Can't prevent asm() from popping 387 stack

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2 total messages Started by Charles Hannum Tue, 05 Jan 1993 09:52

#1585

Author: Charles Hannum
Date: Tue, 05 Jan 1993 09:52

35 lines
1155 bytes

I want to do something like the following:

double
atan2 (double y, double x)
{
  double temp;

  asm ("fpatan"
	: "+t" (temp)
	: "u" (y), "0" (x));

  return (temp);
}

The `fpatan' instruction pops one item from the top of the floating stack,
so there is only one left.  Unfortunately, GCC also seems to think it
should pop the second element on the stack:

	.file	"foo.c"
gcc2_compiled.:
.text
	.align 2
.globl _atan2
_atan2:
	fldl 12(%esp)
	fldl 4(%esp)
	fxch %st(1)
#APP
	fpatan
#NO_APP
	fstp %st(1)
	ret

I can't find any way to prevent this.  The only thing I've been able to do
is insert an extra `fld %st(0)' so it doesn't do any harm.

Re: Can't prevent asm() from popping 387 stack

#1593

Author: Charles Hannum
Date: Wed, 06 Jan 1993 08:43

9 lines
629 bytes

Oops.  I sent the wrong bit of C code.  This:

> 	: "+t" (temp)

should have been:

>	: "=t" (temp)

Any suggestions?

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