[PATCH] D56331: AMDGPU: test for uniformity of branch instruction, not its condition

[Rhys Perry via Phabricator via llvm-commits]

pendingchaos updated this revision to Diff 180477.
pendingchaos added a comment.

Add test.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56331/new/

https://reviews.llvm.org/D56331

Files:
  lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
  lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
  test/CodeGen/AMDGPU/divergent-branch-uniform-condition.ll


Index: test/CodeGen/AMDGPU/divergent-branch-uniform-condition.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AMDGPU/divergent-branch-uniform-condition.ll
@@ -0,0 +1,45 @@
+; RUN: llc -march=amdgcn -mcpu=gfx900 -verify-machineinstrs < %s | FileCheck %s
+
+; This module creates a divergent branch. The branch is marked as divergent by
+; the divergence analysis but the condition is not. This test ensures that the
+; divergence of the branch is tested, not its condition, so that branch is
+; correctly emitted as divergent.
+
+; FUNC-LABEL: {{^}}main:
+; CHECK: v_sqrt_f32_e32
+; CHECK-NEXT: BB0_{{[0-9]+}}:
+; CHECK-NEXT: s_or_b64 exec, exec
+define amdgpu_ps void @main(i32, float) {
+start:
+  %v0 = call float @llvm.amdgcn.interp.p1(float %1, i32 0, i32 0, i32 %0)
+  br label %loop
+
+loop:
+  %v1 = phi i32 [ 0, %main_body ], [ %v5, %endif2 ]
+  %v2 = icmp ugt i32 %v1, 31
+  br i1 %v2, label %if1, label %endif1
+
+if1:
+  %v3 = call float @llvm.sqrt.f32(float %v0)
+  br label %endloop
+
+endif1:
+  %v4 = fcmp ogt float %v0, 0.000000e+00
+  br i1 %v4, label %endloop, label %endif2
+
+endif2:
+  %v5 = add i32 %v1, 1
+  br label %loop
+
+endloop:
+  %v6 = phi float [ %v3, %if1 ], [ 0.0, %endif1 ]
+  call void @llvm.amdgcn.exp.v4f32(i32 0, i32 15, float %v6, float %v6, float %v6, float %v6, i1 true, i1 true)
+  ret void
+}
+
+declare float @llvm.sqrt.f32(float) #1
+declare float @llvm.amdgcn.interp.p1(float, i32, i32, i32) #1
+declare void @llvm.amdgcn.exp.v4f32(i32, i32, float, float, float, float, i1, i1) #0
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }
Index: lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
===================================================================
--- lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
+++ lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
@@ -155,7 +155,7 @@
 /// Is the branch condition uniform or did the StructurizeCFG pass
 /// consider it as such?
 bool SIAnnotateControlFlow::isUniform(BranchInst *T) {
-  return DA->isUniform(T->getCondition()) ||
+  return DA->isUniform(T) ||
          T->getMetadata("structurizecfg.uniform") != nullptr;
 }
 
Index: lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
+++ lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
@@ -117,14 +117,8 @@
 }
 
 void AMDGPUAnnotateUniformValues::visitBranchInst(BranchInst &I) {
-  if (I.isUnconditional())
-    return;
-
-  Value *Cond = I.getCondition();
-  if (!DA->isUniform(Cond))
-    return;
-
-  setUniformMetadata(I.getParent()->getTerminator());
+  if (DA->isUniform(&I))
+    setUniformMetadata(I.getParent()->getTerminator());
 }
 
 void AMDGPUAnnotateUniformValues::visitLoadInst(LoadInst &I) {


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