llvm-project/clang/test/CodeGen/debug-info-extern-callback.c

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BPF: emit debuginfo for Function of DeclRefExpr if requested Commit e3d8ee35e4ad ("reland "[DebugInfo] Support to emit debugInfo for extern variables"") added support to emit debugInfo for extern variables if requested by the target. Currently, only BPF target enables this feature by default. As BPF ecosystem grows, callback function started to get support, e.g., recently bpf_for_each_map_elem() is introduced (https://lwn.net/Articles/846504/) with a callback function as an argument. In the future we may have something like below as a demonstration of use case : extern int do_work(int); long bpf_helper(void *callback_fn, void *callback_ctx, ...); long prog_main() { struct { ... } ctx = { ... }; return bpf_helper(&do_work, &ctx, ...); } Basically bpf helper may have a callback function and the callback function is defined in another file or in the kernel. In this case, we would like to know the debuginfo types for do_work(), so the verifier can proper verify the safety of bpf_helper() call. For the following example, extern int do_work(int); long bpf_helper(void *callback_fn); long prog() { return bpf_helper(&do_work); } Currently, there is no debuginfo generated for extern function do_work(). In the IR, we have, ... define dso_local i64 @prog() local_unnamed_addr #0 !dbg !7 { entry: %call = tail call i64 @bpf_helper(i8* bitcast (i32 (i32)* @do_work to i8*)) #2, !dbg !11 ret i64 %call, !dbg !12 } ... declare dso_local i32 @do_work(i32) #1 ... This patch added support for the above callback function use case, and the generated IR looks like below: ... declare !dbg !17 dso_local i32 @do_work(i32) #1 ... !17 = !DISubprogram(name: "do_work", scope: !1, file: !1, line: 1, type: !18, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2) !18 = !DISubroutineType(types: !19) !19 = !{!20, !20} !20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) The TargetInfo.allowDebugInfoForExternalVar is renamed to TargetInfo.allowDebugInfoForExternalRef as now it guards both extern variable and extern function debuginfo generation. Differential Revision: https://reviews.llvm.org/D100567
2021-04-15 01:43:22 +08:00
// RUN: %clang_cc1 -x c -debug-info-kind=limited -triple bpf-linux-gnu -emit-llvm %s -o - | FileCheck %s
extern int do_work1(int);
long bpf_helper1(void *callback_fn);
long prog1() {
return bpf_helper1(&do_work1);
}
extern int do_work2();
long prog2_1() {
return (long)&do_work2;
}
int do_work2() { return 0; }
long prog2_2() {
return (long)&do_work2;
}
// CHECK: declare !dbg ![[FUNC1:[0-9]+]] i32 @do_work1
// CHECK: define dso_local i32 @do_work2() #{{[0-9]+}} !dbg ![[FUNC2:[0-9]+]]
// CHECK: ![[FUNC1]] = !DISubprogram(name: "do_work1"
// CHECK: ![[FUNC2]] = distinct !DISubprogram(name: "do_work2"