[PATCH] [3.2 branch] Fix PR optimization/9279

[Roger Sayle]

On Sun, 26 Jan 2003, David Edelsohn wrote:
>         2002-07-10  Roger Sayle  <roger@eyesopen.com>
>
>         PR c/2454
>         * combine.c (nonzero_bits): LOAD_EXTEND_OP should only apply
>         to SUBREGs of MEMs.  (num_sign_bit_copies): Likewise.
>
> Doesn't this patch now introduce a performance regression for targets that
> don't expose a zero-extend in RTL for sub-word loads from memory?

No.

Like it says in the ChangeLog entry, all this patch does is ensure
that the implicit extensions only apply to "sub-word loads from
memory" (SUBREGs of MEMs).  Sub-word loads from other registers, for
example, aren't covered by the semantics of LOAD_EXTEND_OP.

Roger
--
Roger Sayle,                         E-mail: roger@eyesopen.com
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