message: Connect O1 to "all_on" off
diff: @@ -131,7 +131,10 @@ static void usage(int ret) {
  printf(" [--nostdlib]\t\t\tDon't make the ispc standard library available\n");
  printf(" [--nocpp]\t\t\t\tDon't run the C preprocessor\n");
  printf(" [-o <name>/--outfile=<name>]\tOutput filename (may be \"-\" for standard output)\n");
  - printf(" [-O0/-O(1/2/3)]\t\t\tSet optimization level (off or on). Optimizations are on by default.\n");
  + printf(" [-O0/-O(1/2/3)]\t\t\tSet optimization level. Default behavior is to optimize for speed.\n");
  + printf(" -O0\t\t\t\tOptimizations disabled.\n");
  + printf(" -O1\t\t\t\tOptimization for size.\n");
  + printf(" -O2/O3\t\t\t\tOptimization for speed.\n");
  printf(" [--opt=<option>]\t\t\tSet optimization option\n");
  printf(" disable-assertions\t\tRemove assertion statements from final code.\n");
  printf(" disable-fma\t\t\tDisable 'fused multiply-add' instructions (on targets that support them)\n");
  @@ -635,6 +638,8 @@ int main(int Argc, char *Argv[]) {
  !strcmp(argv[i], "-O3")) {
  g->opt.level = 1;
  g->codegenOptLevel = Globals::CodegenOptLevel::Aggressive;
  + if (!strcmp(argv[i], "-O1"))
  + g->opt.disableCoherentControlFlow = true;
  } else if (!strcmp(argv[i], "-"))
  ;
  else if (!strcmp(argv[i], "--nostdlib"))
  