Subzero. Moar performance tweaks.

src/main.cpp

 //===- subzero/src/main.cpp - Entry point for bitcode translation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// \brief Defines the entry point for translating PNaCl bitcode into native
 /// code.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "IceBrowserCompileServer.h"
 #include "IceBuildDefs.h"
 #include "IceCompileServer.h"
 
+#ifdef __pnacl__
+#include <malloc.h>
+#endif // __pnacl__
+
 /// Depending on whether we are building the compiler for the browser or
 /// standalone, we will end up creating a Ice::BrowserCompileServer or
 /// Ice::CLCompileServer object. Method
 /// Ice::CompileServer::runAndReturnErrorCode is used for the invocation.
 /// There are no real commandline arguments in the browser case. They are
 /// supplied via IPC so argc, and argv are not used in that case.
 /// We can only compile the Ice::BrowserCompileServer object with the PNaCl
 /// compiler toolchain, when building Subzero as a sandboxed translator.
 int main(int argc, char **argv) {
+#ifdef __pnacl__
+#define M_GRANULARITY (-2)
+  // PNaCl's default malloc implementation grabs small chunks of memory with
+  // mmap at a time, hence causing significant slowdowns. This call ensures that
+  // mmap is used to allocate 16MB at a time, to amortize the system call cost.
+  mallopt(M_GRANULARITY, 16 * 1024 * 1024);
+#undef M_GRANULARITY
+#endif // __pnacl__
+
   if (Ice::BuildDefs::browser()) {
     assert(argc == 1);
     return Ice::BrowserCompileServer().runAndReturnErrorCode();
   }
   return Ice::CLCompileServer(argc, argv).runAndReturnErrorCode();
 }