Reduce wait times for very large PEXE files.

src/IceGlobalContext.cpp

 //===- subzero/src/IceGlobalContext.cpp - Global context defs -------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 271 matching lines @@
   }
   Str << "\n";
   if (Func != nullptr) {
     Str << "|" << Name << "|Cfg Memory       |" << Func->getTotalMemoryMB()
         << " MB\n";
     Str << "|" << Name << "|Liveness Memory  |" << Func->getLivenessMemoryMB()
         << " MB\n";
   }
 }
 
+namespace {
+
+// By default, wake up the main parser thread when the OptQ gets half empty.
+static constexpr size_t DefaultOptQWakeupSize = GlobalContext::MaxOptQSize >> 1;
+
+} // end of anonymous namespace
+
 GlobalContext::GlobalContext(Ostream *OsDump, Ostream *OsEmit, Ostream *OsError,
                              ELFStreamer *ELFStr)
     : Strings(new StringPool()), ConstPool(new ConstantPool()), ErrorStatus(),
       StrDump(OsDump), StrEmit(OsEmit), StrError(OsError), IntrinsicsInfo(this),
-      ObjectWriter(), OptQ(/*Sequential=*/getFlags().isSequential(),
-                           /*MaxSize=*/
-                           getFlags().isParseParallel()
-                               ? MaxOptQSize
-                               : getFlags().getNumTranslationThreads()),
+      ObjectWriter(),
+      OptQWakeupSize(std::max(DefaultOptQWakeupSize,
+                              size_t(getFlags().getNumTranslationThreads()))),
+      OptQ(/*Sequential=*/getFlags().isSequential(),
+           /*MaxSize=*/
+           getFlags().isParseParallel()
+               ? MaxOptQSize
+               : getFlags().getNumTranslationThreads()),
       // EmitQ is allowed unlimited size.
       EmitQ(/*Sequential=*/getFlags().isSequential()),
       DataLowering(TargetDataLowering::createLowering(this)) {
   assert(OsDump && "OsDump is not defined for GlobalContext");
   assert(OsEmit && "OsEmit is not defined for GlobalContext");
   assert(OsError && "OsError is not defined for GlobalContext");
   // Make sure thread_local fields are properly initialized before any
   // accesses are made.  Do this here instead of at the start of
   // main() so that all clients (e.g. unit tests) can benefit for
   // free.
@@ skipping 621 matching lines @@
   {
     TimerMarker _(TimerStack::TT_qTransPush, this);
     OptQ.blockingPush(std::move(Item));
   }
   if (getFlags().isSequential())
     translateFunctions();
 }
 
 std::unique_ptr<OptWorkItem> GlobalContext::optQueueBlockingPop() {
   TimerMarker _(TimerStack::TT_qTransPop, this);
-  return std::unique_ptr<OptWorkItem>(OptQ.blockingPop());
+  return OptQ.blockingPop(OptQWakeupSize);
 }
 
 void GlobalContext::emitQueueBlockingPush(
     std::unique_ptr<EmitterWorkItem> Item) {
   assert(Item);
   {
     TimerMarker _(TimerStack::TT_qEmitPush, this);
     EmitQ.blockingPush(std::move(Item));
   }
   if (getFlags().isSequential())
@@ skipping 76 matching lines @@
 void TimerMarker::pushCfg(const Cfg *Func) {
   Ctx = Func->getContext();
   Active = Func->getFocusedTiming() || getFlags().getSubzeroTimingEnabled();
   if (Active)
     Ctx->pushTimer(ID, StackID);
 }
 
 ICE_TLS_DEFINE_FIELD(GlobalContext::ThreadContext *, GlobalContext, TLS);
 
 } // end of namespace Ice