Re: [patch] Improve detection of widening multiplication in the vectorizer

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Jun 7, 2011 at 1:50 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Jun 1, 2011 at 2:23 AM, Ira Rosen <ira.rosen@linaro.org> wrote:
>> Hi,
>>
>> The vectorizer expects widening multiplication pattern to be:
>>
>>     type a_t, b_t;
>>     TYPE a_T, b_T, prod_T;
>>
>>     a_T = (TYPE) a_t;
>>     b_T = (TYPE) b_t;
>>     prod_T = a_T * b_T;
>>
>> where type 'TYPE' is double the size of type 'type'. This works fine
>> when the types are signed. For the unsigned types the code looks like:
>>
>>     unsigned type a_t, b_t;
>>     unsigned TYPE u_prod_T;
>>     TYPE a_T, b_T, prod_T;
>>
>>      a_T = (TYPE) a_t;
>>      b_T = (TYPE) b_t;
>>      prod_T = a_T * b_T;
>>      u_prod_T = (unsigned TYPE) prod_T;
>>
>> i.e., the multiplication is done on signed, followed by a cast to unsigned.
>> This patch adds a support of such patterns and generates
>> WIDEN_MULT_EXPR for the unsigned type.
>>
>> Another unsupported case is multiplication by a constant (e.g., b_T is
>> a constant). This patch checks that the constant fits the smaller type
>> 'type' and recognizes such cases as widening multiplication.
>>
>> Bootstrapped and tested on powerpc64-suse-linux. Tested the
>> vectorization testsuite on arm-linux-gnueabi.
>> I'll commit the patch shortly if there are no comments/objections.
>>
>> Ira
>>
>> ChangeLog:
>>
>>       * tree-vectorizer.h (vect_recog_func_ptr): Make last argument to be
>>       a pointer.
>>       * tree-vect-patterns.c (vect_recog_widen_sum_pattern,
>>       vect_recog_widen_mult_pattern, vect_recog_dot_prod_pattern,
>>       vect_recog_pow_pattern): Likewise.
>>       (vect_pattern_recog_1): Remove declaration.
>>       (widened_name_p): Remove declaration.  Add new argument to specify
>>       whether to check that both types are either signed or unsigned.
>>       (vect_recog_widen_mult_pattern): Update documentation.  Handle
>>       unsigned patterns and multiplication by constants.
>>       (vect_pattern_recog_1): Update vect_recog_func references.  Use
>>       statement information from the statement returned from pattern
>>       detection functions.
>>       (vect_pattern_recog): Update vect_recog_func reference.
>>       * tree-vect-stmts.c (vectorizable_type_promotion): For widening
>>       multiplication by a constant use the type of the other operand.
>>
> .
>
> This caused:
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49318
>

This also caused:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49478


-- 
H.J.