[PATCH] D113820: [lld-macho] Parallelize scanning the symbol tables in export/unexport-ing.

[Vy Nguyen via Phabricator via llvm-commits]

oontvoo created this revision.
oontvoo added a reviewer: int3.
Herald added a reviewer: gkm.
Herald added a project: lld-macho.
Herald added a reviewer: lld-macho.
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(Split from D113167 <https://reviews.llvm.org/D113167>)
Benchmarking on one of our large apps which exports a few thousands symbols,
this showed an improvement of ~17%.

x ./LLD_no_parallel.txt
+ ./LLD_with_parallel.txt

  N           Min           Max        Median           Avg        Stddev

x  10         84.01         89.41         88.64        87.693     1.7424061
+  10          71.9         74.29         72.63        72.753    0.77734663
Difference at 95.0% confidence
	-14.94 +/- 1.26763
	-17.0367% +/- 1.44553%
	(Student's t, pooled s = 1.34912)

(wallclock)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113820

Files:
  lld/MachO/Driver.cpp


Index: lld/MachO/Driver.cpp
===================================================================
--- lld/MachO/Driver.cpp
+++ lld/MachO/Driver.cpp
@@ -1462,7 +1462,7 @@
     createSyntheticSymbols();
 
     if (!config->exportedSymbols.empty()) {
-      for (Symbol *sym : symtab->getSymbols()) {
+      parallelForEach(symtab->getSymbols(), [](Symbol *sym) {
         if (auto *defined = dyn_cast<Defined>(sym)) {
           StringRef symbolName = defined->getName();
           if (config->exportedSymbols.match(symbolName)) {
@@ -1474,12 +1474,13 @@
             defined->privateExtern = true;
           }
         }
-      }
+      });
     } else if (!config->unexportedSymbols.empty()) {
-      for (Symbol *sym : symtab->getSymbols())
+      parallelForEach(symtab->getSymbols(), [](Symbol *sym) {
         if (auto *defined = dyn_cast<Defined>(sym))
           if (config->unexportedSymbols.match(defined->getName()))
             defined->privateExtern = true;
+      });
     }
 
     for (const Arg *arg : args.filtered(OPT_sectcreate)) {


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