diff options
| -rwxr-xr-x | SConstruct | 42 | ||||
| -rwxr-xr-x | src/SConscript | 16 |
2 files changed, 55 insertions, 3 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 diff --git a/src/SConscript b/src/SConscript index ed59bd228..519a0a986 100755 --- a/src/SConscript +++ b/src/SConscript @@ -957,7 +957,7 @@ def variantd(*path): # environment 'env' with modified object suffix and optional stripped # binary. Additional keyword arguments are appended to corresponding # build environment vars. -def makeEnv(env, label, objsfx, strip = False, **kwargs): +def makeEnv(env, label, objsfx, strip=False, disable_partial=False, **kwargs): # SCons doesn't know to append a library suffix when there is a '.' in the # name. Use '_' instead. libname = variant('gem5_' + label) @@ -1059,6 +1059,14 @@ def makeEnv(env, label, objsfx, strip = False, **kwargs): if not srcs: continue + # If partial linking is disabled, add these sources to the build + # directly, and short circuit this loop. + if disable_partial: + for s in srcs: + static_objs.append(make_obj(s, True)) + shared_objs.append(make_obj(s, False)) + continue + # Set up the static partially linked objects. source_objs = [ make_obj(s, True) for s in srcs ] file_name = new_env.subst("${OBJPREFIX}lib${OBJSUFFIX}.partial") @@ -1204,10 +1212,14 @@ def makeEnvirons(target, source, env): # "Fast" binary if 'fast' in needed_envs: + disable_partial = \ + env.get('BROKEN_INCREMENTAL_LTO', False) and \ + GetOption('force_lto') makeEnv(env, 'fast', '.fo', strip = True, CCFLAGS = Split(ccflags['fast']), CPPDEFINES = ['NDEBUG', 'TRACING_ON=0'], - LINKFLAGS = Split(ldflags['fast'])) + LINKFLAGS = Split(ldflags['fast']), + disable_partial=disable_partial) # Profiled binary using gprof if 'prof' in needed_envs: |