alok added a comment. In D99160#2700326 <https://reviews.llvm.org/D99160#2700326>, @alok wrote:
> In D99160#2699038 <https://reviews.llvm.org/D99160#2699038>, @dblaikie wrote: > >> In D99160#2698980 <https://reviews.llvm.org/D99160#2698980>, @alok wrote: >> >>> In D99160#2671899 <https://reviews.llvm.org/D99160#2671899>, @dblaikie >>> wrote: >>> >>>> In D99160#2670460 <https://reviews.llvm.org/D99160#2670460>, @djtodoro >>>> wrote: >>>> >>>>> In D99160#2669576 <https://reviews.llvm.org/D99160#2669576>, @dblaikie >>>>> wrote: >>>>> >>>>>> In D99160#2668977 <https://reviews.llvm.org/D99160#2668977>, @djtodoro >>>>>> wrote: >>>>>> >>>>>>> I think that the Debug Entry Values feature should not be enabled by >>>>>>> default for non optimized code, so the >>>>>>> `TargetOptions::ShouldEmitDebugEntryValues()` should be patched with >>>>>>> checking of optimization level (it should be > 0). >>>>>> >>>>>> That's currently intended to be already handled by the frontend, right? >>>>>> (clang only sets `EnableDebugEntryValues` (which >>>>>> `ShouldEmitDebugEntryValues` checks (hmm, it checks under 'or', not >>>>>> 'and', so I'm not sure where the "only above -O0" is implemented, but it >>>>>> is implemented somewhere?) if optimizations are enabled, yeah?) >>>>>> >>>>>> Oh, is entry_values actually not conditionalized? It's only the >>>>>> call_site support that's currently conditionalized on "above -O0"? >>>>> >>>>> Looks like there is no explicit check of optimization level (above >>>>> "-O0"), neither on frontend nor backend for entry-values generation. I >>>>> think it is the situation since there should not be any optimization (at >>>>> least that I am aware of, in the case of C/C++) that would cause the >>>>> entry-values generation... >>>>> >>>>>> Hmm - If that's the case, and we currently have some cases where >>>>>> entry_values are emitted at -O0, I'm not sure /not/ emitting those is >>>>>> the right call either. If we believe/have data to show that there are so >>>>>> few useful uses of entry_value at -O0 that it's not worth the DWARF size >>>>>> growth to put call_sites in at -O0, then I think it might still be worth >>>>>> leaving the entry_values in (unless they take up a bunch of extra space) >>>>>> for the cases of mixed optimization compilation (-O0 some code you're >>>>>> debugging, but building the rest with optimizations). >>>>> >>>>> Yeah... That is valuable example... I am thinking in that direction as >>>>> well, and I am closer to the enabling it for -O0 case if that is useful >>>>> (and there is no dramatic cost in terms of DWARF size). >>>> >>>> Does anyone have this example (where DW_OP_entry_value is used at -O0)? >>>> It'd be great to look at it & see if it's a case of unnecessarily losing >>>> the location, or legitimately losing it and using entry_value for >>>> best-effort recovery (& then a question of whether the loss is appropriate >>>> at -O0, or if we want to pessimize -O0 further to avoid the loss). >> >> I think this ^ still needs understanding/investigation. Do you have an >> example with OP_entry_value at -O0? >> >>>> I'd worry about turning on call_sites at -O0 - there'd be a lot more calls >>>> (especially for C++ code with lots of implicit operations), but numbers >>>> will be needed in any case, so not worth much speculation. >>> >>> Sorry for late response. >>> I tried building >>> https://github.com/flang-compiler/classic-flang-llvm-project.git (branch >>> release_11x) with compiler (current patch (https://reviews.llvm.org/D99160) >>> and https://reviews.llvm.org/D99238) with -O0 -g . >>> Interestingly there was no difference. >>> Reason: https://reviews.llvm.org/D99238 is not sufficient for clang/clang++ >>> to enable call-site generation with FastISel though it is sufficient for >>> Flang compiler. >>> Below additional patch is needed to generate call-sites >>> >>> ````````````````````````````````````` >>> >>> diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp >>> b/clang/lib/CodeGen/CGDebugInfo.cpp >>> index a77f52bd235b..8d4e11faa018 100644 >>> >>> - a/clang/lib/CodeGen/CGDebugInfo.cpp >>> >>> +++ b/clang/lib/CodeGen/CGDebugInfo.cpp >>> @@ -5149,9 +5149,9 @@ llvm::DebugLoc >>> CGDebugInfo::SourceLocToDebugLoc(SourceLocation Loc) { >>> } >>> >>> llvm::DINode::DIFlags CGDebugInfo::getCallSiteRelatedAttrs() const { >>> >>> - // Call site-related attributes are only useful in optimized programs, and >>> - // when there's a possibility of debugging backtraces. >>> - if (!CGM.getLangOpts().Optimize || DebugKind == >>> codegenoptions::NoDebugInfo || >>> >>> + // Call site-related attributes are useful when there's a possibility of >>> + // debugging backtraces. >>> + if (DebugKind == codegenoptions::NoDebugInfo || >>> >>> DebugKind == codegenoptions::LocTrackingOnly) >>> return llvm::DINode::FlagZero; >>> >>> ````````````````````````````````````` >>> >>> With this patch Clang/Clang++ turn on LLVM IR flag >>> "DIFlagAllCallsDescribed", in absence of this LLVM does not generate >>> call-site. >>> >>> With the above patch applied below is the comparison of sizes of shared >>> libraries. >>> >>> Name of shared library - Size (without callsite) - Size (with callsites) - >>> % incresase in size >>> >>> >>> ``````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````` >>> >>> PipSqueak.so 73192 75048 2% >>> SecondLib.so 73192 75048 2% >>> TestPlugin.so 1694024 1700704 0% >>> libLLVMDlltoolDriver.so 336568 347872 3% >>> libLLVMDebugInfoPDB.so 14463832 15360784 6% >>> libLLVMOrcError.so 108880 111184 2% >>> libLLVMTarget.so 2645104 2677448 1% >>> libLLVMFrontendOpenMP.so 2354728 2505232 6% >>> libLLVMProfileData.so 7901688 8373632 5% >>> libLLVMOrcJIT.so 28838432 30490640 5% >>> libLLVMRemarks.so 3311680 3551856 7% >>> libgtest.so 2374120 2523112 6% >>> libLLVMDemangle.so 1350616 1490832 10% >>> libLLVMAsmParser.so 6961216 7366040 5% >>> LLVMHello.so 394624 396120 0% >>> libLLVMGlobalISel.so 18886648 19698008 4% >>> libLLVMDebugInfoMSF.so 1288376 1365040 5% >>> libLLVMCoverage.so 4225224 4502104 6% >>> libLLVMFuzzMutate.so 3859968 3973808 2% >>> libRemarks.so 6696 6696 0% >>> libLLVMDebugInfoDWARF.so 11914848 12750784 7% >>> libLLVMMCParser.so 6419464 6873000 7% >>> libLLVMTableGen.so 4855536 5180760 6% >>> libLLVMDWARFLinker.so 5407528 5628576 4% >>> Bye.so 1858848 1872672 0% >>> libLLVMMCJIT.so 1470952 1526544 3% >>> libLLVMMC.so 16931504 17741376 4% >>> libLLVMipo.so 43554712 46019392 5% >>> libLLVMLineEditor.so 208216 216360 3% >>> libbenchmark_main.so 18904 19408 2% >>> libbenchmark.so 3308304 3507632 6% >>> libLTO.so 2240720 2277408 1% >>> libLLVMInterpreter.so 2614696 2749128 5% >>> libLLVMTransformUtils.so 47925248 50476512 5% >>> libLLVMX86Desc.so 8047928 8213152 2% >>> libLLVMCoroutines.so 6478080 6766880 4% >>> libLLVMJITLink.so 5590936 6066736 8% >>> libLLVMVectorize.so 19557808 20665544 5% >>> libLLVMX86Disassembler.so 2820056 2849376 1% >>> libLLVMBitReader.so 8282648 8823240 6% >>> libLLVMMCA.so 3242016 3405624 5% >>> libLLVMBitWriter.so 6544032 6867976 4% >>> libLLVMMIRParser.so 5739688 5980104 4% >>> libLLVMLTO.so 13272272 13786192 3% >>> libLLVMCore.so 46109224 48840008 5% >>> libLLVMBitstreamReader.so 561896 600624 6% >>> libLLVMObjectYAML.so 23110160 24648160 6% >>> libLLVMSupport.so 20349728 21953112 7% >>> libLLVMIRReader.so 1215672 1237960 1% >>> libLLVMX86Info.so 76488 76624 0% >>> libLLVMSelectionDAG.so 34358968 36876128 7% >>> libLLVMExecutionEngine.so 2962160 3073224 3% >>> libLLVMSymbolize.so 1980760 2089728 5% >>> libLLVMPasses.so 18574960 19459712 4% >>> libLLVMOption.so 869784 920976 5% >>> libLLVMObject.so 15138656 16383168 8% >>> libLLVMTextAPI.so 3191272 3384560 6% >>> libLLVMX86CodeGen.so 55202744 58068088 5% >>> libLLVMAggressiveInstCombine.so 2354936 2419048 2% >>> libLLVMExtensions.so 23904 23904 0% >>> libLLVMWindowsManifest.so 351608 370168 5% >>> libLLVMObjCARCOpts.so 4964488 5150120 3% >>> libLLVMBinaryFormat.so 1325752 1431448 7% >>> libLLVMDebugInfoGSYM.so 2909272 3094616 6% >>> libLLVMTestingSupport.so 623608 656640 5% >>> libgtest_main.so 42856 43608 1% >>> libLLVMLinker.so 3070264 3210248 4% >>> libLLVMCFGuard.so 1082488 1096104 1% >>> libLLVMCodeGen.so 139859816 146452160 4% >>> libLLVMDebugInfoCodeView.so 7742896 8497704 9% >>> libLLVMX86AsmParser.so 2590816 2714008 4% >>> libLLVMRuntimeDyld.so 6592016 7094048 7% >>> libLLVMInstCombine.so 18194728 19705184 8% >>> BugpointPasses.so 780112 788304 1% >>> libLLVMScalarOpts.so 73110536 77534912 6% >>> libLLVMXRay.so 3993696 4251280 6% >>> libLLVMMCDisassembler.so 1292912 1313536 1% >>> libLLVMFrontendOpenACC.so 96008 102656 6% >>> libLLVMInstrumentation.so 21038808 22351384 6% >>> libLLVMLibDriver.so 1595936 1638704 2% >>> libLLVMAsmPrinter.so 25818000 26842816 3% >>> libLLVMAnalysis.so 79615056 83995856 5% >>> >>> ````````````````````````````````````````````````````````````````````` >>> >>> sum 79615057 83995857 5% >>> >>> So the conclusion is, >>> >>> - We have a Flag which can help us if we want to enable callsite generation >>> selectively (only for Flang) >> >> It doesn't seem to me, so far, like this is a place where Flang and Clang >> should diverge - they're both doing the same sort of thing for the same >> reasons/likely with the same sort of tradeoffs of location accuracy V size >> cost. >> >>> - If we are fine with 5% increase in size, we can enable call-site >>> generation by default. >> >> I'd actually be somewhat more worried about object size, rather than/in >> addition to executable size, due to the increase in relocations (especially >> with DWARFv5 (& especially with the `-mllvm -minimize-addr-in-v5=Ranges` >> which further reduces debug_addr, but can't handle labels and call sites >> (unlike `-minimize-addr-in-v5=Expressions` or `-minimize-addr-in-v5=Form`)), >> which does a lot to reduce the number of relocations by using debug_addr and >> address sharing on debug_rnglists/loclists/etc) which can't be compressed, >> etc. > > Below is the comparison of total size of object files (*.o) for same build > (default (O0) + -g). > > sum 3535044960 3680496672 4% > > I shall come back with numbers for options O0 -gdwarf-5 -mllvm > -minimize-addr-in-v5=Ranges . Below are the results. PipSqueak.so 74376 75048 0% SecondLib.so 74376 75048 0% TestPlugin.so 1699776 1700704 0% libLLVMDlltoolDriver.so 338224 347872 2% libLLVMDebugInfoPDB.so 14276632 15360784 7% libLLVMOrcError.so 111168 111184 0% libLLVMTarget.so 2670776 2677448 0% libLLVMFrontendOpenMP.so 2351736 2505232 6% libLLVMProfileData.so 7782224 8373632 7% libLLVMOrcJIT.so 28408664 30490640 7% libLLVMRemarks.so 3253472 3551856 9% libgtest.so 2338592 2523112 7% libLLVMDemangle.so 1339416 1490832 11% libLLVMAsmParser.so 6885320 7366040 6% LLVMHello.so 403544 396120 -1% libLLVMGlobalISel.so 18813752 19698008 4% libLLVMDebugInfoMSF.so 1272328 1365040 7% libLLVMCoverage.so 4167336 4502104 8% libLLVMFuzzMutate.so 3860488 3973808 2% libRemarks.so 7216 6696 -7% libLLVMDebugInfoDWARF.so 11690048 12750784 9% libLLVMMCParser.so 6378536 6873000 7% libLLVMTableGen.so 4790168 5180760 8% libLLVMDWARFLinker.so 5352344 5628576 5% Bye.so 1862216 1872672 0% libLLVMMCJIT.so 1461496 1526544 4% libLLVMMC.so 16848920 17741376 5% libLLVMipo.so 42955408 46019392 7% libLLVMLineEditor.so 209704 216360 3% libbenchmark_main.so 19880 19408 -2% libbenchmark.so 3270440 3507632 7% libLTO.so 2233464 2277408 1% libLLVMInterpreter.so 2611408 2749128 5% libLLVMTransformUtils.so 47500376 50476512 6% libLLVMX86Desc.so 8234536 8213152 0% libLLVMCoroutines.so 6424104 6766880 5% libLLVMJITLink.so 5481928 6066736 10% libLLVMVectorize.so 19318304 20665544 6% libLLVMX86Disassembler.so 2859328 2849376 0% libLLVMBitReader.so 8152552 8823240 8% libLLVMMCA.so 3218504 3405624 5% libLLVMBitWriter.so 6472160 6867976 6% libLLVMMIRParser.so 5702232 5980104 4% libLLVMLTO.so 13115600 13786192 5% libLLVMCore.so 45551816 48840008 7% libLLVMBitstreamReader.so 555824 600624 8% libLLVMObjectYAML.so 22643568 24648160 8% libLLVMSupport.so 20110440 21953112 9% libLLVMIRReader.so 1217592 1237960 1% libLLVMX86Info.so 80080 76624 -4% libLLVMSelectionDAG.so 34103008 36876128 8% libLLVMExecutionEngine.so 2956728 3073224 3% libLLVMSymbolize.so 1959536 2089728 6% libLLVMPasses.so 18367064 19459712 5% libLLVMOption.so 866616 920976 6% libLLVMObject.so 14939568 16383168 9% libLLVMTextAPI.so 3158584 3384560 7% libLLVMX86CodeGen.so 56063440 58068088 3% libLLVMAggressiveInstCombine.so 2353832 2419048 2% libLLVMExtensions.so 25280 23904 -5% libLLVMWindowsManifest.so 350240 370168 5% libLLVMObjCARCOpts.so 4946928 5150120 4% libLLVMBinaryFormat.so 1323744 1431448 8% libLLVMDebugInfoGSYM.so 2862936 3094616 8% libLLVMTestingSupport.so 621208 656640 5% libgtest_main.so 45168 43608 -3% libLLVMLinker.so 3038736 3210248 5% libLLVMCFGuard.so 1090016 1096104 0% libLLVMCodeGen.so 138864176 146452160 5% libLLVMDebugInfoCodeView.so 7612904 8497704 11% libLLVMX86AsmParser.so 2620696 2714008 3% libLLVMRuntimeDyld.so 6503104 7094048 9% libLLVMInstCombine.so 17916992 19705184 9% BugpointPasses.so 785784 788304 0% libLLVMScalarOpts.so 72114960 77534912 7% libLLVMXRay.so 3939008 4251280 7% libLLVMMCDisassembler.so 1299632 1313536 1% libLLVMFrontendOpenACC.so 97360 102656 5% libLLVMInstrumentation.so 20774464 22351384 7% libLLVMLibDriver.so 1589136 1638704 3% libLLVMAsmPrinter.so 25641320 26842816 4% libLLVMAnalysis.so 78794136 83995856 6% sum 944078696 1005246112 6% CHANGES SINCE LAST ACTION https://reviews.llvm.org/D99160/new/ https://reviews.llvm.org/D99160 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
