https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64412
Uroš Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|target |middle-end
--- Comment #13 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to H.J. Lu from comment #12)
> Created attachment 34361 [details]
> A new patch
>
> Please try the new patch.
No, this approach is wrong. ix86_fixup_binary_operands should not be used to
legitimize PIC address. The -fpic expansion is already wrong, since it
produces:
;; ivtmp.9_4 = (unsigned long) _37;
(insn 59 58 0 (parallel [
(set (reg:DI 123 [ ivtmp.9 ])
(plus:DI (reg:DI 124 [ D.3980 ])
(symbol_ref:DI ("G") <var_decl 0x7f8c6facc900 G>)))
(clobber (reg:CC 17 flags))
]) -1
(nil))
This is similar to:
--cut here--
typedef __SIZE_TYPE__ size_t;
extern char G[8];
char *a (size_t z)
{
return &G[z];
}
--cut here--
Without -fpic, the compiler expands to:
6: {r90:DI=r89:DI+`G';clobber flags:CC;}
Compare this with -fpic expansion:
6: r92:DI=[const(unspec[`G'] 2)]
7: r91:DI=r92:DI
REG_EQUAL `G'
8: {r90:DI=r89:DI+r91:DI;clobber flags:CC;}
Looking at the above, it looks the problem is in the middle-end, where symbol
address should be legitimized through ix86_legitimize_address (a.k.a
TARGET_LEGITIMIZE_ADDRESS).
