On Tue, Aug 3, 2010 at 6:06 PM, Richard Guenther
<richard.guenther@gmail.com> wrote:
On Tue, Aug 3, 2010 at 6:01 PM, Bernd Schmidt<bernds@codesourcery.com> wrote:
On 08/03/2010 05:44 PM, Richard Guenther wrote:
It's not safe on RTL, please do not add FP reassociation there.
(config/i386/i386.c:ix86_expand_{round,trunc,...} would start
to break).
Not a problem (I guess a !FLOAT_MODE_P || flag_associative_math test is
needed), but I guess I don't understand how things would break - I see
no multiply operations in these i386 functions. Can you elaborate?
It was just a general comment to re-associations of FP on RTL,
but more important is that we not start doing constant folding,
re-associating should be fine as long as they are valid without
any fancy math flags.
Btw, doing more elaborate re-association on RTL would need
carrying PAREN_EXPR support down to RTL, which is an
explicit re-association barrier (dropped during expansion because
we do not re-associate FP on RTL - sofar).