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Revert "Re-submit b23c47ae6dbe285e02627803eac0604cfaaa1e78"

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This reverts commit a70b1eb58b because
it's too risky to include it into 1.4.0.
This commit is contained in:
Rui Ueyama 2022-08-04 20:46:09 +08:00
parent 10c211f1ab
commit da2f3fe12c
2 changed files with 4 additions and 78 deletions
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45
elf/gc-sections.cc
View File

@ -4,7 +4,6 @@
#include "mold.h"
#include <tbb/concurrent_set.h>
#include <tbb/concurrent_vector.h>
#include <tbb/parallel_for_each.h>
@ -73,44 +72,9 @@ static void visit(Context<E> &ctx, InputSection<E> *isec,
}
}
// We synthesize `__start_foo` and `__stop_foo` symbols for section
// `foo` if the section name is valid as a C identifier (i.e. it
// doesn't start with a '.' and doesn't contain punctuations).
//
// Such references are implicit, so we need to handle them separately.
// In this function, we scan all symbols and keep section `foo` if
// there is `__start_foo` or `__stop_foo` symbol.
template <typename E>
void
collect_start_stop_sections(Context<E> &ctx,
tbb::concurrent_vector<InputSection<E> *> &rootset) {
Timer t(ctx, "collect_start_stop_sections");
tbb::concurrent_set<std::string_view> set;
tbb::parallel_for_each(ctx.objs, [&](ObjectFile<E> *file) {
for (Symbol<E> *sym : file->symbols)
if (!sym->file)
if (std::string_view s = sym->name();
remove_prefix(s, "__start_") || remove_prefix(s, "__stop_"))
set.insert(s);
});
if (set.empty())
return;
tbb::parallel_for_each(ctx.objs, [&](ObjectFile<E> *file) {
for (std::unique_ptr<InputSection<E>> &isec : file->sections)
if (isec && isec->is_alive && is_c_identifier(isec->name()) &&
set.contains(isec->name()) && isec->is_visited.exchange(true))
rootset.push_back(isec.get());
});
}
template <typename E>
static void
collect_root_set(Context<E> &ctx,
tbb::concurrent_vector<InputSection<E> *> &rootset) {
static void collect_root_set(Context<E> &ctx,
tbb::concurrent_vector<InputSection<E> *> &rootset) {
Timer t(ctx, "collect_root_set");
auto enqueue_section = [&](InputSection<E> *isec) {
@ -141,8 +105,8 @@ collect_root_set(Context<E> &ctx,
if (!(flags & SHF_ALLOC))
isec->is_visited = true;
if (is_init_fini(*isec) || (flags & SHF_GNU_RETAIN) ||
isec->shdr().sh_type == SHT_NOTE)
if (is_init_fini(*isec) || is_c_identifier(isec->name()) ||
(flags & SHF_GNU_RETAIN) || isec->shdr().sh_type == SHT_NOTE)
enqueue_section(isec.get());
}
});
@ -225,7 +189,6 @@ void gc_sections(Context<E> &ctx) {
mark_nonalloc_fragments(ctx);
tbb::concurrent_vector<InputSection<E> *> rootset;
collect_start_stop_sections(ctx, rootset);
collect_root_set(ctx, rootset);
mark(ctx, rootset);
sweep(ctx);

37
test/elf/gc-sections-start-stop-symbols.sh
View File

@ -1,37 +0,0 @@
#!/bin/bash
export LC_ALL=C
set -e
CC="${TEST_CC:-cc}"
CXX="${TEST_CXX:-c++}"
GCC="${TEST_GCC:-gcc}"
GXX="${TEST_GXX:-g++}"
OBJDUMP="${OBJDUMP:-objdump}"
MACHINE="${MACHINE:-$(uname -m)}"
testname=$(basename "$0" .sh)
echo -n "Testing $testname ... "
t=out/test/elf/$MACHINE/$testname
mkdir -p $t
cat <<EOF | $CC -o $t/a.o -c -xc -
int x1 __attribute__((section("foo_section"))) = 3;
int x2 __attribute__((section("bar_section"))) = 5;
EOF
cat <<EOF | $CC -o $t/b.o -c -xc -
#include <stdio.h>
extern int __start_foo_section[];
int main() {
printf("foo=%d\n", __start_foo_section[0]);
}
EOF
$CC -B. -o $t/exe $t/a.o $t/b.o -Wl,-gc-sections
$QEMU $t/exe | grep -q 'foo=3'
readelf --sections $t/exe > $t/log
grep -q foo_section $t/log
! grep -q bar_section $t/log || false
echo OK