[llvm-branch-commits] [llvm] [AMDGPU] Push amdgpu-preload-kern-arg-prolog after livedebugvalues (PR #126148)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Scott Linder (slinder1)

<details>
<summary>Changes</summary>

This is effectively a workaround for a bug in livedebugvalues, but seems
to potentially be a general improvement, as BB sections seems like it
could ruin the special 256-byte prelude scheme that
amdgpu-preload-kern-arg-prolog requires anyway. Moving it even later
doesn't seem to have any material impact, and just adds livedebugvalues
to the list of things which no longer have to deal with pseudo
multiple-entry functions.

AMDGPU debug-info isn't supported upstream yet, so the bug being avoided
isn't testable here. I am posting the patch upstream to avoid an
unnecessary diff with AMD's fork.

---
Full diff: https://github.com/llvm/llvm-project/pull/126148.diff


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp (+6) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
index fffd30b26dc1d5..67b155e4e74001 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -1147,6 +1147,7 @@ class GCNPassConfig final : public AMDGPUPassConfig {
   void addPostRegAlloc() override;
   void addPreSched2() override;
   void addPreEmitPass() override;
+  void addPostBBSections() override;
 };
 
 } // end anonymous namespace
@@ -1686,6 +1687,11 @@ void GCNPassConfig::addPreEmitPass() {
     addPass(&AMDGPUInsertDelayAluID);
 
   addPass(&BranchRelaxationPassID);
+}
+
+void GCNPassConfig::addPostBBSections() {
+  // We run this later to avoid passes like livedebugvalues and BBSections
+  // having to deal with the apparent multi-entry functions we may generate.
   addPass(createAMDGPUPreloadKernArgPrologLegacyPass());
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/126148