If llvm.dbg.value and the value instruction it refers to are far apart then iSel may not be able to find corresponding Node for llvm.dbg.value during DAG construction. Make iSel's life easier by removing this distance between llvm.dbg.value and its value instruction.

llvm-svn: 132151

1 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 483bfe36552..7ba92ba2565 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -548,7 +548,19 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
 
   // From here on out we're working with named functions.
   if (CI->getCalledFunction() == 0) return false;
-  
+
+  // llvm.dbg.value is far away from the value then iSel may not be able
+  // handle it properly. iSel will drop llvm.dbg.value if it can not 
+  // find a node corresponding to the value.
+  if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(CI))
+    if (Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue()))
+      if (DVI->getParent() != VI->getParent() || DT->dominates(DVI, VI)) {
+        DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI);
+        DVI->removeFromParent();
+        DVI->insertAfter(VI);
+        return true;
+      }
+
   // We'll need TargetData from here on out.
   const TargetData *TD = TLI ? TLI->getTargetData() : 0;
   if (!TD) return false;