[PIX] Record only real resource accesses, including samplers by damyanp · Pull Request #8847 · microsoft/DirectXShaderCompiler

Damyan Pepper (damyanp) · 2026-08-27T23:37:31Z

Part 6 of 14 in the PIX instrumentation stack. It targets users/damyanp/pix-fixes-05. Its content depends on PR 2 for the shared helpers.

The shader access tracking pass records an access for each DXIL operation that takes a resource handle. Two of these operations are not accesses. annotateHandle attaches type information to a handle. barrierByMemoryHandle puts accesses in order. The pass therefore reports a read or a write at a point where the shader touches no memory.

The pass also matches a library handle against the UAVs, the SRVs, and the constant buffers, but not against the samplers. A sampler access in a library shader gets no record, so the sampler binding looks unused.

An access that consumes an annotated handle keeps its record. The pass still looks through the annotation to reach the resource.

PIX receives fewer incorrect records and more sampler records. A tool that counts records will see different totals.

Assisted-by: Copilot

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

_{Stack created with GitHub Stacks CLI • Give Feedback 💬}

Copilot

Pull request overview

Corrects PIX shader access tracking to record genuine resource accesses, including library samplers, while excluding annotations and barriers.

Changes:

Adds sampler matching for library handles.
Excludes AnnotateHandle and resource barriers from access records.
Adds FileCheck and validation coverage.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`lib/DxilPIXPasses/DxilShaderAccessTracking.cpp`	Updates resource matching and non-access exclusions.
`tools/clang/unittests/HLSL/PixTest.cpp`	Extends pass configuration and validation tests.
`tools/clang/test/HLSLFileCheck/pix/AccessTrackingLibAnnotateHandleIsNotAnAccess.hlsl`	Tests annotation exclusion.
`tools/clang/test/HLSLFileCheck/pix/AccessTrackingLibAnnotatedHandleReadStillRecorded.hlsl`	Tests accesses through annotated handles.
`tools/clang/test/HLSLFileCheck/pix/AccessTrackingBarrierIsNotAnAccess.hlsl`	Tests barrier exclusion.

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

+  std::string needle = "i32 " + std::to_string(byteOffset);
+  for (auto const &line : lines) {
+    if (line.find("dx.op.bufferStore") != std::string::npos &&
+        line.find(needle) != std::string::npos) {
+      return true;
+    }
+  }


+  auto compiled = Compile(m_dllSupport, hlsl, L"lib_6_6", {L"-Od"});
+  auto output = RunShaderAccessTrackingPass(
+      compiled, L"S0:0:4i0;M0:20:4i0;U0:40:4i0;.0;0;0.");
+  auto lines = Split(Disassemble(output.blob), '\n');


+})x";
+
+  auto compiled = Compile(m_dllSupport, source, L"ps_6_0", {L"-Od"});
+  auto output = RunShaderAccessTrackingPass(compiled);


+    return textures[index].Sample(samp, pos.xy);
+})x";
+
+  auto compiled = Compile(m_dllSupport, source, L"ps_6_0", {L"-Od"});


+        if (global == Sampler->GetGlobalSymbol()) {
+          binding =
+              hlsl::resource_helper::loadBindingFromResourceBase(Sampler.get());
+          ret.registerType = RegisterType::Sampler;


Copilot

Copilot review overview

🟢 Approval recommended

The focused behavior changes have targeted coverage; remaining feedback is non-blocking style cleanup.

Review effort: Balanced
Findings: 2 · 4

Open (6)

The default pass configuration declares only UAV ranges, but this shader accesses an SRV and a…
This helper does not actually constrain the match to the byte-offset operand: i32 264 in any…
Spell out the inferred types explicitly · New
This changes user-visible PIX access records and fixes sampler bindings being reported as unused,…
Please spell out this simple return type under the repository's almost-never-auto convention;…
Please use explicit types for these straightforward locals under the repository's…

+  auto compiled = Compile(m_dllSupport, source, L"ps_6_0", {L"-Od"});
+  auto output = RunShaderAccessTrackingPass(compiled);


Copilot

Copilot review overview

🟢 Approval recommended

The implementation is focused and adequately tested, with only minor style and spelling feedback outstanding.

Review effort: Balanced
Findings: 2 · 6

Open (8)

The default pass configuration declares only UAV ranges, but this shader accesses an SRV and a…
This helper does not actually constrain the match to the byte-offset operand: i32 264 in any…
Fix misspelling of delimiter · New
Use explicit std::string type instead of auto · New
Spell out the inferred types explicitly
This changes user-visible PIX access records and fixes sampler bindings being reported as unused,…
Please spell out this simple return type under the repository's almost-never-auto convention;…
Please use explicit types for these straightforward locals under the repository's…

  ValidateAccessTrackingMods(hlsl, true);
 }

+std::vector<std::string> Split(std::string str, char delimeter);


+static bool HasBufferStoreWithByteOffset(std::vector<std::string> const &lines,
+                                         unsigned byteOffset) {
+  std::string needle = "i32 " + std::to_string(byteOffset);
+  for (auto const &line : lines) {


Copilot

Copilot review overview

🔵 Needs a closer look

The sampler regression assertion can falsely accept an incorrect byte offset, and new declarations violate the explicit-type convention.

