r226915 - Process the -fno-signed-zeros optimization flag (PR20870)

Tom Stellard tom at stellard.net
Tue Apr 7 15:05:09 PDT 2015 

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.

-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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