Author: Andy Kaylor Date: 2024-04-29T13:22:08-07:00 New Revision: 8ba880b587074ad6c8624ed45ea2b289f653667f
URL: https://github.com/llvm/llvm-project/commit/8ba880b587074ad6c8624ed45ea2b289f653667f DIFF: https://github.com/llvm/llvm-project/commit/8ba880b587074ad6c8624ed45ea2b289f653667f.diff LOG: [Driver] Clean up denormal handling with fast-math-related options (#89477) This change cleans up the clang driver handling of umbrella options like -ffast-math, -funsafe-math-optimizations, and -ffp-model, and aligns the behavior of -ffp-model=fast with -ffast-math with regard to the linking of crtfastmath.o. We agreed in a previous review that the fast-math options should not attempt to change the -fdenormal-fp-math option, which is inherently target-specific. The clang user's manual claims that -ffp-model=fast "behaves identically to specifying both -ffast-math and -ffp-contract=fast." Since -ffast-math causes crtfastmath.o to be linked if it is available, that should also happen with -ffp-model=fast. I am going to be proposing further changes to -ffp-model=fast, decoupling it from -ffast-math and introducing a new -ffp-model=aggressive that matches the current behavior, but I wanted to solidfy the current behavior before I do that. Added: Modified: clang/docs/UsersManual.rst clang/lib/Driver/ToolChain.cpp clang/lib/Driver/ToolChains/Clang.cpp clang/test/Driver/fp-model.c clang/test/Driver/linux-ld.c clang/test/Driver/solaris-ld.c Removed: ################################################################################ diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst index a7fc7ec87a161f..6ba0a531fedf9b 100644 --- a/clang/docs/UsersManual.rst +++ b/clang/docs/UsersManual.rst @@ -1452,8 +1452,6 @@ floating point semantic models: precise (the default), strict, and fast. "fenv_access", "off", "on", "off" "rounding_mode", "tonearest", "dynamic", "tonearest" "contract", "on", "off", "fast" - "denormal_fp_math", "IEEE", "IEEE", "IEEE" - "denormal_fp32_math", "IEEE","IEEE", "IEEE" "support_math_errno", "on", "on", "off" "no_honor_nans", "off", "off", "on" "no_honor_infinities", "off", "off", "on" @@ -1462,6 +1460,14 @@ floating point semantic models: precise (the default), strict, and fast. "allow_approximate_fns", "off", "off", "on" "allow_reassociation", "off", "off", "on" +The ``-ffp-model`` option does not modify the ``fdenormal-fp-math`` +setting, but it does have an impact on whether ``crtfastmath.o`` is +linked. Because linking ``crtfastmath.o`` has a global effect on the +program, and because the global denormal handling can be changed in +other ways, the state of ``fdenormal-fp-math`` handling cannot +be assumed in any function based on fp-model. See :ref:`crtfastmath.o` +for more details. + .. option:: -ffast-math Enable fast-math mode. This option lets the @@ -1537,7 +1543,6 @@ floating point semantic models: precise (the default), strict, and fast. Also, this option resets following options to their target-dependent defaults. * ``-f[no-]math-errno`` - * ``-fdenormal-fp-math=<value>`` There is ambiguity about how ``-ffp-contract``, ``-ffast-math``, and ``-fno-fast-math`` behave when combined. To keep the value of @@ -1560,8 +1565,7 @@ floating point semantic models: precise (the default), strict, and fast. ``-ffp-contract`` setting is determined by the default value of ``-ffp-contract``. - Note: ``-fno-fast-math`` implies ``-fdenormal-fp-math=ieee``. - ``-fno-fast-math`` causes ``crtfastmath.o`` to not be linked with code + Note: ``-fno-fast-math`` causes ``crtfastmath.o`` to not be linked with code unless ``-mdaz-ftz`` is present. .. option:: -fdenormal-fp-math=<value> @@ -1694,7 +1698,6 @@ floating point semantic models: precise (the default), strict, and fast. * ``-fsigned-zeros`` * ``-ftrapping-math`` * ``-ffp-contract=on`` - * ``-fdenormal-fp-math=ieee`` There is ambiguity about how ``-ffp-contract``, ``-funsafe-math-optimizations``, and ``-fno-unsafe-math-optimizations`` diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp index 341d6202a9ca3c..0e86bc07e0ea2c 100644 --- a/clang/lib/Driver/ToolChain.cpp +++ b/clang/lib/Driver/ToolChain.cpp @@ -1316,14 +1316,19 @@ bool ToolChain::isFastMathRuntimeAvailable(const ArgList &Args, // (to keep the linker options consistent with gcc and clang itself). if (Default && !isOptimizationLevelFast(Args)) { // Check if -ffast-math or -funsafe-math. - Arg *A = - Args.getLastArg(options::OPT_ffast_math, options::OPT_fno_fast_math, - options::OPT_funsafe_math_optimizations, - options::OPT_fno_unsafe_math_optimizations); + Arg *A = Args.getLastArg( + options::OPT_ffast_math, options::OPT_fno_fast_math, + options::OPT_funsafe_math_optimizations, + options::OPT_fno_unsafe_math_optimizations, options::OPT_ffp_model_EQ); if (!A || A->getOption().getID() == options::OPT_fno_fast_math || A->getOption().getID() == options::OPT_fno_unsafe_math_optimizations) Default = false; + if (A && A->getOption().getID() == options::OPT_ffp_model_EQ) { + StringRef Model = A->getValue(); + if (Model != "fast") + Default = false; + } } // Whatever decision came as a result of the above implicit settings, either diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp index 651a2b5aac368b..250dc078edf242 100644 --- a/clang/lib/Driver/ToolChains/Clang.cpp +++ b/clang/lib/Driver/ToolChains/Clang.cpp @@ -2743,13 +2743,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D, StringRef FPExceptionBehavior = ""; // -ffp-eval-method options: double, extended, source StringRef FPEvalMethod = ""; - const llvm::DenormalMode DefaultDenormalFPMath = + llvm::DenormalMode DenormalFPMath = TC.getDefaultDenormalModeForType(Args, JA); - const llvm::DenormalMode DefaultDenormalFP32Math = + llvm::DenormalMode DenormalFP32Math = TC.getDefaultDenormalModeForType(Args, JA, &llvm::APFloat::IEEEsingle()); - llvm::DenormalMode DenormalFPMath = DefaultDenormalFPMath; - llvm::DenormalMode DenormalFP32Math = DefaultDenormalFP32Math; // CUDA and HIP don't rely on the frontend to pass an ffp-contract option. // If one wasn't given by the user, don't pass it here. StringRef FPContract; @@ -2899,11 +2897,6 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D, SignedZeros = true; // -fno_fast_math restores default denormal and fpcontract handling FPContract = "on"; - DenormalFPMath = llvm::DenormalMode::getIEEE(); - - // FIXME: The target may have picked a non-IEEE default mode here based on - // -cl-denorms-are-zero. Should the target consider -fp-model interaction? - DenormalFP32Math = llvm::DenormalMode::getIEEE(); StringRef Val = A->getValue(); if (OFastEnabled && !Val.equals("fast")) { @@ -3122,9 +3115,6 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D, TrappingMath = true; FPExceptionBehavior = "strict"; - // The target may have opted to flush by default, so force IEEE. - DenormalFPMath = llvm::DenormalMode::getIEEE(); - DenormalFP32Math = llvm::DenormalMode::getIEEE(); if (!JA.isDeviceOffloading(Action::OFK_Cuda) && !JA.isOffloading(Action::OFK_HIP)) { if (LastSeenFfpContractOption != "") { @@ -3154,9 +3144,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D, ReciprocalMath = false; ApproxFunc = false; SignedZeros = true; - // -fno_fast_math restores default denormal and fpcontract handling - DenormalFPMath = DefaultDenormalFPMath; - DenormalFP32Math = llvm::DenormalMode::getIEEE(); + // -fno_fast_math restores default fpcontract handling if (!JA.isDeviceOffloading(Action::OFK_Cuda) && !JA.isOffloading(Action::OFK_HIP)) { if (LastSeenFfpContractOption != "") { @@ -3171,8 +3159,6 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D, // subsequent options conflict then emit warning diagnostic. if (HonorINFs && HonorNaNs && !AssociativeMath && !ReciprocalMath && SignedZeros && TrappingMath && RoundingFPMath && !ApproxFunc && - DenormalFPMath == llvm::DenormalMode::getIEEE() && - DenormalFP32Math == llvm::DenormalMode::getIEEE() && FPContract.equals("off")) // OK: Current Arg doesn't conflict with -ffp-model=strict ; diff --git a/clang/test/Driver/fp-model.c b/clang/test/Driver/fp-model.c index a464729edb45c3..9d12452399119b 100644 --- a/clang/test/Driver/fp-model.c +++ b/clang/test/Driver/fp-model.c @@ -64,7 +64,8 @@ // RUN: %clang -### -ffp-model=strict -fdenormal-fp-math=preserve-sign,preserve-sign -c %s 2>&1 \ // RUN: | FileCheck --check-prefix=WARN10 %s -// WARN10: warning: overriding '-ffp-model=strict' option with '-fdenormal-fp-math=preserve-sign,preserve-sign' [-Woverriding-option] +// WARN10: "-cc1" +// WARN10-NOT: warning: overriding '-ffp-model=strict' option with '-fdenormal-fp-math=preserve-sign,preserve-sign' [-Woverriding-option] // RUN: %clang -### -ffp-model=fast -ffp-model=strict -c %s 2>&1 | FileCheck \ // RUN: --check-prefix=WARN11 %s @@ -128,6 +129,7 @@ // RUN: | FileCheck --check-prefix=CHECK-NO-EXCEPT %s // RUN: %clang -### -nostdinc -ffp-model=strict -Ofast -c %s 2>&1 \ // RUN: | FileCheck --check-prefix=CHECK-NO-EXCEPT %s +// CHECK-NO-EXCEPT: "-cc1" // CHECK-NO-EXCEPT-NOT: "-ffp-exception-behavior=strict" // RUN: %clang -### -nostdinc -ffp-exception-behavior=strict -c %s 2>&1 \ diff --git a/clang/test/Driver/linux-ld.c b/clang/test/Driver/linux-ld.c index e2043ab22afcbf..28fb075a80dbbc 100644 --- a/clang/test/Driver/linux-ld.c +++ b/clang/test/Driver/linux-ld.c @@ -1406,6 +1406,9 @@ // RUN: %clang --target=x86_64-unknown-linux -no-pie -### %s -funsafe-math-optimizations\ // RUN: --sysroot=%S/Inputs/basic_linux_tree 2>&1 \ // RUN: | FileCheck --check-prefix=CHECK-CRTFASTMATH %s +// RUN: %clang --target=x86_64-unknown-linux -no-pie -### %s -ffp-model=fast \ +// RUN: --sysroot=%S/Inputs/basic_linux_tree 2>&1 \ +// RUN: | FileCheck --check-prefix=CHECK-CRTFASTMATH %s // RUN: %clang --target=x86_64-unknown-linux -no-pie -### %s -Ofast\ // RUN: --sysroot=%S/Inputs/basic_linux_tree 2>&1 \ // RUN: | FileCheck --check-prefix=CHECK-CRTFASTMATH %s diff --git a/clang/test/Driver/solaris-ld.c b/clang/test/Driver/solaris-ld.c index 6d74389e89222c..ce0728d392bf23 100644 --- a/clang/test/Driver/solaris-ld.c +++ b/clang/test/Driver/solaris-ld.c @@ -193,6 +193,9 @@ // RUN: %clang --target=sparc-sun-solaris2.11 -### %s -ffast-math \ // RUN: --sysroot=%S/Inputs/solaris_sparc_tree 2>&1 \ // RUN: | FileCheck --check-prefix=CHECK-CRTFASTMATH-SPARC32 %s +// RUN: %clang --target=sparc-sun-solaris2.11 -### %s -ffp-model=fast \ +// RUN: --sysroot=%S/Inputs/solaris_sparc_tree 2>&1 \ +// RUN: | FileCheck --check-prefix=CHECK-CRTFASTMATH-SPARC32 %s // CHECK-CRTFASTMATH-SPARC32: "-isysroot" "[[SYSROOT:[^"]+]]" // CHECK-CRTFASTMATH-SPARC32: "[[SYSROOT]]/usr/gcc/4.8/lib/gcc/sparc-sun-solaris2.11/4.8.2{{/|\\\\}}crtfastmath.o" // CHECK-NOCRTFASTMATH-SPARC32-NOT: crtfastmath.o _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
