[DebugInfo][LoopVectorize] Preserve DL in generated phi instruction

When creating `phi` instructions to resume at the scalar part of the loop,
copy the DebugLoc from the original phi over to the new one.

Differential Revision: https://reviews.llvm.org/D48769

llvm-svn: 336256

lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -2912,6 +2912,8 @@ BasicBlock *InnerLoopVectorizer::createVectorizedLoopSkeleton() {
     // Create phi nodes to merge from the  backedge-taken check block.
     PHINode *BCResumeVal = PHINode::Create(
         OrigPhi->getType(), 3, "bc.resume.val", ScalarPH->getTerminator());
+    // Copy original phi DL over to the new one.
+    BCResumeVal->setDebugLoc(OrigPhi->getDebugLoc());
     Value *&EndValue = IVEndValues[OrigPhi];
     if (OrigPhi == OldInduction) {
       // We know what the end value is.

test/Transforms/LoopVectorize/preserve-dbg-loc-and-loop-metadata.ll

@@ -1,10 +1,14 @@
 ; RUN: opt < %s -loop-vectorize -S 2>&1 | FileCheck %s
+; RUN: opt < %s -debugify -loop-vectorize -S | FileCheck %s -check-prefix DEBUGLOC
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; This test makes sure we don't duplicate the loop vectorizer's metadata
 ; while marking them as already vectorized (by setting width = 1), even
 ; at lower optimization levels, where no extra cleanup is done
 
+; DEBUGLOC-LABEL: define void @_Z3fooPf(
+; Check that the phi to resume the scalar part of the loop
+; has Debug Location.
 define void @_Z3fooPf(float* %a) {
 entry:
   br label %for.body
@@ -19,6 +23,11 @@ for.body:                                         ; preds = %for.body, %entry
   %exitcond = icmp eq i64 %indvars.iv.next, 1024
   br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
 
+; DEBUGLOC: scalar.ph:
+; DEBUGLOC-NEXT:    %bc.resume.val = phi {{.*}} !dbg ![[DbgLoc:[0-9]+]]
+;
+; DEBUGLOC: ![[DbgLoc]] = !DILocation(line: 2
+
 for.end:                                          ; preds = %for.body
   ret void
 }