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[LLD][ELF] Fix SHF_MERGE misalignment when spilled #119289

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Merged
merged 3 commits into from
Dec 10, 2024
Merged

[LLD][ELF] Fix SHF_MERGE misalignment when spilled #119289

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2f4b8f5
[LLD][ELF] Fix SHF_MERGE misalignment when spilled
mysterymath Dec 6, 2024
a8e632c
clang-format
mysterymath Dec 9, 2024
87dae38
Address review feedback
mysterymath Dec 10, 2024
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16 changes: 15 additions & 1 deletion lld/ELF/OutputSections.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -253,8 +253,22 @@ void OutputSection::finalizeInputSections() {
for (InputSection *s : isd->sections)
commitSection(s);
}
for (auto *ms : mergeSections)
for (auto *ms : mergeSections) {
// Merging may have increased the alignment of a spillable section. Update
// the alignment of potential spill sections and their containing output
// sections.
if (!script->potentialSpillLists.empty()) {
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@MaskRay MaskRay Dec 10, 2024

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The empty() test is redundant

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@mysterymath mysterymath Dec 10, 2024

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Removed.

if (auto it = script->potentialSpillLists.find(ms);
it != script->potentialSpillLists.end()) {
for (PotentialSpillSection *s = it->second.head; s; s = s->next) {
s->addralign = std::max(s->addralign, ms->addralign);
s->parent->addralign = std::max(s->parent->addralign, s->addralign);
}
}
}

ms->finalizeContents();
}
}

static void sortByOrder(MutableArrayRef<InputSection *> in,
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10 changes: 6 additions & 4 deletions lld/test/ELF/linkerscript/section-class.test
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Expand Up @@ -310,17 +310,19 @@ SECTIONS {
.byte 0x12, 0x34

.section .b,"aM",@progbits,1
.p2align 1
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@MaskRay MaskRay Dec 10, 2024

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An alignment of 2 works, but a larger alignment makes the effect clearer.

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@MaskRay MaskRay Dec 10, 2024

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We also need to dump the section content (e.g. -x second )

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@mysterymath mysterymath Dec 10, 2024

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Done.

.byte 0x12

# RUN: llvm-mc -n -filetype=obj -triple=x86_64 merge.s -o merge.o

#--- spill-merge.lds
## SHF_MERGE sections are spilled according to the class refs of the first
## merged input section (the one giving the resulting section its name).
## Spills take into account increases in section alignment due to merging.
MEMORY {
a : ORIGIN = 0, LENGTH = 1
b : ORIGIN = 1, LENGTH = 2
c : ORIGIN = 3, LENGTH = 2
b : ORIGIN = 1, LENGTH = 4
c : ORIGIN = 5, LENGTH = 4
}

SECTIONS {
Expand All @@ -336,8 +338,8 @@ SECTIONS {

# SPILL-MERGE: Name Type Address Off Size
# SPILL-MERGE: .first PROGBITS 0000000000000000 000190 000000
# SPILL-MERGE-NEXT: .second PROGBITS 0000000000000001 001001 000002
# SPILL-MERGE-NEXT: .third PROGBITS 0000000000000003 001003 000000
# SPILL-MERGE-NEXT: .second PROGBITS 0000000000000002 001002 000003
# SPILL-MERGE-NEXT: .third PROGBITS 0000000000000006 001006 000000

#--- link-order.s
.section .a,"a",@progbits
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