Re: PATCH - [tree-ssa] regrouping of expression tree for singlemultiply add.

[Roger Sayle <roger at eyesopen dot com>]

On Mon, 22 Mar 2004, Fariborz Jahanian wrote:
> This is the revised patch; incorporating Roger's comments. This patch
> has been bootstrapped, dejagnu tested on ppc-darwin. It has also been
> tested against SPEC2000 with IMA on ppc-darwin. I am proposing this
> patch for tree-ssa because it is an 'improvement' patch and I believe
> mainline is frozen for improvement patches.
>
> OK for tree-ssa?

As Diego has pointed out, tree-ssa is frozen for regression only fixes
prior its merge with mainline.  mainline, however, is still in stage1
[accepting any suitable improvement] and is where this patch should go.


> 2004-03-17  Fariborz Jahanian <fjahanian@apple.com>
>
>          * fold-const.c (fold): reassociate multiply expression
>          with an adjacent non-multiply expression to use
>          architecture's multiply-add instruction.
>

Almost.  The patch looks much better, however, in the first "clause"
you need to check that *both* tree10 and tree11 are MULT_EXPR, and in
the second clause, you need to check both tree00 and tree01 are MULT_EXPR.

Finally, I also like the way your comments show the reassociation, which
also makes is clear that the left-to-right evaluation order is unchanged
by this transformation.  So as its currently written, you don't need to
test reorder_operands_p!  [Sorry for not noticing this the way these
expressions/transformations were originally written].

Hence all you need to do is replace reorder_operands_p with a TREE_CODE
test for the other operand, in each clause.  Ok for *mainline* with those
changes [after the usual bootstrap and regression testing].  You'll also
need to capitalize "Reassociate" in your ChangeLog entry :>

Thanks,

Roger
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