[DebugInfo][GVNSink] Merging debug locations of sinked instructions (#92859)

Fix #85069 .

3 files changed, 120 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVNSink.cpp b/llvm/lib/Transforms/Scalar/GVNSink.cpp
index b0f716c..3dfa2dd 100644
--- a/llvm/lib/Transforms/Scalar/GVNSink.cpp
+++ b/llvm/lib/Transforms/Scalar/GVNSink.cpp
@@ -921,8 +921,10 @@ void GVNSink::sinkLastInstruction(ArrayRef<BasicBlock *> Blocks,
     }
 
   for (auto *I : Insts)
-    if (I != I0)
+    if (I != I0) {
       I->replaceAllUsesWith(I0);
+      I0->applyMergedLocation(I0->getDebugLoc(), I->getDebugLoc());
+    }
   foldPointlessPHINodes(BBEnd);
 
   // Finally nuke all instructions apart from the common instruction.
diff --git a/llvm/test/Transforms/GVNSink/sink-common-code-dbg.ll b/llvm/test/Transforms/GVNSink/sink-common-code-dbg.ll
new file mode 100644
index 0000000..6f8ca4d
--- /dev/null
+++ b/llvm/test/Transforms/GVNSink/sink-common-code-dbg.ll
@@ -0,0 +1,112 @@
+; RUN: opt < %s -passes=gvn-sink -S | FileCheck %s
+
+; Test that GVNSink correctly merges the debug locations of sinked instruction
+
+define zeroext i1 @test18(i32 %flag, i32 %blksA, i32 %blksB, i32 %nblks) !dbg !5 {
+; CHECK:       if.end:
+; CHECK-NEXT:    [[CMP2_SINK:%.*]] = phi i1 [ %cmp2, %if.then2 ], [ %cmp, %if.then ], [ %cmp3, %if.then3 ]
+; CHECK-NEXT:    [[FROMBOOL4:%.*]] = zext i1 [[CMP2_SINK]] to i8, !dbg [[DBG17:![0-9]+]]
+;
+entry:
+  switch i32 %flag, label %if.then3 [
+  i32 0, label %if.then
+  i32 1, label %if.then2
+  ], !dbg !8
+
+if.then:                                          ; preds = %entry
+  %cmp = icmp uge i32 %blksA, %nblks, !dbg !9
+  %frombool1 = zext i1 %cmp to i8, !dbg !10
+  br label %if.end, !dbg !11
+
+if.then2:                                         ; preds = %entry
+  %add = add i32 %nblks, %blksB, !dbg !12
+  %cmp2 = icmp ule i32 %add, %blksA, !dbg !13
+  %frombool3 = zext i1 %cmp2 to i8, !dbg !14
+  br label %if.end, !dbg !15
+
+if.then3:                                         ; preds = %entry
+  %add2 = add i32 %nblks, %blksA, !dbg !16
+  %cmp3 = icmp ule i32 %add2, %blksA, !dbg !17
+  %frombool4 = zext i1 %cmp3 to i8, !dbg !18
+  br label %if.end, !dbg !19
+
+if.end:                                           ; preds = %if.then3, %if.then2, %if.then
+  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.then2 ], [ %frombool4, %if.then3 ], !dbg !20
+  %tobool4 = icmp ne i8 %obeys.0, 0, !dbg !21
+  ret i1 %tobool4, !dbg !22
+}
+
+define zeroext i1 @test_pr30244(i1 zeroext %flag, i1 zeroext %flag2, i32 %blksA, i32 %blksB, i32 %nblks) !dbg !23 {
+; CHECK:       if.end.gvnsink.split:
+; CHECK-NEXT:    [[CMP2_SINK:%.*]] = phi i1 [ %cmp2, %if.then2 ], [ %cmp, %if.then ]
+; CHECK-NEXT:    [[FROMBOOL1:%.*]] = zext i1 [[CMP2_SINK]] to i8, !dbg [[DBG29:![0-9]+]]
+;
+entry:
+  %p = alloca i8, align 1, !dbg !24
+  br i1 %flag, label %if.then, label %if.else, !dbg !25
+
+if.then:                                          ; preds = %entry
+  %cmp = icmp uge i32 %blksA, %nblks, !dbg !26
+  %frombool1 = zext i1 %cmp to i8, !dbg !27
+  store i8 %frombool1, ptr %p, align 1, !dbg !28
+  br label %if.end, !dbg !29
+
+if.else:                                          ; preds = %entry
+  br i1 %flag2, label %if.then2, label %if.end, !dbg !30
+
+if.then2:                                         ; preds = %if.else
+  %add = add i32 %nblks, %blksB, !dbg !31
+  %cmp2 = icmp ule i32 %add, %blksA, !dbg !32
+  %frombool3 = zext i1 %cmp2 to i8, !dbg !33
+  store i8 %frombool3, ptr %p, align 1, !dbg !34
+  br label %if.end, !dbg !35
+
+if.end:                                           ; preds = %if.then2, %if.else, %if.then
+  ret i1 true, !dbg !36
+}
+
+!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: "sink-common-code.ll", directory: "/")
+!2 = !{i32 28}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "test18", linkageName: "test18", 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)
+!9 = !DILocation(line: 2, column: 1, scope: !5)
+!10 = !DILocation(line: 3, column: 1, scope: !5)
+!11 = !DILocation(line: 4, column: 1, scope: !5)
+!12 = !DILocation(line: 5, column: 1, scope: !5)
+!13 = !DILocation(line: 6, column: 1, scope: !5)
+!14 = !DILocation(line: 7, column: 1, scope: !5)
+!15 = !DILocation(line: 8, column: 1, scope: !5)
+!16 = !DILocation(line: 9, column: 1, scope: !5)
+!17 = !DILocation(line: 10, column: 1, scope: !5)
+!18 = !DILocation(line: 11, column: 1, scope: !5)
+!19 = !DILocation(line: 12, column: 1, scope: !5)
+!20 = !DILocation(line: 13, column: 1, scope: !5)
+!21 = !DILocation(line: 14, column: 1, scope: !5)
+!22 = !DILocation(line: 15, column: 1, scope: !5)
+!23 = distinct !DISubprogram(name: "test_pr30244", linkageName: "test_pr30244", scope: null, file: !1, line: 16, type: !6, scopeLine: 16, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!24 = !DILocation(line: 16, column: 1, scope: !23)
+!25 = !DILocation(line: 17, column: 1, scope: !23)
+!26 = !DILocation(line: 18, column: 1, scope: !23)
+!27 = !DILocation(line: 19, column: 1, scope: !23)
+!28 = !DILocation(line: 20, column: 1, scope: !23)
+!29 = !DILocation(line: 21, column: 1, scope: !23)
+!30 = !DILocation(line: 22, column: 1, scope: !23)
+!31 = !DILocation(line: 23, column: 1, scope: !23)
+!32 = !DILocation(line: 24, column: 1, scope: !23)
+!33 = !DILocation(line: 25, column: 1, scope: !23)
+!34 = !DILocation(line: 26, column: 1, scope: !23)
+!35 = !DILocation(line: 27, column: 1, scope: !23)
+!36 = !DILocation(line: 28, column: 1, scope: !23)
+;.
+; CHECK: [[DBG17]] = !DILocation(line: 0
+; CHECK: [[DBG29]] = !DILocation(line: 0
+;.
diff --git a/llvm/test/Transforms/GVNSink/sink-ignore-dbg-intrinsics.ll b/llvm/test/Transforms/GVNSink/sink-ignore-dbg-intrinsics.ll
index 8aafd68..e54a17a 100644
--- a/llvm/test/Transforms/GVNSink/sink-ignore-dbg-intrinsics.ll
+++ b/llvm/test/Transforms/GVNSink/sink-ignore-dbg-intrinsics.ll
@@ -1,6 +1,8 @@
 ; RUN: opt < %s -passes=gvn-sink -S | FileCheck %s
 
