| Message ID | AANLkTi==ByATdy=JQrZJ05LwwcvoC0x+opVApWAEiMyr@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Aug 12, 2010 at 7:06 PM, H.J. Lu <hjl.tools@gmail.com> wrote: >>>>>> 2010-08-12 H.J. Lu <hongjiu.lu@intel.com> >>>>>> Uros Bizjak <ubizjak@gmail.com> >>>>>> >>>>>> * config.gcc: Handle --enable-frame-pointer. >>>>>> >>>>>> * configure.ac: Add --enable-frame-pointer. >>>>>> * configure: Regenerated. >>>>>> >>>>>> * config/i386/i386.c (USE_IX86_FRAME_POINTER): Default to 0. >>>>>> (override_options): Enable -fomit-frame-pointer for 32bit code >>>>>> if compiling for TARGET_MACHO and not optimizing for size >>>>>> unless configured with --enable-frame-pointer. Enable >>>>>> -fasynchronous-unwind-tables unless configured with >>>>>> --enable-frame-pointer. Enable -maccumulate-outgoing-args >>>>>> by default unless configured with --enable-frame-pointer. >>>>>> >>>>> >>>>> Please change the ChangeLog text to something like: >>>>> >>>>> If not configured with --enable-frame-pointer, enable >>>>> -fomit-frame-pointer (but not for TARGET_MACHO or when optimizing for >>>>> size), enable -fasynchronous-unwind-tables and >>>>> -maccumulate-outgoing-args by default. >>>>> >>>> >>>> I checked it in with updated ChangeLog. >>>> >>>> How should we document it? We currently have >>>> >>>> -- >>>> @item -fomit-frame-pointer >>>> @opindex fomit-frame-pointer >>>> Don't keep the frame pointer in a register for functions that >>>> don't need one. This avoids the instructions to save, set up and >>>> restore frame pointers; it also makes an extra register available >>>> in many functions. @strong{It also makes debugging impossible on >>>> some machines.} >>>> >>>> On some machines, such as the VAX, this flag has no effect, because >>>> the standard calling sequence automatically handles the frame pointer >>>> and nothing is saved by pretending it doesn't exist. The >>>> machine-description macro @code{FRAME_POINTER_REQUIRED} controls >>>> whether a target machine supports this flag. @xref{Registers,,Register >>>> Usage, gccint, GNU Compiler Collection (GCC) Internals}. >>>> >>>> Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. >>>> -- >>>> >>>> It was never correct for x86 and is wrong today. >>> >>> Perhaps something like: >>> >>> Index: invoke.texi >>> =================================================================== >>> --- invoke.texi (revision 163191) >>> +++ invoke.texi (working copy) >>> @@ -5993,6 +5993,11 @@ >>> whether a target machine supports this flag. @xref{Registers,,Register >>> Usage, gccint, GNU Compiler Collection (GCC) Internals}. >>> >>> +Starting from GCC version 4.6, the default setting for 32-bit x86 targets >>> +has been changed to @option{-fomit-frame-pointer}. New behavior can be >>> +reverted back to @option{-fno-omit-frame-pointer} by configuring GCC with >>> +the @option{--enable-frame-pointer} configure option. >>> + >>> Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. >>> >>> @item -foptimize-sibling-calls >>> >> >> We default to --disable-frame-pointer only for 32bit x86 Linux and >> MACHO target always has -fno-omit-frame-pointer as default. >> >> > > How about this patch? > > > -- > H.J. > 2010-08-12 Uros Bizjak <ubizjak@gmail.com> > > * doc/invoke.texi: Update -fomit-frame-pointer for 32-bit Linux > x86 targets. > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > index edce703..dbcc212 100644 > --- a/gcc/doc/invoke.texi > +++ b/gcc/doc/invoke.texi > @@ -5993,6 +5993,11 @@ machine-description macro > @code{FRAME_POINTER_REQUIRED} controls > whether a target machine supports this flag. @xref{Registers,,Register > Usage, gccint, GNU Compiler Collection (GCC) Internals}. > > +Starting from GCC version 4.6, the default setting for 32-bit Linux x86 > +targets has been changed to @option{-fomit-frame-pointer}. New behavior > +can be reverted back to @option{-fno-omit-frame-pointer} by configuring > +GCC with the @option{--enable-frame-pointer} configure option. > + > Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. > > @item -foptimize-sibling-calls "... the default setting for 32-bit non-Darwin x86 targets has been changed to @option{-fomit-frame-pointer} when not optimizing for size." is what the source says ;) Uros.
