[llvm] AMDGPU/UniformityAnalysis: For G_AMDGPU_WHOLE_WAVE_FUNC_SETUP, always divergent (PR #203000)

[via llvm-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Petar Avramovic (petar-avramovic)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/203000.diff


2 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/SIInstrInfo.cpp (+4) 
- (added) llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform-gmir.mir (+13) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index b4fa13c8ebae3..cf19ef63dce31 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -10992,6 +10992,10 @@ SIInstrInfo::getGenericValueUniformity(const MachineInstr &MI) const {
   if (Opcode == TargetOpcode::G_DYN_STACKALLOC)
     return ValueUniformity::AlwaysUniform;
 
+  if (Opcode == AMDGPU::G_AMDGPU_WHOLE_WAVE_FUNC_SETUP) {
+    return ValueUniformity::NeverUniform;
+  }
+
   return ValueUniformity::Default;
 }
 
diff --git a/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform-gmir.mir b/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform-gmir.mir
new file mode 100644
index 0000000000000..e59410179b526
--- /dev/null
+++ b/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform-gmir.mir
@@ -0,0 +1,13 @@
+# RUN: llc -mtriple=amdgcn-- -run-pass=print-machine-uniformity -o - %s 2>&1 | FileCheck %s
+# RUN: llc -mtriple=amdgcn-- -passes='print<machine-uniformity>' -filetype=null %s 2>&1 | FileCheck %s
+
+# whole wave func setup (original exec mask) is a divergence source
+---
+name:            whole_wave_func_setup
+body:             |
+  bb.0:
+    ; CHECK-LABEL: MachineUniformityInfo for function:  @whole_wave_func_setup
+    ; CHECK: DIVERGENT: %0: %0:_(s1) = G_AMDGPU_WHOLE_WAVE_FUNC_SETUP
+    %0:_(s1) = G_AMDGPU_WHOLE_WAVE_FUNC_SETUP
+    G_AMDGPU_WHOLE_WAVE_FUNC_RETURN %0(s1)
+...

``````````

</details>


https://github.com/llvm/llvm-project/pull/203000