Re: another IEE related problem

[Bernd Schmidt <crux at starsky dot Informatik dot RWTH-Aachen dot DE>]

> Compiling this little piece of code on a ix86 machine
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> extern inline float
> bar (float x)
> {
>   float res;
>   asm ("fsqrt" : "=t" (res) : "0" (x));
>   return res;
> }
> extern float fabsf (float);
> 
> float
> foo (float x)
> {
>   float res = fabsf (bar (x));
>   return res;
> }
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> The generated code with -O3 -momit-leaf-frame-pointer
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> foo:
>         flds 4(%esp)
> #APP
>         fsqrt
> #NO_APP
>         ret
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[the fabs statement is missing]

This is a bug in the combiner. When trying to simplify an
(ABS:SF (ASM_OPERANDS ...)) expression it thinks that the ASM_OPERANDS is
always positive.
This can be fixed with the patch I have appended.

> Another bug preventing the glibc test suite to be passed.

Ulrich, do you have more unsolved bugs that affect glibc?

Bernd

*** ./combine.c.orig-1	Tue Dec  9 10:53:39 1997
--- ./combine.c	Tue Dec  9 10:55:52 1997
*************** simplify_rtx (x, op0_mode, last, in_dest
*** 4092,4101 ****
      case XOR:
        return simplify_logical (x, last);
  
!     case ABS:
        /* (abs (neg <foo>)) -> (abs <foo>) */
        if (GET_CODE (XEXP (x, 0)) == NEG)
  	SUBST (XEXP (x, 0), XEXP (XEXP (x, 0), 0));
  
        /* If operand is something known to be positive, ignore the ABS.  */
        if (GET_CODE (XEXP (x, 0)) == FFS || GET_CODE (XEXP (x, 0)) == ABS
--- 4092,4106 ----
      case XOR:
        return simplify_logical (x, last);
  
!     case ABS:      
        /* (abs (neg <foo>)) -> (abs <foo>) */
        if (GET_CODE (XEXP (x, 0)) == NEG)
  	SUBST (XEXP (x, 0), XEXP (XEXP (x, 0), 0));
+ 
+       /* If the mode of the operand is VOIDmode (i.e. if it is ASM_OPERANDS),
+          do nothing.  */
+       if (GET_MODE (XEXP (x, 0)) == VOIDmode)
+ 	break;
  
        /* If operand is something known to be positive, ignore the ABS.  */
        if (GET_CODE (XEXP (x, 0)) == FFS || GET_CODE (XEXP (x, 0)) == ABS