Update phis in AMDGPUUnifyDivergentExitNodes

Original patch https://reviews.llvm.org/D63659 from
Steven Perron <stevenperron@google.com>

The pass AMDGPUUnifyDivergentExitNodes does not update the phi nodes in
the successors of blocks that is splits. This is fixed by calling
BasicBlock::splitBasicBlock to split the block instead of doing it
manually. This does extra work because a new conditional branch is
created in BB which is immediately replaced, but I think the simplicity
is worth it. It also helps make the code more future proof in case other
things need to be updated.

llvm-svn: 364342

1 files changed, 4 insertions, 7 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp b/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp
index 6550dc362b0..396e0ed2e76 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUUnifyDivergentExitNodes.cpp
@@ -198,14 +198,11 @@ bool AMDGPUUnifyDivergentExitNodes::runOnFunction(Function &F) {
         BranchInst::Create(LoopHeaderBB, DummyReturnBB, BoolTrue, BB);
       } else { // Conditional branch.
         // Create a new transition block to hold the conditional branch.
-        BasicBlock *TransitionBB = BasicBlock::Create(F.getContext(),
-                                                      "TransitionBlock", &F);
+        BasicBlock *TransitionBB = BB->splitBasicBlock(BI, "TransitionBlock");
 
-        // Move BI from BB to the new transition block.
-        BI->removeFromParent();
-        TransitionBB->getInstList().push_back(BI);
-
-        // Create a branch that will always branch to the transition block.
+        // Create a branch that will always branch to the transition block and
+        // references DummyReturnBB.
+        BB->getTerminator()->eraseFromParent();
         BranchInst::Create(TransitionBB, DummyReturnBB, BoolTrue, BB);
       }
     }