[llvm] [DebugInfo][SimpleLoopUnswitch] Fix missing debug location updates for new terminators (PR #98789)

[Stephen Tozer via llvm-commits]

================
@@ -0,0 +1,98 @@
+; RUN: opt -passes='loop(simple-loop-unswitch)' -S < %s | FileCheck %s
+; RUN: opt -passes='loop-mssa(simple-loop-unswitch)' -S < %s | FileCheck %s
+
+; Check that SimpleLoopUnswitch's unswitchTrivialBranch() and unswitchTrivialSwitch()
+; propagates debug locations to the new terminators replacing the old ones.
+
+define i32 @test1(ptr %var, i1 %cond1, i1 %cond2) !dbg !5 {
+; CHECK-LABEL: define i32 @test1(
+; CHECK:       loop_begin:
+; CHECK-NEXT:    br label %[[CONTINUE:.*]], !dbg [[DBG8:![0-9]+]]
+;
+entry:
+  br label %loop_begin, !dbg !8
+
+loop_begin:                                       ; preds = %do_something, %entry
+  br i1 %cond1, label %continue, label %loop_exit, !dbg !9
+
+continue:                                         ; preds = %loop_begin
+  %var_val = load i32, ptr %var, align 4, !dbg !10
+  br i1 %cond2, label %do_something, label %loop_exit, !dbg !11
+
+do_something:                                     ; preds = %continue
+  call void @some_func(), !dbg !12
+  br label %loop_begin, !dbg !13
+
+loop_exit:                                        ; preds = %continue, %loop_begin
+  ret i32 0, !dbg !14
+}
+
+define i32 @test7(i32 %cond1, i32 %x, i32 %y) !dbg !15 {
+; CHECK-LABEL: define i32 @test7(
+; CHECK-SAME: i32 [[COND1:%.*]], i32 [[X:%.*]], i32 [[Y:%.*]])
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    switch i32 [[COND1]], label %[[ENTRY_SPLIT:.*]] [
+; CHECK-NEXT:      i32 0, label %[[LOOP_EXIT:.*]]
+; CHECK-NEXT:      i32 1, label %[[LOOP_EXIT]]
+; CHECK-NEXT:    ], !dbg [[DBG16:![0-9]+]]
+; CHECK:       loop_begin:
+; CHECK-NEXT:    br label %[[LATCH:.*]], !dbg [[DBG17:![0-9]+]]
+;
+entry:
+  br label %loop_begin, !dbg !16
+
+loop_begin:                                       ; preds = %latch, %entry
+  switch i32 %cond1, label %latch [
+  i32 0, label %loop_exit
+  i32 1, label %loop_exit
+  ], !dbg !17
+
+latch:                                            ; preds = %loop_begin
+  call void @some_func(), !dbg !18
+  br label %loop_begin, !dbg !19
+
+loop_exit:                                        ; preds = %loop_begin, %loop_begin
+  %result1 = phi i32 [ %x, %loop_begin ], [ %x, %loop_begin ], !dbg !20
+  %result2 = phi i32 [ %y, %loop_begin ], [ %y, %loop_begin ], !dbg !21
+  %result = add i32 %result1, %result2, !dbg !22
+  ret i32 %result, !dbg !23
+}
+
+; Function Attrs: noreturn
+declare void @some_func()
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+; CHECK: [[DBG8]] = !DILocation(line: 2,
+
+; CHECK: [[DBG16]] = !DILocation(line: 8,
+; CHECK: [[DBG17]] = !DILocation(line: 9,
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "test2.ll", directory: "/")
+!2 = !{i32 15}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "test1", linkageName: "test1", 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 = distinct !DISubprogram(name: "test7", linkageName: "test7", scope: null, file: !1, line: 8, type: !6, scopeLine: 8, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!16 = !DILocation(line: 8, column: 1, scope: !15)
+!17 = !DILocation(line: 9, column: 1, scope: !15)
+!18 = !DILocation(line: 10, column: 1, scope: !15)
+!19 = !DILocation(line: 11, column: 1, scope: !15)
+!20 = !DILocation(line: 12, column: 1, scope: !15)
+!21 = !DILocation(line: 13, column: 1, scope: !15)
+!22 = !DILocation(line: 14, column: 1, scope: !15)
+!23 = !DILocation(line: 15, column: 1, scope: !15)
+
----------------
SLTozer wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/98789