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Add a llvm::shuffle and use it in lld 

With this --shuffle-sections=seed produces the same result in every
host.

Reviewed By: grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D74971
This commit is contained in:
Rafael Ávila de Espíndola 2020-02-22 09:51:02 -08:00 committed by Fangrui Song
parent e48849a240
commit 7b44f0428a
4 changed files with 23 additions and 10 deletions
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2
lld/ELF/Writer.cpp
View File

@ -1218,7 +1218,7 @@ static void maybeShuffle(DenseMap<const InputSectionBase *, int> &order) {
prio = curPrio++;
uint32_t seed = *config->shuffleSectionSeed;
std::mt19937 g(seed ? seed : std::random_device()());
std::shuffle(priorities.begin(), priorities.end(), g);
llvm::shuffle(priorities.begin(), priorities.end(), g);
int prioIndex = 0;
for (InputSectionBase *sec : inputSections) {
if (order.try_emplace(sec, priorities[prioIndex]).second)

11
lld/test/ELF/shuffle-sections-init-fini.s
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@ -21,12 +21,12 @@
# CHECK: Hex dump of section '.init_array'
# CHECK-NEXT: 0x{{[0-9a-f]+}} ff
# ORDERED-SAME: 000102 03040506 0708090a 0b
# SHUFFLED-NOT: 000102 03040506 0708090a 0b
# SHUFFLED-SAME: 04000b 06010a08 09070203 05
# CHECK: Hex dump of section '.fini_array'
# CHECK-NEXT: 0x{{[0-9a-f]+}} ff
# ORDERED-SAME: 000102 03040506 0708090a 0b
# SHUFFLED-NOT: 000102 03040506 0708090a 0b
# ORDERED-SAME: 000102 03040506 0708090a 0b
# SHUFFLED-SAME: 090401 070b0003 080a0605 02
## With a SECTIONS command, SHT_INIT_ARRAY prirotities are ignored.
## All .init_array* are shuffled together.
@ -40,11 +40,8 @@
# CHECK2: Hex dump of section '.init_array'
# ORDERED2-NEXT: 0x{{[0-9a-f]+}} 00010203 04050607 08090a0b ff
# SHUFFLED2-NOT: 0x{{[0-9a-f]+}} 00010203 04050607 08090a0b ff
# SHUFFLED2-NEXT: 0x{{[0-9a-f]+}} 04000b06 010a0809 07ff0203 05
## std::shuffle have different implementations.
## When the number of input sections are large, it is almost guaranteed
## to have an unordered result with --shuffle-sections=.
.irp i,0,1,2,3,4,5,6,7,8,9,10,11
.section .init,"ax",@progbits,unique,\i
.byte \i

10
lld/test/ELF/shuffle-sections.s
View File

@ -6,6 +6,12 @@
# CHECK: Hex dump of section '.text':
# CHECK-NEXT: 01020304
## --shuffle-sections= shuffles input sections.
# RUN: ld.lld --shuffle-sections=1 %t.o -o %t1.out
# RUN: llvm-readelf -x .text %t1.out | FileCheck %s --check-prefix=SHUFFLE1
# SHUFFLE1: Hex dump of section '.text':
# SHUFFLE1-NEXT: 0204cccc 0103
## Test that --shuffle-sections= can be used with --symbol-ordering-file
# RUN: echo "foo" > %t_order.txt
# RUN: echo "_start " >> %t_order.txt
@ -13,12 +19,12 @@
# RUN: ld.lld --symbol-ordering-file %t_order.txt --shuffle-sections=2 %t.o -o %t2.out
# RUN: llvm-readelf -x .text %t2.out | FileCheck %s --check-prefix=SHUFFLE2
# SHUFFLE2: Hex dump of section '.text':
# SHUFFLE2-NEXT: 02cccccc 01{{....}}
# SHUFFLE2-NEXT: 02cccccc 010304
# RUN: ld.lld --symbol-ordering-file %t_order.txt --shuffle-sections=3 %t.o -o %t3.out
# RUN: llvm-readelf -x .text %t3.out | FileCheck %s --check-prefix=SHUFFLE3
# SHUFFLE3: Hex dump of section '.text':
# SHUFFLE3-NEXT: 02cccccc 01{{....}}
# SHUFFLE3-NEXT: 02cccccc 010403
## .text has an alignment of 4.
.global _start

10
llvm/include/llvm/ADT/STLExtras.h
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@ -1007,6 +1007,16 @@ struct are_base_of<T, U, Ts...> {
// Extra additions for arrays
//===----------------------------------------------------------------------===//
// We have a copy here so that LLVM behaves the same when using different
// standard libraries.
template <class Iterator, class RNG>
void shuffle(Iterator first, Iterator last, RNG &&g) {
// It would be better to use a std::uniform_int_distribution,
// but that would be stdlib dependent.
for (auto size = last - first; size > 1; ++first, (void)--size)
std::iter_swap(first, first + g() % size);
}
/// Find the length of an array.
template <class T, std::size_t N>
constexpr inline size_t array_lengthof(T (&)[N]) {