InlineNonEntryFunctions(M.GetOrCreateDxilModule(),
+                                          &UninlinedFunctions);


Copilot

Copilot review overview

🟡 Changes recommended

Inlining can produce invalid function attributes and two passes fail to report inlining-only module changes.

Review effort: Balanced
Findings: 1 · 3

Open (4)

Preserve noinline on surviving optnone helpers · New
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…

+      // llvm::InlineFunction is the mechanical inliner and ignores inlining
+      // attributes. Clear the attribute so the module carries no claim that
+      // contradicts its own shape.
+      function->removeFnAttr(llvm::Attribute::NoInline);


Copilot

Copilot review overview

🟡 Changes recommended

Recursive IR can cause unbounded inlining, and two passes incorrectly discard their inlining change status.

Review effort: Balanced
Findings: 2 · 3 · 2

Open (7)

Handle recursive call graphs to prevent nonterminating inlining · New
Preserve noinline on surviving optnone helpers
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Add a release note for the PIX instrumentation fix · New
Use explicit hlsl::DxilResource pointer type · New

+  // HLSL has no recursion, so the call graph is acyclic and inlining leaf-ward
+  // terminates. A fixed-point loop also reaches a helper that loses its last
+  // caller only once another helper is inlined away.
+  bool inlinedACallThisRound = true;
+  while (inlinedACallThisRound) {
+    inlinedACallThisRound = false;


+    // RawBufferStore is only legal from shader model 6.2 onwards. PIX also
+    // instruments 6.0 and 6.1 shaders, so fall back to BufferStore (legal from
+    // 6.0) on those. The two differ only in the trailing alignment operand.
+    const bool SupportsRawBufferStore = BC.DM.GetShaderModel()->IsSM62Plus();


+    return false;
+  }
+
+  auto *uav = PIXPassHelpers::CreateGlobalUAVResource(DM, HLSLBindId, "PIXUAV");


Copilot

Copilot review overview

🟡 Changes recommended

Multiple passes mutate the module without consistently reporting the change, risking stale cached analyses.

Review effort: Balanced
Findings: 2 · 3 · 8

Open (13)

Handle recursive call graphs to prevent nonterminating inlining
Preserve noinline on surviving optnone helpers
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Use the explicit loop element type · New
Use the explicit cast target type · New
Use explicit types instead of auto · New
Use explicit result types instead of auto · New
Spell out CComPtr<IDxcBlob> instead of auto · New
Use explicit result types instead of auto · New
Use explicit hlsl::DxilResource pointer type
Add a release note for the PIX instrumentation fix

+
+  auto *uav = PIXPassHelpers::CreateGlobalUAVResource(DM, HLSLBindId, "PIXUAV");
+  bool modified = false;
+  for (auto *function : functionsToInstrument) {


+      // Collect the call sites first, because inlining rewrites the use list.
+      llvm::SmallVector<llvm::CallInst *, 8> callSites;
+      for (llvm::User *user : function->users()) {
+        if (auto *call = llvm::dyn_cast<llvm::CallInst>(user)) {


+  auto compiled = Compile(m_dllSupport, source, L"lib_6_6", {L"-Od"});
+  CComPtr<IDxcBlob> dxil = FindModule(DFCC_ShaderDebugInfoDXIL, compiled);
+  auto output = RunDebugPass(dxil);


+  auto compiled = Compile(m_dllSupport, kDebugStoreOpcodeComputeShader,
+                          L"cs_6_0", {L"-Od"});
+  auto output = RunDebugPass(compiled);


+  auto compiled =
+      Compile(m_dllSupport, kHullShaderWithHelper, L"hs_6_2", {L"-Od"});


+  auto compiled = Compile(m_dllSupport, source, L"ps_6_0", {L"-Od"});
+  std::string outputText;
+  auto output =
+      RunDxilNonUniformResourceIndexInstrumentation(compiled, outputText);


Copilot

Copilot review overview

🟡 Changes recommended

Several mutation paths incorrectly report no module modification, and the user-visible fixes need release-note coverage.

Review effort: Balanced
Findings: 2 · 3 · 9

Open (14)

Handle recursive call graphs to prevent nonterminating inlining
Preserve noinline on surviving optnone helpers
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Add PIX debugging fixes to the release notes · New
Use explicit result types instead of auto
Spell out CComPtr<IDxcBlob> instead of auto
Use explicit result types instead of auto
Use explicit types instead of auto
Use the explicit cast target type
Use the explicit loop element type
Use explicit hlsl::DxilResource pointer type
Add a release note for the PIX instrumentation fix

+// Inlines each function that the runtime does not invoke into its callers, and
+// erases the inlined-away body.


