Index: CodeGen/MachineBlockPlacement.cpp
===================================================================
--- CodeGen/MachineBlockPlacement.cpp
+++ CodeGen/MachineBlockPlacement.cpp
@@ -41,6 +41,7 @@
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachinePostDominators.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/TailDuplicator.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/CommandLine.h"
@@ -2651,8 +2652,9 @@
   bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
                          PassConfig->getEnableTailMerge() &&
                          BranchFoldPlacement;
+  bool isPreRegAlloc = MF.getRegInfo().isSSA();
   // No tail merging opportunities if the block number is less than four.
-  if (MF.size() > 3 && EnableTailMerge) {
+  if (MF.size() > 3 && EnableTailMerge && !isPreRegAlloc) {
     unsigned TailMergeSize = TailDupPlacementThreshold + 1;
     BranchFolder BF(/*EnableTailMerge=*/true, /*CommonHoist=*/false, *MBFI,
                     *MBPI, TailMergeSize);