Skip to content

Reland "[LLD][ELF] Don't spill to same memory region" #130851

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 1 commit into from
Mar 11, 2025
Merged

Reland "[LLD][ELF] Don't spill to same memory region" #130851

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
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
47 changes: 38 additions & 9 deletions lld/ELF/LinkerScript.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -563,7 +563,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *cmd,
continue;

if (!cmd->matchesFile(*sec->file) || pat.excludesFile(*sec->file) ||
sec->parent == &outCmd || !flagsMatch(sec))
!flagsMatch(sec))
continue;

if (sec->parent) {
Expand Down Expand Up @@ -626,7 +626,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *cmd,

for (InputSectionDescription *isd : scd->sc.commands) {
for (InputSectionBase *sec : isd->sectionBases) {
if (sec->parent == &outCmd || !flagsMatch(sec))
if (!flagsMatch(sec))
continue;
bool isSpill = sec->parent && isa<OutputSection>(sec->parent);
if (!sec->parent || (isSpill && outCmd.name == "/DISCARD/")) {
Expand Down Expand Up @@ -1559,6 +1559,8 @@ bool LinkerScript::spillSections() {
if (potentialSpillLists.empty())
return false;

DenseSet<PotentialSpillSection *> skippedSpills;

bool spilled = false;
for (SectionCommand *cmd : reverse(sectionCommands)) {
auto *osd = dyn_cast<OutputDesc>(cmd);
Expand All @@ -1585,16 +1587,34 @@ bool LinkerScript::spillSections() {
if (isa<PotentialSpillSection>(isec))
continue;

// Find the next potential spill location and remove it from the list.
auto it = potentialSpillLists.find(isec);
if (it == potentialSpillLists.end())
continue;
break;

// Consume spills until finding one that might help, then consume it.
auto canSpillHelp = [&](PotentialSpillSection *spill) {
// Spills to the same region that overflowed cannot help.
if (hasRegionOverflowed(osec->memRegion) &&
spill->getParent()->memRegion == osec->memRegion)
return false;
if (hasRegionOverflowed(osec->lmaRegion) &&
spill->getParent()->lmaRegion == osec->lmaRegion)
return false;
return true;
};
PotentialSpillList &list = it->second;
PotentialSpillSection *spill = list.head;
if (spill->next)
list.head = spill->next;
else
potentialSpillLists.erase(isec);
PotentialSpillSection *spill;
for (spill = list.head; spill; spill = spill->next) {
if (list.head->next)
list.head = spill->next;
else
potentialSpillLists.erase(isec);
if (canSpillHelp(spill))
break;
skippedSpills.insert(spill);
}
if (!spill)
continue;

// Replace the next spill location with the spilled section and adjust
// its properties to match the new location. Note that the alignment of
Expand Down Expand Up @@ -1629,6 +1649,15 @@ bool LinkerScript::spillSections() {
}
}

// Clean up any skipped spills.
DenseSet<InputSectionDescription *> isds;
for (PotentialSpillSection *s : skippedSpills)
isds.insert(s->isd);
for (InputSectionDescription *isd : isds)
llvm::erase_if(isd->sections, [&](InputSection *s) {
return skippedSpills.contains(dyn_cast<PotentialSpillSection>(s));
});

return spilled;
}

Expand Down
100 changes: 100 additions & 0 deletions lld/test/ELF/linkerscript/section-class.test
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -450,3 +450,103 @@ SECTIONS {

# TO-DISCARD: error: section '.two_byte_section' cannot spill from/to /DISCARD/
# TO-DISCARD-WARN: warning: section '.two_byte_section' cannot spill from/to /DISCARD/

