[Bug middle-end/51895] [4.7 Regression] ICE in simplify_subreg

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51895

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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           Priority|P3                          |P1

--- Comment #6 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-01-19 13:03:14 UTC ---
(In reply to comment #5)
> Created attachment 26377 [details]
> gcc47-pr51895.patch
> 
> Untested patch that attempts to fix BLKmode MEM_REF expansion with
> non-DECL_ADDRESSABLE non-BLKmode base.  It creates abysmal code, so IMNSHO
> eipa_sra should be fixed not to do this.

Hm, can't we do better using extract_bit_field?  I mean, it definitely
should work to do any BIT_FIELD_REF on an rvalue, even if it is a register.
The patch from comment #1 doesn't look completely wrong, it just seems that
the caller should have catered for using the mode of the reg.  The docs
of operand_subword also say 'MODE is the mode of OP in case it is a CONST_INT'
so MODE should be irrelevant if REG_P (op) ...

Seems to be a tricky area, but using a stack temporary looks like overkill.