[RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

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Hello.

After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
introduce --with-stage1-cflags where one can provide such options.

Apart from that, maybe it would be handy to automatically enable "-O2" when
one has a recent compiler? Do we have an example where we detect host compiler
and it's version?

Martin

[-- Attachment #2: 0001-Introduce-configure-flag-with-stage1-cflags.patch --]
[-- Type: text/x-patch, Size: 4008 bytes --]

From 5c44f79237125ad2bc29fcd1fb06a249c05b277d Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Thu, 25 May 2017 11:17:29 +0200
Subject: [PATCH] Introduce configure flag --with-stage1-cflags.

ChangeLog:

2017-05-25  Martin Liska  <mliska@suse.cz>

	* configure.ac: Introduce configure flag --with-stage1-cflags.
	* configure: Regenerate.
---
 configure    | 40 +++++++++++++++++++++++++++-------------
 configure.ac | 31 +++++++++++++++++++------------
 2 files changed, 46 insertions(+), 25 deletions(-)

diff --git a/configure b/configure
index 2c2fe644cfa..442f78d9565 100755
--- a/configure
+++ b/configure
@@ -559,7 +559,6 @@ compare_exclusions
 host_shared
 stage2_werror_flag
 stage1_checking
-stage1_cflags
 MAINT
 MAINTAINER_MODE_FALSE
 MAINTAINER_MODE_TRUE
@@ -652,6 +651,7 @@ isllibs
 poststage1_ldflags
 poststage1_libs
 stage1_ldflags
+stage1_cflags
 stage1_libs
 extra_isl_gmp_configure_flags
 extra_mpc_mpfr_configure_flags
@@ -771,6 +771,7 @@ with_gmp
 with_gmp_include
 with_gmp_lib
 with_stage1_libs
+with_stage1_cflags
 with_stage1_ldflags
 with_boot_libs
 with_boot_ldflags
@@ -1542,6 +1543,8 @@ Optional Packages:
   --with-gmp-include=PATH specify directory for installed GMP include files
   --with-gmp-lib=PATH     specify directory for the installed GMP library
   --with-stage1-libs=LIBS libraries for stage1
+  --with-stage1-cflags=FLAGS
+                          compiler flags for stage1
   --with-stage1-ldflags=FLAGS
                           linker flags for stage1
   --with-boot-libs=LIBS   libraries for stage2 and later
@@ -5804,6 +5807,29 @@ fi
 
 
 
+# Compiler flags to use for stage1 or when not bootstrapping.
+
+# Check whether --with-stage1-cflags was given.
+if test "${with_stage1_cflags+set}" = set; then :
+  withval=$with_stage1_cflags; if test "$withval" = "no" -o "$withval" = "yes"; then
+   stage1_cflags=
+ else
+   stage1_cflags=$withval
+ fi
+else
+  stage1_cflags="-g"
+  case $build in
+    vax-*-*)
+      case ${GCC} in
+	yes) stage1_cflags="-g -Wa,-J" ;;
+	*) stage1_cflags="-g -J" ;;
+      esac ;;
+  esac
+fi
+
+
+
+
 # Linker flags to use for stage1 or when not bootstrapping.
 
 # Check whether --with-stage1-ldflags was given.
@@ -14544,18 +14570,6 @@ MAINT=$MAINTAINER_MODE_TRUE
 # GCC bootstrap support
 # ---------------------
 
-# Stage specific cflags for build.
-stage1_cflags="-g"
-case $build in
-  vax-*-*)
-    case ${GCC} in
-      yes) stage1_cflags="-g -Wa,-J" ;;
-      *) stage1_cflags="-g -J" ;;
-    esac ;;
-esac
-
-
-
 # Enable --enable-checking in stage1 of the compiler.
 # Check whether --enable-stage1-checking was given.
 if test "${enable_stage1_checking+set}" = set; then :
diff --git a/configure.ac b/configure.ac
index 865dd543fa3..7b7902240c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1637,6 +1637,25 @@ AC_ARG_WITH(stage1-libs,
 [stage1_libs=])
 AC_SUBST(stage1_libs)
 
