diff options
Diffstat (limited to 'SConstruct')
| -rwxr-xr-x | SConstruct | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/SConstruct b/SConstruct index bc1e1e296..146b156d1 100755 --- a/SConstruct +++ b/SConstruct @@ -183,6 +183,9 @@ AddLocalOption('--ignore-style', dest='ignore_style', action='store_true', help='Disable style checking hooks') AddLocalOption('--no-lto', dest='no_lto', action='store_true', help='Disable Link-Time Optimization for fast') +AddLocalOption('--force-lto', dest='force_lto', action='store_true', + help='Use Link-Time Optimization instead of partial linking' + + ' when the compiler doesn\'t support using them together.') AddLocalOption('--update-ref', dest='update_ref', action='store_true', help='Update test reference outputs') AddLocalOption('--verbose', dest='verbose', action='store_true', @@ -198,6 +201,10 @@ AddLocalOption('--with-ubsan', dest='with_ubsan', action='store_true', AddLocalOption('--with-asan', dest='with_asan', action='store_true', help='Build with Address Sanitizer if available') +if GetOption('no_lto') and GetOption('force_lto'): + print '--no-lto and --force-lto are mutually exclusive' + Exit(1) + termcap = get_termcap(GetOption('use_colors')) ######################################################################## @@ -719,6 +726,28 @@ if main['GCC']: main['GCC_VERSION'] = gcc_version + if compareVersions(gcc_version, '4.9') >= 0: + # Incremental linking with LTO is currently broken in gcc versions + # 4.9 and above. A version where everything works completely hasn't + # yet been identified. + # + # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67548 + main['BROKEN_INCREMENTAL_LTO'] = True + if compareVersions(gcc_version, '6.0') >= 0: + # gcc versions 6.0 and greater accept an -flinker-output flag which + # selects what type of output the linker should generate. This is + # necessary for incremental lto to work, but is also broken in + # current versions of gcc. It may not be necessary in future + # versions. We add it here since it might be, and as a reminder that + # it exists. It's excluded if lto is being forced. + # + # https://gcc.gnu.org/gcc-6/changes.html + # https://gcc.gnu.org/ml/gcc-patches/2015-11/msg03161.html + # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69866 + if not GetOption('force_lto'): + main.Append(PSHLINKFLAGS='-flinker-output=rel') + main.Append(PLINKFLAGS='-flinker-output=rel') + # gcc from version 4.8 and above generates "rep; ret" instructions # to avoid performance penalties on certain AMD chips. Older # assemblers detect this as an error, "Error: expecting string @@ -749,10 +778,21 @@ if main['GCC']: 'Warning: UBSan is only supported using gcc 4.9 and later.' + \ termcap.Normal + disable_lto = GetOption('no_lto') + if not disable_lto and main.get('BROKEN_INCREMENTAL_LTO', False) and \ + not GetOption('force_lto'): + print termcap.Yellow + termcap.Bold + \ + 'Warning: Your compiler doesn\'t support incremental linking' + \ + ' and lto at the same time, so lto is being disabled. To force' + \ + ' lto on anyway, use the --force-lto option. That will disable' + \ + ' partial linking.' + \ + termcap.Normal + disable_lto = True + # Add the appropriate Link-Time Optimization (LTO) flags # unless LTO is explicitly turned off. Note that these flags # are only used by the fast target. - if not GetOption('no_lto'): + if not disable_lto: # Pass the LTO flag when compiling to produce GIMPLE # output, we merely create the flags here and only append # them later |