Magic-Mirror/llvm-capstone
1
0
Fork 0
mirror of https://github.com/capstone-engine/llvm-capstone.git synced 2025-02-26 21:38:13 +00:00
Code Issues Actions 2 Packages Projects Releases Wiki Activity

[lld-macho] Sort data-in-code entries

Browse Source 
Previously, we would add entries to DataInCodeSection in the order they
appeared in input files. Because of this, entries would not be sorted if
sections were reordered due to e.g. `-order_file` or call graph profile
sorting. ld64 always keeps data-in-code information sorted.

This commit also fixes an incorrect assertion. The original assertion
from D103006 used to check that data-in-code entries are sorted in the
input objects -- likely because we use binary search on that data. In
D115556, the assertion was moved into `collectDataInCodeEntries`, but
the checked variable's name was not changed, so it ended up checking the
final contents of the DataInCodeSection.

We no longer crash when building LLVM with PGO using an asserts build of
LLD as the linker.

Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=1265937

Numbers for linking the Chromium Framework reproducer from #48001, which
has 6829 data-in-code entries:

  x before
  + after
      N           Min           Max        Median           Avg        Stddev
  x  20     2.1076453     2.3059683     2.1132485     2.1350302   0.049905767
  +  20     2.1069031     2.3915262       2.14465     2.1728429   0.084065898
  No difference proven at 95.0% confidence

Differential Revision: https://reviews.llvm.org/D133581
This commit is contained in:
Daniel Bertalan 2022-09-09 17:18:10 +02:00
parent d8a57c7788
commit 025a5b22c8
No known key found for this signature in database
3 changed files with 50 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lld/MachO/SyntheticSections.cpp
View File

@ -933,8 +933,8 @@ static std::vector<MachO::data_in_code_entry> collectDataInCodeEntries() {
if (entries.empty())
continue;
assert(is_sorted(dataInCodeEntries, [](const data_in_code_entry &lhs,
const data_in_code_entry &rhs) {
assert(is_sorted(entries, [](const data_in_code_entry &lhs,
const data_in_code_entry &rhs) {
return lhs.offset < rhs.offset;
}));
// For each code subsection find 'data in code' entries residing in it.
@ -963,6 +963,12 @@ static std::vector<MachO::data_in_code_entry> collectDataInCodeEntries() {
}
}
}
// ld64 emits the table in sorted order too.
llvm::sort(dataInCodeEntries,
[](const data_in_code_entry &lhs, const data_in_code_entry &rhs) {
return lhs.offset < rhs.offset;
});
return dataInCodeEntries;
}

5
lld/MachO/SyntheticSections.h
View File

@ -380,8 +380,9 @@ private:
size_t size = 0;
};
// Stores 'data in code' entries that describe the locations of
// data regions inside code sections.
// Stores 'data in code' entries that describe the locations of data regions
// inside code sections. This is used by llvm-objdump to distinguish jump tables
// and stop them from being disassembled as instructions.
class DataInCodeSection final : public LinkEditSection {
public:
DataInCodeSection();

39
lld/test/MachO/data-in-code-section-ordering.s Normal file
View File

@ -0,0 +1,39 @@
# REQUIRES: x86
# RUN: rm -rf %t; split-file %s %t
## Check that data-in-code information is sorted even if
## sections are reordered compared to the input order.
# RUN: sed -e s/SYM/_first/ %t/input.s | \
# RUN: llvm-mc -filetype=obj --triple=x86_64-apple-darwin -o %t/first.o
# RUN: sed -e s/SYM/_second/ %t/input.s | \
# RUN: llvm-mc -filetype=obj --triple=x86_64-apple-darwin -o %t/second.o
# RUN: sed -e s/SYM/_third/ %t/input.s | \
# RUN: llvm-mc -filetype=obj --triple=x86_64-apple-darwin -o %t/third.o
# RUN: %lld -dylib -lSystem -order_file %t/order.txt %t/first.o %t/second.o %t/third.o -o %t/out
# RUN: llvm-objdump --macho --syms %t/out > %t/dump.txt
# RUN: llvm-objdump --macho --data-in-code %t/out >> %t/dump.txt
# RUN: FileCheck %s < %t/dump.txt
# CHECK-LABEL: SYMBOL TABLE:
# CHECK-DAG: [[#%x, SECOND:]] g F __TEXT,__text _second
# CHECK-DAG: [[#%x, FIRST:]] g F __TEXT,__text _first
# CHECK-DAG: [[#%x, THIRD:]] g F __TEXT,__text _third
# CHECK-LABEL: Data in code table (3 entries)
# CHECK-NEXT: offset length kind
# CHECK-NEXT: 0x[[#%.8x, SECOND]] 4 JUMP_TABLE32
# CHECK-NEXT: 0x[[#%.8x, FIRST]] 4 JUMP_TABLE32
# CHECK-NEXT: 0x[[#%.8x, THIRD]] 4 JUMP_TABLE32
#--- order.txt
_second
_first
_third
#--- input.s
.globl SYM
SYM:
.data_region jt32
.long 0
.end_data_region