[lld] e42ad84 - [lld-macho][nfc] Refactor MarkLive
Jez Ng via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 23 06:04:13 PST 2022
Author: Jez Ng
Date: 2022-02-23T08:58:26-05:00
New Revision: e42ad84ba02220f5954c6cbc6fa9f77120ac8c06
URL: https://github.com/llvm/llvm-project/commit/e42ad84ba02220f5954c6cbc6fa9f77120ac8c06
DIFF: https://github.com/llvm/llvm-project/commit/e42ad84ba02220f5954c6cbc6fa9f77120ac8c06.diff
LOG: [lld-macho][nfc] Refactor MarkLive
This mirrors the code structure in `lld/ELF`. It also paves the way for
an upcoming diff where I templatize things.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D120376
Added:
Modified:
lld/MachO/MarkLive.cpp
Removed:
################################################################################
diff --git a/lld/MachO/MarkLive.cpp b/lld/MachO/MarkLive.cpp
index 4269c8342c656..4790e55738651 100644
--- a/lld/MachO/MarkLive.cpp
+++ b/lld/MachO/MarkLive.cpp
@@ -21,44 +21,96 @@ namespace macho {
using namespace llvm;
using namespace llvm::MachO;
-// Set live bit on for each reachable chunk. Unmarked (unreachable)
-// InputSections will be ignored by Writer, so they will be excluded
-// from the final output.
-void markLive() {
- TimeTraceScope timeScope("markLive");
-
- // We build up a worklist of sections which have been marked as live. We only
- // push into the worklist when we discover an unmarked section, and we mark
- // as we push, so sections never appear twice in the list.
- // Literal sections cannot contain references to other sections, so we only
- // store ConcatInputSections in our worklist.
+class MarkLive {
+public:
+ void enqueue(InputSection *isec, uint64_t off);
+ void addSym(Symbol *s);
+ void markTransitively();
+
+private:
+ // We build up a worklist of sections which have been marked as live. We
+ // only push into the worklist when we discover an unmarked section, and we
+ // mark as we push, so sections never appear twice in the list. Literal
+ // sections cannot contain references to other sections, so we only store
+ // ConcatInputSections in our worklist.
SmallVector<ConcatInputSection *, 256> worklist;
+};
+
+void MarkLive::enqueue(InputSection *isec, uint64_t off) {
+ if (isec->isLive(off))
+ return;
+ isec->markLive(off);
+ if (auto s = dyn_cast<ConcatInputSection>(isec)) {
+ assert(!s->isCoalescedWeak());
+ worklist.push_back(s);
+ }
+}
+
+void MarkLive::addSym(Symbol *s) {
+ if (s->used)
+ return;
+ s->used = true;
+ if (auto *d = dyn_cast<Defined>(s)) {
+ if (d->isec)
+ enqueue(d->isec, d->value);
+ if (d->unwindEntry)
+ enqueue(d->unwindEntry, 0);
+ }
+}
+
+void MarkLive::markTransitively() {
+ do {
+ // Mark things reachable from GC roots as live.
+ while (!worklist.empty()) {
+ ConcatInputSection *s = worklist.pop_back_val();
+ assert(s->live && "We mark as live when pushing onto the worklist!");
- auto enqueue = [&](InputSection *isec, uint64_t off) {
- if (isec->isLive(off))
- return;
- isec->markLive(off);
- if (auto s = dyn_cast<ConcatInputSection>(isec)) {
- assert(!s->isCoalescedWeak());
- worklist.push_back(s);
+ // Mark all symbols listed in the relocation table for this section.
+ for (const Reloc &r : s->relocs) {
+ if (auto *s = r.referent.dyn_cast<Symbol *>())
+ addSym(s);
+ else
+ enqueue(r.referent.get<InputSection *>(), r.addend);
+ }
+ for (Defined *d : s->symbols)
+ addSym(d);
}
- };
-
- auto addSym = [&](Symbol *s) {
- if (s->used)
- return;
- s->used = true;
- if (auto *d = dyn_cast<Defined>(s)) {
- if (d->isec)
- enqueue(d->isec, d->value);
- if (d->unwindEntry)
- enqueue(d->unwindEntry, 0);
+
+ // S_ATTR_LIVE_SUPPORT sections are live if they point _to_ a live
+ // section. Process them in a second pass.
+ for (ConcatInputSection *isec : inputSections) {
+ // FIXME: Check if copying all S_ATTR_LIVE_SUPPORT sections into a
+ // separate vector and only walking that here is faster.
+ if (!(isec->getFlags() & S_ATTR_LIVE_SUPPORT) || isec->live)
+ continue;
+
+ for (const Reloc &r : isec->relocs) {
+ bool referentLive;
+ if (auto *s = r.referent.dyn_cast<Symbol *>())
+ referentLive = s->isLive();
+ else
+ referentLive = r.referent.get<InputSection *>()->isLive(r.addend);
+ if (referentLive)
+ enqueue(isec, 0);
+ }
}
- };
+ // S_ATTR_LIVE_SUPPORT could have marked additional sections live,
+ // which in turn could mark additional S_ATTR_LIVE_SUPPORT sections live.
