[Bug target/44046] New: Intel Core i5 M520 CPU detected as atom with -march=native

[Bug target/44046] New: Intel Core i5 M520 CPU detected as atom with -march=native

[dirtyepic at gentoo dot org]

We have a user that is getting illegal instruction errors while building
xulrunner.

/var/tmp/portage/net-libs/xulrunner-1.9.2.3-r1/work/mozilla-1.9.2/dist/bin/xpidl
-m typelib -w -I. -I../../dist/idl -e _xpidlgen/nsIConsoleListener.xpt -d
.deps/nsIConsoleListener.pp nsIConsoleListener.idl
make[4]: *** [_xpidlgen/nsIConsoleListener.xpt] Illegal instruction

It turns out that using -march=native with his Core i5 processor results in
-march=atom being used, specifically:

gcc version 4.5.0 (Gentoo 4.5.0 p1.0) 
COLLECT_GCC_OPTIONS= '-v' '-o' 'test'
 /usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.0/cc1 -quiet -v test.c
-D_FORTIFY_SOURCE=2 -march=atom -mcx16 -msahf -maes -mpclmul -mpopcnt -msse4.2
--param l1-cache-size=32 --param l1-cache-line-size=64 --param
l2-cache-size=3072 -mtune=core2 -quiet -dumpbase test.c -auxbase test -version
-o /tmp/ccmAagyo.s

I believe the issue is that this processor doesn't support mmovbe, which
-march=atom enables (the error doesn't occur w/ -march=atom -mno-movbe).  Am I
right in guessing that it should instead be using -march=core2 + a bunch of -m
flags?

I will attach his /proc/cpuinfo.  Let me know what other info you need.

http://bugs.gentoo.org/317513


-- 
           Summary: Intel Core i5 M520 CPU detected as atom with -
                    march=native
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dirtyepic at gentoo dot org
 GCC build triplet: x86_64-pc-linux-gnu
  GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[dirtyepic at gentoo dot org]

------- Comment #1 from dirtyepic at gentoo dot org  2010-05-09 04:48 -------
Created an attachment (id=20610)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20610&action=view)
/proc/cpuinfo


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[ubizjak at gmail dot com]

------- Comment #2 from ubizjak at gmail dot com  2010-05-09 07:25 -------
>From config/driver-i386.c

    [...]
    case PROCESSOR_PENTIUMPRO:
      if (model == 28)
        cpu = "atom";
      else if (model >= 28 && l2sizekb < 2048)
        /* Assume it's a small core if there's less than 2MB cache */
        cpu = "atom";
      else if (has_longmode)
        cpu = "core2";

And from cpuid:

cpu family      : 6
model           : 37
cache size      : 3072 KB

driver detects --param l2-cache-size=3072 and -march=atom ... WTF ?

Can you please step through the driver with debugger and determine _exact_
values of model and l2sizekb in the above source? It is around line 540 in
gcc/config/i386/driver-i386.c.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl dot tools at gmail dot com]

------- Comment #3 from hjl dot tools at gmail dot com  2010-05-09 14:43 -------
A patch is posted at

http://gcc.gnu.org/ml/gcc-patches/2010-05/msg00606.html


-- 

hjl dot tools at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |http://gcc.gnu.org/ml/gcc-
                   |                            |patches/2010-
                   |                            |05/msg00606.html
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-05-09 14:43:11
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl at gcc dot gnu dot org]

------- Comment #4 from hjl at gcc dot gnu dot org  2010-05-09 14:50 -------
Subject: Bug 44046

Author: hjl
Date: Sun May  9 14:49:53 2010
New Revision: 159202

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=159202
Log:
Properly detect Atom, Core 2 and Core i7.

2010-05-09  H.J. Lu  <hongjiu.lu@intel.com>

        PR target/44046
        * config/i386/driver-i386.c (host_detect_local_cpu): Properly
        detect Atom, Core 2 and Core i7.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/driver-i386.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl at gcc dot gnu dot org]

------- Comment #5 from hjl at gcc dot gnu dot org  2010-05-09 14:53 -------
Subject: Bug 44046

Author: hjl
Date: Sun May  9 14:53:00 2010
New Revision: 159203

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=159203
Log:
Properly detect Atom, Core 2 and Core i7.

2010-05-09  H.J. Lu  <hongjiu.lu@intel.com>

        Backport from mainline
        2010-05-09  H.J. Lu  <hongjiu.lu@intel.com>

        PR target/44046
        * config/i386/driver-i386.c (host_detect_local_cpu): Properly
        detect Atom, Core 2 and Core i7.

Modified:
    branches/gcc-4_5-branch/gcc/ChangeLog
    branches/gcc-4_5-branch/gcc/config/i386/driver-i386.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl dot tools at gmail dot com]

-- 

hjl dot tools at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.5.1 4.6.0
   Target Milestone|---                         |4.4.6


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[dirtyepic at gentoo dot org]

------- Comment #6 from dirtyepic at gentoo dot org  2010-05-09 18:39 -------
Created an attachment (id=20614)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20614&action=view)
gcc45-PR44046-core2.patch


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[dirtyepic at gentoo dot org]

------- Comment #7 from dirtyepic at gentoo dot org  2010-05-09 18:44 -------
sorry, wrong bugzilla. ;)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl dot tools at gmail dot com]

------- Comment #8 from hjl dot tools at gmail dot com  2010-05-10 03:52 -------
Fixed. No need to change gcc 4.4.


-- 

hjl dot tools at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|4.4.6                       |4.5.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[jakub at gcc dot gnu dot org]

------- Comment #9 from jakub at gcc dot gnu dot org  2010-08-11 18:44 -------
Apparently some KVM versions claim to be GenuineIntel family 6 model 6 with lm,
but not ssse3, see
https://bugzilla.redhat.com/show_bug.cgi?id=620562
Perhaps the has_longmode -> core2 test should be restored...


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl dot tools at gmail dot com]

------- Comment #10 from hjl dot tools at gmail dot com  2010-08-11 19:12 -------
(In reply to comment #9)
> Apparently some KVM versions claim to be GenuineIntel family 6 model 6 with lm,
> but not ssse3, see
> https://bugzilla.redhat.com/show_bug.cgi?id=620562
> Perhaps the has_longmode -> core2 test should be restored...
> 

There are no such processors from Intel. If you look at SSE3 and LM, it
sounds like Nocona. But it also has family 6 and model 6. It looks like
Pentium-M. If we pass -march=core2, it will generate SSSE3, which isn't
supported. The bug is in KVM. It should never make up fake Intel processors.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046

[Bug target/44046] Intel Core i5 M520 CPU detected as atom with -march=native

[hjl dot tools at gmail dot com]

------- Comment #11 from hjl dot tools at gmail dot com  2010-08-11 20:31 -------
Maybe we can improve the unknown processor support:

1. For 32bit, use i686 + -mSSEx.
2. For 64bit, use x86_64 + -mSSEx.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44046