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Re: Patch: Consistently generate widening multiplies
On 02/17/2010 11:24 AM, Richard Guenther wrote:
I think this sort of stuff (and also possible FMA detection) fits
in a re-association framework (not necessarily that we have right now,
that needs some TLC anyway ...).
That would be between 3 and 4 in the steps of tree-ssa-reassoc?
1. Breaking up subtract operations into addition + negate, where
it would promote the reassociation of adds.
2. Left linearization of the expression trees, so that (A+B)+(C+D)
becomes (((A+B)+C)+D), which is easier for us to rewrite later.
During linearization, we place the operands of the binary
expressions into a vector of operand_entry_t
3. Optimization of the operand lists, eliminating things like a +
-a, a & a, etc.
4. Rewrite the expression trees we linearized and optimized so
they are in proper rank order.
?
This is much better than doing it in fwprop.c (which anyway was
rewritten so you couldn't do it there anymore...).
Paolo