+ // Iterate. In practice, the second iteration won't mark additional
+ // S_ATTR_LIVE_SUPPORT sections live.
+ } while (!worklist.empty());
+}
+
+// Set live bit on for each reachable chunk. Unmarked (unreachable)
+// InputSections will be ignored by Writer, so they will be excluded
+// from the final output.
+void markLive() {
+ TimeTraceScope timeScope("markLive");
+ MarkLive marker;
// Add GC roots.
if (config->entry)
- addSym(config->entry);
+ marker.addSym(config->entry);
for (Symbol *sym : symtab->getSymbols()) {
if (auto *defined = dyn_cast<Defined>(sym)) {
// -exported_symbol(s_list)
@@ -69,17 +121,18 @@ void markLive() {
// explicitUndefineds code below would handle this automatically.
assert(!defined->privateExtern &&
"should have been rejected by driver");
- addSym(defined);
+ marker.addSym(defined);
continue;
}
// public symbols explicitly marked .no_dead_strip
if (defined->referencedDynamically || defined->noDeadStrip) {
- addSym(defined);
+ marker.addSym(defined);
continue;
}
- // FIXME: When we implement these flags, make symbols from them GC roots:
+ // FIXME: When we implement these flags, make symbols from them GC
+ // roots:
// * -reexported_symbol(s_list)
// * -alias(-list)
// * -init
@@ -89,80 +142,40 @@ void markLive() {
bool externsAreRoots =
config->outputType != MH_EXECUTE || config->exportDynamic;
if (externsAreRoots && !defined->privateExtern) {
- addSym(defined);
+ marker.addSym(defined);
continue;
}
}
}
// -u symbols
for (Symbol *sym : config->explicitUndefineds)
- addSym(sym);
+ marker.addSym(sym);
// local symbols explicitly marked .no_dead_strip
for (const InputFile *file : inputFiles)
if (auto *objFile = dyn_cast<ObjFile>(file))
for (Symbol *sym : objFile->symbols)
if (auto *defined = dyn_cast_or_null<Defined>(sym))
if (!defined->isExternal() && defined->noDeadStrip)
- addSym(defined);
+ marker.addSym(defined);
if (auto *stubBinder =
dyn_cast_or_null<DylibSymbol>(symtab->find("dyld_stub_binder")))
- addSym(stubBinder);
+ marker.addSym(stubBinder);
for (ConcatInputSection *isec : inputSections) {
// Sections marked no_dead_strip
if (isec->getFlags() & S_ATTR_NO_DEAD_STRIP) {
- enqueue(isec, 0);
+ marker.enqueue(isec, 0);
continue;
}
// mod_init_funcs, mod_term_funcs sections
if (sectionType(isec->getFlags()) == S_MOD_INIT_FUNC_POINTERS ||
sectionType(isec->getFlags()) == S_MOD_TERM_FUNC_POINTERS) {
- enqueue(isec, 0);
+ marker.enqueue(isec, 0);
continue;
}
}
- do {
- // Mark things reachable from GC roots as live.
- while (!worklist.empty()) {
- ConcatInputSection *s = worklist.pop_back_val();
- assert(s->live && "We mark as live when pushing onto the worklist!");
-
- // Mark all symbols listed in the relocation table for this section.
- for (const Reloc &r : s->relocs) {
- if (auto *s = r.referent.dyn_cast<Symbol *>())
- addSym(s);
- else
- enqueue(r.referent.get<InputSection *>(), r.addend);
- }
- for (Defined *d : s->symbols)
- addSym(d);
- }
-
- // S_ATTR_LIVE_SUPPORT sections are live if they point _to_ a live section.
- // Process them in a second pass.
- for (ConcatInputSection *isec : inputSections) {
- // FIXME: Check if copying all S_ATTR_LIVE_SUPPORT sections into a
- // separate vector and only walking that here is faster.
- if (!(isec->getFlags() & S_ATTR_LIVE_SUPPORT) || isec->live)
- continue;
-
- for (const Reloc &r : isec->relocs) {
- bool referentLive;
- if (auto *s = r.referent.dyn_cast<Symbol *>())
- referentLive = s->isLive();
- else
- referentLive = r.referent.get<InputSection *>()->isLive(r.addend);
- if (referentLive)
- enqueue(isec, 0);
- }
- }
-
- // S_ATTR_LIVE_SUPPORT could have marked additional sections live,
- // which in turn could mark additional S_ATTR_LIVE_SUPPORT sections live.
- // Iterate. In practice, the second iteration won't mark additional
- // S_ATTR_LIVE_SUPPORT sections live.
- } while (!worklist.empty());
+ marker.markTransitively();
}
} // namespace macho
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