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...res, some floating point options like unsafe-fp-math, etc., those are (or can be made) explicit in the IR. Is that the way to go? We currently don't emit some of them in the IR, but I see that Clang does, so perhaps we should just mimic that. But some other options are not expressed in IR (e.g. FunctionSections, relocation model). I see that I can pass LLVM options to the plugin, so one way is to pass all non-default options as plugin-opt cmdline flags. I can't find code in Clang that does that though. Thanks for your advice, Johan -------------- next part -------------- An HTML attachment was...

...for LTO as the llvm pass needs to be run after >> all inlining decisions have been made and LTO codegen has to be done with >> -ffunction-sections. >> > So this is just an implementation issue, right? You can make LTO run with > -ffunction-sections (by setting TargetOptions.FunctionSections=true) and > insert your pass in the appropriate place in the pipeline. > Yeah, just an implementation issue. Just need to build the pass pipeline differently for LTO and add a way to do -ffunction-sections in lld. - Michael Spencer > > Thanks, > Tobias > > -- > Qualc...

...n after >>>> all inlining decisions have been made and LTO codegen has to be done with >>>> -ffunction-sections. >>>> >>> So this is just an implementation issue, right? You can make LTO run >>> with -ffunction-sections (by setting TargetOptions.FunctionSections=true) >>> and insert your pass in the appropriate place in the pipeline. >>> >> >> Yeah, just an implementation issue. Just need to build the pass pipeline >> differently for LTO and add a way to do -ffunction-sections in lld. >> >> - Michael Spen...

...ining decisions have been made and LTO codegen has to be done >>>>>> with -ffunction-sections. >>>>>> >>>>> So this is just an implementation issue, right? You can make LTO run >>>>> with -ffunction-sections (by setting TargetOptions.FunctionSections=true) >>>>> and insert your pass in the appropriate place in the pipeline. >>>>> >>>> >>>> Yeah, just an implementation issue. Just need to build the pass >>>> pipeline differently for LTO and add a way to do -ffunction-sections...

I've recently implemented profile guided section layout in llvm + lld using the Call-Chain Clustering (C³) heuristic from https://research.fb.com/wp-content/uploads/2017/01/cgo2017-hfsort-final1.pdf . In the programs I've tested it on I've gotten from 0% to 5% performance improvement over standard PGO with zero cases of slowdowns and up to 15% reduction in ITLB misses. There are

...ZL18EnableRealignStack", "EnableRealignStack"}, {"_ZL19DisableSwitchTables", "DisableSwitchTables"}, {"_ZL19EnableStrongPHIElim", "EnableStrongPHIElim"}, {"_ZL12DataSections", "DataSections"}, {"_ZL16FunctionSections", "FunctionSections"}, {"_ZL15AttributesLists", "AttributesLists"}, {"_ZN4llvmL7ALMutexE", "llvm::ALMutex"}, {"_ZL13VerifyDomInfo", "VerifyDomInfo"}, {"_ZL14VerifyDomInfoX", "VerifyDomI...