[Qemu-devel] [PATCH] support for Mac OS X default compiler

[Qemu-devel] [PATCH] support for Mac OS X default compiler

[Joachim Henke]

I know that you have already discussed this on the list, and that you don't
want to actively support GCC 4. But (at least on Mac OS X) only a fix in
the build configuration is necessary to do the magic: op.c must be compiled
with -fno-tree-ch (as already mentioned on this mailing list).

GCC 4.0 is the default compiler since Mac OS 10.4 (Tiger). Apple still
ships GCC 3.3 20030304 with Xcode 2.2, but doesn't seem to update it
anymore. As the thread
http://lists.gnu.org/archive/html/qemu-devel/2005-12/msg00077.html
turned out, this old compiler has some obvious bugs (further bugs have been
reported on the web - even with code that is less complex than QEMU).

So why not support GCC 4 out of the box? The patch below does this, and
should not hurt anybody. Users are still required to pass
--disable-gcc-check to the configure script - but if they do, GCC 4 will
get it's right command line options.

I tested this with GCC 4.0.1 from Xcode 2.2, and all six softmmu targets
were build without errors. Maybe it works on Linux PPC too?

Would be nice, if you could apply this patch. It makes testing and building
with GCC 4 easier.

Best regards
Jo.


Index: Makefile.target
===================================================================
RCS file: /sources/qemu/qemu/Makefile.target,v
retrieving revision 1.90
diff -u -r1.90 Makefile.target
--- Makefile.target	6 Dec 2005 21:42:17 -0000	1.90
+++ Makefile.target	19 Dec 2005 17:54:59 -0000
@@ -151,6 +151,10 @@
 OP_CFLAGS+=-fno-reorder-blocks -fno-optimize-sibling-calls
 endif
 
+ifeq ($(HAVE_GCC4),yes)
+OP_CFLAGS+=-fno-tree-ch
+endif
+
 ifeq ($(CONFIG_DARWIN),yes)
 OP_CFLAGS+= -mdynamic-no-pic
 LIBS+=-lmx
Index: configure
===================================================================
RCS file: /sources/qemu/qemu/configure,v
retrieving revision 1.79
diff -u -r1.79 configure
--- configure	18 Dec 2005 19:14:49 -0000	1.79
+++ configure	19 Dec 2005 17:55:01 -0000
@@ -283,20 +283,23 @@
 fi
 
 # Check for gcc4
-if test "$check_gcc" = "yes" ; then
-    cat > $TMPC <<EOF
+cat > $TMPC <<EOF
 #if __GNUC__ >= 4
 #error gcc4
 #endif
 int main(){return 0;}
 EOF
-    if ! $cc -o $TMPO $TMPC 2>/dev/null ; then
+
+have_gcc4="no"
+if ! $cc -o $TMPO $TMPC 2>/dev/null ; then
+    if test "$check_gcc" = "yes" ; then
         echo "ERROR: \"$cc\" looks like gcc 4.x"
         echo "QEMU is known to have problems when compiled with gcc 4.x"
         echo "It is recommended that you use gcc 3.x to build QEMU"
         echo "To use this compiler anyway, configure with --disable-gcc-check"
         exit 1;
     fi
+    have_gcc4="yes"
 fi
 
 ##########################################
@@ -527,6 +530,9 @@
 if test "$have_gcc3_options" = "yes" ; then
   echo "HAVE_GCC3_OPTIONS=yes" >> $config_mak
 fi
+if test "$have_gcc4" = "yes" ; then
+  echo "HAVE_GCC4=yes" >> $config_mak
+fi
 echo "HOST_CC=$host_cc" >> $config_mak
 echo "AR=$ar" >> $config_mak
 echo "STRIP=$strip -s -R .comment -R .note" >> $config_mak

Re: [Qemu-devel] [PATCH] support for Mac OS X default compiler

[Fabrice Bellard]

Does -fno-tree-ch works on PC ?

Fabrice.

