[Bug target/37216] [cygming] Invalid alignment for SSE store to .comm data generated with -O3

[dannysmith at users dot sourceforge dot net]

------- Comment #41 from dannysmith at users dot sourceforge dot net  2008-10-06 20:18 -------
(In reply to comment #35)

> As I suspected.  The PE/COFF file format does not provide for specifying 
> the alignment of commons.
> 
> Hmm, I wonder if gcc should complain if it finds aligned commons with 
> COFF backends or if we should try to generate a GNU extension to the 
> COFF format.
> 

Aligned commons are not part of the PE COFF spec and AFAICT neither MASM nor
NASM provide a way to specify aligned commons.  I am afraid that a GNU
extension will cause object incompatibility, so it would it need to be a
non-default option.  We already have
 -fno-common
__attribute__((no_common)) 
#pragma gcc optimize (no_common)  

G++ already puts commons in .bss

Perhaps a new option -fno_large_common that applies -fcommon only to objects
with align <= 4 bytes?

A warning would be useful in any case.

Danny


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37216