AMDGPU/SI: Detect uniform branches and emit s_cbranch instructions

Reviewers: arsenm

Subscribers: mareko, MatzeB, qcolombet, arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D16603

llvm-svn: 260765

1 files changed, 17 insertions, 1 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp b/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
index dfddc345f28..673066aeec3 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
@@ -43,6 +43,7 @@ public:
     AU.setPreservesAll();
  }
 
+  void visitBranchInst(BranchInst &I);
   void visitLoadInst(LoadInst &I);
 
 };
@@ -57,13 +58,28 @@ INITIALIZE_PASS_END(AMDGPUAnnotateUniformValues, DEBUG_TYPE,
 
 char AMDGPUAnnotateUniformValues::ID = 0;
 
+static void setUniformMetadata(Instruction *I) {
+  I->setMetadata("amdgpu.uniform", MDNode::get(I->getContext(), {}));
+}
+
+void AMDGPUAnnotateUniformValues::visitBranchInst(BranchInst &I) {
+  if (I.isUnconditional())
+    return;
+
+  Value *Cond = I.getCondition();
+  if (!DA->isUniform(Cond))
+    return;
+
+  setUniformMetadata(I.getParent()->getTerminator());
+}
+
 void AMDGPUAnnotateUniformValues::visitLoadInst(LoadInst &I) {
   Value *Ptr = I.getPointerOperand();
   if (!DA->isUniform(Ptr))
     return;
 
   if (Instruction *PtrI = dyn_cast<Instruction>(Ptr))
-    PtrI->setMetadata("amdgpu.uniform", MDNode::get(I.getContext(), {}));
+    setUniformMetadata(PtrI);
 
 }