[PATCH] D148204: [Assignment Tracking] Skip empty-metadata dbg.declares in AssignmentTrackingPass

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

Orlando created this revision.
Orlando added reviewers: StephenTozer, jmorse, rupprecht.
Orlando added a project: debug-info.
Herald added a subscriber: hiraditya.
Herald added a project: All.
Orlando requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Debug intrinsics sometimes end up with empty metadata location operands. The debug intrinsic interfaces return nullptr when retrieving location operand in this case.

Skip empty-metadata dbg.declares to avoid dereferencing the nullptr. This doesn't affect the final debug info in any way.

N.B. my "empty metadata is the same as poison" patch stack (D140902 <https://reviews.llvm.org/D140902>) hasn't landed yet as I'm focussing on assignment tracking for now.


https://reviews.llvm.org/D148204

Files:
  llvm/lib/IR/DebugInfo.cpp
  llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/nullptr-declare.ll


Index: llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/nullptr-declare.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/nullptr-declare.ll
@@ -0,0 +1,32 @@
+; RUN: opt test.ll  -passes=declare-to-assign -S | FileCehck %s
+
+;; Check AssignmentTrackingPass ignores a dbg.declare with an empty metadata
+;; location operand.
+
+; CHECK:      call void @llvm.dbg.declare
+; CHECK-NOT:  call void @llvm.dbg.assign
+
+define dso_local void @_Z3funv() #0 !dbg !10 {
+entry:
+  call void @llvm.dbg.declare(metadata !13, metadata !14, metadata !DIExpression()), !dbg !16
+  ret void
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 17.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", directory: "/")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 17.0.0"}
+!10 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funv", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !13)
+!11 = !DISubroutineType(types: !12)
+!12 = !{null}
+!13 = !{}
+!14 = !DILocalVariable(name: "x", scope: !10, file: !1, line: 1, type: !15)
+!15 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!16 = !DILocation(line: 1, column: 18, scope: !10)
Index: llvm/lib/IR/DebugInfo.cpp
===================================================================
--- llvm/lib/IR/DebugInfo.cpp
+++ llvm/lib/IR/DebugInfo.cpp
@@ -1998,6 +1998,8 @@
       // leave dbg.declares with non-empty expressions in place.
       if (DDI->getExpression()->getNumElements() != 0)
         continue;
+      if (!DDI->getAddress())
+        continue;
       if (AllocaInst *Alloca =
               dyn_cast<AllocaInst>(DDI->getAddress()->stripPointerCasts())) {
         // FIXME: Skip VLAs for now (let these variables use dbg.declares).


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D148204.513130.patch
Type: text/x-patch
Size: 2266 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230413/149f8d7c/attachment.bin>