I'm running one of my Sage instances on quite old machine, 2xPentium
III 1GHz. It doesn't even have sse2, but until 5.2 everything worked
and was quite usable when not used by more than 2 users at a time.
Today I tried to update and it compiled fine, but I got following
doctest failures comming from ecm, all seems to be related to
factorisation. This is first time I see Illegal instruction coming out
when building from source, so it seems quite bizarre to me. I'm trying
to rebuild ecm to see what can be the cause. Any ideas how to proceed
with this one?

Thanks,
Andrzej.

sage -t --long -force_lib "devel/sage/sage/libs/libecm.pyx"
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/libs/libecm.pyx", line 81:
    sage: print "ignore this";  ecmfactor(N, 1e2)  # random
Exception raised:
    Traceback (most recent call last):
      File "/usr/local/sage/sage-5.2/local/bin/ncadoctest.py", line
1231, in run_one_test
        self.run_one_example(test, example, filename, compileflags)
      File "/usr/local/sage/sage-5.2/local/bin/sagedoctest.py", line
38, in run_one_example
        OrigDocTestRunner.run_one_example(self, test, example,
filename, compileflags)
      File "/usr/local/sage/sage-5.2/local/bin/ncadoctest.py", line
1172, in run_one_example
        compileflags, 1) in test.globs
      File "<doctest __main__.example_1[6]>", line 1, in <module>
        print "ignore this";  ecmfactor(N, RealNumber('1e2'))  #
random###line 81:
    sage: print "ignore this";  ecmfactor(N, 1e2)  # random
      File "libecm.pyx", line 152, in sage.libs.libecm.ecmfactor
(sage/libs/libecm.c:1986)
    RuntimeError: Illegal instruction
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/libs/libecm.pyx", line 91:
    sage: ecmfactor(N, 1e3)
Exception raised:
    Traceback (most recent call last):
      File "/usr/local/sage/sage-5.2/local/bin/ncadoctest.py", line
1231, in run_one_test
        self.run_one_example(test, example, filename, compileflags)
      File "/usr/local/sage/sage-5.2/local/bin/sagedoctest.py", line
38, in run_one_example
        OrigDocTestRunner.run_one_example(self, test, example,
filename, compileflags)
      File "/usr/local/sage/sage-5.2/local/bin/ncadoctest.py", line
1172, in run_one_example
        compileflags, 1) in test.globs
      File "<doctest __main__.example_1[9]>", line 1, in <module>
        ecmfactor(N, RealNumber('1e3'))###line 91:
    sage: ecmfactor(N, 1e3)
      File "libecm.pyx", line 152, in sage.libs.libecm.ecmfactor
(sage/libs/libecm.c:1986)
    RuntimeError: Illegal instruction
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/libs/libecm.pyx", line 112:
    sage: ecmfactor(N/11, 100, verbose=True)
Exception raised:
    Traceback (most recent call last):
      File "/usr/local/sage/sage-5.2/local/bin/ncadoctest.py", line
1231, in run_one_test
        self.run_one_example(test, example, filename, compileflags)
      File "/usr/local/sage/sage-5.2/local/bin/sagedoctest.py", line
38, in run_one_example
        OrigDocTestRunner.run_one_example(self, test, example,
filename, compileflags)
      File "/usr/local/sage/sage-5.2/local/bin/ncadoctest.py", line
1172, in run_one_example
        compileflags, 1) in test.globs
      File "<doctest __main__.example_1[16]>", line 1, in <module>
        ecmfactor(N/Integer(11), Integer(100), verbose=True)###line 112:
    sage: ecmfactor(N/11, 100, verbose=True)
      File "libecm.pyx", line 152, in sage.libs.libecm.ecmfactor
(sage/libs/libecm.c:1986)
    RuntimeError: Illegal instruction
**********************************************************************
1 items had failures:
   3 of  22 in __main__.example_1
***Test Failed*** 3 failures.

and

sage -t --long -force_lib "devel/sage/sage/interfaces/ecm.py"
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 173:
    sage: f.one_curve(n, B1=10000, sigma=1022170541)
Expected:
    [79792266297612017, 6366805760909027985741435139224233]
Got:
    [1, 508021860739623467191080372196682785441177798407961]
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 176:
    sage: f.one_curve(n, B1=500000, algorithm="P-1")
Expected:
    [67872792749091946529, 6366805760909027985741435139224233]
Got:
    [1, 432132887883903108009802143314445113500016816977037257]
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 179:
    sage: f.one_curve(n, B1=2000, algorithm="P+1", x0=5)
Expected:
    [328006342451, 6366805760909027985741435139224233]
Got:
    [1, 2088352670731726262548647919416588631875815083]
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 243:
    sage: f.find_factor(n)
Expected:
    [79792266297612017, 6366805760909027985741435139224233]
Got:
    [508021860739623467191080372196682785441177798407961]
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 333:
    sage: ecm.factor(602400691612422154516282778947806249229526581)
Expected:
    [45949729863572179, 13109994191499930367061460439]
Got:
    [602400691612422154516282778947806249229526581]
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 336:
    sage: ecm.factor((2^197 + 1)/3)           # takes a long time
Expected:
    [197002597249, 1348959352853811313, 251951573867253012259144010843]
Got:
    [66955751844124594814248420514215108438425124740949701470891]
**********************************************************************
File "/usr/local/sage/sage-5.2/devel/sage/sage/interfaces/ecm.py", line 377:
    sage: ecm.factor((2^197 + 1)/3)             # long time
Expected:
    [197002597249, 1348959352853811313, 251951573867253012259144010843]
Got:
    [66955751844124594814248420514215108438425124740949701470891]
**********************************************************************
4 items had failures:
   3 of  11 in __main__.example_6
   1 of   8 in __main__.example_7
   2 of   5 in __main__.example_8
   1 of   5 in __main__.example_9
***Test Failed*** 7 failures.

Anyway, setting ECM_CONFIGURE=--disable-sse2 manually fixed the issue,
seems that before it was able to detect it, but no longer - maybe
because of gcc update (I'm using system wide gcc and fortran, version
4.7.1)? Or maybe I did not noticed it failing before, if yes then
sorry for noise. Anyway, it's working now with this environment
variable set. Seems it was local issue.

Thanks,
Andrzej.