[CodeGenPrepare] Preserve debug locs in OptimizeExtractBits

CodeGenPrepare has a transform that sinks {lshr, trunc} pairs to make it
easier for the backend to emit fancy extract-bits instructions (e.g UBFX).

Teach it to preserve debug locations and salvage debug values.

llvm-svn: 342319

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index cf1966f4677..ec4451ffa75 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -1405,6 +1405,7 @@ SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
       else
         InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
                                                    "", &*InsertPt);
+      InsertedShift->setDebugLoc(ShiftI->getDebugLoc());
 
       // Sink the trunc
       BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
@@ -1413,6 +1414,7 @@ SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
 
       InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
                                        TruncI->getType(), "", &*TruncInsertPt);
+      InsertedTrunc->setDebugLoc(TruncI->getDebugLoc());
 
       MadeChange = true;
 
@@ -1504,6 +1506,7 @@ static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI,
       else
         InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
                                                    "", &*InsertPt);
+      InsertedShift->setDebugLoc(ShiftI->getDebugLoc());
 
       MadeChange = true;
     }
@@ -1513,8 +1516,10 @@ static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI,
   }
 
   // If we removed all uses, nuke the shift.
-  if (ShiftI->use_empty())
+  if (ShiftI->use_empty()) {
+    salvageDebugInfo(*ShiftI);
     ShiftI->eraseFromParent();
+  }
 
   return MadeChange;
 }