llvm-6502/test/MC/ELF/comdat-reloc.s
Rafael Espindola b4b0b34181 Write relocation sections contiguously.
Linkers normally read all the relocations upfront to compute the references
between sections. Putting them together is a bit more cache friendly.

I benchmarked linking a Release+Asserts clang with gold on a vm. I tried all
4 combinations of --gc-sections/no --gc-section hot and cold cache.

I cleared the cache with

echo 3 > /proc/sys/vm/drop_caches

and warmed it up by running the link once before timing the subsequent ones.

With cold cache and --gc-sections the time goes from

1.86130781665 +- 0.01713126697463843 seconds
to
1.82370735105 +- 0.014127522318814516 seconds

With cold cache and no --gc-sections the time goes from

1.6087245435500002 +- 0.012999066825178644 seconds
to
1.5687122041500001 +- 0.013145850126026619 seconds

With hot cache and no --gc-sections the time goes from

0.926200939 ( +-  0.33% ) seconds
to
0.907200079 ( +-  0.31% ) seconds

With hot cache and gc sections the time goes from

1.183038049 ( +-  0.34% ) seconds
to
1.147355862 ( +-  0.39% ) seconds

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235165 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-17 08:11:38 +00:00

30 lines
607 B
ArmAsm

// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -s -sd | FileCheck %s
.text
.globl hello
.type hello,@function
hello:
call world
ret
.section .text.world,"axG",@progbits,world,comdat
.type world,@function
world:
call doctor
ret
// CHECK: Name: .group
// CHECK-NOT: SectionData
// CHECK: SectionData
// CHECK-NEXT: 0000: 01000000 05000000 07000000
// CHECK: Index: 5
// CHECK-NEXT: Name: .text.world
// CHECK-NOT: Section {
// CHECK: SHF_GROUP
// CHECK: Index: 7
// CHECK-NEXT: Name: .rela.text.world
// CHECK-NOT: Section {
// CHECK: SHF_GROUP