Author: Vlad Serebrennikov Date: 2024-07-18T11:49:53+04:00 New Revision: 2ef7cbf71c98246d6f3a9c63dea75b76c7b5e928
URL: https://github.com/llvm/llvm-project/commit/2ef7cbf71c98246d6f3a9c63dea75b76c7b5e928 DIFF: https://github.com/llvm/llvm-project/commit/2ef7cbf71c98246d6f3a9c63dea75b76c7b5e928.diff LOG: [clang] Add deprecation warning for `-Ofast` driver option (#98736) This patch implements consensus on the corresponding RFC documented here: https://discourse.llvm.org/t/rfc-deprecate-ofast/78687/72 Specifically, I added a deprecation warning for `-Ofast`, that suggests to use `-O3` or `-O3` with `-ffast-math`, and a new diagnostic group for aforementioned warning. Deprecation period is going to be lengthy, so I hope this PR can be merged in time for Clang 19. Added: Modified: clang/docs/CommandGuide/clang.rst clang/docs/ReleaseNotes.rst clang/include/clang/Basic/DiagnosticDriverKinds.td clang/include/clang/Basic/DiagnosticGroups.td clang/include/clang/Driver/Options.td clang/lib/Driver/ToolChains/Clang.cpp clang/test/Driver/Ofast.c Removed: ################################################################################ diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst index 29154292dc7a5..663aca1f6ddcb 100644 --- a/clang/docs/CommandGuide/clang.rst +++ b/clang/docs/CommandGuide/clang.rst @@ -429,7 +429,8 @@ Code Generation Options :option:`-Ofast` Enables all the optimizations from :option:`-O3` along with other aggressive optimizations that may violate strict compliance with - language standards. + language standards. This is deprecated in favor of :option:`-O3` + in combination with :option:`-ffast-math`. :option:`-Os` Like :option:`-O2` with extra optimizations to reduce code size. diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 1c1b874273a7c..469510d175887 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -473,6 +473,13 @@ New Compiler Flags Deprecated Compiler Flags ------------------------- +- The ``-Ofast`` command-line option has been deprecated. This option both + enables the ``-O3`` optimization-level, as well as enabling non-standard + ``-ffast-math`` behaviors. As such, it is somewhat misleading as an + "optimization level". Users are advised to switch to ``-O3 -ffast-math`` if + the use of non-standard math behavior is intended, and ``-O3`` otherwise. + See `RFC <https://discourse.llvm.org/t/rfc-deprecate-ofast/78687>`_ for details. + Modified Compiler Flags ----------------------- - Added a new diagnostic flag ``-Wreturn-mismatch`` which is grouped under diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td index 359c0de7f811c..cfa897f28b4c0 100644 --- a/clang/include/clang/Basic/DiagnosticDriverKinds.td +++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td @@ -442,6 +442,10 @@ def warn_drv_deprecated_arg : Warning< def warn_drv_deprecated_arg_no_relaxed_template_template_args : Warning< "argument '-fno-relaxed-template-template-args' is deprecated">, InGroup<DeprecatedNoRelaxedTemplateTemplateArgs>; +def warn_drv_deprecated_arg_ofast : Warning< + "argument '-Ofast' is deprecated; use '-O3 -ffast math' for the same behavior," + " or '-O3' to enable only conforming optimizations">, + InGroup<DeprecatedOFast>; def warn_drv_deprecated_custom : Warning< "argument '%0' is deprecated, %1">, InGroup<Deprecated>; def warn_drv_assuming_mfloat_abi_is : Warning< diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td index 2241f8481484e..d7dba76a0fcf8 100644 --- a/clang/include/clang/Basic/DiagnosticGroups.td +++ b/clang/include/clang/Basic/DiagnosticGroups.td @@ -103,6 +103,7 @@ def EnumConversion : DiagGroup<"enum-conversion", EnumFloatConversion, EnumCompareConditional]>; def DeprecatedNoRelaxedTemplateTemplateArgs : DiagGroup<"deprecated-no-relaxed-template-template-args">; +def DeprecatedOFast : DiagGroup<"deprecated-ofast">; def ObjCSignedCharBoolImplicitIntConversion : DiagGroup<"objc-signed-char-bool-implicit-int-conversion">; def Shorten64To32 : DiagGroup<"shorten-64-to-32">; @@ -228,6 +229,7 @@ def Deprecated : DiagGroup<"deprecated", [DeprecatedAnonEnumEnumConversion, DeprecatedPragma, DeprecatedRegister, DeprecatedNoRelaxedTemplateTemplateArgs, + DeprecatedOFast, DeprecatedThisCapture, DeprecatedType, DeprecatedVolatile, diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td index 25555e4620523..1675e435d210c 100644 --- a/clang/include/clang/Driver/Options.td +++ b/clang/include/clang/Driver/Options.td @@ -931,7 +931,9 @@ def O : Joined<["-"], "O">, Group<O_Group>, def O_flag : Flag<["-"], "O">, Visibility<[ClangOption, CC1Option, FC1Option]>, Alias<O>, AliasArgs<["1"]>; def Ofast : Joined<["-"], "Ofast">, Group<O_Group>, - Visibility<[ClangOption, CC1Option, FlangOption]>; + Visibility<[ClangOption, CC1Option, FlangOption]>, + HelpText<"Deprecated; use '-O3 -ffast math' for the same behavior," + " or '-O3' to enable only conforming optimizations">; def P : Flag<["-"], "P">, Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>, Group<Preprocessor_Group>, diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp index a8a7cef09972e..1fd6fba210042 100644 --- a/clang/lib/Driver/ToolChains/Clang.cpp +++ b/clang/lib/Driver/ToolChains/Clang.cpp @@ -5725,6 +5725,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA, options::OPT_fno_zero_initialized_in_bss); bool OFastEnabled = isOptimizationLevelFast(Args); + if (OFastEnabled) + D.Diag(diag::warn_drv_deprecated_arg_ofast); // If -Ofast is the optimization level, then -fstrict-aliasing should be // enabled. This alias option is being used to simplify the hasFlag logic. OptSpecifier StrictAliasingAliasOption = diff --git a/clang/test/Driver/Ofast.c b/clang/test/Driver/Ofast.c index 8b7f2217eca2f..4c63caf9865d5 100644 --- a/clang/test/Driver/Ofast.c +++ b/clang/test/Driver/Ofast.c @@ -3,19 +3,21 @@ // RUN: %clang -fno-fast-math -Ofast -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST %s // RUN: %clang -fno-strict-aliasing -Ofast -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST %s // RUN: %clang -fno-vectorize -Ofast -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST %s -// RUN: %clang -Ofast -O2 -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-O2 \ +// RUN: %clang -Ofast -O2 -### -Werror %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-O2 \ // RUN: %if target={{.*-windows-msvc.*}} %{ --check-prefix=CHECK-OFAST-O2-ALIASING-MSVC %} \ // RUN: %else %{ --check-prefix=CHECK-OFAST-O2-ALIASING %} %s // RUN: %clang -Ofast -fno-fast-math -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-NO-FAST-MATH %s // RUN: %clang -Ofast -fno-strict-aliasing -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-NO-STRICT-ALIASING %s // RUN: %clang -Ofast -fno-vectorize -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-NO-VECTORIZE %s +// CHECK-OFAST: use '-O3 -ffast math' for the same behavior, or '-O3' to enable only conforming optimizations // CHECK-OFAST: -cc1 // CHECK-OFAST-NOT: -relaxed-aliasing // CHECK-OFAST: -ffast-math // CHECK-OFAST: -Ofast // CHECK-OFAST: -vectorize-loops +// Lack of warning about '-Ofast' deprecation is checked via -Werror // CHECK-OFAST-O2: -cc1 // CHECK-OFAST-O2-ALIASING-NOT: -relaxed-aliasing // CHECK-OFAST-O2-ALIASING-MSVC: -relaxed-aliasing @@ -23,18 +25,21 @@ // CHECK-OFAST-O2-NOT: -Ofast // CHECK-OFAST-O2: -vectorize-loops +// CHECK-OFAST-NO-FAST-MATH: use '-O3 -ffast math' for the same behavior, or '-O3' to enable only conforming optimizations // CHECK-OFAST-NO-FAST-MATH: -cc1 // CHECK-OFAST-NO-FAST-MATH-NOT: -relaxed-aliasing // CHECK-OFAST-NO-FAST-MATH-NOT: -ffast-math // CHECK-OFAST-NO-FAST-MATH: -Ofast // CHECK-OFAST-NO-FAST-MATH: -vectorize-loops +// CHECK-OFAST-NO-STRICT-ALIASING: use '-O3 -ffast math' for the same behavior, or '-O3' to enable only conforming optimizations // CHECK-OFAST-NO-STRICT-ALIASING: -cc1 // CHECK-OFAST-NO-STRICT-ALIASING: -relaxed-aliasing // CHECK-OFAST-NO-STRICT-ALIASING: -ffast-math // CHECK-OFAST-NO-STRICT-ALIASING: -Ofast // CHECK-OFAST-NO-STRICT-ALIASING: -vectorize-loops +// CHECK-OFAST-NO-VECTORIZE: use '-O3 -ffast math' for the same behavior, or '-O3' to enable only conforming optimizations // CHECK-OFAST-NO-VECTORIZE: -cc1 // CHECK-OFAST-NO-VECTORIZE-NOT: -relaxed-aliasing // CHECK-OFAST-NO-VECTORIZE: -ffast-math _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
