loop-rotate: avoid duplicating dbg.value intrinsics in the entry block.

This fixes the second half of PR35113.

llvm-svn: 317106

2 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 8581198cc7d..2f8dfaee7c5 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -25,6 +25,7 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/CFG.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IntrinsicInst.h"
@@ -307,6 +308,22 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
   // For the rest of the instructions, either hoist to the OrigPreheader if
   // possible or create a clone in the OldPreHeader if not.
   TerminatorInst *LoopEntryBranch = OrigPreheader->getTerminator();
+
+  // Record all debug intrinsics preceding LoopEntryBranch to avoid duplication.
+  using DbgIntrinsicHash =
+      std::pair<std::pair<Value *, DILocalVariable *>, DIExpression *>;
+  auto makeHash = [](DbgInfoIntrinsic *D) -> DbgIntrinsicHash {
+    return {{D->getVariableLocation(), D->getVariable()}, D->getExpression()};
+  };
+  SmallDenseSet<DbgIntrinsicHash, 8> DbgIntrinsics;
+  for (auto I = std::next(OrigPreheader->rbegin()), E = OrigPreheader->rend();
+       I != E; ++I) {
+    if (auto *DII = dyn_cast<DbgInfoIntrinsic>(&*I))
+      DbgIntrinsics.insert(makeHash(DII));
+    else
+      break;
+  }
+
   while (I != E) {
     Instruction *Inst = &*I++;
 
@@ -330,6 +347,13 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
     RemapInstruction(C, ValueMap,
                      RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 
+    // Avoid inserting the same intrinsic twice.
+    if (auto *DII = dyn_cast<DbgInfoIntrinsic>(C))
+      if (DbgIntrinsics.count(makeHash(DII))) {
+        C->deleteValue();
+        continue;
+      }
+
     // With the operands remapped, see if the instruction constant folds or is
     // otherwise simplifyable.  This commonly occurs because the entry from PHI
     // nodes allows icmps and other instructions to fold.
diff --git a/llvm/test/Transforms/LoopRotate/dbg-value-duplicates.ll b/llvm/test/Transforms/LoopRotate/dbg-value-duplicates.ll
index ad47cbfb55b..10c708e7e1f 100644
--- a/llvm/test/Transforms/LoopRotate/dbg-value-duplicates.ll
+++ b/llvm/test/Transforms/LoopRotate/dbg-value-duplicates.ll
@@ -10,6 +10,8 @@ entry:
   call void @llvm.dbg.value(metadata i64 %n, metadata !16, metadata !DIExpression()), !dbg !21
   call void @llvm.dbg.value(metadata i64 %s, metadata !17, metadata !DIExpression()), !dbg !22
   call void @llvm.dbg.value(metadata i64 0, metadata !18, metadata !DIExpression()), !dbg !23
+  ; CHECK:   call void @llvm.dbg.value(metadata i64 0, metadata !18, metadata !DIExpression()), !dbg !23
+  ; CHECK-NOT:   call void @llvm.dbg.value(metadata i64 0, metadata !18, metadata !DIExpression()), !dbg !23
   br label %for.cond, !dbg !24
 
 for.cond:                                         ; preds = %for.body, %entry