[llvm] r234159 - Don't use -ffunction-sections -fdata-sections on debug builds.

[David Blaikie]

On Mon, Apr 6, 2015 at 8:09 AM, Rafael Espíndola <rafael.espindola at gmail.com
> wrote:

> No problem. Thanks for noticing.
>
> I also disabled the linker optimizations, so Debug builds should be a
> bit faster too.
>

Yeah, saw that - what sort of optimizations does the linker do with that
anyway? (I assume not enough to recoup the 3 seconds on one or two
executions of the program, at least)


>
> On 6 April 2015 at 10:47, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> > On Mon, Apr 6, 2015 at 7:34 AM, Rafael Espindola
> > <rafael.espindola at gmail.com> wrote:
> >>
> >> Author: rafael
> >> Date: Mon Apr  6 09:34:43 2015
> >> New Revision: 234159
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=234159&view=rev
> >> Log:
> >> Don't use -ffunction-sections -fdata-sections on debug builds.
> >
> >
> > Thanks a bunch!
> >
> >>
> >>
> >> Unfortunately, on ELF there is not used attribute on the .o files,
> >> so there is no easy way to keep the dump function alive.
> >>
> >> If we are not gcing, we may as well produce non gcable files and
> >> avoid the cost.
> >>
> >> Linking a debug clang now takes 18.856225992 seconds, before it
> >> took 21.206897447.
> >>
> >> I will try avoiding --gc-sections -O3 on a followup patch.
> >>
> >> Modified:
> >>     llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
> >>
> >> Modified: llvm/trunk/cmake/modules/HandleLLVMOptions.cmake
> >> URL:
> >>
> http://llvm.org/viewvc/llvm-project/llvm/trunk/cmake/modules/HandleLLVMOptions.cmake?rev=234159&r1=234158&r2=234159&view=diff
> >>
> >>
> ==============================================================================
> >> --- llvm/trunk/cmake/modules/HandleLLVMOptions.cmake (original)
> >> +++ llvm/trunk/cmake/modules/HandleLLVMOptions.cmake Mon Apr  6 09:34:43
> >> 2015
> >> @@ -486,7 +486,8 @@ endif()
> >>  # But MinSizeRel seems to add that automatically, so maybe disable
> these
> >>  # flags instead if LLVM_NO_DEAD_STRIP is set.
> >>  if(NOT CYGWIN AND NOT WIN32)
> >> -  if(NOT ${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
> >> +  if(NOT ${CMAKE_SYSTEM_NAME} MATCHES "Darwin" AND
> >> +     NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
> >>      check_c_compiler_flag("-Werror -fno-function-sections"
> >> C_SUPPORTS_FNO_FUNCTION_SECTIONS)
> >>      if (C_SUPPORTS_FNO_FUNCTION_SECTIONS)
> >>        # Don't add -ffunction-section if it can be disabled with
> >> -fno-function-sections.
> >>
> >>
> >> _______________________________________________
> >> llvm-commits mailing list
> >> llvm-commits at cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >
> >
>
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