revert: "Remove debug location from common tail when tail-merging"

This reverts r285093, as it caused unexpected buildbot failures on
clang-ppc64le-linux, clang-ppc64be-linux, clang-ppc64be-linux-multistage
and clang-ppc64be-linux-lnt.  Failing test ubsan/TestCases/TypeCheck/vptr.cpp.

llvm-svn: 285110

1 files changed, 2 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 20c36a923df..71074513c89 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -720,6 +720,8 @@ bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
     SameTails[commonTailIndex].getTailStartPos();
   MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
 
+  // If the common tail includes any debug info we will take it pretty
+  // randomly from one of the inputs.  Might be better to remove it?
   DEBUG(dbgs() << "\nSplitting BB#" << MBB->getNumber() << ", size "
                << maxCommonTailLength);
 
@@ -896,11 +898,6 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
     // Recompute common tail MBB's edge weights and block frequency.
     setCommonTailEdgeWeights(*MBB);
 
-    // Remove the original debug location from the common tail.
-    for (auto &MI : *MBB)
-      if (!MI.isDebugValue())
-        MI.setDebugLoc(DebugLoc());
-
     // MBB is common tail.  Adjust all other BB's to jump to this one.
     // Traversal must be forwards so erases work.
     DEBUG(dbgs() << "\nUsing common tail in BB#" << MBB->getNumber()