[LoopRotate] Update dbg.value intrinsics

Propagate debug info through the newly inserted PHI nodes.

Differential Revision: https://reviews.llvm.org/D30190


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297132 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LoopRotation.cpp

@@ -79,15 +79,16 @@ class LoopRotate {
 /// to merge the two values.  Do this now.
 static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
                                             BasicBlock *OrigPreheader,
-                                            ValueToValueMapTy &ValueMap) {
+                                            ValueToValueMapTy &ValueMap,
+                                SmallVectorImpl<PHINode*> *InsertedPHIs) {
   // Remove PHI node entries that are no longer live.
   BasicBlock::iterator I, E = OrigHeader->end();
   for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
     PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreheader));
 
   // Now fix up users of the instructions in OrigHeader, inserting PHI nodes
   // as necessary.
-  SSAUpdater SSA;
+  SSAUpdater SSA(InsertedPHIs);
   for (I = OrigHeader->begin(); I != E; ++I) {
     Value *OrigHeaderVal = &*I;
 
@@ -174,6 +175,38 @@ static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
   }
 }
 
+/// Propagate dbg.value intrinsics through the newly inserted Phis.
+static void insertDebugValues(BasicBlock *OrigHeader,
+                              SmallVectorImpl<PHINode*> &InsertedPHIs) {
+  ValueToValueMapTy DbgValueMap;
+
+  // Map existing PHI nodes to their dbg.values.
+  for (auto &I : *OrigHeader) {
+    if (auto DbgII = dyn_cast<DbgInfoIntrinsic>(&I)) {
+      if (isa<PHINode>(DbgII->getVariableLocation()))
+        DbgValueMap.insert({DbgII->getVariableLocation(), DbgII});
+    }
+  }
+
+  // Then iterate through the new PHIs and look to see if they use one of the
+  // previously mapped PHIs. If so, insert a new dbg.value intrinsic that will
+  // propagate the info through the new PHI.
+  LLVMContext &C = OrigHeader->getContext();
+  for (auto PHI : InsertedPHIs) {
+    for (auto VI : PHI->operand_values()) {
+      auto V = DbgValueMap.find(VI);
+      if (V != DbgValueMap.end()) {
+        auto *DbgII = dyn_cast<DbgInfoIntrinsic>(V->second);
+        Instruction *NewDbgII = DbgII->clone();
+        auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
+        NewDbgII->setOperand(0, PhiMAV);
+        BasicBlock *Parent = PHI->getParent();
+        NewDbgII->insertBefore(Parent->getFirstNonPHIOrDbgOrLifetime());
+      }
+    }
+  }
+}
+
 /// Rotate loop LP. Return true if the loop is rotated.
 ///
 /// \param SimplifiedLatch is true if the latch was just folded into the final
@@ -347,9 +380,18 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
   // remove the corresponding incoming values from the PHI nodes in OrigHeader.
   LoopEntryBranch->eraseFromParent();
 
+
+  SmallVector<PHINode*, 2> InsertedPHIs;
   // If there were any uses of instructions in the duplicated block outside the
   // loop, update them, inserting PHI nodes as required
-  RewriteUsesOfClonedInstructions(OrigHeader, OrigPreheader, ValueMap);
+  RewriteUsesOfClonedInstructions(OrigHeader, OrigPreheader, ValueMap,
+                                  &InsertedPHIs);
+
+  // Attach dbg.value intrinsics to the new phis if that phi uses a value that
+  // previously had debug metadata attached. This keeps the debug info
+  // up-to-date in the loop body.
+  if (!InsertedPHIs.empty())
+    insertDebugValues(OrigHeader, InsertedPHIs);
 
