[DeadStoreElimination] Salvage debug info from dead insts

According to `llvm-dwarfdump --statistics` this salvages 43 additional
unique source variables in a stage2 build of clang. It increases the
size of the .debug_loc section by 0.002% (or 2864 bytes).

Differential Revision: https://reviews.llvm.org/D43220

llvm-svn: 325035

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 53ceb89d4d0..e6f0bb21dd5 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -115,6 +115,9 @@ deleteDeadInstruction(Instruction *I, BasicBlock::iterator *BBI,
     Instruction *DeadInst = NowDeadInsts.pop_back_val();
     ++NumFastOther;
 
+    // Try to preserve debug information attached to the dead instruction.
+    salvageDebugInfo(*DeadInst);
+
     // This instruction is dead, zap it, in stages.  Start by removing it from
     // MemDep, which needs to know the operands and needs it to be in the
     // function.