[llvm] ff11c4f - [Assignment Tracking] Ignore VLA-backed variables

[via llvm-commits]

Author: OCHyams
Date: 2023-04-12T17:07:48+01:00
New Revision: ff11c4f184caa51095db22a0cf0ee3546d4a7b09

URL: https://github.com/llvm/llvm-project/commit/ff11c4f184caa51095db22a0cf0ee3546d4a7b09
DIFF: https://github.com/llvm/llvm-project/commit/ff11c4f184caa51095db22a0cf0ee3546d4a7b09.diff

LOG: [Assignment Tracking] Ignore VLA-backed variables

VLA backed variables currently trip an assertion in SROA with D146987 (enabling
assignment tracking). Disable assignment tracking for VLA variables until that
can be investigated.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D148140

Added: 
    llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/vla.ll

Modified: 
    llvm/lib/IR/DebugInfo.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index 0272ef2647a6..542890880c89 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -2000,6 +2000,9 @@ bool AssignmentTrackingPass::runOnFunction(Function &F) {
         continue;
       if (AllocaInst *Alloca =
               dyn_cast<AllocaInst>(DDI->getAddress()->stripPointerCasts())) {
+        // FIXME: Skip VLAs for now (let these variables use dbg.declares).
+        if (!Alloca->isStaticAlloca())
+          continue;
         DbgDeclares[Alloca].insert(DDI);
         Vars[Alloca].insert(VarRecord(DDI));
       }

diff  --git a/llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/vla.ll b/llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/vla.ll
new file mode 100644
index 000000000000..72d54cba7b4b
--- /dev/null
+++ b/llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/vla.ll
@@ -0,0 +1,61 @@
+; RUN: opt -S %s -passes=declare-to-assign -o - | FileCheck %s
+
+;; Check declare-to-assign ignores VLA-backed variables (for now).
+;; From C++ source:
+;; __attribute__ ((nodebug)) int sz;
+;; void fun() {
+;;   int x[sz];
+;; }
+
+; CHECK: llvm.dbg.declare(metadata ptr %vla, metadata ![[#]], metadata !DIExpression())
+
+ at sz = dso_local global i32 0, align 4
+
+define dso_local void @_Z3funv() #0 !dbg !10 {
+entry:
+  %saved_stack = alloca ptr, align 8
+  %__vla_expr0 = alloca i64, align 8
+  %0 = load i32, ptr @sz, align 4, !dbg !14
+  %1 = zext i32 %0 to i64, !dbg !15
+  %2 = call ptr @llvm.stacksave(), !dbg !15
+  store ptr %2, ptr %saved_stack, align 8, !dbg !15
+  %vla = alloca i32, i64 %1, align 16, !dbg !15
+  store i64 %1, ptr %__vla_expr0, align 8, !dbg !15
+  ;; Ignore this artificial variable for the purpose of the test.
+  ; call void @llvm.dbg.declare(metadata ptr %__vla_expr0, metadata !16, metadata !DIExpression()), !dbg !18
+  call void @llvm.dbg.declare(metadata ptr %vla, metadata !19, metadata !DIExpression()), !dbg !24
+  %3 = load ptr, ptr %saved_stack, align 8, !dbg !25
+  call void @llvm.stackrestore(ptr %3), !dbg !25
+  ret void, !dbg !25
+}
+
+declare ptr @llvm.stacksave() #1
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #2
+declare void @llvm.stackrestore(ptr) #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}
+!8 = !{i32 7, !"frame-pointer", i32 2}
+!9 = !{!"clang version 17.0.0"}
+!10 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funv", scope: !1, file: !1, line: 2, type: !11, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !13)
+!11 = !DISubroutineType(types: !12)
+!12 = !{null}
+!13 = !{}
+!14 = !DILocation(line: 3, column: 9, scope: !10)
+!15 = !DILocation(line: 3, column: 3, scope: !10)
+!16 = !DILocalVariable(name: "__vla_expr0", scope: !10, type: !17, flags: DIFlagArtificial)
+!17 = !DIBasicType(name: "unsigned long", size: 64, encoding: DW_ATE_unsigned)
+!18 = !DILocation(line: 0, scope: !10)
+!19 = !DILocalVariable(name: "x", scope: !10, file: !1, line: 3, type: !20)
+!20 = !DICompositeType(tag: DW_TAG_array_type, baseType: !21, elements: !22)
+!21 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!22 = !{!23}
+!23 = !DISubrange(count: !16)
+!24 = !DILocation(line: 3, column: 7, scope: !10)
+!25 = !DILocation(line: 4, column: 1, scope: !10)