r226915 - Process the -fno-signed-zeros optimization flag (PR20870)
Sean Silva
chisophugis at gmail.com
Tue Apr 7 20:37:49 PDT 2015
On Tue, Apr 7, 2015 at 6:36 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> On Tue, Apr 7, 2015 at 5:59 PM, Tom Stellard <tom at stellard.net> wrote:
>
>> On Tue, Apr 07, 2015 at 05:45:20PM -0700, Richard Smith wrote:
>> > On Tue, Apr 7, 2015 at 4:36 PM, Tom Stellard <tom at stellard.net> wrote:
>> >
>> > > On Tue, Apr 07, 2015 at 03:11:44PM -0700, Richard Smith wrote:
>> > > > On Tue, Apr 7, 2015 at 3:05 PM, Tom Stellard <tom at stellard.net>
>> wrote:
>> > > >
>> > > > > On Fri, Jan 23, 2015 at 04:40:50PM -0000, Sanjay Patel wrote:
>> > > > > > Author: spatel
>> > > > > > Date: Fri Jan 23 10:40:50 2015
>> > > > > > New Revision: 226915
>> > > > > >
>> > > > > > URL: http://llvm.org/viewvc/llvm-project?rev=226915&view=rev
>> > > > > > Log:
>> > > > > > Process the -fno-signed-zeros optimization flag (PR20870)
>> > > > > >
>> > > > > > The driver currently accepts but ignores the -fno-signed-zeros
>> flag.
>> > > > > > This patch passes the flag through and enables 'nsz'
>> fast-math-flag
>> > > > > > generation in IR.
>> > > > > >
>> > > > > > The existing OpenCL flag for the same functionality is made
>> into an
>> > > > > > alias here. It may be removed in a subsequent patch.
>> > > > > >
>> > > > >
>> > > > > What is the reason for removing this option? This will break
>> OpenCL
>> > > > > implementations that use clang.
>> > > >
>> > > >
>> > > > We do not provide any stability guarantees for Clang's -cc1
>> interface in
>> > > > general. Are these implementations running -cc1 directly, or
>> passing this
>> > > > flag via -Xclang? If the latter, we should add a proper (stable)
>> > > > driver-level flag for it.
>> > > >
>> > >
>> > > I understand there are no stability guarantees, but regardless I feel
>> > > like it's useful to keep it around as an alias since it is part of
>> > > the OpenCL spec. Is there a high cost involved in keeping it?
>> > >
>> >
>> > It's not really reasonable to expect Clang's -cc1 to implement the flags
>> > required by the OpenCL spec. Your OpenCL driver should be recognizing
>> those
>> > flags and handling them in whatever manner is appropriate.
>> >
>>
>> What's the difference between -cc1 flags and 'proper driver-level flags'
>> ?
>
>
> The driver-level flags are the ones in Options.td; these are accepted by
> the GCC-compatible 'clang' driver -- though it sounds like this isn't the
> right thing for clover's case, since it seems you're not using the clang
> driver.
>
> > In the OpenCL implementation I'm working on (clover), we are using the
>> > > C++ API, so the argument is being passed via:
>> > > clang::CompilerInvocation::CreateFromArgs()
>> >
>> >
>> > Could you instead set NoSignedZeros directly on the CodeGenOptions of
>> the
>> > CompilerInvocation after calling CreateFromArgs?
>>
>> I could do this, but I'm wondering if there still might be a way to add
>> the OpenCL flags to clang. It is still useful if you want to do offline
>> compilation.
>
>
> We could keep these options as a convenience. However, we generally desire
> to keep the -cc1 interface minimal, as essentially a serialized form of the
> options structs that CompilerInvocation::CreateFromArgs initializes.
>
Heh, that's a neat way of looking at it.
-- Sean Silva
> As such, having two different flags that do the same thing doesn't make a
> lot of sense. Users are generally not expected to directly supply arguments
> to -cc1 invocations, so the benefit seems questionable.
