58ecfccd0d
D14468 added these dummy sections. This patch adds `__attribute__((used))` so
that when compiled by GCC>=11 or (expected, D96838) Clang>=13 on some ELF platforms,
these sections will get SHF_GNU_RETAIN to make sure they will not be discarded
by ld --gc-sections.
We are trying to get rid of LLD's "__start_/__stop_ references retain C identifier name sections" rule.
If LLD drops the rule in the future (we will retain compatibility for `__llvm_prf_*` for a while),
`__llvm_prf_*` will need to have the SHF_GNU_RETAIN flag, otherwise:
```
// __llvm_prf_cnts/__llvm_prf_data usually exist, but {names,vnds} may not exist.
// Such diagnostics will happen with {cnts,data} as well if no input object file is instrumented.
% clang++ -fprofile-generate a.cc -fuse-ld=lld -Wl,--gc-sections
ld.lld: error: undefined hidden symbol: __start___llvm_prf_names
>>> referenced by InstrProfilingPlatformLinux.c
>>> InstrProfilingPlatformLinux.c.o:(__llvm_profile_begin_names) in archive /tmp/RelA/lib/clang/13.0.0/lib/linux/libclang_rt.profile-x86_64.a
...
```
Differential Revision: https://reviews.llvm.org/D96902
88 lines
3.5 KiB
C
88 lines
3.5 KiB
C
/*===- InstrProfilingPlatformLinux.c - Profile data Linux platform ------===*\
|
|
|*
|
|
|* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
|* See https://llvm.org/LICENSE.txt for license information.
|
|
|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
|*
|
|
\*===----------------------------------------------------------------------===*/
|
|
|
|
#if defined(__linux__) || defined(__FreeBSD__) || defined(__Fuchsia__) || \
|
|
(defined(__sun__) && defined(__svr4__)) || defined(__NetBSD__)
|
|
|
|
#include <stdlib.h>
|
|
|
|
#include "InstrProfiling.h"
|
|
|
|
#define PROF_DATA_START INSTR_PROF_SECT_START(INSTR_PROF_DATA_COMMON)
|
|
#define PROF_DATA_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_DATA_COMMON)
|
|
#define PROF_NAME_START INSTR_PROF_SECT_START(INSTR_PROF_NAME_COMMON)
|
|
#define PROF_NAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_NAME_COMMON)
|
|
#define PROF_CNTS_START INSTR_PROF_SECT_START(INSTR_PROF_CNTS_COMMON)
|
|
#define PROF_CNTS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_CNTS_COMMON)
|
|
#define PROF_ORDERFILE_START INSTR_PROF_SECT_START(INSTR_PROF_ORDERFILE_COMMON)
|
|
#define PROF_VNODES_START INSTR_PROF_SECT_START(INSTR_PROF_VNODES_COMMON)
|
|
#define PROF_VNODES_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VNODES_COMMON)
|
|
|
|
/* Declare section start and stop symbols for various sections
|
|
* generated by compiler instrumentation.
|
|
*/
|
|
extern __llvm_profile_data PROF_DATA_START COMPILER_RT_VISIBILITY;
|
|
extern __llvm_profile_data PROF_DATA_STOP COMPILER_RT_VISIBILITY;
|
|
extern uint64_t PROF_CNTS_START COMPILER_RT_VISIBILITY;
|
|
extern uint64_t PROF_CNTS_STOP COMPILER_RT_VISIBILITY;
|
|
extern uint32_t PROF_ORDERFILE_START COMPILER_RT_VISIBILITY;
|
|
extern char PROF_NAME_START COMPILER_RT_VISIBILITY;
|
|
extern char PROF_NAME_STOP COMPILER_RT_VISIBILITY;
|
|
extern ValueProfNode PROF_VNODES_START COMPILER_RT_VISIBILITY;
|
|
extern ValueProfNode PROF_VNODES_STOP COMPILER_RT_VISIBILITY;
|
|
|
|
/* Add dummy data to ensure the section is always created. Add used attribute so
|
|
* that they are linker GC roots on supported ELF platforms.
|
|
*/
|
|
__llvm_profile_data __prof_data_sect_data[0] COMPILER_RT_SECTION(
|
|
INSTR_PROF_DATA_SECT_NAME) COMPILER_RT_USED;
|
|
uint64_t __prof_cnts_sect_data[0] COMPILER_RT_SECTION(INSTR_PROF_CNTS_SECT_NAME)
|
|
COMPILER_RT_USED;
|
|
uint32_t __prof_orderfile_sect_data[0] COMPILER_RT_SECTION(
|
|
INSTR_PROF_ORDERFILE_SECT_NAME) COMPILER_RT_USED;
|
|
const char __prof_nms_sect_data[0] COMPILER_RT_SECTION(
|
|
INSTR_PROF_NAME_SECT_NAME) COMPILER_RT_USED;
|
|
ValueProfNode __prof_vnodes_sect_data[0] COMPILER_RT_SECTION(
|
|
INSTR_PROF_VNODES_SECT_NAME) COMPILER_RT_USED;
|
|
|
|
COMPILER_RT_VISIBILITY const __llvm_profile_data *
|
|
__llvm_profile_begin_data(void) {
|
|
return &PROF_DATA_START;
|
|
}
|
|
COMPILER_RT_VISIBILITY const __llvm_profile_data *
|
|
__llvm_profile_end_data(void) {
|
|
return &PROF_DATA_STOP;
|
|
}
|
|
COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_names(void) {
|
|
return &PROF_NAME_START;
|
|
}
|
|
COMPILER_RT_VISIBILITY const char *__llvm_profile_end_names(void) {
|
|
return &PROF_NAME_STOP;
|
|
}
|
|
COMPILER_RT_VISIBILITY uint64_t *__llvm_profile_begin_counters(void) {
|
|
return &PROF_CNTS_START;
|
|
}
|
|
COMPILER_RT_VISIBILITY uint64_t *__llvm_profile_end_counters(void) {
|
|
return &PROF_CNTS_STOP;
|
|
}
|
|
COMPILER_RT_VISIBILITY uint32_t *__llvm_profile_begin_orderfile(void) {
|
|
return &PROF_ORDERFILE_START;
|
|
}
|
|
|
|
COMPILER_RT_VISIBILITY ValueProfNode *
|
|
__llvm_profile_begin_vnodes(void) {
|
|
return &PROF_VNODES_START;
|
|
}
|
|
COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) {
|
|
return &PROF_VNODES_STOP;
|
|
}
|
|
COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START;
|
|
COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP;
|
|
|
|
#endif
|