+# Compiler flags to use for stage1 or when not bootstrapping.
+AC_ARG_WITH(stage1-cflags,
+[AS_HELP_STRING([--with-stage1-cflags=FLAGS], [compiler flags for stage1])],
+[if test "$withval" = "no" -o "$withval" = "yes"; then
+   stage1_cflags=
+ else
+   stage1_cflags=$withval
+ fi],
+[stage1_cflags="-g"
+  case $build in
+    vax-*-*)
+      case ${GCC} in
+	yes) stage1_cflags="-g -Wa,-J" ;;
+	*) stage1_cflags="-g -J" ;;
+      esac ;;
+  esac])
+
+AC_SUBST(stage1_cflags)
+
 # Linker flags to use for stage1 or when not bootstrapping.
 AC_ARG_WITH(stage1-ldflags,
 [AS_HELP_STRING([--with-stage1-ldflags=FLAGS], [linker flags for stage1])],
@@ -3421,18 +3440,6 @@ AC_SUBST(MAINT)dnl
 # GCC bootstrap support
 # ---------------------
 
-# Stage specific cflags for build.
-stage1_cflags="-g"
-case $build in
-  vax-*-*)
-    case ${GCC} in
-      yes) stage1_cflags="-g -Wa,-J" ;;
-      *) stage1_cflags="-g -J" ;;
-    esac ;;
-esac
-
-AC_SUBST(stage1_cflags)
-
 # Enable --enable-checking in stage1 of the compiler.
 AC_ARG_ENABLE(stage1-checking,
 [AS_HELP_STRING([[--enable-stage1-checking[=all]]],
-- 
2.12.2

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Richard Biener]

On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
> Hello.
>
> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
> enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
> introduce --with-stage1-cflags where one can provide such options.

I don't think this is necessary -- you can always override with STAGE1_CFLAGS.

> Apart from that, maybe it would be handy to automatically enable "-O2" when
> one has a recent compiler? Do we have an example where we detect host compiler
> and it's version?

Don't know about version but configury already detects that we use GCC, so that
knowledge should be readily available.

Richard.

>
> Martin

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Jakub Jelinek]

On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
> > Hello.
> >
> > After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
> > enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
> > introduce --with-stage1-cflags where one can provide such options.
> 
> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
> 
> > Apart from that, maybe it would be handy to automatically enable "-O2" when
> > one has a recent compiler? Do we have an example where we detect host compiler
> > and it's version?
> 
> Don't know about version but configury already detects that we use GCC, so that
> knowledge should be readily available.

Well, it certainly shouldn't be -O2 by default for any system GCC, more
something like if it is major of the configured configure minus 1 or newer
(or minus 2?), then use -O2, otherwise default to -O0 as before.

	Jakub

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Richard Biener]

On Fri, May 26, 2017 at 1:51 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
>> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
>> > Hello.
>> >
>> > After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
>> > enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
>> > introduce --with-stage1-cflags where one can provide such options.
>>
>> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
>>
>> > Apart from that, maybe it would be handy to automatically enable "-O2" when
>> > one has a recent compiler? Do we have an example where we detect host compiler
>> > and it's version?
>>
>> Don't know about version but configury already detects that we use GCC, so that
>> knowledge should be readily available.
>
> Well, it certainly shouldn't be -O2 by default for any system GCC, more
> something like if it is major of the configured configure minus 1 or newer
> (or minus 2?), then use -O2, otherwise default to -O0 as before.

I'd still default to -O0 on release branches regardless of version and then
for development we can probably simply use "any GCC" when people have
the chance to override.

At least for me host GCC 4.8 works quite well with -O2.

Richard.

>         Jakub

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

[-- Attachment #1: Type: text/plain, Size: 1552 bytes --]

On 05/26/2017 01:55 PM, Richard Biener wrote:
> On Fri, May 26, 2017 at 1:51 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>> On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
>>> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
>>>> Hello.
>>>>
>>>> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
>>>> enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
>>>> introduce --with-stage1-cflags where one can provide such options.
>>>
>>> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
>>>
>>>> Apart from that, maybe it would be handy to automatically enable "-O2" when
>>>> one has a recent compiler? Do we have an example where we detect host compiler
>>>> and it's version?
>>>
>>> Don't know about version but configury already detects that we use GCC, so that
>>> knowledge should be readily available.
>>
>> Well, it certainly shouldn't be -O2 by default for any system GCC, more
>> something like if it is major of the configured configure minus 1 or newer
>> (or minus 2?), then use -O2, otherwise default to -O0 as before.
> 
> I'd still default to -O0 on release branches regardless of version and then
> for development we can probably simply use "any GCC" when people have
> the chance to override.

Ok, sending new patch that does that on experimental branches for ${CC} --version
being a GCC newer than 4.9.