>
> -Tom
>> >
>> > -Tom
>> > >
>> > >
>> > >
>> > > > -Tom
>> > > > >
>> > > > > > This should resolve bug 20870 (
>> > > > > http://llvm.org/bugs/show_bug.cgi?id=20870 );
>> > > > > > patches for the optimizer were checked in at:
>> > > > > >
>> http://llvm.org/viewvc/llvm-project?view=revision&revision=225050
>> > > > > >
>> http://llvm.org/viewvc/llvm-project?view=revision&revision=224583
>> > > > > >
>> > > > > > Differential Revision: http://reviews.llvm.org/D6873
>> > > > > >
>> > > > > >
>> > > > > > Modified:
>> > > > > > cfe/trunk/include/clang/Driver/CC1Options.td
>> > > > > > cfe/trunk/include/clang/Driver/Options.td
>> > > > > > cfe/trunk/lib/Driver/Tools.cpp
>> > > > > > cfe/trunk/lib/Frontend/CompilerInvocation.cpp
>> > > > > > cfe/trunk/test/CodeGen/finite-math.c
>> > > > > > cfe/trunk/test/Driver/fast-math.c
>> > > > > >
>> > > > > > Modified: cfe/trunk/include/clang/Driver/CC1Options.td
>> > > > > > URL:
>> > > > >
>> > >
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/CC1Options.td?rev=226915&r1=226914&r2=226915&view=diff
>> > > > > >
>> > > > >
>> > >
>> ==============================================================================
>> > > > > > --- cfe/trunk/include/clang/Driver/CC1Options.td (original)
>> > > > > > +++ cfe/trunk/include/clang/Driver/CC1Options.td Fri Jan 23
>> 10:40:50
>> > > 2015
>> > > > > > @@ -580,7 +580,7 @@ def cl_finite_math_only : Flag<["-"], "c
>> > > > > > HelpText<"OpenCL only. Allow floating-point optimizations
>> that
>> > > assume
>> > > > > arguments and results are not NaNs or +-Inf.">;
>> > > > > > def cl_kernel_arg_info : Flag<["-"], "cl-kernel-arg-info">,
>> > > > > > HelpText<"OpenCL only. Generate kernel argument metadata.">;
>> > > > > > -def cl_no_signed_zeros : Flag<["-"], "cl-no-signed-zeros">,
>> > > > > > +def : Flag<["-"], "cl-no-signed-zeros">,
>> Alias<fno_signed_zeros>,
>> > > > > > HelpText<"OpenCL only. Allow optimizations to ignore the
>> > > signedness
>> > > > > of the floating-point zero.">;
>> > > > > > def cl_unsafe_math_optimizations : Flag<["-"],
>> > > > > "cl-unsafe-math-optimizations">,
>> > > > > > HelpText<"OpenCL only. Allow unsafe floating-point
>> optimizations.