Review effort: Balanced
Findings: 2 · 6

Open (8)

The default pass configuration declares only UAV ranges, but this shader accesses an SRV and a…
This helper does not actually constrain the match to the byte-offset operand: i32 264 in any…
Use explicit std::string type instead of auto
Fix misspelling of delimiter
Spell out the inferred types explicitly
This changes user-visible PIX access records and fixes sampler bindings being reported as unused,…
Please spell out this simple return type under the repository's almost-never-auto convention;…
Please use explicit types for these straightforward locals under the repository's…

Copilot

Copilot review overview

🟢 Approval recommended

The implementation is focused and well tested; the remaining findings are minor explicit-type convention issues.

Review effort: Balanced
Findings: 2 · 6

Open (8)

The default pass configuration declares only UAV ranges, but this shader accesses an SRV and a…
This helper does not actually constrain the match to the byte-offset operand: i32 264 in any…
Use explicit std::string type instead of auto
Fix misspelling of delimiter
Spell out the inferred types explicitly
This changes user-visible PIX access records and fixes sampler bindings being reported as unused,…
Please spell out this simple return type under the repository's almost-never-auto convention;…
Please use explicit types for these straightforward locals under the repository's…

Shader access tracking no longer records annotateHandle or barrierByMemoryHandle as accesses, still looks through annotated handles to the resource, and matches library handles against samplers so sampler accesses are recorded. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 40dc9de3-617e-4caf-ab0d-fba0a033ed93

Copilot

Copilot review overview

🟢 Approval recommended

The behavioral changes have focused regression coverage; remaining feedback concerns only explicit-type conventions.

Review effort: Balanced
Findings: 2 · 6

Open (8)

The default pass configuration declares only UAV ranges, but this shader accesses an SRV and a…
This helper does not actually constrain the match to the byte-offset operand: i32 264 in any…
Use explicit std::string type instead of auto
Fix misspelling of delimiter
Spell out the inferred types explicitly
This changes user-visible PIX access records and fixes sampler bindings being reported as unused,…
Please spell out this simple return type under the repository's almost-never-auto convention;…
Please use explicit types for these straightforward locals under the repository's…

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 23:37

Damyan Pepper (damyanp) marked this pull request as ready for review August 27, 2026 23:38

Copilot AI balanced review requested due to automatic review settings August 27, 2026 23:38

Copilot started reviewing on behalf of Damyan Pepper (damyanp) August 27, 2026 23:39 View session

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

View reviewed changes

Copilot AI reviewed Aug 27, 2026

View reviewed changes

Copilot AI review requested due to automatic review settings September 29, 2026 02:24

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 29, 2026 02:24 View session

Copilot AI reviewed Sep 29, 2026

View reviewed changes

Comment thread tools/clang/unittests/HLSL/PixTest.cpp

Comment on lines +4894 to +4895

auto compiled = Compile(m_dllSupport, source, L"ps_6_0", {L"-Od"});

auto output = RunShaderAccessTrackingPass(compiled);

Copilot AI review requested due to automatic review settings September 29, 2026 16:26

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 29, 2026 16:27 View session

Copilot AI reviewed Sep 29, 2026

View reviewed changes

Copilot AI balanced review requested due to automatic review settings September 30, 2026 00:03

Copilot started reviewing on behalf of Damyan Pepper (damyanp) September 30, 2026 00:04 View session

Copilot AI reviewed Sep 30, 2026

View reviewed changes

Copilot AI balanced review requested due to automatic review settings October 1, 2026 21:58

Damyan Pepper (damyanp) force-pushed the users/damyanp/pix-fixes-06 branch from 80a9c34 to 79770f0 Compare October 1, 2026 21:58

Copilot started reviewing on behalf of Damyan Pepper (damyanp) October 1, 2026 21:58 View session

Copilot AI reviewed Oct 1, 2026

View reviewed changes

Copilot AI balanced review requested due to automatic review settings October 1, 2026 23:10

Damyan Pepper (damyanp) force-pushed the users/damyanp/pix-fixes-06 branch from 79770f0 to 810a923 Compare October 1, 2026 23:10

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

Navigation Menu

[PIX] Record only real resource accesses, including samplers - #8847

[PIX] Record only real resource accesses, including samplers#8847
Damyan Pepper (damyanp) wants to merge 1 commit into
users/damyanp/pix-fixes-05from
users/damyanp/pix-fixes-06

Damyan Pepper (damyanp) commented Aug 27, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

		auto compiled = Compile(m_dllSupport, source, L"ps_6_0", {L"-Od"});
		auto output = RunShaderAccessTrackingPass(compiled);

Conversation

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

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot review overview

🟢 Approval recommended

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot review overview

🟢 Approval recommended

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot review overview

🔵 Needs a closer look

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot review overview

🟢 Approval recommended

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot review overview

🟢 Approval recommended

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Damyan Pepper (damyanp) commented Aug 27, 2026 •

edited

Loading