On Mon, Jul 20, 2009 at 7:02 PM, David T. Lewislewis@mail.msen.com wrote:
On Sat, Jul 18, 2009 at 05:25:48PM +0200, Andrew Gaylard wrote:
The main issue that I'm facing at the moment is that gcc-4.4.0 generates code that causes unaligned accesses in fetchFloatAtinto; the same code works in gcc-4.2.4 on SPARC. Until I or someone else (hint!) fixes this, I'm continuing to build with gcc-4.2.4.
fetchFloatAtInto() is implemented in platforms/Cross/vm/sqMemoryAccess.h in the form of cpp macros. It might be tricky to debug this, but I note that the implementation depends on DOUBLE_WORD_ALIGNMENT, which is a macro that would have been set when you run configure. You might playing with this setting to see if it gives you the results you want. For example, as a complete SWAG, it might be the case that SPARC plus gcc-4.2.4 needs this macro defined but for some reason configure is not setting it for you.
David, thanks for the tip. This message from configure showed you are right (the 'yes' should be 'no'):
checking whether unaligned access to doubles is ok... yes
It turns out that newer GCCs, from 4.3.x onward, are smart enough to optimise out the code used to detect strict alignment:
bash-3.2$ gcc -O2 double-test.c double-test.c: In function 'main': double-test.c:6: warning: passing argument 1 of 'f' makes integer from pointer without a cast double-test.c:1: note: expected 'int' but argument is of type 'char *' bash-3.2$ ./a.out bash-3.2$ echo $? 0
But when compiling without optimisation:
bash-3.2$ gcc double-test.c double-test.c: In function 'main': double-test.c:6: warning: passing argument 1 of 'f' makes integer from pointer without a cast double-test.c:1: note: expected 'int' but argument is of type 'char *' bash-3.2$ ./a.out Bus Error (core dumped)
... as expected.
This patch complicates the code sufficiently (by using the results of the function) so that it triggers a bus error both with and without optimisation, as would be expected. Of course, configure needs to be regenerated after applying this patch.
Running our internal benchmark reveals that it is worth it getting 4.4.1 to work:
gcc-4.4.1:
real 61m45.975s user 56m16.247s sys 4m57.253s
gcc-4.2.4:
real 67m29.260s user 61m40.666s sys 5m7.937s
This means the VM is sped up by 9%.
- Andrew
--- Squeak-3.10-4/platforms/unix/config/acinclude.m4.orig 2008-09-02 20:49:43.000000000 +0200 +++ Squeak-3.10-4/platforms/unix/config/acinclude.m4 2009-07-30 16:16:55.828929831 +0200 @@ -230,10 +230,33 @@
AC_DEFUN([AC_C_DOUBLE_ALIGNMENT], [AC_CACHE_CHECK([whether unaligned access to doubles is ok], ac_cv_double_align, - AC_TRY_RUN([f(int i){*(double *)i=*(double *)(i+4);} - int main(){char b[[12]];f(b);return 0;}], + AC_TRY_RUN([ + +int f(void* i){ + *(double *)i=*(double *)(i+4); + return *(char*)i; +} +int main(){ + char b[[12]]; + b[[0]]=1; + b[[1]]=2; + b[[2]]=3; + b[[3]]=4; + b[[4]]=0; + b[[5]]=0; + b[[6]]=0; + b[[7]]=0; + b[[8]]=0; + b[[9]]=0; + b[[10]]=0; + b[[11]]=0; + + return f(b); +} +], + ac_cv_double_align="yes", ac_cv_double_align="no")) test "$ac_cv_double_align" = "no" && AC_DEFINE(DOUBLE_WORD_ALIGNMENT)])
AC_DEFUN([AC_C_DOUBLE_ORDER],
Excellent, thanks for the follow up Andrew.
Ian,
There is a patch for platforms/unix/config/acinclude.m4 at the end of this email that addresses an issue for newer GCCs on SPARC. When you get a chance, can you please update the acinclude.m4 and do a make configure?
Thanks,
Dave
On Thu, Jul 30, 2009 at 10:47:23PM +0200, Andrew Gaylard wrote:
On Mon, Jul 20, 2009 at 7:02 PM, David T. Lewislewis@mail.msen.com wrote:
On Sat, Jul 18, 2009 at 05:25:48PM +0200, Andrew Gaylard wrote:
The main issue that I'm facing at the moment is that gcc-4.4.0 generates code that causes unaligned accesses in fetchFloatAtinto; the same code works in gcc-4.2.4 on SPARC. ?Until I or someone else (hint!) fixes this, I'm continuing to build with gcc-4.2.4.
fetchFloatAtInto() is implemented in platforms/Cross/vm/sqMemoryAccess.h in the form of cpp macros. It might be tricky to debug this, but I note that the implementation depends on DOUBLE_WORD_ALIGNMENT, which is a macro that would have been set when you run configure. You might playing with this setting to see if it gives you the results you want. For example, as a complete SWAG, it might be the case that SPARC plus gcc-4.2.4 needs this macro defined but for some reason configure is not setting it for you.
David, thanks for the tip. This message from configure showed you are right (the 'yes' should be 'no'):
checking whether unaligned access to doubles is ok... yes
It turns out that newer GCCs, from 4.3.x onward, are smart enough to optimise out the code used to detect strict alignment:
bash-3.2$ gcc -O2 double-test.c double-test.c: In function 'main': double-test.c:6: warning: passing argument 1 of 'f' makes integer from pointer without a cast double-test.c:1: note: expected 'int' but argument is of type 'char *' bash-3.2$ ./a.out bash-3.2$ echo $? 0
But when compiling without optimisation:
bash-3.2$ gcc double-test.c double-test.c: In function 'main': double-test.c:6: warning: passing argument 1 of 'f' makes integer from pointer without a cast double-test.c:1: note: expected 'int' but argument is of type 'char *' bash-3.2$ ./a.out Bus Error (core dumped)
... as expected.
