Fix crash when heap subscript result is discarded - #8749
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Chris B (llvm-beanz) wants to merge 3 commits into
Open
Fix crash when heap subscript result is discarded#8749Chris B (llvm-beanz) wants to merge 3 commits into
Chris B (llvm-beanz) wants to merge 3 commits into
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Without this change DXC crashes if the result of a descriptor heap subscript is discarded. The crash is caused by not correctly handling lifetime marker intrinsics when rewriting resources that otherwise have no uses. The fix here ignores bitcasts to i8* which are associated with lifetime markers when rewriting resource accesses. This fix is a targeted "avoid the crash" fix, rather than wholistic since this rewriting _really_ shouldn't be happening at the end of IR generation, it should likely be in a separate IR pass. Assisted by: Copilot, Claude Sonnet 5. ../tools/clang/test/CodeGenDXIL/discarded_dynamic_res.hlsl
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Pull request overview
Prevents DXC from crashing when discarded descriptor-heap subscripts leave lifetime-marker-only resource uses.
Changes:
- Preserves lifetime-marker bitcasts during resource rewriting.
- Adds regression coverage for resource and sampler heaps.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
tools/clang/lib/CodeGen/CGHLSLMSFinishCodeGen.cpp |
Handles lifetime-only bitcasts safely. |
tools/clang/test/CodeGenDXIL/discarded_dynamic_res.hlsl |
Tests discarded heap subscript expressions. |
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| // later legalization passes (which already know how to handle | ||
| // bitcasts that are onlyUsedByLifetimeMarkers) will clean them up | ||
| // once resPtr has no other real uses. | ||
| if (BCI->getType()->getPointerElementType()->isIntegerTy(8)) { |
Damyan Pepper (damyanp)
approved these changes
Aug 10, 2026
Joshua Batista (bob80905)
approved these changes
Aug 10, 2026
Joshua Batista (bob80905)
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Joshua Batista (bob80905)
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LGTM. Only nit is that the comments could be seen as verbose.
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Pull request overview
Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.
Suppressed comments (1)
docs/ReleaseNotes.md:35
CONTRIBUTING.md:136-140requires release-note entries to be a single sentence and not link to specific PRs. This entry uses two sentences and links to a discussion on PR #8517; please condense it and remove the PR link.
- Fix a crash generating DXIL from sources containing a dynamic resource heap
access that was discarded. Identified during development of SPIR-V support for
[descriptor heaps](https://github.com/microsoft/DirectXShaderCompiler/pull/8517#discussion_r3752113078).
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Without this change DXC crashes if the result of a descriptor heap subscript is discarded. The crash is caused by not correctly handling lifetime marker intrinsics when rewriting resources that otherwise have no uses.
The fix here ignores bitcasts to i8* which are associated with lifetime markers when rewriting resource accesses.
This fix is a targeted "avoid the crash" fix, rather than wholistic since this rewriting really shouldn't be happening at the end of IR generation, it should likely be in a separate IR pass.
Assisted by: Copilot, Claude Sonnet 5.