Copilot

Copilot review overview

🔵 Needs a closer look

Several passes fail to report inlining mutations accurately, survivor attributes are altered incorrectly, and release-note coverage is missing.

Review effort: Balanced
Findings: 2 · 3 · 9

Open (14)

Handle recursive call graphs to prevent nonterminating inlining
Preserve noinline on surviving optnone helpers
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Add PIX debugging fixes to the release notes
Use explicit result types instead of auto
Spell out CComPtr<IDxcBlob> instead of auto
Use explicit result types instead of auto
Use explicit types instead of auto
Use the explicit cast target type
Use the explicit loop element type
Use explicit hlsl::DxilResource pointer type
Add a release note for the PIX instrumentation fix

Previously missed (1)

In code that hasn't changed since last review

Spell out explicit types instead of using type deduction

lib/DxilPIXPasses/DxilDebugInstrumentation.cpp:1356

These three types are short and unambiguous, so type deduction conflicts with the repository's explicit “almost never auto” convention. Spell out the shader-model pointer, shader kind, and binding-index types here.

Copilot

Copilot review overview

🔵 Needs a closer look

Several new inlining paths report no modification despite changing the module, and release-note coverage remains unresolved.

Review effort: Balanced
Findings: 2 · 3 · 9

Open (14)

Handle recursive call graphs to prevent nonterminating inlining
Preserve noinline on surviving optnone helpers
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Add PIX debugging fixes to the release notes
Use explicit result types instead of auto
Spell out CComPtr<IDxcBlob> instead of auto
Use explicit result types instead of auto
Use explicit types instead of auto
Use the explicit cast target type
Use the explicit loop element type
Use explicit hlsl::DxilResource pointer type
Add a release note for the PIX instrumentation fix

Copilot

Copilot review overview

🟡 Changes recommended

Modification reporting, survivor reporting, and release-note coverage need correction before approval.

Review effort: Balanced
Findings: 2 · 4 · 9

Open (15)

Handle recursive call graphs to prevent nonterminating inlining
Preserve noinline on surviving optnone helpers
Populate surviving functions when no entry function exists · New
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Add PIX debugging fixes to the release notes
Use explicit result types instead of auto
Spell out CComPtr<IDxcBlob> instead of auto
Use explicit result types instead of auto
Use explicit types instead of auto
Use the explicit cast target type
Use the explicit loop element type
Use explicit hlsl::DxilResource pointer type
Add a release note for the PIX instrumentation fix

+  if (entryFunction == nullptr) {
+    return false;
+  }


Inline non-entry helpers before numbering so each invocation maps to one function, emit only stores legal for the shader model, avoid creating the tools UAV when nothing is instrumented, instrument hull-shader patch-constant functions, and report functions that survive inlining. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 40dc9de3-617e-4caf-ab0d-fba0a033ed93

Copilot

Copilot review overview

🟡 Changes recommended

Core pass-reporting bugs and numerous unrelated compiler regressions must be resolved before approval.

Review effort: Balanced
Findings: 3 · 11 · 11

Open (25)

Reject LinAlg matrices in unsupported storage contexts · New
Handle recursive call graphs to prevent nonterminating inlining
Preserve noinline on surviving optnone helpers
Preserve invocation counting at zero record capacity · New
Restore HLSL static_assert keyword support · New
Restore default initialization for ExpandTokPastingArg · New
Exclude LinAlgMatrix from numeric aggregate types · New
Restore LinAlg vector compatibility constraints · New
Preserve HLSL 202x const method support · New
Require a digit boundary when matching expected counts · New
Populate surviving functions when no entry function exists
The inliner’s change result is ignored here, while this pass eventually reports only whether a…
Removing NoInline mutates the IR even when no call is inlined and the body survives (for example,…
InlineNonEntryFunctions can rewrite calls and delete helper bodies, but its result is discarded…
Restore Version 1.9.2609 release heading · New
Use explicit llvm::Value pointer declarations · New
Add PIX debugging fixes to the release notes
Use explicit result types instead of auto
Spell out CComPtr<IDxcBlob> instead of auto
Use explicit result types instead of auto

And 5 more that still need to be addressed.