This patch complicates the code sufficiently (by using the results of the function) so that it triggers a bus error both with and without optimisation, as would be expected. Of course, configure needs to be regenerated after applying this patch.
Running our internal benchmark reveals that it is worth it getting 4.4.1 to work:
gcc-4.4.1:
real 61m45.975s user 56m16.247s sys 4m57.253s
gcc-4.2.4:
real 67m29.260s user 61m40.666s sys 5m7.937s
This means the VM is sped up by 9%.
- Andrew
--- Squeak-3.10-4/platforms/unix/config/acinclude.m4.orig 2008-09-02 20:49:43.000000000 +0200 +++ Squeak-3.10-4/platforms/unix/config/acinclude.m4 2009-07-30 16:16:55.828929831 +0200 @@ -230,10 +230,33 @@
AC_DEFUN([AC_C_DOUBLE_ALIGNMENT], [AC_CACHE_CHECK([whether unaligned access to doubles is ok], ac_cv_double_align,
- AC_TRY_RUN([f(int i){*(double *)i=*(double *)(i+4);}
int main(){char b[[12]];f(b);return 0;}],
- AC_TRY_RUN([
+int f(void* i){
*(double *)i=*(double *)(i+4);
return *(char*)i;
+} +int main(){
char b[[12]];
b[[0]]=1;
b[[1]]=2;
b[[2]]=3;
b[[3]]=4;
b[[4]]=0;
b[[5]]=0;
b[[6]]=0;
b[[7]]=0;
b[[8]]=0;
b[[9]]=0;
b[[10]]=0;
b[[11]]=0;
return f(b);
+} +],
- ac_cv_double_align="yes", ac_cv_double_align="no"))
test "$ac_cv_double_align" = "no" && AC_DEFINE(DOUBLE_WORD_ALIGNMENT)])
AC_DEFUN([AC_C_DOUBLE_ORDER],
Hi Dave,
On Jul 30, 2009, at 7:47 PM, David T. Lewis wrote:
Ian, There is a patch for platforms/unix/config/acinclude.m4 at the end of this email that addresses an issue for newer GCCs on SPARC. When you get a chance, can you please update the acinclude.m4 and do a make configure?
I already did.
Cheers, Ian
On Fri, Jul 31, 2009 at 5:05 AM, Ian Piumartapiumarta@speakeasy.net wrote:
On Jul 30, 2009, at 7:47 PM, David T. Lewis wrote:
Ian, There is a patch for platforms/unix/config/acinclude.m4 at the end of this email that addresses an issue for newer GCCs on SPARC. When you get a chance, can you please update the acinclude.m4 and do a make configure?
I already did.
Ian & David,
Thanks a lot for adding this patch to the tree so quickly. I have several other patches which we rely on to fix various issues, including:
- building on Solaris - using sound on Solaris - setting the X bitmap icon - pasting from the clipboard - changing the signal-handling code from signal() to sigaction()
The latter three are useful on both Solaris and Linux.
Would it be possible to get these patches into the tree too?
I've submitted them over the years, but there's been no feedback whether or not they're the right fixes for these various problems.
Thanks, Andrew
On Fri, Jul 31, 2009 at 08:14:34PM +0200, Andrew Gaylard wrote:
On Fri, Jul 31, 2009 at 5:05 AM, Ian Piumartapiumarta@speakeasy.net wrote:
On Jul 30, 2009, at 7:47 PM, David T. Lewis wrote:
Ian, There is a patch for platforms/unix/config/acinclude.m4 at the end of this email that addresses an issue for newer GCCs on SPARC. When you get a chance, can you please update the acinclude.m4 and do a make configure?
I already did.
Ian & David,
Thanks a lot for adding this patch to the tree so quickly. I have several other patches which we rely on to fix various issues, including:
- building on Solaris
- using sound on Solaris
- setting the X bitmap icon
- pasting from the clipboard
- changing the signal-handling code from signal() to sigaction()
The latter three are useful on both Solaris and Linux.
Would it be possible to get these patches into the tree too?
I've submitted them over the years, but there's been no feedback whether or not they're the right fixes for these various problems.
Hi Andrew,
Ian can answer with respect to added the patches, but from my point of view can I suggest that you add an issue on the Mantis bug tracking system (http://bugs.squeak.org) and attach your patches there. Use bug category "VM".
This won't guarantee anything getting done, but it does guarantee that we will not lose your work. Patches posted to the list do have a tendency to get lost in the ether sometimes.
Dave
Andrew,
I have several other patches which we rely on to fix various issues
I have fix-to-build-solaris.diff and new-solaris-sound-driver.diff. If there's anything else, please send it my way. (I spent yesterday afternoon trying to persuade Solaris 10 to install under kvm and failed. I'll try again this weekend with VirtualBox.)
BTW: Subbu pointed out that the caps lock bug (where it's reported as shift pressed) crept back in during an olpc merge. While fixing that I loaded Dave's latest VMM and rebuilt the interpreter. SVN and the 3.10-6 archives should have working closure support. Binaries are there for Mac PPC+386, Ubuntu 8.04 386 and FreeBSD 7.2 386.
Cheers, Ian
vm-dev@lists.squeakfoundation.org