IndVarSimplify: preserve debug information attached to widened PHI nodes.

This fixes PR35015.

https://bugs.llvm.org/show_bug.cgi?id=35015

Differential Revision: https://reviews.llvm.org/D39345

llvm-svn: 317282

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index 9ce42a06825..abb50f27f1c 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -48,6 +48,7 @@
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
@@ -1624,6 +1625,15 @@ PHINode *WidenIV::createWideIV(SCEVExpander &Rewriter) {
     if (DU.NarrowDef->use_empty())
       DeadInsts.emplace_back(DU.NarrowDef);
   }
+
+  // Attach any debug information to the new PHI. Since OrigPhi and WidePHI
+  // evaluate the same recurrence, we can just copy the debug info over.
+  SmallVector<DbgValueInst *, 1> DbgValues;
+  llvm::findDbgValues(DbgValues, OrigPhi);
+  auto *MDPhi = MetadataAsValue::get(WidePhi->getContext(),
+                                     ValueAsMetadata::get(WidePhi));
+  for (auto &DbgValue : DbgValues)
+    DbgValue->setOperand(0, MDPhi);
   return WidePhi;
 }