Propagate DebugLocs on phis in BreakCriticalEdges

Author: OCHyams

llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp

@@ -445,13 +445,16 @@ bool llvm::SplitIndirectBrCriticalEdges(Function &F,
       PHINode *NewIndPHI = PHINode::Create(IndPHI->getType(), 1, "ind", InsertPt);
       NewIndPHI->addIncoming(IndPHI->getIncomingValueForBlock(IBRPred),
                              IBRPred);
+      NewIndPHI->setDebugLoc(IndPHI->getDebugLoc());
 
       // Create a PHI in the body block, to merge the direct and indirect
       // predecessors.
       PHINode *MergePHI = PHINode::Create(IndPHI->getType(), 2, "merge");
       MergePHI->insertBefore(MergeInsert);
       MergePHI->addIncoming(NewIndPHI, Target);
       MergePHI->addIncoming(DirPHI, DirectSucc);
+      MergePHI->applyMergedLocation(DirPHI->getDebugLoc(),
+                                    IndPHI->getDebugLoc());
 
       IndPHI->replaceAllUsesWith(MergePHI);
       IndPHI->eraseFromParent();

llvm/test/Transforms/CodeGenPrepare/X86/split-dbg.ll

@@ -0,0 +1,49 @@
+; RUN: opt -passes='require<profile-summary>,function(codegenprepare)' -S -mtriple=x86_64 < %s \
+; RUN: | FileCheck %s
+
+;; Check debug locations are propagated onto new PHIs.
+
+; CHECK: .split:
+; CHECK-NEXT: %merge = phi i32 [ poison, %while.body ], [ %dest.sroa.clone, %while.body.clone ], !dbg [[DBG:!.*]]
+
+; CHECK: while.body.clone:
+; CHECK-NEXT: %dest.sroa.clone = phi i32 [ %1, %.split ], [ poison, %if.else ], !dbg [[DBG]]
+
+define void @test(i1 %c) !dbg !5 {
+entry:
+  br label %if.else
+
+if.else:                                          ; preds = %if.else1, %entry
+  br i1 %c, label %while.body, label %preheader
+
+preheader:                                        ; preds = %if.else
+  br label %if.else1
+
+if.then:                                          ; preds = %if.else1
+  unreachable
+
+while.body:                                       ; preds = %if.else1, %while.body, %if.else
+  %dest.sroa = phi i32 [ %1, %while.body ], [ poison, %if.else1 ], [ poison, %if.else ], !dbg !8
+  %0 = inttoptr i32 %dest.sroa to ptr
+  %incdec.ptr = getelementptr inbounds i8, ptr %0, i32 -1
+  %1 = ptrtoint ptr %incdec.ptr to i32
+  store i8 0, ptr %incdec.ptr, align 1
+  br label %while.body
+
+if.else1:                                         ; preds = %if.else1, %preheader
+  indirectbr ptr poison, [label %if.then, label %while.body, label %if.else, label %if.else1]
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "test.ll", directory: "/")
+!2 = !{i32 11}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "test", linkageName: "test", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !DILocation(line: 1, column: 1, scope: !5)