>> > > > > Also implies -cl-no-signed-zeros and -cl-mad-enable">;
>> > > > > >
>> > > > > > Modified: cfe/trunk/include/clang/Driver/Options.td
>> > > > > > URL:
>> > > > >
>> > >
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/Options.td?rev=226915&r1=226914&r2=226915&view=diff
>> > > > > >
>> > > > >
>> > >
>> ==============================================================================
>> > > > > > --- cfe/trunk/include/clang/Driver/Options.td (original)
>> > > > > > +++ cfe/trunk/include/clang/Driver/Options.td Fri Jan 23
>> 10:40:50
>> > > 2015
>> > > > > > @@ -566,7 +566,9 @@ def fno_reciprocal_math : Flag<["-"], "f
>> > > > > > def ffinite_math_only : Flag<["-"], "ffinite-math-only">,
>> > > > > Group<f_Group>, Flags<[CC1Option]>;
>> > > > > > def fno_finite_math_only : Flag<["-"], "fno-finite-math-only">,
>> > > > > Group<f_Group>;
>> > > > > > def fsigned_zeros : Flag<["-"], "fsigned-zeros">,
>> Group<f_Group>;
>> > > > > > -def fno_signed_zeros : Flag<["-"], "fno-signed-zeros">,
>> > > Group<f_Group>;
>> > > > > > +def fno_signed_zeros :
>> > > > > > + Flag<["-"], "fno-signed-zeros">, Group<f_Group>,
>> > > Flags<[CC1Option]>,
>> > > > > > + HelpText<"Allow optimizations that ignore the sign of
>> floating
>> > > point
>> > > > > zeros">;
>> > > > > > def fhonor_nans : Flag<["-"], "fhonor-nans">, Group<f_Group>;
>> > > > > > def fno_honor_nans : Flag<["-"], "fno-honor-nans">,
>> Group<f_Group>;
>> > > > > > def fhonor_infinities : Flag<["-"], "fhonor-infinities">,
>> > > > > Group<f_Group>;
>> > > > > >
>> > > > > > Modified: cfe/trunk/lib/Driver/Tools.cpp
>> > > > > > URL:
>> > > > >
>> > >
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=226915&r1=226914&r2=226915&view=diff
>> > > > > >
>> > > > >
>> > >
>> ==============================================================================
>> > > > > > --- cfe/trunk/lib/Driver/Tools.cpp (original)
>> > > > > > +++ cfe/trunk/lib/Driver/Tools.cpp Fri Jan 23 10:40:50 2015
>> > > > > > @@ -2955,6 +2955,8 @@ void Clang::ConstructJob(Compilation &C,
>> > > > > > !TrappingMath)
>> > > > > > CmdArgs.push_back("-menable-unsafe-fp-math");
>> > > > > >
>> > > > > > + if (!SignedZeros)
>> > > > > > + CmdArgs.push_back("-fno-signed-zeros");
>> > > > > >
>> > > > > > // Validate and pass through -fp-contract option.
>> > > > > > if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
>> > > > > FastMathAliasOption,
>> > > > > >
>> > > > > > Modified: cfe/trunk/lib/Frontend/CompilerInvocation.cpp
>> > > > > > URL:
>> > > > >
>> > >
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/CompilerInvocation.cpp?rev=226915&r1=226914&r2=226915&view=diff
>> > > > > >
>> > > > >
>> > >
>> ==============================================================================
>> > > > > > --- cfe/trunk/lib/Frontend/CompilerInvocation.cpp (original)
>> > > > > > +++ cfe/trunk/lib/Frontend/CompilerInvocation.cpp Fri Jan 23
>> 10:40:50
>> > > > > 2015
>> > > > > > @@ -441,7 +441,7 @@ static bool ParseCodeGenArgs(CodeGenOpti
>> > > > > >
>> > > Args.hasArg(OPT_cl_unsafe_math_optimizations) ||
>> > > > > > Args.hasArg(OPT_cl_finite_math_only) ||
>> > > > > > Args.hasArg(OPT_cl_fast_relaxed_math));
>> > > > > > - Opts.NoSignedZeros = Args.hasArg(OPT_cl_no_signed_zeros);
>> > > > > > + Opts.NoSignedZeros = Args.hasArg(OPT_fno_signed_zeros);
>> > > > > > Opts.NoZeroInitializedInBSS =
