[DebugInfo][SimplifyCFG] Fully propagate merged invoke DILocations

[SLTozer]

Currently when we merge invokes as part of SimplifyCFG we apply a merge of the invoke DILocations to the merged invoke. We also insert an unconditional branch to the merged invoke at the positions previously occupied by the original invokes; as this branch is part of the substitution for the invoke it has replaced, we should propagate the original invoke DebugLoc to it.

Found using #107279.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-debuginfo

Author: Stephen Tozer (SLTozer)

Changes

Currently when we merge invokes as part of SimplifyCFG we apply a merge of the invoke DILocations to the merged invoke. We also insert an unconditional branch to the merged invoke at the positions previously occupied by the original invokes; as this branch is part of the substitution for the invoke it has replaced, we should propagate the original invoke DebugLoc to it.

---

Full diff: https://github.com/llvm/llvm-project/pull/114235.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Utils/SimplifyCFG.cpp (+4-1)
• (added) llvm/test/Transforms/SimplifyCFG/dbgloc-merge-invoke.ll (+74)

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 72228b445a8b6e..9c8a465fd876fd 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2917,7 +2917,10 @@ static void mergeCompatibleInvokesImpl(ArrayRef<InvokeInst *> Invokes,
     // to the block with the merged `invoke`.
     for (BasicBlock *OrigSuccBB : successors(II->getParent()))
       OrigSuccBB->removePredecessor(II->getParent());
-    BranchInst::Create(MergedInvoke->getParent(), II->getParent());
+    auto *BI = BranchInst::Create(MergedInvoke->getParent(), II->getParent());
+    // The unconditional branch is part of the replacement for the original
+    // invoke, so should use its DebugLoc.
+    BI->setDebugLoc(II->getDebugLoc());
     bool Success = MergedInvoke->tryIntersectAttributes(II);
     assert(Success && "Merged invokes with incompatible attributes");
     // For NDEBUG Compile
diff --git a/llvm/test/Transforms/SimplifyCFG/dbgloc-merge-invoke.ll b/llvm/test/Transforms/SimplifyCFG/dbgloc-merge-invoke.ll
new file mode 100644
index 00000000000000..8f6ffd0dbd0c88
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/dbgloc-merge-invoke.ll
@@ -0,0 +1,74 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -p="simplifycfg<sink-common-insts>" -S | FileCheck %s
+
+;; Tests that when we merge the invokes and use a select to choose the argument
+;; value, the merged invoke and select use the merged DILocation from the
+;; original invokes.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare ptr @baz()
+
+define i32 @foo(i1 %call66, ptr %.str.8) personality ptr null {
+; CHECK-LABEL: define i32 @foo(
+; CHECK-SAME: i1 [[CALL66:%.*]], ptr [[DOTSTR_8:%.*]]) personality ptr null {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL661:%.*]] = invoke i1 @bar(ptr null)
+; CHECK-NEXT:            to label %[[INVOKE_CONT65:.*]] unwind label %[[LPAD45_LOOPEXIT_SPLIT_LP_LOOPEXIT_SPLIT_LP:.*]]
+; CHECK:       [[COMMON_RET:.*]]:
+; CHECK-NEXT:    ret i32 0
+; CHECK:       [[LPAD45_LOOPEXIT_SPLIT_LP_LOOPEXIT_SPLIT_LP]]:
+; CHECK-NEXT:    [[LPAD_LOOPEXIT_SPLIT_LP1114:%.*]] = landingpad { ptr, i32 }
+; CHECK-NEXT:            cleanup
+; CHECK-NEXT:    br label %[[COMMON_RET]]
+; CHECK:       [[INVOKE_CONT65]]:
+; CHECK-NEXT:    [[DOTSTR_8_:%.*]] = select i1 [[CALL66]], ptr [[DOTSTR_8]], ptr null, !dbg [[DBG3:![0-9]+]]
+; CHECK-NEXT:    [[TMP0:%.*]] = invoke ptr @baz(ptr null, ptr [[DOTSTR_8_]])
+; CHECK-NEXT:            to label %[[COMMON_RET]] unwind label %[[LPAD45_LOOPEXIT_SPLIT_LP_LOOPEXIT_SPLIT_LP]], !dbg [[DBG3]]
+;
+entry:
+  %call661 = invoke i1 @bar(ptr null)
+  to label %invoke.cont65 unwind label %lpad45.loopexit.split-lp.loopexit.split-lp
+
+common.ret:                                       ; preds = %if.else, %if.then67, %lpad45.loopexit.split-lp.loopexit.split-lp
+  ret i32 0
+
+lpad45.loopexit.split-lp.loopexit.split-lp:       ; preds = %if.else, %if.then67, %entry
+  %lpad.loopexit.split-lp1114 = landingpad { ptr, i32 }
+  cleanup
+  br label %common.ret
+
+invoke.cont65:                                    ; preds = %entry
+  br i1 %call66, label %if.then67, label %if.else
+
+if.then67:                                        ; preds = %invoke.cont65
+  %call69 = invoke ptr @baz(ptr null, ptr %.str.8)
+  to label %common.ret unwind label %lpad45.loopexit.split-lp.loopexit.split-lp, !dbg !4
+
+if.else:                                          ; preds = %invoke.cont65
+  %call71 = invoke ptr @baz(ptr null, ptr null)
+  to label %common.ret unwind label %lpad45.loopexit.split-lp.loopexit.split-lp, !dbg !8
+}
+
+declare i1 @bar()
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 20.0.0git")
+!1 = !DIFile(filename: "List.cpp", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !DILocation(line: 10, column: 20, scope: !6)
+!6 = distinct !DISubprogram(name: "ListArchives", linkageName: "foo", scope: !1, file: !1, line: 416, type: !7, scopeLine: 425, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!7 = distinct !DISubroutineType(types: !2)
+!8 = !DILocation(line: 10, column: 10, scope: !6)
+;.
+; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: false, runtimeVersion: 0, emissionKind: NoDebug)
+; CHECK: [[META1]] = !DIFile(filename: "List.cpp", directory: {{.*}})
+; CHECK: [[DBG3]] = !DILocation(line: 10, scope: [[META4:![0-9]+]])
+; CHECK: [[META4]] = distinct !DISubprogram(name: "ListArchives", linkageName: "foo", scope: [[META1]], file: [[META1]], line: 416, type: [[META5:![0-9]+]], scopeLine: 425, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META6:![0-9]+]])
+; CHECK: [[META5]] = distinct !DISubroutineType(types: [[META6]])
+; CHECK: [[META6]] = !{}
+;.