[llvm] [DebugInfo] Fix faulty DIExpression::appendToStack assert (PR #85255)

[via llvm-commits]

llvmbot wrote:


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

@llvm/pr-subscribers-llvm-ir

Author: David Stenberg (dstenb)

<details>
<summary>Changes</summary>

The appendToStack() function asserts that no DW_OP_stack_value or
DW_OP_LLVM_fragment operations are present in the operations to be
appended. The function did that by iterating over all elements in the
array rather than just the operations, leading it to falsely asserting
on the following input produced by getExt(), since 159 (0x9f) is the
DWARF code for DW_OP_stack_value:

  {dwarf::DW_OP_LLVM_convert, 159, dwarf::DW_ATE_signed}

Fix this by using expr_op iterators.


---
Full diff: https://github.com/llvm/llvm-project/pull/85255.diff


2 Files Affected:

- (modified) llvm/lib/IR/DebugInfoMetadata.cpp (+6-5) 
- (added) llvm/test/DebugInfo/Generic/append-to-stack-assert.ll (+49) 


``````````diff
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 28f96653d815b5..f37add2120f13b 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -1880,11 +1880,12 @@ DIExpression *DIExpression::append(const DIExpression *Expr,
 DIExpression *DIExpression::appendToStack(const DIExpression *Expr,
                                           ArrayRef<uint64_t> Ops) {
   assert(Expr && !Ops.empty() && "Can't append ops to this expression");
-  assert(none_of(Ops,
-                 [](uint64_t Op) {
-                   return Op == dwarf::DW_OP_stack_value ||
-                          Op == dwarf::DW_OP_LLVM_fragment;
-                 }) &&
+  assert(std::none_of(expr_op_iterator(Ops.begin()),
+                      expr_op_iterator(Ops.end()),
+                      [](auto Op) {
+                        return Op.getOp() == dwarf::DW_OP_stack_value ||
+                               Op.getOp() == dwarf::DW_OP_LLVM_fragment;
+                      }) &&
          "Can't append this op");
 
   // Append a DW_OP_deref after Expr's current op list if it's non-empty and
diff --git a/llvm/test/DebugInfo/Generic/append-to-stack-assert.ll b/llvm/test/DebugInfo/Generic/append-to-stack-assert.ll
new file mode 100644
index 00000000000000..0c0677f782aa64
--- /dev/null
+++ b/llvm/test/DebugInfo/Generic/append-to-stack-assert.ll
@@ -0,0 +1,49 @@
+; RUN: opt -passes=instcombine -S < %s | FileCheck %s
+
+ at f = dso_local local_unnamed_addr global i16 0, align 1, !dbg !0
+ at e = dso_local local_unnamed_addr global i159 0, align 1, !dbg !5
+
+; Function Attrs: nounwind
+define dso_local void @g() local_unnamed_addr #0 !dbg !14 {
+; CHECK:    [[TMP0:%.*]] = load i16, ptr @f, align 1
+; CHECK:    [[CONV1:%.*]] = sext i16 [[TMP0]] to i159
+; CHECK:    tail call void @llvm.dbg.value(metadata i159 [[CONV1]], metadata {{![0-9]+}}, metadata !DIExpression(DW_OP_LLVM_convert, 159, DW_ATE_signed, DW_OP_LLVM_convert, 256, DW_ATE_signed, DW_OP_stack_value))
+entry:
+  %0 = load i16, ptr @f, align 1, !dbg !21
+  %conv = sext i16 %0 to i256, !dbg !21
+  tail call void @llvm.dbg.value(metadata i256 %conv, metadata !18, metadata !DIExpression()), !dbg !22
+  %conv1 = trunc i256 %conv to i159, !dbg !23
+  store i159 %conv1, ptr @e, align 1, !dbg !23
+  ret void, !dbg !23
+}
+
+attributes #0 = { nounwind }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!9, !10, !11, !12}
+!llvm.ident = !{!13}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "f", scope: !2, file: !3, line: 7, type: !8, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, producer: "clang version 19.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "bbi-93380.c", directory: "/")
+!4 = !{!0, !5}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "e", scope: !2, file: !3, line: 8, type: !7, isLocal: false, isDefinition: true)
+!7 = !DIBasicType(name: "_BitInt", size: 160, encoding: DW_ATE_signed)
+!8 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+!9 = !{i32 7, !"Dwarf Version", i32 4}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!11 = !{i32 1, !"wchar_size", i32 1}
+!12 = !{i32 7, !"frame-pointer", i32 2}
+!13 = !{!"clang version 19.0.0git"}
+!14 = distinct !DISubprogram(name: "g", scope: !3, file: !3, line: 9, type: !15, scopeLine: 9, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !17)
+!15 = !DISubroutineType(types: !16)
+!16 = !{null}
+!17 = !{!18}
+!18 = !DILocalVariable(name: "d", scope: !19, file: !3, line: 9, type: !20)
+!19 = distinct !DILexicalBlock(scope: !14, file: !3, line: 9)
+!20 = !DIBasicType(name: "_BitInt", size: 256, encoding: DW_ATE_signed)
+!21 = !DILocation(line: 9, scope: !19)
+!22 = !DILocation(line: 0, scope: !19)
+!23 = !DILocation(line: 9, scope: !14)

``````````

</details>


https://github.com/llvm/llvm-project/pull/85255