#--- same-mem-region.lds
## Spills to the same memory region that overflowed do not consume address assignment passes.
MEMORY {
a : ORIGIN = 0, LENGTH = 0
b : ORIGIN = 0, LENGTH = 3
c : ORIGIN = 3, LENGTH = 3
d : ORIGIN = 6, LENGTH = 3
}
SECTIONS {
CLASS(class) { *(.one_byte_section .two_byte_section) }
.a00 : { CLASS(class) } >a AT>c
.a01 : { CLASS(class) } >a AT>d
.a02 : { CLASS(class) } >a AT>d
.a03 : { CLASS(class) } >a AT>d
.a04 : { CLASS(class) } >a AT>d
.a05 : { CLASS(class) } >a AT>d
.a06 : { CLASS(class) } >a AT>d
.a07 : { CLASS(class) } >a AT>d
.a08 : { CLASS(class) } >a AT>d
.a09 : { CLASS(class) } >a AT>d
.a10 : { CLASS(class) } >a AT>d
.a11 : { CLASS(class) } >a AT>d
.a12 : { CLASS(class) } >a AT>d
.a13 : { CLASS(class) } >a AT>d
.a14 : { CLASS(class) } >a AT>d
.a15 : { CLASS(class) } >a AT>d
.a16 : { CLASS(class) } >a AT>d
.a17 : { CLASS(class) } >a AT>d
.a18 : { CLASS(class) } >a AT>d
.a19 : { CLASS(class) } >a AT>d
.a20 : { CLASS(class) } >a AT>d
.a21 : { CLASS(class) } >a AT>d
.a22 : { CLASS(class) } >a AT>d
.a23 : { CLASS(class) } >a AT>d
.a24 : { CLASS(class) } >a AT>d
.a25 : { CLASS(class) } >a AT>d
.a26 : { CLASS(class) } >a AT>d
.a27 : { CLASS(class) } >a AT>d
.a28 : { CLASS(class) } >a AT>d
.a29 : { CLASS(class) } >a AT>d
.a30 : { CLASS(class) } >a AT>d
.b : { CLASS(class) } >b AT>d
}

# RUN: ld.lld -T same-mem-region.lds -o same-mem-region spill.o
# RUN: llvm-readelf -S same-mem-region | FileCheck %s --check-prefix=SAME-MEM-REGION

# SAME-MEM-REGION: Name Type Address Off Size
# SAME-MEM-REGION: .b PROGBITS 0000000000000000 001000 000003

#--- same-lma-region.lds
## Spills to the same load region that overflowed do not consume address assignment passes.
MEMORY {
a : ORIGIN = 0, LENGTH = 0
b : ORIGIN = 0, LENGTH = 3
c : ORIGIN = 3, LENGTH = 3
d : ORIGIN = 6, LENGTH = 3
}
SECTIONS {
CLASS(class) { *(.one_byte_section .two_byte_section) }
.a00 : { CLASS(class) } >c AT>a
.a01 : { CLASS(class) } >d AT>a
.a02 : { CLASS(class) } >d AT>a
.a03 : { CLASS(class) } >d AT>a
.a04 : { CLASS(class) } >d AT>a
.a05 : { CLASS(class) } >d AT>a
.a06 : { CLASS(class) } >d AT>a
.a07 : { CLASS(class) } >d AT>a
.a08 : { CLASS(class) } >d AT>a
.a09 : { CLASS(class) } >d AT>a
.a10 : { CLASS(class) } >d AT>a
.a11 : { CLASS(class) } >d AT>a
.a12 : { CLASS(class) } >d AT>a
.a13 : { CLASS(class) } >d AT>a
.a14 : { CLASS(class) } >d AT>a
.a15 : { CLASS(class) } >d AT>a
.a16 : { CLASS(class) } >d AT>a
.a17 : { CLASS(class) } >d AT>a
.a18 : { CLASS(class) } >d AT>a
.a19 : { CLASS(class) } >d AT>a
.a20 : { CLASS(class) } >d AT>a
.a21 : { CLASS(class) } >d AT>a
.a22 : { CLASS(class) } >d AT>a
.a23 : { CLASS(class) } >d AT>a
.a24 : { CLASS(class) } >d AT>a
.a25 : { CLASS(class) } >d AT>a
.a26 : { CLASS(class) } >d AT>a
.a27 : { CLASS(class) } >d AT>a
.a28 : { CLASS(class) } >d AT>a
.a29 : { CLASS(class) } >d AT>a
.a30 : { CLASS(class) } >d AT>a
.b : { CLASS(class) } >d AT>b
}

# RUN: ld.lld -T same-lma-region.lds -o same-lma-region spill.o
# RUN: llvm-readelf -S same-lma-region | FileCheck %s --check-prefix=SAME-LMA-REGION

# SAME-LMA-REGION: Name Type Address Off Size
# SAME-LMA-REGION: .b PROGBITS 0000000000000006 001006 000003
Loading