Re: workaround for "error: more than 30 operands in 'asm'"?

[Andrew Haley <aph@redhat.com>]

Ian Lance Taylor wrote:
> "Clem Taylor" <clem.taylor@gmail.com> writes:
> 
>> I'm working on taking PowerPC VMX code that uses altivec intrinsics
>> and rescheduling it with inline assembly. gcc is making some fairly
>> bad scheduling choices in with the code, resulting in code that is
>> running 4x slower then I was hoping for. I have a simplified version
>> working, but with the real version gcc is failing with: "error: more
>> than 30 operands in 'asm'". The code is using 28 vector registers and
>> 6 serial registers.
>>
>> The code is a mixture of setup code in C and only the inner loop is in
>> assembly, so it wouldn't be convenient to write this directly in
>> assembly. Also, because the code is highly pipelined (to overcome the
>> latency of the VMX floating point unit) it is a mess to split this up
>> into multiple asm() statements. Beyond recompiling gcc with a larger
>> operand count, is there a workaround for this problem?
> 
> Use fewer operands?  Otherwise, no.  It's a hard limit in gcc.
> 
> Since you mention the number of registers you are using, note that
> that only matters if they are inputs or outputs.  If you need a
> temporary register, just pick one, and add it the clobber list.  But
> if you really have that many inputs and outputs, then you are stuck.

Isn't this trivially fixed by changing:

  /* Allow at least 30 operands for the sake of asm constructs.  */
  /* ??? We *really* ought to reorganize things such that there
     is no fixed upper bound.  */
  max_recog_operands = 29;  /* We will add 1 later.  */
  max_dup_operands = 1;

in genconfig.c ?

Andrew.