[AMDGPU] Run `unreachable-mbb-elimination` after isel to clean up PHIs.
Summary:
- As LCSSA is turned on just before isel, it may create PHI of the flow,
which is consumed by pseudo structurized CFG instructions. When that
PHIs are eliminated in O0, COPY may be placed wrongly as the these
pseudo structurized CFG instructions are considering prologue of MBB.
- Run extra `unreachable-mbb-elimination` at the end of isel to clean up
PHIs.
Reviewers: arsenm, rampitec
Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D64353
llvm-svn: 367023
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
index 0ea8db0..5f0c6a7 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -882,6 +882,9 @@
addPass(createSILowerI1CopiesPass());
addPass(createSIFixupVectorISelPass());
addPass(createSIAddIMGInitPass());
+ // FIXME: Remove this once the phi on CF_END is cleaned up by either removing
+ // LCSSA or other ways.
+ addPass(&UnreachableMachineBlockElimID);
return false;
}