AMDGPU: test for uniformity of branch instruction, not its condition

Summary:
If a divergent branch instruction is marked as divergent by propagation
rule 2 in DivergencePropagator::exploreSyncDependency() and its condition
is uniform, that branch would incorrectly be assumed to be uniform.

Reviewers: arsenm, tstellar

Reviewed By: arsenm

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D56331

llvm-svn: 350532

2 files changed, 3 insertions, 9 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp b/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
index 4e0cc736bad..f88e3b0dac8 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
@@ -117,14 +117,8 @@ bool AMDGPUAnnotateUniformValues::isClobberedInFunction(LoadInst * Load) {
 }
 
 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) {
diff --git a/llvm/lib/Target/AMDGPU/SIAnnotateControlFlow.cpp b/llvm/lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
index 90f430d5ca4..98e9ea66232 100644
--- a/llvm/lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
+++ b/llvm/lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
@@ -155,7 +155,7 @@ bool SIAnnotateControlFlow::doInitialization(Module &M) {
 /// 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;
 }