Re: [PATCH 1/8]middle-end: Recognize scalar reductions from bitfields and array_refs

[Jeff Law <jeffreyalaw@gmail.com>]

On 10/31/22 05:56, Tamar Christina wrote:
> Hi All,
>
> This patch series is to add recognition of pairwise operations (reductions)
> in match.pd such that we can benefit from them even at -O1 when the vectorizer
> isn't enabled.
>
> Ths use of these allow for a lot simpler codegen in AArch64 and allows us to
> avoid quite a lot of codegen warts.
>
> As an example a simple:
>
> typedef float v4sf __attribute__((vector_size (16)));
>
> float
> foo3 (v4sf x)
> {
>    return x[1] + x[2];
> }
>
> currently generates:
>
> foo3:
>          dup     s1, v0.s[1]
>          dup     s0, v0.s[2]
>          fadd    s0, s1, s0
>          ret
>
> while with this patch series now generates:
>
> foo3:
> 	ext	v0.16b, v0.16b, v0.16b, #4
> 	faddp	s0, v0.2s
> 	ret
>
> This patch will not perform the operation if the source is not a gimple
> register and leaves memory sources to the vectorizer as it's able to deal
> correctly with clobbers.
>
> The use of these instruction makes a significant difference in codegen quality
> for AArch64 and Arm.
>
> NOTE: The last entry in the series contains tests for all of the previous
> patches as it's a bit of an all or nothing thing.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
> and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> 	* match.pd (adjacent_data_access_p): Import.
> 	Add new pattern for bitwise plus, min, max, fmax, fmin.
> 	* tree-cfg.cc (verify_gimple_call): Allow function arguments in IFNs.
> 	* tree.cc (adjacent_data_access_p): New.
> 	* tree.h (adjacent_data_access_p): New.

Nice stuff.  I'd pondered some similar stuff at Tachyum, but got dragged 
away before it could be implemented.





> diff --git a/gcc/tree.cc b/gcc/tree.cc
> index 007c9325b17076f474e6681c49966c59cf6b91c7..5315af38a1ead89ca5f75dc4b19de9841e29d311 100644
> --- a/gcc/tree.cc
> +++ b/gcc/tree.cc
> @@ -10457,6 +10457,90 @@ bitmask_inv_cst_vector_p (tree t)
>     return builder.build ();
>   }
>   
> +/* Returns base address if the two operands represent adjacent access of data
> +   such that a pairwise operation can be used.  OP1 must be a lower subpart
> +   than OP2.  If POS is not NULL then on return if a value is returned POS
> +   will indicate the position of the lower address.  If COMMUTATIVE_P then
> +   the operation is also tried by flipping op1 and op2.  */
> +
> +tree adjacent_data_access_p (tree op1, tree op2, poly_uint64 *pos,
> +			     bool commutative_p)

Formatting nit.  Return type on a different line.


OK with that fixed.


jeff