Martin

> 
> At least for me host GCC 4.8 works quite well with -O2.
> 
> Richard.
> 
>>         Jakub


[-- Attachment #2: 0001-Add-O2-to-stage1_cflags-for-experimental-branch.patch --]
[-- Type: text/x-patch, Size: 3017 bytes --]

From 56acea8345eaa0961f12bfc2383c14676054665d Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Fri, 26 May 2017 14:58:39 +0200
Subject: [PATCH] Add -O2 to stage1_cflags for experimental branch.

ChangeLog:

2017-05-26  Martin Liska  <mliska@suse.cz>

	* configure.ac: Add -O2 to stage1_cflags for experimental branch.
	* configure: Regenerate.
---
 configure    | 23 +++++++++++++++++++++++
 configure.ac | 21 +++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/configure b/configure
index 82aa619fad1..079bad6bf34 100755
--- a/configure
+++ b/configure
@@ -7080,6 +7080,24 @@ fi
 $as_echo "$BUILD_CONFIG" >&6; }
 
 
+# Detect if compiler is GCC >= 4.8.x
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking CC is recent compiler" >&5
+$as_echo_n "checking CC is recent compiler... " >&6; }
+cc_is_recent_gcc=
+version_output=`${CC} -v 2>&1 | grep 'gcc version'`
+
+if test "x${version_output}" != x; then
+  version=`echo ${version_output} | sed 's/gcc version \([^ ]*\).*/\\1/'`
+  major=`echo ${version} | cut -d. -f1`
+  minor=`echo ${version} | cut -d. -f2`
+
+  if test "${major}" -ge 5 || ( test "${major}" -eq 4 && test "${minor}" -ge 8 ); then
+    cc_is_recent_gcc=yes
+  fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $cc_is_recent_gcc" >&5
+$as_echo "$cc_is_recent_gcc" >&6; }
+
 # Use same top-level configure hooks in libgcc/libstdc++/libvtv.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for --enable-vtable-verify" >&5
 $as_echo_n "checking for --enable-vtable-verify... " >&6; }
@@ -14655,6 +14673,11 @@ if test -d ${srcdir}/gcc && test x"`cat $srcdir/gcc/DEV-PHASE`" = xexperimental;
   "")
       stage2_werror_flag="--enable-werror-always" ;;
   esac
+
+  if test "$cc_is_recent_gcc" = "yes"; then
+    stage1_cflags="$stage1_cflags -O2"
+
+  fi
 fi
 
 
diff --git a/configure.ac b/configure.ac
index 78d2d593106..d312e2e8347 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2667,6 +2667,22 @@ fi
 AC_MSG_RESULT($BUILD_CONFIG)
 AC_SUBST(BUILD_CONFIG)
 
+# Detect if compiler is GCC >= 4.8.x
+AC_MSG_CHECKING(CC is recent compiler)
+cc_is_recent_gcc=
+version_output=`${CC} -v 2>&1 | grep 'gcc version'`
+
+if test "x${version_output}" != x; then
+  version=`echo ${version_output} | sed 's/gcc version \([[^ ]]*\).*/\\1/'`
+  major=`echo ${version} | cut -d. -f1`
+  minor=`echo ${version} | cut -d. -f2`
+
+  if test "${major}" -ge 5 || ( test "${major}" -eq 4 && test "${minor}" -ge 8 ); then
+    cc_is_recent_gcc=yes
+  fi
+fi
+AC_MSG_RESULT($cc_is_recent_gcc)
+
 # Use same top-level configure hooks in libgcc/libstdc++/libvtv.
 AC_MSG_CHECKING([for --enable-vtable-verify])
 AC_ARG_ENABLE(vtable-verify,
@@ -3521,6 +3537,11 @@ if test -d ${srcdir}/gcc && test x"`cat $srcdir/gcc/DEV-PHASE`" = xexperimental;
   "")
       stage2_werror_flag="--enable-werror-always" ;;
   esac
+
+  if test "$cc_is_recent_gcc" = "yes"; then
+    stage1_cflags="$stage1_cflags -O2"
+    AC_SUBST(stage1_cflags)
+  fi
 fi
 
 AC_SUBST(stage2_werror_flag)
-- 
2.12.2

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

On 05/26/2017 03:00 PM, Martin Liška wrote:
> Ok, sending new patch that does that on experimental branches for ${CC} --version
> being a GCC newer than 4.9.

s/4.9/4.8/

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

PING^1

Richi are you fine with the suggested change? I basically followed your advises :)

