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[LLD][ELF] Fix performance regression when using linker scripts (#194668)

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The addition of the support for `--enable-non-contiguous-regions` from
PR #90007 moved an "early out" condition in
`LinkerScript::computeInputSections()`. This could result in other
relatively expensive checks, i.e. `pat.sectionPat.match`,
`cmd->matchesFile`, `pat.excludesFile` and `flagsMatch`, to be performed
unnecessarily in the default situation where
`--enable-non-contiguous-regions` is disabled.

This fix restores the "early out" condition and shows an ~14%
improvement for the Linux kernel benchmark link and has been seen to
improve performance by up to ~30% for a large UE5 link.
This commit is contained in:
Andrew Ng
2026-04-29 11:29:43 +01:00
committed by GitHub
parent 6cbe31c399
commit dbdbf1e63d
1 changed files with 7 additions and 6 deletions
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13
lld/ELF/LinkerScript.cpp
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@@ -558,14 +558,17 @@ LinkerScript::computeInputSections(const InputSectionDescription *cmd,
ctx.arg.sortSection, SortSectionPolicy::None);
};
bool enableNonContiguousRegions = ctx.arg.enableNonContiguousRegions;
for (const SectionPattern &pat : cmd->sectionPatterns) {
size_t sizeBeforeCurrPat = ret.size();
for (size_t i = 0, e = sections.size(); i != e; ++i) {
// Skip if the section is dead or has been matched by a previous pattern
// in this input section description.
// Skip if the section is dead, has been matched by a previous input
// section description with non-contiguous regions disabled, or has been
// matched by a previous pattern in this input section description.
InputSectionBase *sec = sections[i];
if (!sec->isLive() || seen.contains(i))
if (!sec->isLive() || (!enableNonContiguousRegions && sec->parent) ||
seen.contains(i))
continue;
// For --emit-relocs we have to ignore entries like
@@ -586,9 +589,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *cmd,
continue;
if (sec->parent) {
// Skip if not allowing multiple matches.
if (!ctx.arg.enableNonContiguousRegions)
continue;
assert(ctx.arg.enableNonContiguousRegions);
// Disallow spilling into /DISCARD/; special handling would be needed
// for this in address assignment, and the semantics are nebulous.