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Re: [PATCH] loop invariant motion expensive codes
On Thu, 2005-03-31 at 12:10 -0500, David Edelsohn wrote:
> >>>>> Jeffrey A Law writes:
>
> Jeff> First, to move the divide you must be sure the division will always
> Jeff> execute in its original position. Otherwise you can introduce a
> Jeff> spurious divide by zero fault.
>
> Jeff> We have also avoided hoisting division operations in the past as
> Jeff> doing so changes the point at which a divide by zero fault will
> Jeff> occur.
>
> This patch does not change whether the optimization can or does
> hoist a FP divide. The loop invariant motion pass tests the safety of the
> motion elsewhere. The pass has a cost model and the patch makes the cost
> model consistent for all types of divides.
Ah OK. Ignore my comments then.
Thanks for the clarification.
jeff