Re: [PATCH] Add vcond_gen_code optab and expand VEC_COND_EXPR

[Devang Patel <dpatel at apple dot com>]

On Sep 23, 2004, at 12:37 AM, Richard Henderson wrote:

> On Tue, Sep 21, 2004 at 04:52:39PM -0700, Devang Patel wrote:
> > Auto Vectorizer wants to see if operation is supported without
> > generating insn at that time.
>
> Then you are confused about how you're supposed to check for that.
> Adding a dummy boolean operand is definitely not ok.

Before auto-vectorizing loop, vectorizer checks all loop statements. It 
checks whether relevant statements can be replaced by vector statements 
or not. Once loop is flagged as vectorizable, all relevant statements 
are vectorized. For the conditional modify expr., I need to check if it 
can be vectorized or not. I think, checking existance vcond insn for 
given mode is not sufficient. So in expand_vec_cond_expr_p(), I create 
dummy rtx for vec_cond_expr operands and ask target to return insns for 
given mode and code using dummy rtx.  I used boolean operand to 
instruct target not emit any insn if it is only for checking purposes. 
In the updated patch, I just sent few minutes ago, I've removed boolean 
flag. Now I check if vcond insn fail or not. If it fails than statement 
can not be vectorized. If it succeeds than statement can be vectorized 
and generated insn are ignored.

As I said earlier this is weakest part of this patch. Thoughts?
Thanks,
-
Devang