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Reland "[LLD][ELF] Don't spill to same memory region" (#130851)
Relands #129795 Remove skipped potential spills from their parent input section descriptions to prevent undefined behavior.
This commit is contained in:
Daniel Thornburgh
GitHub
parent
89fa592b68
commit
009dfb435f
@ -563,7 +563,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *cmd,
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continue;
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if (!cmd->matchesFile(*sec->file) || pat.excludesFile(*sec->file) ||
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sec->parent == &outCmd || !flagsMatch(sec))
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!flagsMatch(sec))
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continue;
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if (sec->parent) {
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@ -626,7 +626,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *cmd,
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for (InputSectionDescription *isd : scd->sc.commands) {
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for (InputSectionBase *sec : isd->sectionBases) {
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if (sec->parent == &outCmd || !flagsMatch(sec))
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if (!flagsMatch(sec))
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continue;
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bool isSpill = sec->parent && isa<OutputSection>(sec->parent);
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if (!sec->parent || (isSpill && outCmd.name == "/DISCARD/")) {
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@ -1559,6 +1559,8 @@ bool LinkerScript::spillSections() {
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if (potentialSpillLists.empty())
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return false;
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DenseSet<PotentialSpillSection *> skippedSpills;
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bool spilled = false;
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for (SectionCommand *cmd : reverse(sectionCommands)) {
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auto *osd = dyn_cast<OutputDesc>(cmd);
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@ -1585,16 +1587,34 @@ bool LinkerScript::spillSections() {
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if (isa<PotentialSpillSection>(isec))
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continue;
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// Find the next potential spill location and remove it from the list.
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auto it = potentialSpillLists.find(isec);
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if (it == potentialSpillLists.end())
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continue;
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break;
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// Consume spills until finding one that might help, then consume it.
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auto canSpillHelp = [&](PotentialSpillSection *spill) {
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// Spills to the same region that overflowed cannot help.
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if (hasRegionOverflowed(osec->memRegion) &&
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spill->getParent()->memRegion == osec->memRegion)
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return false;
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if (hasRegionOverflowed(osec->lmaRegion) &&
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spill->getParent()->lmaRegion == osec->lmaRegion)
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return false;
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return true;
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};
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PotentialSpillList &list = it->second;
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PotentialSpillSection *spill = list.head;
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if (spill->next)
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PotentialSpillSection *spill;
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for (spill = list.head; spill; spill = spill->next) {
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if (list.head->next)
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list.head = spill->next;
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else
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potentialSpillLists.erase(isec);
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if (canSpillHelp(spill))
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break;
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skippedSpills.insert(spill);
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}
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if (!spill)
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continue;
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// Replace the next spill location with the spilled section and adjust
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// its properties to match the new location. Note that the alignment of
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@ -1629,6 +1649,15 @@ bool LinkerScript::spillSections() {
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}
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}
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// Clean up any skipped spills.
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DenseSet<InputSectionDescription *> isds;
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for (PotentialSpillSection *s : skippedSpills)
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isds.insert(s->isd);
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for (InputSectionDescription *isd : isds)
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llvm::erase_if(isd->sections, [&](InputSection *s) {
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return skippedSpills.contains(dyn_cast<PotentialSpillSection>(s));
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});
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return spilled;
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}
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@ -450,3 +450,103 @@ SECTIONS {
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# TO-DISCARD: error: section '.two_byte_section' cannot spill from/to /DISCARD/
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# TO-DISCARD-WARN: warning: section '.two_byte_section' cannot spill from/to /DISCARD/
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#--- same-mem-region.lds
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## Spills to the same memory region that overflowed do not consume address assignment passes.
