Allow Subzero to parse function blocks in parallel.

src/IceCompiler.cpp

Index: src/IceCompiler.cpp
diff --git a/src/IceCompiler.cpp b/src/IceCompiler.cpp
index bd5e8343a554bf1ada85fd1da831f64ce6007770..46e7c5c607a4309c263aac51e453b830559ca789 100644
--- a/src/IceCompiler.cpp
+++ b/src/IceCompiler.cpp
@@ -63,8 +63,6 @@ void Compiler::run(const Ice::ClFlags &Flags, GlobalContext &Ctx,
   // allows only --filetype=obj. Check here to avoid cryptic error messages
   // downstream.
   if (!BuildDefs::dump() && Ctx.getFlags().getOutFileType() != FT_Elf) {
-    // TODO(stichnot): Access the actual command-line argument via
-    // llvm::Option.ArgStr and .ValueStr .
     Ctx.getStrError()
         << "Error: only --filetype=obj is supported in this build.\n";
     Ctx.getErrorStatus()->assign(EC_Args);
@@ -90,6 +88,7 @@ void Compiler::run(const Ice::ClFlags &Flags, GlobalContext &Ctx,
       Ctx.getStrError()
           << "non BuildOnRead is not supported w/ PNACL_BROWSER_TRANSLATOR\n";
       Ctx.getErrorStatus()->assign(EC_Args);
+      Ctx.waitForWorkerThreads();
       return;
     }
     // Globals must be kept alive after lowering when converting from LLVM to
@@ -108,6 +107,7 @@ void Compiler::run(const Ice::ClFlags &Flags, GlobalContext &Ctx,
     if (!Mod) {
       Err.print(Flags.getAppName().c_str(), llvm::errs());
       Ctx.getErrorStatus()->assign(EC_Bitcode);
+      Ctx.waitForWorkerThreads();
       return;
     }
 
@@ -118,6 +118,7 @@ void Compiler::run(const Ice::ClFlags &Flags, GlobalContext &Ctx,
     Ctx.getStrError() << "Error: Build doesn't allow LLVM IR, "
                       << "--build-on-read=0 not allowed\n";
     Ctx.getErrorStatus()->assign(EC_Args);
+    Ctx.waitForWorkerThreads();
     return;
   }