Joachim Henke wrote:
> I know that you have already discussed this on the list, and that you don't
> want to actively support GCC 4. But (at least on Mac OS X) only a fix in
> the build configuration is necessary to do the magic: op.c must be compiled
> with -fno-tree-ch (as already mentioned on this mailing list).
> 
> GCC 4.0 is the default compiler since Mac OS 10.4 (Tiger). Apple still
> ships GCC 3.3 20030304 with Xcode 2.2, but doesn't seem to update it
> anymore. As the thread
> http://lists.gnu.org/archive/html/qemu-devel/2005-12/msg00077.html
> turned out, this old compiler has some obvious bugs (further bugs have been
> reported on the web - even with code that is less complex than QEMU).
> 
> So why not support GCC 4 out of the box? The patch below does this, and
> should not hurt anybody. Users are still required to pass
> --disable-gcc-check to the configure script - but if they do, GCC 4 will
> get it's right command line options.
> 
> I tested this with GCC 4.0.1 from Xcode 2.2, and all six softmmu targets
> were build without errors. Maybe it works on Linux PPC too?
> 
> Would be nice, if you could apply this patch. It makes testing and building
> with GCC 4 easier.
> 
> Best regards
> Jo.

Re: [Qemu-devel] [PATCH] support for Mac OS X default compiler

[Joshua Root]

>Does -fno-tree-ch works on PC ?
>>
>>Fabrice.

Yes. According to the GCC docs[1], -ftree-ch is enabled by -O1 and 
above on all architectures.

[1] http://gcc.gnu.org/onlinedocs/gcc-4.0.2/gcc/Optimize-Options.html

- Josh

Re: [Qemu-devel] [PATCH] support for Mac OS X default compiler

[Daniel Egger]

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On 19.12.2005, at 23:35, Fabrice Bellard wrote:

> Does -fno-tree-ch works on PC ?

Yes. However using it might introduce a performance hit.

Servus,
       Daniel


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Re: [Qemu-devel] [PATCH] support for Mac OS X default compiler

[Johannes Schindelin]

Hi,

On Tue, 20 Dec 2005, Daniel Egger wrote:

> On 19.12.2005, at 23:35, Fabrice Bellard wrote:
> 
> > Does -fno-tree-ch works on PC ?
> 
> Yes. However using it might introduce a performance hit.

Why not just test for Darwin *and* for GCC 4, and be done with it?

Ciao,
Dscho

Re: [Qemu-devel] [PATCH] support for Mac OS X default compiler

[Gwenole Beauchesne]

On Tue, 20 Dec 2005, Daniel Egger wrote:

> On 19.12.2005, at 23:35, Fabrice Bellard wrote:
> 
> > Does -fno-tree-ch works on PC ?
> 
> Yes. However using it might introduce a performance hit.

I think Fabrice meant does the -fno-tree-ch trick works on x86 with gcc4 
too? The answer is no.

Re: [Qemu-devel] [PATCH] support for Mac OS X default compiler

[Joachim Henke]

Please note that '-fno-tree-ch' is passed to GCC4 only for compiling  
op.c, so that 'dyngen' doesn't fail, when it is working on op.o  
afterwards! All other source files are still compiled without this flag.

On x86 GCC4 fails during compilation of op.c anyway. But '-fno-tree- 
ch' could also help for Linux PPC and MIPS, SPARC, etc. I would  
encourage users of these systems to test, if compiling with GCC4  
works with this patch.

This patch shouldn't break anything. It just disables some  
optimizations - and only for op.o

Jo.


Johannes Schindelin wrote:
> Hi,
>
> On Tue, 20 Dec 2005, Daniel Egger wrote:
>
>> On 19.12.2005, at 23:35, Fabrice Bellard wrote:
>>
>>> Does -fno-tree-ch works on PC ?
>>
>> Yes. However using it might introduce a performance hit.
>
> Why not just test for Darwin *and* for GCC 4, and be done with it?
>
> Ciao,
> Dscho