[PATCH] D156446: [BPF] Emit better error on missing line info

[Tamir Duberstein via Phabricator via llvm-commits]

tamird added a comment.

In D156446#4554118 <https://reviews.llvm.org/D156446#4554118>, @eddyz87 wrote:

> This error could be detected using the following test case:
>
>   $ cat test2.c
>   ; ModuleID = 'test2.c'
>   source_filename = "test2.c"
>   target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128"
>   target triple = "bpf"
>   
>   ; Function Attrs: noinline nounwind optnone
>   define dso_local i64 @foo() {
>   entry:
>     ret i64 42
>   }
>   
>   !llvm.dbg.cu = !{!0}
>   !llvm.module.flags = !{!2, !3, !4, !5}
>   
>   !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "foo", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
>   !1 = !DIFile(filename: "file.c", directory: "/some/dir", checksumkind: CSK_MD5, checksum: "f58a7abbd9253986370acb1013fc9e55")
>   !2 = !{i32 7, !"Dwarf Version", i32 5}
>   !3 = !{i32 2, !"Debug Info Version", i32 3}
>   !4 = !{i32 1, !"wchar_size", i32 4}
>   !5 = !{i32 7, !"frame-pointer", i32 2}
>   !6 = !{!"clang version 18.0.0 (/home/eddy/work/llvm-project/clang 61cd4a1d35aa7c0f7b312b8f43ed3bff33f20d55)"}
>   
>   $ llc test2.ll -o /dev/null
>   /home/eddy/work/llvm-project/llvm/lib/Target/BPF/BTFDebug.cpp:1640:42: runtime error: member call on null pointer of type 'llvm::DISubprogram'
>   SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/eddy/work/llvm-project/llvm/lib/Target/BPF/BTFDebug.cpp:1640:42 in 
>
> Necessary conditions are: module with debug attributes (llvm.dbg.cu -> DICompileUnit) and a function and instruction w/o debug metadata. I think such test case should be added to the suite.
> Also, I don't see a point in reporting this (either as warning or as error). Absence of DISubprogram is ignored in `BTFDebug::processFuncPrototypes` and it two other places `getSubprogram()` can't return null. I think the following patch should suffice:
>
>   diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp
>   index d886edaff555..6df421934b70 100644
>   --- a/llvm/lib/Target/BPF/BTFDebug.cpp
>   +++ b/llvm/lib/Target/BPF/BTFDebug.cpp
>   @@ -1634,8 +1635,8 @@ void BTFDebug::beginInstruction(const MachineInstr *MI) {
>      if (!DL || PrevInstLoc == DL) {
>        // This instruction will be skipped, no LineInfo has
>        // been generated, construct one based on function signature.
>   -    if (LineInfoGenerated == false) {
>   -      auto *S = MI->getMF()->getFunction().getSubprogram();
>   +    DISubprogram *S = MI->getMF()->getFunction().getSubprogram();
>   +    if (!LineInfoGenerated && S) {
>          MCSymbol *FuncLabel = Asm->getFunctionBegin();
>          constructLineInfo(S, FuncLabel, S->getLine(), 0);
>          LineInfoGenerated = true;

Sounds good! I'll do that. Can you share the C source code of the program as well please?


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https://reviews.llvm.org/D156446