+ bool OnlyOptimizeForSize = (TM->getOptLevel() < CodeGenOpt::Aggressive) &&
+ (EnableGlobalMerge == cl::BOU_UNSET);
+ // Merging of extern globals is enabled by default on non-Mach-O as we
+ // expect it to be generally either beneficial or harmless. On Mach-O it
+ // is disabled as we emit the .subsections_via_symbols directive which
+ // means that merging extern globals is not safe.
+ bool MergeExternalByDefault = !TM->getTargetTriple().isOSBinFormatMachO();
+ addPass(createGlobalMergePass(TM, 127, OnlyOptimizeForSize,
+ MergeExternalByDefault));
+ }