>> > > > > Args.hasArg(OPT_mno_zero_initialized_in_bss);
>> > > > > > Opts.BackendOptions =
>> Args.getAllArgValues(OPT_backend_option);
>> > > > > > Opts.NumRegisterParameters = getLastArgIntValue(Args,
>> > > OPT_mregparm,
>> > > > > 0, Diags);
>> > > > > >
>> > > > > > Modified: cfe/trunk/test/CodeGen/finite-math.c
>> > > > > > URL:
>> > > > >
>> > >
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/finite-math.c?rev=226915&r1=226914&r2=226915&view=diff
>> > > > > >
>> > > > >
>> > >
>> ==============================================================================
>> > > > > > --- cfe/trunk/test/CodeGen/finite-math.c (original)
>> > > > > > +++ cfe/trunk/test/CodeGen/finite-math.c Fri Jan 23 10:40:50
>> 2015
>> > > > > > @@ -1,11 +1,15 @@
>> > > > > > -// RUN: %clang_cc1 -ffinite-math-only -emit-llvm -o - %s |
>> > > FileCheck %s
>> > > > > > +// RUN: %clang_cc1 -ffinite-math-only -emit-llvm -o - %s |
>> > > FileCheck %s
>> > > > > -check-prefix=CHECK -check-prefix=FINITE
>> > > > > > +// RUN: %clang_cc1 -fno-signed-zeros -emit-llvm -o - %s |
>> FileCheck
>> > > %s
>> > > > > -check-prefix=CHECK -check-prefix=NSZ
>> > > > > > +
>> > > > > > float f0, f1, f2;
>> > > > > >
>> > > > > > void foo(void) {
>> > > > > > // CHECK-LABEL: define void @foo()
>> > > > > >
>> > > > > > - // CHECK: fadd nnan ninf
>> > > > > > + // FINITE: fadd nnan ninf
>> > > > > > + // NSZ: fadd nsz
>> > > > > > f0 = f1 + f2;
>> > > > > >
>> > > > > > // CHECK: ret
>> > > > > > }
>> > > > > > +
>> > > > > >
>> > > > > > Modified: cfe/trunk/test/Driver/fast-math.c
>> > > > > > URL:
>> > > > >
>> > >
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/fast-math.c?rev=226915&r1=226914&r2=226915&view=diff
>> > > > > >
>> > > > >
>> > >
>> ==============================================================================
>> > > > > > --- cfe/trunk/test/Driver/fast-math.c (original)
>> > > > > > +++ cfe/trunk/test/Driver/fast-math.c Fri Jan 23 10:40:50 2015
>> > > > > > @@ -25,6 +25,21 @@
>> > > > > > // CHECK-NO-INFS-NO-FAST-MATH: "-cc1"
>> > > > > > // CHECK-NO-INFS-NO-FAST-MATH-NOT: "-menable-no-infs"
>> > > > > > //
>> > > > > > +// RUN: %clang -### -fno-signed-zeros -c %s 2>&1 \
>> > > > > > +// RUN: | FileCheck --check-prefix=CHECK-NO-SIGNED-ZEROS %s
>> > > > > > +// CHECK-NO-SIGNED-ZEROS: "-cc1"
>> > > > > > +// CHECK-NO-SIGNED-ZEROS: "-fno-signed-zeros"
>> > > > > > +//
>> > > > > > +// RUN: %clang -### -fno-fast-math -fno-signed-zeros -c %s
>> 2>&1 \
>> > > > > > +// RUN: | FileCheck
>> > > --check-prefix=CHECK-NO-FAST-MATH-NO-SIGNED-ZEROS
>> > > > > %s
>> > > > > > +// CHECK-NO-FAST-MATH-NO-SIGNED-ZEROS: "-cc1"
>> > > > > > +// CHECK-NO-FAST-MATH-NO-SIGNED-ZEROS: "-fno-signed-zeros"
>> > > > > > +//
>> > > > > > +// RUN: %clang -### -fno-signed-zeros -fno-fast-math -c %s
>> 2>&1 \
>> > > > > > +// RUN: | FileCheck
>> > > --check-prefix=CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH
>> > > > > %s
>> > > > > > +// CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH: "-cc1"
>> > > > > > +// CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH-NOT: "-fno-signed-zeros"
>> > > > > > +//
>> > > > > > // RUN: %clang -### -fno-honor-nans -c %s 2>&1 \
>> > > > > > // RUN: | FileCheck --check-prefix=CHECK-NO-NANS %s
>> > > > > > // CHECK-NO-NANS: "-cc1"
>> > > > > >
>> > > > > >
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