Re: Optimizations for the MIPS target

[David Daney <ddaney at avtrex dot com>]

Joe Buck wrote:
> On Thu, May 04, 2006 at 04:31:15PM +0300, Nikolaos Kavvadias wrote:
>
> > My question here is: culdn't "-Os" optimization option force .align 0
> > alignment? Is there any way to use the minimal data memory
> > requirements for global symbols possible?
>
>
> While it could, I hope that it does not go so far as to make the
> reads unaligned (on processors that allow this).  -Os currently
> optimizes well for speed as well as for space, and there's a substantial
> performance penalty for unaligned reads and writes in many cases.

IIRC, On mips they are trapped and emulated in the Linux/(your OS here) 
kernel.  That means that literally hundreds of instructions are executed 
for each unaligned access.

On systems where they are not emulated, you would get a hard failure.

David Daney.