[DCE] Salvage debug info from dead insts

This results in small increases in the size of the .debug_loc section
and the number of unique source variables in a stage2 build of opt.

llvm-svn: 325301

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/DCE.cpp b/llvm/lib/Transforms/Scalar/DCE.cpp
index fa4806e884c..d8575b71a3c 100644
--- a/llvm/lib/Transforms/Scalar/DCE.cpp
+++ b/llvm/lib/Transforms/Scalar/DCE.cpp
@@ -50,6 +50,7 @@ namespace {
       for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
         Instruction *Inst = &*DI++;
         if (isInstructionTriviallyDead(Inst, TLI)) {
+          salvageDebugInfo(*Inst);
           Inst->eraseFromParent();
           Changed = true;
           ++DIEEliminated;
@@ -76,6 +77,8 @@ static bool DCEInstruction(Instruction *I,
                            SmallSetVector<Instruction *, 16> &WorkList,
                            const TargetLibraryInfo *TLI) {
   if (isInstructionTriviallyDead(I, TLI)) {
+    salvageDebugInfo(*I);
+
     // Null out all of the instruction's operands to see if any operand becomes
     // dead as we go.
     for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {