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". > > 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)) 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? > +// 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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