[tree-ssa] Out of SSA status and issues

[Michael S. Zick]

On Tuesday 13 May 2003 08:22 am, Richard Kenner wrote:
>     I see nothing wrong in replacing 'i + 9' with '*p + 9'.  It would
>     probably not be efficient, but I can't see it being wrong.
>
> If an optimizer pessimizes the code, I'd consider that "wrong".
>
> This isn't a machine-dependent issue: with CPU speeds the way they are,
> a memory reference is *always* many times more expensive than an addition.
Nice generalization, but only relevant while considering '*p' to be an
expression.  
Consider instead that '*p' is just the name given a register's
contents.  Neither 'i' nor '9'  are processor internal.  Both are external
to the cpu.  The memory reference for 'i' is source code implicit, the memory
reference for '*p' is source code explicit.
Mike