Martin

On 05/26/2017 03:00 PM, Martin Liška wrote:
> On 05/26/2017 01:55 PM, Richard Biener wrote:
>> On Fri, May 26, 2017 at 1:51 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>>> On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
>>>> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
>>>>> Hello.
>>>>>
>>>>> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
>>>>> enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
>>>>> introduce --with-stage1-cflags where one can provide such options.
>>>>
>>>> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
>>>>
>>>>> Apart from that, maybe it would be handy to automatically enable "-O2" when
>>>>> one has a recent compiler? Do we have an example where we detect host compiler
>>>>> and it's version?
>>>>
>>>> Don't know about version but configury already detects that we use GCC, so that
>>>> knowledge should be readily available.
>>>
>>> Well, it certainly shouldn't be -O2 by default for any system GCC, more
>>> something like if it is major of the configured configure minus 1 or newer
>>> (or minus 2?), then use -O2, otherwise default to -O0 as before.
>>
>> I'd still default to -O0 on release branches regardless of version and then
>> for development we can probably simply use "any GCC" when people have
>> the chance to override.
> 
> Ok, sending new patch that does that on experimental branches for ${CC} --version
> being a GCC newer than 4.9.
> 
> Martin
> 
>>
>> At least for me host GCC 4.8 works quite well with -O2.
>>
>> Richard.
>>
>>>         Jakub
> 

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Richard Biener]

On Mon, Jun 19, 2017 at 12:51 PM, Martin Liška <mliska@suse.cz> wrote:
> PING^1
>
> Richi are you fine with the suggested change? I basically followed your advises :)

Well, I am but as Eric disagrees I think we need input from other
people on this.
I'm comfortably setting STAGE1_CFLAGS here.

Richard.

> Martin
>
> On 05/26/2017 03:00 PM, Martin Liška wrote:
>> On 05/26/2017 01:55 PM, Richard Biener wrote:
>>> On Fri, May 26, 2017 at 1:51 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>>>> On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
>>>>> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
>>>>>> Hello.
>>>>>>
>>>>>> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
>>>>>> enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
>>>>>> introduce --with-stage1-cflags where one can provide such options.
>>>>>
>>>>> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
>>>>>
>>>>>> Apart from that, maybe it would be handy to automatically enable "-O2" when
>>>>>> one has a recent compiler? Do we have an example where we detect host compiler
>>>>>> and it's version?
>>>>>
>>>>> Don't know about version but configury already detects that we use GCC, so that
>>>>> knowledge should be readily available.
>>>>
>>>> Well, it certainly shouldn't be -O2 by default for any system GCC, more
>>>> something like if it is major of the configured configure minus 1 or newer
>>>> (or minus 2?), then use -O2, otherwise default to -O0 as before.
>>>
>>> I'd still default to -O0 on release branches regardless of version and then
>>> for development we can probably simply use "any GCC" when people have
>>> the chance to override.
>>
>> Ok, sending new patch that does that on experimental branches for ${CC} --version
>> being a GCC newer than 4.9.
>>
>> Martin
>>
>>>
>>> At least for me host GCC 4.8 works quite well with -O2.
>>>
>>> Richard.
>>>
>>>>         Jakub
>>
>

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

I would like to ping this. Input from other people will be appreciated ;)

Thanks,
Martin

On 06/19/2017 02:30 PM, Richard Biener wrote:
> On Mon, Jun 19, 2017 at 12:51 PM, Martin Liška <mliska@suse.cz> wrote:
>> PING^1
>>
>> Richi are you fine with the suggested change? I basically followed your advises :)
> 
> Well, I am but as Eric disagrees I think we need input from other
> people on this.
> I'm comfortably setting STAGE1_CFLAGS here.
> 
> Richard.
> 
>> Martin
>>
>> On 05/26/2017 03:00 PM, Martin Liška wrote:
>>> On 05/26/2017 01:55 PM, Richard Biener wrote:
>>>> On Fri, May 26, 2017 at 1:51 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>>>>> On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
>>>>>> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
>>>>>>> Hello.
>>>>>>>
>>>>>>> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
>>>>>>> enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
>>>>>>> introduce --with-stage1-cflags where one can provide such options.
>>>>>>
>>>>>> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
>>>>>>
>>>>>>> Apart from that, maybe it would be handy to automatically enable "-O2" when
>>>>>>> one has a recent compiler? Do we have an example where we detect host compiler
>>>>>>> and it's version?
>>>>>>
>>>>>> Don't know about version but configury already detects that we use GCC, so that
>>>>>> knowledge should be readily available.
>>>>>
>>>>> Well, it certainly shouldn't be -O2 by default for any system GCC, more
>>>>> something like if it is major of the configured configure minus 1 or newer
>>>>> (or minus 2?), then use -O2, otherwise default to -O0 as before.
>>>>
>>>> I'd still default to -O0 on release branches regardless of version and then
>>>> for development we can probably simply use "any GCC" when people have
>>>> the chance to override.
>>>
>>> Ok, sending new patch that does that on experimental branches for ${CC} --version
>>> being a GCC newer than 4.9.
>>>
>>> Martin
>>>
>>>>
>>>> At least for me host GCC 4.8 works quite well with -O2.
>>>>
>>>> Richard.
>>>>
>>>>>         Jakub
>>>
>>

