[llvm] [coroutines] Use DILocation from new storage for hoisted dbg.declare (PR #75402)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-coroutines

Author: Wei Wang (apolloww)

<details>
<summary>Changes</summary>

Make the hoisted dbg.declare inherent the DILocation scope from the new storage.

After hoisting, the dbg.declare is moved into the block that defines the new storage. This could create an inconsistency in the debug location scope hierarchy where the scope of hoisted dbg.declare (i.e. DILexicalBlock) is enclosed with the scope of the block (i.e. DISubprogram). This confuses LiveDebugValues pass to think that the hoisted dbg.declare is killed in that block and does not generate DBG_VALUE in other blocks. Debugger won't be able to track its value anymore.

We do this for unoptimized binary only.

---
Full diff: https://github.com/llvm/llvm-project/pull/75402.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Coroutines/CoroFrame.cpp (+4-2) 
- (modified) llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll (+16-13) 


``````````diff
diff --git a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
index f37b4dc938d304..529f7309a1a273 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2951,9 +2951,11 @@ void coro::salvageDebugInfo(
   // dbg.declare does.
   if (isa<DbgDeclareInst>(DVI)) {
     std::optional<BasicBlock::iterator> InsertPt;
-    if (auto *I = dyn_cast<Instruction>(Storage))
+    if (auto *I = dyn_cast<Instruction>(Storage)) {
       InsertPt = I->getInsertionPointAfterDef();
-    else if (isa<Argument>(Storage))
+      if (!OptimizeFrame && I->getDebugLoc())
+        DVI.setDebugLoc(I->getDebugLoc());
+    } else if (isa<Argument>(Storage))
       InsertPt = F->getEntryBlock().begin();
     if (InsertPt)
       DVI.moveBefore(*(*InsertPt)->getParent(), *InsertPt);
diff --git a/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll b/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll
index 19a89fefd5269d..bf51218590c2f2 100644
--- a/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll
+++ b/llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll
@@ -32,8 +32,8 @@
 ; CHECK:       entry:
 ; CHECK:         %j = alloca i32, align 4
 ; CHECK:         call void @llvm.dbg.declare(metadata ptr %j, metadata ![[JVAR:[0-9]+]], metadata !DIExpression()), !dbg ![[JDBGLOC:[0-9]+]]
-; CHECK:         %[[MEMORY:.*]] = call ptr @new
-; CHECK:         call void @llvm.dbg.declare(metadata ptr %[[MEMORY]], metadata ![[XVAR:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 32)), !dbg ![[IDBGLOC:[0-9]+]]
+; CHECK:         %[[MEMORY:.*]] = call ptr @new({{.+}}), !dbg ![[IDBGLOC:[0-9]+]]
+; CHECK:         call void @llvm.dbg.declare(metadata ptr %[[MEMORY]], metadata ![[XVAR:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 32)), !dbg ![[IDBGLOC]]
 ; CHECK:         call void @llvm.dbg.declare(metadata ptr %[[MEMORY]], metadata ![[IVAR:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 20)), !dbg ![[IDBGLOC]]
 ; CHECK:       await.ready:
 ;
@@ -49,18 +49,20 @@
 ; CHECK:       await.ready:
 ;
 ; CHECK-DAG: ![[IVAR]] = !DILocalVariable(name: "i"
-; CHECK-DAG: ![[SCOPE:[0-9]+]] = distinct !DILexicalBlock(scope: !6, file: !1, line: 23, column: 12)
-; CHECK-DAG: ![[IDBGLOC]] = !DILocation(line: 24, column: 7, scope: ![[SCOPE]])
+; CHECK-DAG: ![[PROG_SCOPE:[0-9]+]] = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov"
+; CHECK-DAG: ![[BLK_SCOPE:[0-9]+]] = distinct !DILexicalBlock(scope: ![[PROG_SCOPE]], file: !1, line: 23, column: 12)
+; CHECK-DAG: ![[IDBGLOC]] = !DILocation(line: 23, column: 6, scope: ![[PROG_SCOPE]])
 ; CHECK-DAG: ![[XVAR]] = !DILocalVariable(name: "x"
 ; CHECK-DAG: ![[JVAR]] = !DILocalVariable(name: "j"
-; CHECK-DAG: ![[JDBGLOC]] = !DILocation(line: 32, column: 7, scope: ![[SCOPE]])
+; CHECK-DAG: ![[JDBGLOC]] = !DILocation(line: 32, column: 7, scope: ![[BLK_SCOPE]])
 
 ; CHECK-DAG: ![[XVAR_RESUME]] = !DILocalVariable(name: "x"
-; CHECK-DAG: ![[IDBGLOC_RESUME]] = !DILocation(line: 24, column: 7, scope: ![[RESUME_SCOPE:[0-9]+]])
-; CHECK-DAG: ![[RESUME_SCOPE]] = distinct !DILexicalBlock(scope: !22, file: !1, line: 23, column: 12)
+; CHECK-DAG: ![[RESUME_PROG_SCOPE:[0-9]+]] = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov"
+; CHECK-DAG: ![[IDBGLOC_RESUME]] = !DILocation(line: 24, column: 7, scope: ![[RESUME_BLK_SCOPE:[0-9]+]])
+; CHECK-DAG: ![[RESUME_BLK_SCOPE]] = distinct !DILexicalBlock(scope: ![[RESUME_PROG_SCOPE]], file: !1, line: 23, column: 12)
 ; CHECK-DAG: ![[IVAR_RESUME]] = !DILocalVariable(name: "i"
 ; CHECK-DAG: ![[JVAR_RESUME]] = !DILocalVariable(name: "j"
-; CHECK-DAG: ![[JDBGLOC_RESUME]] = !DILocation(line: 32, column: 7, scope: ![[RESUME_SCOPE]])
+; CHECK-DAG: ![[JDBGLOC_RESUME]] = !DILocation(line: 32, column: 7, scope: ![[RESUME_BLK_SCOPE]])
 define void @f() presplitcoroutine !dbg !8 {
 entry:
   %__promise = alloca i8, align 8
@@ -72,13 +74,13 @@ entry:
   br i1 %alloc, label %coro.alloc, label %coro.init
 
 coro.alloc:                                       ; preds = %entry
-  %size = call i64 @llvm.coro.size.i64()
-  %memory = call ptr @new(i64 %size)
-  br label %coro.init
+  %size = call i64 @llvm.coro.size.i64(), !dbg !23
+  %memory = call ptr @new(i64 %size), !dbg !23
+  br label %coro.init, !dbg !23
 
 coro.init:                                        ; preds = %coro.alloc, %entry
-  %phi.entry.alloc = phi ptr [ null, %entry ], [ %memory, %coro.alloc ]
-  %begin = call ptr @llvm.coro.begin(token %id, ptr %phi.entry.alloc)
+  %phi.entry.alloc = phi ptr [ null, %entry ], [ %memory, %coro.alloc ], !dbg !23
+  %begin = call ptr @llvm.coro.begin(token %id, ptr %phi.entry.alloc), !dbg !23
   %ready = call i1 @await_ready()
   br i1 %ready, label %init.ready, label %init.suspend
 
@@ -240,3 +242,4 @@ declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg)
 !20 = !DILocation(line: 43, column: 3, scope: !7)
 !21 = !DILocation(line: 43, column: 8, scope: !7)
 !22 = distinct !DILexicalBlock(scope: !8, file: !1, line: 23, column: 12)
+!23 = !DILocation(line: 23, column: 6, scope: !8)

``````````

</details>


https://github.com/llvm/llvm-project/pull/75402