On Mon, Feb 12, 2018 at 3:35 PM, David Blaikie <dblai...@gmail.com> wrote:
> > > On Mon, Feb 12, 2018 at 2:25 PM Eric Fiselier <e...@efcs.ca> wrote: > >> On Mon, Feb 12, 2018 at 9:15 AM, David Blaikie <dblai...@gmail.com> >> wrote: >> >>> >>> >>> On Wed, Feb 7, 2018 at 10:38 AM Eric Fiselier via cfe-commits < >>> cfe-commits@lists.llvm.org> wrote: >>> >>>> Author: ericwf >>>> Date: Wed Feb 7 10:36:51 2018 >>>> New Revision: 324498 >>>> >>>> URL: http://llvm.org/viewvc/llvm-project?rev=324498&view=rev >>>> Log: >>>> [Driver] Add option to manually control discarding value names in LLVM >>>> IR. >>>> >>>> Summary: >>>> Currently, assertion-disabled Clang builds emit value names when >>>> generating LLVM IR. This is controlled by the `NDEBUG` macro, and is not >>>> easily overridable. In order to get IR output containing names from a >>>> release build of Clang, the user must manually construct the CC1 invocation >>>> w/o the `-discard-value-names` option. This is less than ideal. >>>> >>>> For example, Godbolt uses a release build of Clang, and so when asked >>>> to emit LLVM IR the result lacks names, making it harder to read. Manually >>>> invoking CC1 on Compiler Explorer is not feasible. >>>> >>> >>> It wouldn't necessarily have to invoke CC1, it could use "-Xclang >>> -discard-value-names". >>> >> >> If you were using an assertion build, and wanted to disable value names, >> then yes -- that would work. However it's the opposite case that is of >> interest: >> When you're using a non-assertion build and want to keep value names. In >> that case invoking CC1 directly is required; otherwise the driver would pass >> "-discard-value-names". >> > > Ah, thanks for explaining! > > >> >> >>> >>> >>>> >>>> This patch adds the driver options `-fdiscard-value-names` and >>>> `-fno-discard-value-names` which allow the user to override the default >>>> behavior. If neither is specified, the old behavior remains. >>>> >>>> Reviewers: erichkeane, aaron.ballman, lebedev.ri >>>> >>>> Reviewed By: aaron.ballman >>>> >>>> Subscribers: bogner, cfe-commits >>>> >>>> Differential Revision: https://reviews.llvm.org/D42887 >>>> >>>> Modified: >>>> cfe/trunk/docs/UsersManual.rst >>>> cfe/trunk/include/clang/Driver/Options.td >>>> cfe/trunk/lib/Driver/ToolChains/Clang.cpp >>>> cfe/trunk/test/Driver/clang_f_opts.c >>>> >>>> Modified: cfe/trunk/docs/UsersManual.rst >>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/docs/ >>>> UsersManual.rst?rev=324498&r1=324497&r2=324498&view=diff >>>> ============================================================ >>>> ================== >>>> --- cfe/trunk/docs/UsersManual.rst (original) >>>> +++ cfe/trunk/docs/UsersManual.rst Wed Feb 7 10:36:51 2018 >>>> @@ -1855,6 +1855,27 @@ features. You can "tune" the debug info >>>> must come first.) >>>> >>>> >>>> +Controlling LLVM IR Output >>>> +-------------------------- >>>> + >>>> +Controlling Value Names in LLVM IR >>>> +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >>>> + >>>> +Emitting value names in LLVM IR increases the size and verbosity of >>>> the IR. >>>> +By default, value names are only emitted in assertion-enabled builds >>>> of Clang. >>>> +However, when reading IR it can be useful to re-enable the emission of >>>> value >>>> +names to improve readability. >>>> + >>>> +.. option:: -fdiscard-value-names >>>> + >>>> + Discard value names when generating LLVM IR. >>>> + >>>> +.. option:: -fno-discard-value-names >>>> + >>>> + Do not discard value names when generating LLVM IR. This option can >>>> be used >>>> + to re-enable names for release builds of Clang. >>>> + >>>> + >>>> Comment Parsing Options >>>> ----------------------- >>>> >>>> >>>> Modified: cfe/trunk/include/clang/Driver/Options.td >>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/ >>>> clang/Driver/Options.td?rev=324498&r1=324497&r2=324498&view=diff >>>> ============================================================ >>>> ================== >>>> --- cfe/trunk/include/clang/Driver/Options.td (original) >>>> +++ cfe/trunk/include/clang/Driver/Options.td Wed Feb 7 10:36:51 2018 >>>> @@ -790,6 +790,10 @@ def fdiagnostics_show_template_tree : Fl >>>> HelpText<"Print a template comparison tree for differing >>>> templates">; >>>> def fdeclspec : Flag<["-"], "fdeclspec">, Group<f_clang_Group>, >>>> HelpText<"Allow __declspec as a keyword">, Flags<[CC1Option]>; >>>> +def fdiscard_value_names : Flag<["-"], "fdiscard-value-names">, >>>> Group<f_clang_Group>, >>>> + HelpText<"Discard value names in LLVM IR">, Flags<[DriverOption]>; >>>> +def fno_discard_value_names : Flag<["-"], "fno-discard-value-names">, >>>> Group<f_clang_Group>, >>>> + HelpText<"Do not discard value names in LLVM IR">, >>>> Flags<[DriverOption]>; >>>> def fdollars_in_identifiers : Flag<["-"], "fdollars-in-identifiers">, >>>> Group<f_Group>, >>>> HelpText<"Allow '$' in identifiers">, Flags<[CC1Option]>; >>>> def fdwarf2_cfi_asm : Flag<["-"], "fdwarf2-cfi-asm">, >>>> Group<clang_ignored_f_Group>; >>>> >>>> Modified: cfe/trunk/lib/Driver/ToolChains/Clang.cpp >>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/ >>>> ToolChains/Clang.cpp?rev=324498&r1=324497&r2=324498&view=diff >>>> ============================================================ >>>> ================== >>>> --- cfe/trunk/lib/Driver/ToolChains/Clang.cpp (original) >>>> +++ cfe/trunk/lib/Driver/ToolChains/Clang.cpp Wed Feb 7 10:36:51 2018 >>>> @@ -3266,13 +3266,24 @@ void Clang::ConstructJob(Compilation &C, >>>> if (!C.isForDiagnostics()) >>>> CmdArgs.push_back("-disable-free"); >>>> >>>> -// Disable the verification pass in -asserts builds. >>>> #ifdef NDEBUG >>>> - CmdArgs.push_back("-disable-llvm-verifier"); >>>> - // Discard LLVM value names in -asserts builds. >>>> - CmdArgs.push_back("-discard-value-names"); >>>> + const bool IsAssertBuild = false; >>>> +#else >>>> + const bool IsAssertBuild = true; >>>> #endif >>>> >>>> + // Disable the verification pass in -asserts builds. >>>> + if (!IsAssertBuild) >>>> + CmdArgs.push_back("disable-llvm-verifier"); >>>> + >>>> + // Discard value names in assert builds unless otherwise specified. >>>> + if (const Arg *A = Args.getLastArg(options::OPT_ >>>> fdiscard_value_names, >>>> + >>>> options::OPT_fno_discard_value_names)) >>>> { >>>> + if (A->getOption().matches(options::OPT_fdiscard_value_names)) >>>> >>> >>> Should this ^ be: >>> >>> if (Args.hasFlag(options::OPT_fdiscard_value_names, >>> options::OPT_fno_discard_value_names, false)) >>> >> >> Yeah, that looks better, but perhaps this would be even cleaner: >> >> if (Args.hasFlag(options::OPT_fdiscard_value_names, >> options::OPT_fno_discard_value_names, !IsAssertBuild)) >> > > *nod* Looks pretty good to me. > > >> >> >>> >>> instead? (simpler, one operation instead of two, etc) >>> >>> >>>> + CmdArgs.push_back("-discard-value-names"); >>>> + } else if (!IsAssertBuild) >>>> + CmdArgs.push_back("-discard-value-names"); >>>> + >>>> // Set the main file name, so that debug info works even with >>>> // -save-temps. >>>> CmdArgs.push_back("-main-file-name"); >>>> >>>> Modified: cfe/trunk/test/Driver/clang_f_opts.c >>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/ >>>> clang_f_opts.c?rev=324498&r1=324497&r2=324498&view=diff >>>> ============================================================ >>>> ================== >>>> --- cfe/trunk/test/Driver/clang_f_opts.c (original) >>>> +++ cfe/trunk/test/Driver/clang_f_opts.c Wed Feb 7 10:36:51 2018 >>>> @@ -517,3 +517,8 @@ >>>> // RUN: %clang -### -S %s 2>&1 | FileCheck >>>> -check-prefix=CHECK-NO-CF-PROTECTION-BRANCH >>>> %s >>>> // CHECK-CF-PROTECTION-BRANCH: -fcf-protection=branch >>>> // CHECK-NO-CF-PROTECTION-BRANCH-NOT: -fcf-protection=branch >>>> + >>>> +// RUN: %clang -### -S -fdiscard-value-names %s 2>&1 | FileCheck >>>> -check-prefix=CHECK-DISCARD-NAMES %s >>>> >>> >>> Should there also be a RUN line here for the default behavior, when no >>> arg is specified? >>> >> >> AFAIK it is not currently testable, since the result of the test depends >> on the build configuration, and AFAIK that information >> isn't available in the LIT test suite. >> >> I'm sure with a bit of messy CMake I could find a way to transmit if >> assertions are enabled to LIT, add it to the set of available >> features, and write two different tests that have REQUIRE/UNSUPPORTED >> lines which turn them on/off depending on >> the build type. >> >> However, this behavior has gone untested for years, so I wasn't sure a >> test was required now. >> > > Generally good to try to raise the bar a bit where it's been dropped in > parts of the codebase. > > But, yes, since the default changes - you should be able to test the > default in an asserts build correctly (since there's a REQUIRES: Asserts) > but we've deliberately avoided putting in a REQUIRES: NoAsserts, because > generally there should be no functionality behind an assertion failure - > but this sort of behavior slips through the cracks. Meh. > Ah, OK. I didn't see that when I went looking. I'll add tests then. Thankfully I don't need `NoAsserts` since I can write `// UNSUPPORTED: Asserts` instead :-) > > >> >> >>> >>> >>>> +// RUN: %clang -### -S -fno-discard-value-names %s 2>&1 | FileCheck >>>> -check-prefix=CHECK-NO-DISCARD-NAMES %s >>>> +// CHECK-DISCARD-NAMES: "-discard-value-names" >>>> +// CHECK-NO-DISCARD-NAMES-NOT: "-discard-value-names" >>>> >>>> >>>> _______________________________________________ >>>> cfe-commits mailing list >>>> cfe-commits@lists.llvm.org >>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >>>> >>>
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