Subzero: Initial implementation of multithreaded translation.

src/llvm2ice.cpp

Index: src/llvm2ice.cpp
diff --git a/src/llvm2ice.cpp b/src/llvm2ice.cpp
index bd86c57509c7d854ed5d432ce010dfa27e1165f2..7501bc1d45b400f1d4f3be3f396ee50e4f6a5bee 100644
--- a/src/llvm2ice.cpp
+++ b/src/llvm2ice.cpp
@@ -203,6 +203,13 @@ GenerateBuildAtts("build-atts",
                            "this executable."),
                   cl::init(false));
 
+static cl::opt<uint32_t>
+NumThreads("threads",
+           cl::desc("Number of translation threads (0 for purely sequential)"),
+           cl::init(0));

[JF, 2015/01/22 20:50:56]

This should default to std::thread::hardware_concurrency.

It's a bit confusing to have 0 and 1 be sequential, though 1 does generate a
thread whereas 0 doesn't.

[Jim Stichnoth, 2015/01/23 07:55:55]

Well, 1 isn't exactly sequential, as there would be one translation thread in
addition to the parser thread and (eventually) the emitter thread.  0 means
everything is purely sequential with a single thread for everything, just as it
is pre-CL.

I added a comment to the code, but there's not much more space available in the
description string.

As for a std::thread::hardware_concurrency() default: maybe, or maybe that minus
2 to accommodate parser and emitter threads, or some browser max, or some
browser max minus 2, or some other resource balancing logic?  Added a TODO. :) 
For now, I'd keep it 0 to be minimally invasive while the dust settles (and
until I get tsan builds).  Later, at least 2 for recombobulation testing.

+static cl::alias SplitModule("split-module", cl::desc("Alias for -threads"),

[Karl, 2015/01/22 20:41:13]

Not sure this can be an alias. Single threaded for pnacl-llc assume
split-module=1?

[JF, 2015/01/22 20:50:56]

Why add the alias at all?

[Jim Stichnoth, 2015/01/23 07:55:55]

The idea was to make it easier to plumb llvm2ice alongside pnacl-llc in the
pnacl-translate script.  (Despite its misleading name.)

But OK OK I dropped it.

+                             cl::NotHidden, cl::aliasopt(NumThreads));
+
 static int GetReturnValue(int Val) {
   if (AlwaysExitSuccess)
     return 0;
@@ -288,14 +295,15 @@ int main(int argc, char **argv) {
   Flags.DisableTranslation = DisableTranslation;
   Flags.FunctionSections = FunctionSections;
   Flags.DataSections = DataSections;
-  Flags.UseIntegratedAssembler = UseIntegratedAssembler;
   Flags.UseELFWriter = UseELFWriter;
+  Flags.UseIntegratedAssembler = UseIntegratedAssembler;
   Flags.UseSandboxing = UseSandboxing;
   Flags.PhiEdgeSplit = EnablePhiEdgeSplit;
   Flags.DecorateAsm = DecorateAsm;
   Flags.DumpStats = DumpStats;
   Flags.AllowUninitializedGlobals = AllowUninitializedGlobals;
   Flags.TimeEachFunction = TimeEachFunction;
+  Flags.NumTranslationThreads = NumThreads;
   Flags.DefaultGlobalPrefix = DefaultGlobalPrefix;
   Flags.DefaultFunctionPrefix = DefaultFunctionPrefix;
   Flags.TimingFocusOn = TimingFocusOn;
@@ -351,6 +359,8 @@ int main(int argc, char **argv) {
     Ctx.getObjectWriter()->writeInitialELFHeader();
   }
 
+  Ctx.startWorkerThreads();
+
   int ErrorStatus = 0;

[JF, 2015/01/22 20:50:56]

This should also be an std::vector<std::error_code>.

[Jim Stichnoth, 2015/01/23 07:55:55]

Changed to std::error_code.

   if (BuildOnRead) {
     Ice::PNaClTranslator Translator(&Ctx, Flags);
@@ -378,6 +388,10 @@ int main(int argc, char **argv) {
         << "--build-on-read=0 not allowed\n";
     return GetReturnValue(1);
   }
+  // Error status is the combination of the bitcode parser's error
+  // status and the translation error status.
+  ErrorStatus |= Ctx.getErrorStatus();
+
   if (UseELFWriter) {
     Ice::TimerMarker T1(Ice::TimerStack::TT_emit, &Ctx);
     Ctx.getObjectWriter()->writeNonUserSections();