On Thu, Aug 12, 2010 at 10:12 AM, Uros Bizjak <ubizjak@gmail.com> wrote: > On Thu, Aug 12, 2010 at 7:06 PM, H.J. Lu <hjl.tools@gmail.com> wrote: > >>>>>>> 2010-08-12 H.J. Lu <hongjiu.lu@intel.com> >>>>>>> Uros Bizjak <ubizjak@gmail.com> >>>>>>> >>>>>>> * config.gcc: Handle --enable-frame-pointer. >>>>>>> >>>>>>> * configure.ac: Add --enable-frame-pointer. >>>>>>> * configure: Regenerated. >>>>>>> >>>>>>> * config/i386/i386.c (USE_IX86_FRAME_POINTER): Default to 0. >>>>>>> (override_options): Enable -fomit-frame-pointer for 32bit code >>>>>>> if compiling for TARGET_MACHO and not optimizing for size >>>>>>> unless configured with --enable-frame-pointer. Enable >>>>>>> -fasynchronous-unwind-tables unless configured with >>>>>>> --enable-frame-pointer. Enable -maccumulate-outgoing-args >>>>>>> by default unless configured with --enable-frame-pointer. >>>>>>> >>>>>> >>>>>> Please change the ChangeLog text to something like: >>>>>> >>>>>> If not configured with --enable-frame-pointer, enable >>>>>> -fomit-frame-pointer (but not for TARGET_MACHO or when optimizing for >>>>>> size), enable -fasynchronous-unwind-tables and >>>>>> -maccumulate-outgoing-args by default. >>>>>> >>>>> >>>>> I checked it in with updated ChangeLog. >>>>> >>>>> How should we document it? We currently have >>>>> >>>>> -- >>>>> @item -fomit-frame-pointer >>>>> @opindex fomit-frame-pointer >>>>> Don't keep the frame pointer in a register for functions that >>>>> don't need one. This avoids the instructions to save, set up and >>>>> restore frame pointers; it also makes an extra register available >>>>> in many functions. @strong{It also makes debugging impossible on >>>>> some machines.} >>>>> >>>>> On some machines, such as the VAX, this flag has no effect, because >>>>> the standard calling sequence automatically handles the frame pointer >>>>> and nothing is saved by pretending it doesn't exist. The >>>>> machine-description macro @code{FRAME_POINTER_REQUIRED} controls >>>>> whether a target machine supports this flag. @xref{Registers,,Register >>>>> Usage, gccint, GNU Compiler Collection (GCC) Internals}. >>>>> >>>>> Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. >>>>> -- >>>>> >>>>> It was never correct for x86 and is wrong today. >>>> >>>> Perhaps something like: >>>> >>>> Index: invoke.texi >>>> =================================================================== >>>> --- invoke.texi (revision 163191) >>>> +++ invoke.texi (working copy) >>>> @@ -5993,6 +5993,11 @@ >>>> whether a target machine supports this flag. @xref{Registers,,Register >>>> Usage, gccint, GNU Compiler Collection (GCC) Internals}. >>>> >>>> +Starting from GCC version 4.6, the default setting for 32-bit x86 targets >>>> +has been changed to @option{-fomit-frame-pointer}. New behavior can be >>>> +reverted back to @option{-fno-omit-frame-pointer} by configuring GCC with >>>> +the @option{--enable-frame-pointer} configure option. >>>> + >>>> Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. >>>> >>>> @item -foptimize-sibling-calls >>>> >>> >>> We default to --disable-frame-pointer only for 32bit x86 Linux and >>> MACHO target always has -fno-omit-frame-pointer as default. >>> >>> >> >> How about this patch? >> >> >> -- >> H.J. >> 2010-08-12 Uros Bizjak <ubizjak@gmail.com> >> >> * doc/invoke.texi: Update -fomit-frame-pointer for 32-bit Linux >> x86 targets. >> >> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi >> index edce703..dbcc212 100644 >> --- a/gcc/doc/invoke.texi >> +++ b/gcc/doc/invoke.texi >> @@ -5993,6 +5993,11 @@ machine-description macro >> @code{FRAME_POINTER_REQUIRED} controls >> whether a target machine supports this flag. @xref{Registers,,Register >> Usage, gccint, GNU Compiler Collection (GCC) Internals}. >> >> +Starting from GCC version 4.6, the default setting for 32-bit Linux x86 >> +targets has been changed to @option{-fomit-frame-pointer}. New behavior >> +can be reverted back to @option{-fno-omit-frame-pointer} by configuring >> +GCC with the @option{--enable-frame-pointer} configure option. >> + >> Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. >> >> @item -foptimize-sibling-calls > > "... the default setting for 32-bit non-Darwin x86 targets has been > changed to @option{-fomit-frame-pointer} when not optimizing for > size." is what the source says ;) As I said, it is complicated. We only changed the default setting for 32bit Linux x86 targets. All other x86 targets are unchanged.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index edce703..dbcc212 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -5993,6 +5993,11 @@ machine-description macro @code{FRAME_POINTER_REQUIRED} controls whether a target machine supports this flag. @xref{Registers,,Register Usage, gccint, GNU Compiler Collection (GCC) Internals}. +Starting from GCC version 4.6, the default setting for 32-bit Linux x86 +targets has been changed to @option{-fomit-frame-pointer}. New behavior +can be reverted back to @option{-fno-omit-frame-pointer} by configuring +GCC with the @option{--enable-frame-pointer} configure option. + Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.