[cfe-users] fetch variable names through debugInfo attached to load instructors

[David Blaikie via cfe-users]

You'd have to analyze the dbg.declares and track that they refer to the
same thing as the geps/loads you're interested in - from the dbg.declares
(& dbg.values) you can follow those to find the variables they refer to.

On Thu, May 20, 2021 at 12:18 PM Bella V via cfe-users <
cfe-users at lists.llvm.org> wrote:

> Hello All,
>
> I read the documentation and I was able to fetch the variable names and
> source locations attached to metadata for call instructions
> (@llvm.dbg.declare) using dyn_cast<DbgVariableIntrinsic>. I wanted to check
> if we could fetch the variable names in the load/gep instructors using
> debugInfo. I want to collect the use variable object details within the
> function.
>
>
>
> I could only fetch the source locations (not the variable names) using
> !dbg attached to the load instructions. Any pointers if that is allowed.
>
>
> *C code:*
>
> int foo (bar_t *b, int len)
>
> {
>
>     if (b == (bar_t *)NULL) {
>
>         return 0;
>
>     }
>
>     return -1;
>
> }
>
>
>
> *IR optimised code through LTO:*
>
> ; Function Attrs: noinline nounwind optnone uwtable
>
> define i32 @foo(%struct.bar_t*, i32) #0 !dbg !10 {
>
>   %3 = load i64, i64* getelementptr inbounds ([1 x i64], [1 x i64]
>
>   %4 = add i64 %3, 1
>
>   %5 = alloca i32, align 4
>
>   %6 = alloca % struct.bar_t*, align 8
>
>   %7 = alloca i32, align 4
>
>   store % struct.bar_t* %0, % struct.bar_t** %6, align 8
>
>   call void @llvm.dbg.declare(metadata % struct.bar_t** %6, metadata !11,
> metadata !DIExpression()), !dbg !12
>
>   store i32 %1, i32* %7, align 4
>
>   call void @llvm.dbg.declare(metadata i32* %7, metadata !12, metadata
> !DIExpression()), !dbg !14
>
>   %8 = load % struct.bar_t*, % struct.bar_t** %6, align 8, !dbg !15
>
>   %9 = icmp eq % struct.bar_t* %8, null, !dbg !16
>
>   br i1 %9, label %10, label %11, !dbg !17
>
>
>
> Many Thanks.
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>
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