[SPIRV] Emit DebugLexicalScope for forloop controls (#8514)

[Steve Urquhart (SteveUrquhart)]

Adds missing DebugLexicalScope to for-loops, fixes #8514

[Damyan Pepper (damyanp)]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

This PR updates the SPIR-V emitter’s rich debug info generation to introduce an additional lexical scope for for loop controls (the for (<init>; <cond>; <inc>) region), addressing missing scope nesting reported in #8514 and updating FileCheck expectations accordingly.

Changes:

• Emit an extra DebugLexicalBlock for for loop controls and push/pop it during ForStmt emission.
• Update rich debug scope expectations so %for_check, %for_continue, and %for_merge use the new controls lexical scope.
• Refresh DebugLexicalBlock expectations in related SPIR-V debug-info tests (line/column and parent-scope relationships).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tools/clang/test/CodeGenSPIRV/shader.debug.debuglexicalblock.hlsl	Updates NS100 debug lexical block expectations to include a separate for controls lexical scope.
tools/clang/test/CodeGenSPIRV/rich.debug.debugscope.hlsl	Updates rich debug scope expectations for for blocks/labels to reference the new controls scope.
tools/clang/test/CodeGenSPIRV/rich.debug.debuglexicalblock.hlsl	Updates rich debug lexical block expectations to include the new for controls lexical scope.
tools/clang/lib/SPIRV/SpirvEmitter.cpp	Adds push/pop of a new debug lexical scope around for loop emission when rich debug info is enabled.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Steve Urquhart (SteveUrquhart)]

I addressed the points raised by CoPilot.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[Steve Urquhart (SteveUrquhart)]

I accepted the nit, requiring reapproval. Sorry about the noise.

[Steve Urquhart (SteveUrquhart)]

Hi Chris B (@llvm-beanz), can we please merge this?

[Gregory Roth (pow2clk)]

/azp run

[azure-pipelines]

Azure Pipelines:
Successfully started running 1 pipeline(s).

[Damyan Pepper (damyanp)]

[Auto-generated note from Damyan Pepper (@damyanp)]

Did you consider adding a release note?

Per our CONTRIBUTING guidance, user-visible bug fixes and new features usually need an entry in docs/ReleaseNotes.md. If this PR is part of a larger multi-PR effort, a single shared release note across that effort is totally fine.