[lld] b07292f - [ELF] Serialize deleteFallThruJmpInsn to fix concurrency issue

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-12-26T23:26:13-08:00
New Revision: b07292f77a1e82c27fd98105d69f351ef41ac29f

URL: https://github.com/llvm/llvm-project/commit/b07292f77a1e82c27fd98105d69f351ef41ac29f
DIFF: https://github.com/llvm/llvm-project/commit/b07292f77a1e82c27fd98105d69f351ef41ac29f.diff

LOG: [ELF] Serialize deleteFallThruJmpInsn to fix concurrency issue

New deleteFallThruJmpInsn calls `make<JumpInstrMod>` which cannot be called
concurrently. Losing parallelism is unfortunate but we can think of a better
approach if parallelism here justifies itself.

Added: 
    

Modified: 
    lld/ELF/Writer.cpp

Removed: 
    


################################################################################
diff  --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index acc78dd06734..986cca27fdf8 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1774,12 +1774,11 @@ template <class ELFT> void Writer<ELFT>::optimizeBasicBlockJumps() {
     // Delete all fall through jump instructions.  Also, check if two
     // consecutive jump instructions can be flipped so that a fall
     // through jmp instruction can be deleted.
-    parallelForEachN(0, sections.size(), [&](size_t i) {
+    for (size_t i = 0, e = sections.size(); i != e; ++i) {
       InputSection *next = i + 1 < sections.size() ? sections[i + 1] : nullptr;
-      InputSection &is = *sections[i];
-      result[i] =
-          target->deleteFallThruJmpInsn(is, is.getFile<ELFT>(), next) ? 1 : 0;
-    });
+      InputSection &sec = *sections[i];
+      result[i] = target->deleteFallThruJmpInsn(sec, sec.file, next) ? 1 : 0;
+    }
     size_t numDeleted = std::count(result.begin(), result.end(), 1);
     if (numDeleted > 0) {
       script->assignAddresses();