vectorization - Why doesn't this C vector loop auto-vectorise? -

-

i trying optimise code use of avx intrinsics. simple test case compiles tells me loop not vectorised number of reasons don't understand.

this full program, simple.c

#include <math.h> #include <stdlib.h> #include <assert.h> #include <immintrin.h>  int main(void) {    __m256 * x = (__m256 *) calloc(1024,sizeof(__m256));        (int j=0;j<32;j++)     x[j] = _mm256_set1_ps(1.);     return(0); }

this command line: gcc simple.c -o1 -fopenmp -ffast-math -lm -mavx2 -ftree-vectorize -fopt-info-vec-missed

this output:

  • simple.c:11:3: note: not vectorized: unsupported data-type
  • simple.c:11:3: note: can't determine vectorization factor.
  • simple.c:6:5: note: not vectorized: not enough data-refs in basic block.
  • simple.c:11:3: note: not vectorized: not enough data-refs in basic block.
  • simple.c:6:5: note: not vectorized: not enough data-refs in basic block.
  • simple.c:6:5: note: not vectorized: not enough data-refs in basic block.

i have gcc version 5.4.

can me interpret these messages , understand going on?

you're manually vectorizing intrinsics, there's nothing left gcc auto-vectorize. leads uninteresting warnings, assume trying auto-vectorize intrinsic or loop-counter increments.

i asm gcc 5.3 (on godbolt compiler explorer) if don't silly write function optimize away, or try compile -o1.

#include <immintrin.h>  void set_to_1(__m256 * x) {   (int j=0;j<32;j++)     x[j] = _mm256_set1_ps(1.);  }      push    rbp     lea     rax, [rdi+1024]     vmovaps ymm0, ymmword ptr .lc0[rip]     mov     rbp, rsp     push    r10                      # gcc weird r10 in functions ymm vectors .l2:                                 # vector loop     vmovaps ymmword ptr [rdi], ymm0     add     rdi, 32     cmp     rdi, rax     jne     .l2     vzeroupper     pop     r10     pop     rbp     ret  .lc0:     .long   1065353216     ... repeated several times because gcc failed use vbroadcastss load or generate constant on fly

i same asm -o1, using -o1 not optimize things away isn't way see gcc do.


Comments

Post a Comment

Popular posts from this blog

magento2 - Magento 2 admin grid add filter to collection -

-
i created grid in admin xml ui components. need filter collection via url parameter , dont know how achieve that. tried inject requestinterface collection, filter didnt work. di.xml <virtualtype name="slidelistingdataprovider" type="magento\framework\view\element\uicomponent\dataprovider\dataprovider"> <arguments> <argument name="collection" xsi:type="object" shared="false">xxx\xxx\model\resourcemodel\grid\slide\collection</argument> <argument name="filterpool" xsi:type="object" shared="false">slidelistingfilterpool</argument> <!-- define new object filters --> </arguments> </virtualtype> <virtualtype name="slidelistingfilterpool" type="magento\framework\view\element\uicomponent\dataprovider\filterpool"> <arguments> <argument name="applier...
Read more

Android volley - avoid multiple requests of the same kind to the server? -

-
i using volley upload list of images server. happens within service. once image uploaded remove list. problem arises when internet connection breaks. when internet connection breaks , comes again thinking of adding images yet uploaded request queue. this can result in more 1 copy of same image saved on server request same image might have gone through before getting rseponse. how can address scenario? i'm not quite sure why you're using service schedule requests volley automatically runs it's request in seperate thread. nevertheless can listen both request results, successful , unsuccessful adding listeners. you can remove image list schedule request using volley. if succeeds can carry on desired, if fails can add again list. public static request getimageuploadrequest(final string image) { response.listener<t> responselistener = new response.listener<t>() { @override public void onresponse(t response...
Read more

Combining PHP Registration and Login into one class with multiple functions in one PHP file -

-
i'm trying combine registration, activation , login scripts php website backend script front end developer can pass variables different forms to. my question whether appropriate approach this. don't want have lot of php files different pieces of application developing. far have written following 2 functions login, register , activate user front end developer can call: <?php /** * created phpstorm. * user: karl * date: 26/07/2016 * time: 02:25 */ class users { function register_user($email, $password, $user_name) { $server_name = "localhost"; $u_name = "root"; $db_password = "root"; $db_name = "betamath_graspe"; //email notification variable $from_address="info@slack.com"; //registration form $msg_reg_user='username taken. please choose different username'; $msg_reg_email='email registered'; $msg_reg_active=...
Read more