   // NewHeader is now the header of the loop.
   L->moveToHeader(NewHeader);

test/Transforms/LoopRotate/phi-dbgvalue.ll

@@ -0,0 +1,79 @@
+; RUN: opt -S -loop-rotate < %s | FileCheck %s
+
+;CHECK-LABEL: func
+;CHECK-LABEL: entry
+;CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 %a
+;CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 1, i64 0, metadata !13, metadata !11), !dbg !15
+;CHECK-LABEL: for.body:
+;CHECK-NEXT: [[I:%.*]] = phi i32 [ 1, %entry ], [ %inc, %for.body ]
+;CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 [[I]], i64 0, metadata !13, metadata !11), !dbg !15
+
+; Function Attrs: noinline nounwind
+define void @func(i32 %a) local_unnamed_addr #0 !dbg !6 {
+entry:
+  tail call void @llvm.dbg.value(metadata i32 %a, i64 0, metadata !10, metadata !11), !dbg !12
+  tail call void @llvm.dbg.value(metadata i32 1, i64 0, metadata !13, metadata !11), !dbg !15
+  br label %for.cond, !dbg !16
+
+for.cond:                                         ; preds = %for.body, %entry
+  %i.0 = phi i32 [ 1, %entry ], [ %inc, %for.body ]
+  tail call void @llvm.dbg.value(metadata i32 %i.0, i64 0, metadata !13, metadata !11), !dbg !15
+  %cmp = icmp slt i32 %i.0, 10, !dbg !17
+  br i1 %cmp, label %for.body, label %for.end, !dbg !20
+
+for.body:                                         ; preds = %for.cond
+  %add = add nsw i32 %i.0, %a, !dbg !22
+  %call = tail call i32 @func2(i32 %i.0, i32 %add) #3, !dbg !24
+  %inc = add nsw i32 %i.0, 1, !dbg !25
+  tail call void @llvm.dbg.value(metadata i32 %inc, i64 0, metadata !13, metadata !11), !dbg !15
+  br label %for.cond, !dbg !27, !llvm.loop !28
+
+for.end:                                          ; preds = %for.cond
+  ret void, !dbg !31
+}
+
+declare i32 @func2(i32, i32) local_unnamed_addr
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #2
+
+attributes #0 = { noinline nounwind }
+attributes #2 = { nounwind readnone }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 5.0.0 (http://llvm.org/git/clang.git 0f3ed908c1f13f83da4b240f7595eb8d05e0a754) (http://llvm.org/git/llvm.git 8e270f5a6b8ceb0f3ac3ef1ffb83c5e29b44ae68)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "debug-phi.c", directory: "/work/projects/src/tests/debug")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!"clang version 5.0.0 (http://llvm.org/git/clang.git 0f3ed908c1f13f83da4b240f7595eb8d05e0a754) (http://llvm.org/git/llvm.git 8e270f5a6b8ceb0f3ac3ef1ffb83c5e29b44ae68)"}
+!6 = distinct !DISubprogram(name: "func", scope: !1, file: !1, line: 2, type: !7, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !8)
+!8 = !{null, !9}
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !DILocalVariable(name: "a", arg: 1, scope: !6, file: !1, line: 2, type: !9)
+!11 = !DIExpression()
+!12 = !DILocation(line: 2, column: 15, scope: !6)
+!13 = !DILocalVariable(name: "i", scope: !14, file: !1, line: 3, type: !9)
+!14 = distinct !DILexicalBlock(scope: !6, file: !1, line: 3, column: 3)
+!15 = !DILocation(line: 3, column: 11, scope: !14)
+!16 = !DILocation(line: 3, column: 7, scope: !14)
+!17 = !DILocation(line: 3, column: 20, scope: !18)
+!18 = !DILexicalBlockFile(scope: !19, file: !1, discriminator: 1)
+!19 = distinct !DILexicalBlock(scope: !14, file: !1, line: 3, column: 3)
+!20 = !DILocation(line: 3, column: 3, scope: !21)
+!21 = !DILexicalBlockFile(scope: !14, file: !1, discriminator: 1)
+!22 = !DILocation(line: 4, column: 15, scope: !23)
+!23 = distinct !DILexicalBlock(scope: !19, file: !1, line: 3, column: 31)
+!24 = !DILocation(line: 4, column: 5, scope: !23)
+!25 = !DILocation(line: 3, column: 27, scope: !26)
+!26 = !DILexicalBlockFile(scope: !19, file: !1, discriminator: 2)
+!27 = !DILocation(line: 3, column: 3, scope: !26)
+!28 = distinct !{!28, !29, !30}
+!29 = !DILocation(line: 3, column: 3, scope: !14)
+!30 = !DILocation(line: 5, column: 3, scope: !14)
+!31 = !DILocation(line: 6, column: 1, scope: !6)