[Bug middle-end/36359] missed optimization in some cases with PRE VRP and other passes combined together

[edwintorok at gmail dot com]

------- Comment #17 from edwintorok at gmail dot com  2008-11-24 18:33 -------
Created an attachment (id=16761)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16761&action=view)
drivers/scsi/sd.c

Similar problem with drivers/scsi/sd.c

I can compile the attached preprocessed on x86_64 linux:
$ gcc-4.3 -c x.i -o x.o -O2 && nm -u x.o|grep ilog2
$ ~/gcc_inst/bin/gcc -c x.i -o x.o -O2 && nm -u x.o|grep ilog2
U ____ilog2_NaN

IMHO the kernel is abusing gcc as a static analyzer, which gcc is not.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36359