[BDCE] Salvage debug info from dying insts

This results in 15 additional unique source variables in a stage2 build
of FileCheck (at '-Os -g'), with a negligible increase in the size of
the .debug_loc section.

llvm-svn: 325660

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/BDCE.cpp b/llvm/lib/Transforms/Scalar/BDCE.cpp
index 851efa000f6..8a6f7978ad3 100644
--- a/llvm/lib/Transforms/Scalar/BDCE.cpp
+++ b/llvm/lib/Transforms/Scalar/BDCE.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "bdce"
@@ -114,6 +115,7 @@ static bool bitTrackingDCE(Function &F, DemandedBits &DB) {
     if (!DB.isInstructionDead(&I))
       continue;
 
+    salvageDebugInfo(I);
     Worklist.push_back(&I);
     I.dropAllReferences();
     Changed = true;