vector bug?

vector bug?

[Not Real]

Hi, I'm using gcc 3.4.0 20040305, on a pentium 4 red
hat system.  I'm trying to use the vector extensions. 
When I compile the following code with -O0 or -O1, it
does as I expect (it prints whatever was input plus
{1,2,3,4}.  When I compile with -O2 or -O3 on the
other hand, it prints garbage.  From the disassembly,
it is apparent that it is just not putting the right
arguments on the stack for the printf call.  Is my
code incorrect, or is this an optimization bug?

#include <stdio.h>

int main() {
  typedef int v4si __attribute__ ((mode(V4SI)));
  
  int vals[4];
  int ins[4];

  scanf("%d %d %d %d", &ins[0], &ins[1], &ins[2],
&ins[3]);
  v4si a = *(v4si*)ins, b = {1, 2, 3, 4}, c;

  c = a + b;
  *(v4si*)vals = c;
  printf("%d %d %d %d\n", vals[0], vals[1], vals[2],
vals[3]);
}

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Re: vector bug?

[Segher Boessenkool]

>   v4si a = *(v4si*)ins, b = {1, 2, 3, 4}, c;

>   *(v4si*)vals = c;

You can't do this.  Your accessing an object of one type
(int) as an other type (v4si).

You'll have to go through a union to do this safely
(this is a GCC extension).  Like:

	union { v4si v; int i[4]; } convert;
	convert.v = c;

...and then print convert.i[0] etc.


Segher

vector bug?

[Not Real]

Hi, I'm using gcc 3.4.0 20040305, on a pentium 4 red
hat system.  I'm trying to use the vector extensions. 
When I compile the following code with -O0 or -O1, it
does as I expect (it prints whatever was input plus
{1,2,3,4}.  When I compile with -O2 or -O3 on the
other hand, it prints garbage.  From the disassembly,
it is apparent that it is just not putting the right
arguments on the stack for the printf call.  Is my
code incorrect, or is this an optimization bug?

#include <stdio.h>

int main() {
  typedef int v4si __attribute__ ((mode(V4SI)));
  
  int vals[4];
  int ins[4];

  scanf("%d %d %d %d", &ins[0], &ins[1], &ins[2],
&ins[3]);
  v4si a = *(v4si*)ins, b = {1, 2, 3, 4}, c;

  c = a + b;
  *(v4si*)vals = c;
  printf("%d %d %d %d\n", vals[0], vals[1], vals[2],
vals[3]);
}


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