[BranchFolding] skip debug instr to avoid code change

Use the existing helper function in BranchFolding, "countsAsInstruction",
to skip over non-instructions. Otherwise debug instructions can be
identified as the last real instruction in a block, leading to different
codegen decisions when debug is enabled as demonstrated by the test case.

Patch by: yechunliang (Chris Ye)!

Differential Revision: https://reviews.llvm.org/D66467

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 455916e..b6e7c9f4 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -402,11 +402,12 @@ SkipTopCFIAndReturn:
   // the CFI instruction. Later on, this leads to BB2 being 'hacked off' at the
   // wrong place (in ReplaceTailWithBranchTo()) which results in losing this CFI
   // instruction.
-  while (I1 != MBB1->end() && I1->isCFIInstruction()) {
+  // Skip CFI_INSTRUCTION and debugging instruction; necessary to avoid changing the code.
+  while (I1 != MBB1->end() && !countsAsInstruction(*I1)) {
     ++I1;
   }
 
-  while (I2 != MBB2->end() && I2->isCFIInstruction()) {
+  while (I2 != MBB2->end() && !countsAsInstruction(*I2)) {
     ++I2;
   }