 ; Test that GVNSink correctly performs the sink optimization in the presence of debug information
+; Test that GVNSink correctly merges the debug locations of sinked instruction, eg, propagating
+; the merged debug location of `%add` and `%add1` to the sinked add instruction.
 
 ; Function Attrs: noinline nounwind uwtable
 define dso_local i32 @fun(i32 noundef %a, i32 noundef %b) #0 !dbg !10 {
@@ -8,8 +10,9 @@ define dso_local i32 @fun(i32 noundef %a, i32 noundef %b) #0 !dbg !10 {
 ; CHECK-SAME:    i32 noundef [[A:%.*]], i32 noundef [[B:%.*]])
 ; CHECK:       if.end:
 ; CHECK:         [[B_SINK:%.*]] = phi i32 [ [[B]], %if.else ], [ [[A]], %if.then ]
-; CHECK:         [[ADD1:%.*]] = add nsw i32 [[B_SINK]], 1
-; CHECK:         [[XOR2:%.*]] = xor i32 [[ADD1]], 1
+; CHECK:         [[ADD1:%.*]] = add nsw i32 [[B_SINK]], 1, !dbg [[DBG:![0-9]+]]
+; CHECK:         [[XOR2:%.*]] = xor i32 [[ADD1]], 1, !dbg [[DBG:![0-9]+]]
+; CHECK:       [[DBG]] = !DILocation(line: 0,
 ;
 entry:
   tail call void @llvm.dbg.value(metadata i32 %a, metadata !15, metadata !DIExpression()), !dbg !16