Skip to content

[lld][elf] Skip BP ordering input sections with null data #149265

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jul 18, 2025
+18 −9
Merged

[lld][elf] Skip BP ordering input sections with null data #149265

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
4fba85b
[lld][elf] Skip BP ordering input sections with null data
Colibrow Jul 17, 2025
f0944cc
Address comments.
Colibrow Jul 17, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 3 additions & 3 deletions lld/ELF/BPSectionOrderer.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -76,10 +76,10 @@ DenseMap<const InputSectionBase *, int> elf::runBalancedPartitioning(
if (!d)
return;
auto *sec = dyn_cast_or_null<InputSection>(d->section);
// Skip empty, discarded, ICF folded sections. Skipping ICF folded sections
// reduces duplicate detection work in BPSectionOrderer.
// Skip empty, discarded, ICF folded sections, .bss. Skipping ICF folded
// sections reduces duplicate detection work in BPSectionOrderer.
if (!sec || sec->size == 0 || !sec->isLive() || sec->repl != sec ||
!orderer.secToSym.try_emplace(sec, d).second)
!orderer.secToSym.try_emplace(sec, d).second || !sec->content().data())
Copy link
Contributor

@ellishg ellishg Jul 17, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Why not move the check to before we add the section to secToSym?

Copy link
Contributor Author

@Colibrow Colibrow Jul 17, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yeah. Fixed it.

return;
rootSymbolToSectionIdxs[CachedHashStringRef(
lld::utils::getRootSymbol(sym.getName()))]
Expand Down
21 changes: 15 additions & 6 deletions lld/test/ELF/bp-section-orderer.s
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -26,28 +26,28 @@

# RUN: ld.lld -o out.s a.o --irpgo-profile=a.profdata --bp-startup-sort=function
# RUN: llvm-nm -jn out.s | tr '\n' , | FileCheck %s --check-prefix=STARTUP
# STARTUP: s5,s4,s3,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d3,d2,d1,{{$}}
# STARTUP: s5,s4,s3,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d3,d2,d1,g1,{{$}}

# RUN: ld.lld -o out.os a.o --irpgo-profile=a.profdata --bp-startup-sort=function --symbol-ordering-file a.txt
# RUN: llvm-nm -jn out.os | tr '\n' , | FileCheck %s --check-prefix=ORDER-STARTUP
# ORDER-STARTUP: s2,s1,s5,s4,s3,A,F,E,D,B,C,merged1,merged2,_start,d3,d2,d4,d1,{{$}}
# ORDER-STARTUP: s2,s1,s5,s4,s3,A,F,E,D,B,C,merged1,merged2,_start,d3,d2,d4,d1,g1,{{$}}

# RUN: ld.lld -o out.cf a.o --verbose-bp-section-orderer --bp-compression-sort=function 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-FUNC
# RUN: ld.lld -o out.cf.icf a.o --verbose-bp-section-orderer --bp-compression-sort=function --icf=all --gc-sections 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-ICF-FUNC
# RUN: llvm-nm -jn out.cf | tr '\n' , | FileCheck %s --check-prefix=CFUNC
# CFUNC: s5,s4,s3,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d3,d2,d1,{{$}}
# CFUNC: s5,s4,s3,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d3,d2,d1,g1,{{$}}

# RUN: ld.lld -o out.cd a.o --verbose-bp-section-orderer --bp-compression-sort=data 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-DATA
# RUN: llvm-nm -jn out.cd | tr '\n' , | FileCheck %s --check-prefix=CDATA
# CDATA: s5,s3,s4,s2,s1,F,C,E,D,B,A,merged1,merged2,_start,d4,d1,d3,d2,{{$}}
# CDATA: s5,s3,s4,s2,s1,F,C,E,D,B,A,merged1,merged2,_start,d4,d1,d3,d2,g1,{{$}}

# RUN: ld.lld -o out.cb a.o --verbose-bp-section-orderer --bp-compression-sort=both 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-BOTH
# RUN: llvm-nm -jn out.cb | tr '\n' , | FileCheck %s --check-prefix=CBOTH
# CBOTH: s5,s3,s4,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d1,d3,d2,{{$}}
# CBOTH: s5,s3,s4,s2,s1,A,F,merged1,merged2,C,E,D,B,_start,d4,d1,d3,d2,g1,{{$}}

# RUN: ld.lld -o out.cbs a.o --verbose-bp-section-orderer --bp-compression-sort=both --irpgo-profile=a.profdata --bp-startup-sort=function 2>&1 | FileCheck %s --check-prefix=BP-COMPRESSION-BOTH
# RUN: llvm-nm -jn out.cbs | tr '\n' , | FileCheck %s --check-prefix=CBOTH-STARTUP
# CBOTH-STARTUP: s5,s3,s4,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d1,d3,d2,{{$}}
# CBOTH-STARTUP: s5,s3,s4,s2,s1,A,B,C,F,E,D,merged1,merged2,_start,d4,d1,d3,d2,g1,{{$}}

# BP-COMPRESSION-FUNC: Ordered 9 sections ([[#]] bytes) using balanced partitioning
# BP-COMPRESSION-ICF-FUNC: Ordered 8 sections ([[#]] bytes) using balanced partitioning
Expand Down Expand Up @@ -108,6 +108,7 @@ d3
d2

#--- a.c
int g1;
const char s5[] = "engineering";
const char s4[] = "computer program";
const char s3[] = "hardware engineer";
Expand Down Expand Up @@ -377,6 +378,14 @@ d1:
.word 6 // 0x6
.size d1, 16

.type g1,@object // @g1
.section .bss.g1,"aw",@nobits
.globl g1
.p2align 2, 0x0
g1:
.word 0 // 0x0
.size g1, 4

.section ".note.GNU-stack","",@progbits
.addrsig
.addrsig_sym F
Expand Down
Loading