  HLSLExternalSource *Source = HLSLExternalSource::FromSema(&S);
-
-  const Type *CanonTy = Ty.getCanonicalType().getTypePtr();
-  if (CanonTy->isAttributedLinAlgMatrixType() ||
-      CanonTy->isLinAlgMatrixType()) {
-    Empty = false;
-    if (!CheckObjects || AllowLinAlgMatrixInContext(ObjDiagContext))
-      return false;
-    S.Diag(Loc, diag::err_hlsl_unsupported_object_context)
-        << Ty << ObjDiagContextIdx;
-    if (FD)
-      S.Diag(FD->getLocation(), diag::note_field_declared_here)
-          << FD->getType() << FD->getSourceRange();
-    return true;
-  }
-
  ArTypeObjectKind ShapeKind = Source->GetTypeObjectKind(Ty);
  switch (ShapeKind) {


+  // A zero-entry log has no space for records.
+  if (m_MaxNumEntriesInLog == 0) {
+    return false;
+  }


 CXX11_KEYWORD(noexcept              , 0)
 CXX11_KEYWORD(nullptr               , 0)
-CXX11_KEYWORD(static_assert         , KEYHLSL2026) // HLSL Change - 2026 adds static_assert
+CXX11_KEYWORD(static_assert         , 0)


  PreprocessorOptions()
      : UsePredefines(true), DetailedRecord(false),
-        // HLSL Change Begin - ignore line directives.
-        IgnoreLineDirectives(false), ExpandTokPastingArg(false),
-        // HLSL Change End
+        IgnoreLineDirectives(false), // HLSL Change - ignore line directives.
        DisablePCHValidation(false), AllowPCHWithCompilerErrors(false),


  // Chars can only appear as part of strings, which we don't consider numeric.
-  // LinAlg matrix handles are opaque objects, not numeric data.
  const BuiltinType *BuiltinTy = dyn_cast<BuiltinType>(Ty);
  return BuiltinTy != nullptr &&
-         BuiltinTy->getKind() != BuiltinType::Kind::Char_S &&
-         BuiltinTy->getKind() != BuiltinType::Kind::LinAlgMatrix;
+         BuiltinTy->getKind() != BuiltinType::Kind::Char_S;


+template <ComponentEnum DT, typename T, int N>
+InterpretedVector<T, N, DT> MakeInterpretedVector(vector<T, N> Vec) {
+  InterpretedVector<T, N, DT> IV = {Vec};
  return IV;


+        // HLSL Change Starts
+        if (getLangOpts().HLSL) {
+          Diag(DS.getSourceRange().getEnd(),
+               diag::err_hlsl_unsupported_construct)
+              << "qualifiers";
+        }


+  const std::string expectedSuffix = ", " + std::to_string(expectedEntryCount);
+  for (auto const &line : lines) {
+    if (line.find("icmp ult i32 %EntryIndexResult") != std::string::npos &&
+        line.find(expectedSuffix) != std::string::npos) {
+      return true;
    }


 - Fixed an optimizer crash when scalarizing an out-of-bounds vector access
  [#8940](https://github.com/microsoft/DirectXShaderCompiler/issues/8940).
-
-### Upcoming Preview Release
-
-These changes apply to experimental preview shader models only and will not be
-part of the next non-preview release.
-
-#### Experimental Shader Model 6.11
-
- Added experimental Shader Model 6.11 target profiles.
-
-### Version 1.9.2609
-
-#### Bug Fixes
-
 - Fixed derivative operations being moved into divergent control flow, which


+    auto EntryOffset = Builder.CreateMul(
        EntryIndex, HlslOP->GetU32Const(numBytesPerEntry), "EntryOffset");
-    Value *EntryOffsetPlus16 = Builder.CreateAdd(
+    auto EntryOffsetPlus16 = Builder.CreateAdd(
        EntryOffset, HlslOP->GetU32Const(16), "EntryOffsetPlus16");
-    Value *EntryOffsetPlus32 = Builder.CreateAdd(
+    auto EntryOffsetPlus32 = Builder.CreateAdd(
        EntryOffset, HlslOP->GetU32Const(32), "EntryOffsetPlus32");
-    Value *EntryOffsetPlus48 = Builder.CreateAdd(
+    auto EntryOffsetPlus48 = Builder.CreateAdd(


github-project-automation Bot added this to HLSL Roadmap Aug 28, 2026

github-project-automation Bot moved this to New in HLSL Roadmap Aug 28, 2026

Damyan Pepper (damyanp) requested a review from Austin Kinross (austinkinross) August 28, 2026 03:56

Damyan Pepper (damyanp) marked this pull request as ready for review August 28, 2026 03:57

Copilot AI balanced review requested due to automatic review settings August 28, 2026 03:57

Copilot started reviewing on behalf of Damyan Pepper (damyanp) August 28, 2026 03:58 View session

Copilot AI reviewed Aug 28, 2026

View reviewed changes

Austin Kinross (austinkinross) approved these changes Aug 28, 2026

View reviewed changes

Copilot AI review requested due to automatic review settings September 29, 2026 04:04

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 29, 2026 04:05 View session