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Jeff Law]

On 07/31/2017 01:47 AM, Martin Liška wrote:
> I would like to ping this. Input from other people will be appreciated ;)
I think the thing to keep in mind here is that IIUC this only affects
things when we've configured using the --with-stage1-cflags option.

So questions about is -O1 more stable than -O2, should we restrict -O2
to newer compilers, etc are really more about the defaults we set.

My understanding is the patch is just adding the capability and does not
change the default.  Assuming that's the case, then I'm comfortable
acking the raw infrastructure.

jeff

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Richard Biener]

On Fri, Aug 25, 2017 at 9:51 PM, Jeff Law <law@redhat.com> wrote:
> On 07/31/2017 01:47 AM, Martin Liška wrote:
>> I would like to ping this. Input from other people will be appreciated ;)
> I think the thing to keep in mind here is that IIUC this only affects
> things when we've configured using the --with-stage1-cflags option.
>
> So questions about is -O1 more stable than -O2, should we restrict -O2
> to newer compilers, etc are really more about the defaults we set.
>
> My understanding is the patch is just adding the capability and does not
> change the default.  Assuming that's the case, then I'm comfortable
> acking the raw infrastructure.

OTOH you can simply set STAGE1_CFLAGS so the value of this
as a configure option is somewhat questionable.

> jeff

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

On 08/28/2017 02:24 PM, Richard Biener wrote:
> On Fri, Aug 25, 2017 at 9:51 PM, Jeff Law <law@redhat.com> wrote:
>> On 07/31/2017 01:47 AM, Martin Liška wrote:
>>> I would like to ping this. Input from other people will be appreciated ;)
>> I think the thing to keep in mind here is that IIUC this only affects
>> things when we've configured using the --with-stage1-cflags option.
>>
>> So questions about is -O1 more stable than -O2, should we restrict -O2
>> to newer compilers, etc are really more about the defaults we set.
>>
>> My understanding is the patch is just adding the capability and does not
>> change the default.  Assuming that's the case, then I'm comfortable
>> acking the raw infrastructure.
> 
> OTOH you can simply set STAGE1_CFLAGS so the value of this
> as a configure option is somewhat questionable.

Yes, STAGE1_CFLAGS is a working solution. I'm not planning to install the patch.

Martin

> 
>> jeff

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Eric Botcazou]

> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a
> recent enough compiler can significantly speed up bootstrap. Thus I'm
> suggesting to introduce --with-stage1-cflags where one can provide such
> options.

-O1 is sufficient in my experience and far less risky than -O2 in this case.

-- 
Eric Botcazou

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Richard Biener]

On Mon, May 29, 2017 at 1:13 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a
>> recent enough compiler can significantly speed up bootstrap. Thus I'm
>> suggesting to introduce --with-stage1-cflags where one can provide such
>> options.
>
> -O1 is sufficient in my experience and far less risky than -O2 in this case.

Are you sure?  In my experience -O2 gets the most test coverage during lifetime
of a particular release.

Richard.

> --
> Eric Botcazou

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Eric Botcazou]

> Are you sure?  In my experience -O2 gets the most test coverage during
> lifetime of a particular release.

Yes, some older GCC releases have aliasing issues that are exposed at -O2 only 
because of -fstrict-aliasing and -fschedule-insns.

-- 
Eric Botcazou

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Martin Liška]

On 05/30/2017 11:43 AM, Eric Botcazou wrote:
>> Are you sure?  In my experience -O2 gets the most test coverage during
>> lifetime of a particular release.
> 
> Yes, some older GCC releases have aliasing issues that are exposed at -O2 only 
> because of -fstrict-aliasing and -fschedule-insns.
> 

That's why we decided to enable -O2 just with GCC 4.8+.

Martin

Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Eric Botcazou]

> That's why we decided to enable -O2 just with GCC 4.8+.

IMO it's too dangerous on non-x86 platforms and -O1 would be much safer.

-- 
Eric Botcazou