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MEMORY {
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a : ORIGIN = 0, LENGTH = 0
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b : ORIGIN = 0, LENGTH = 3
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c : ORIGIN = 3, LENGTH = 3
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d : ORIGIN = 6, LENGTH = 3
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}
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SECTIONS {
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CLASS(class) { *(.one_byte_section .two_byte_section) }
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.a00 : { CLASS(class) } >a AT>c
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.a01 : { CLASS(class) } >a AT>d
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.a02 : { CLASS(class) } >a AT>d
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.a03 : { CLASS(class) } >a AT>d
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.a04 : { CLASS(class) } >a AT>d
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.a05 : { CLASS(class) } >a AT>d
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.a06 : { CLASS(class) } >a AT>d
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.a07 : { CLASS(class) } >a AT>d
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.a08 : { CLASS(class) } >a AT>d
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.a09 : { CLASS(class) } >a AT>d
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.a10 : { CLASS(class) } >a AT>d
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.a11 : { CLASS(class) } >a AT>d
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.a12 : { CLASS(class) } >a AT>d
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.a13 : { CLASS(class) } >a AT>d
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.a14 : { CLASS(class) } >a AT>d
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.a15 : { CLASS(class) } >a AT>d
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.a16 : { CLASS(class) } >a AT>d
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.a17 : { CLASS(class) } >a AT>d
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.a18 : { CLASS(class) } >a AT>d
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.a19 : { CLASS(class) } >a AT>d
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.a20 : { CLASS(class) } >a AT>d
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.a21 : { CLASS(class) } >a AT>d
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.a22 : { CLASS(class) } >a AT>d
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.a23 : { CLASS(class) } >a AT>d
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.a24 : { CLASS(class) } >a AT>d
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.a25 : { CLASS(class) } >a AT>d
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.a26 : { CLASS(class) } >a AT>d
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.a27 : { CLASS(class) } >a AT>d
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.a28 : { CLASS(class) } >a AT>d
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.a29 : { CLASS(class) } >a AT>d
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.a30 : { CLASS(class) } >a AT>d
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.b : { CLASS(class) } >b AT>d
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}
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# RUN: ld.lld -T same-mem-region.lds -o same-mem-region spill.o
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# RUN: llvm-readelf -S same-mem-region | FileCheck %s --check-prefix=SAME-MEM-REGION
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# SAME-MEM-REGION: Name Type Address Off Size
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# SAME-MEM-REGION: .b PROGBITS 0000000000000000 001000 000003
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#--- same-lma-region.lds
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## Spills to the same load region that overflowed do not consume address assignment passes.
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MEMORY {
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a : ORIGIN = 0, LENGTH = 0
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b : ORIGIN = 0, LENGTH = 3
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c : ORIGIN = 3, LENGTH = 3
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d : ORIGIN = 6, LENGTH = 3
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}
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SECTIONS {
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CLASS(class) { *(.one_byte_section .two_byte_section) }
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.a00 : { CLASS(class) } >c AT>a
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.a01 : { CLASS(class) } >d AT>a
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.a02 : { CLASS(class) } >d AT>a
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.a03 : { CLASS(class) } >d AT>a
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.a04 : { CLASS(class) } >d AT>a
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.a05 : { CLASS(class) } >d AT>a
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.a06 : { CLASS(class) } >d AT>a
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.a07 : { CLASS(class) } >d AT>a
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.a08 : { CLASS(class) } >d AT>a
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.a09 : { CLASS(class) } >d AT>a
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.a10 : { CLASS(class) } >d AT>a
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.a11 : { CLASS(class) } >d AT>a
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.a12 : { CLASS(class) } >d AT>a
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.a13 : { CLASS(class) } >d AT>a
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.a14 : { CLASS(class) } >d AT>a
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.a15 : { CLASS(class) } >d AT>a
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.a16 : { CLASS(class) } >d AT>a
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.a17 : { CLASS(class) } >d AT>a
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.a18 : { CLASS(class) } >d AT>a
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.a19 : { CLASS(class) } >d AT>a
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.a20 : { CLASS(class) } >d AT>a
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.a21 : { CLASS(class) } >d AT>a
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.a22 : { CLASS(class) } >d AT>a
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.a23 : { CLASS(class) } >d AT>a
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.a24 : { CLASS(class) } >d AT>a
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.a25 : { CLASS(class) } >d AT>a
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.a26 : { CLASS(class) } >d AT>a
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.a27 : { CLASS(class) } >d AT>a
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.a28 : { CLASS(class) } >d AT>a
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.a29 : { CLASS(class) } >d AT>a
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.a30 : { CLASS(class) } >d AT>a
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.b : { CLASS(class) } >d AT>b
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}
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# RUN: ld.lld -T same-lma-region.lds -o same-lma-region spill.o
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# RUN: llvm-readelf -S same-lma-region | FileCheck %s --check-prefix=SAME-LMA-REGION
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# SAME-LMA-REGION: Name Type Address Off Size
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# SAME-LMA-REGION: .b PROGBITS 0000000000000006 001006 000003
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