Optimizer is putting result of a log into the wrong reg

[Singh, Kirat]

cool, so I will whack my local include file to do the right thing. Guess we
should send mail to the glibc list about it too.

Thanks for the help!

-Kirat

	-----Original Message-----
	From:	Bernd Schmidt [SMTP:bernds@cygnus.co.uk]
	Sent:	Thursday, September 23, 1999 10:59 AM
	To:	Singh, Kirat
	Cc:	'moshier@mediaone.net'; egcs-bugs@egcs.cygnus.com;
drepper@cygnus.com
	Subject:	RE: Optimizer is putting result of a log into the
wrong reg


	> Oops, sorry about that. I am now passing doubles where doubles are
expected
	> (I also simplified it a bit). But it *still* puts a NaN into the
variable
	> DiscRate whereas it clearly should be 0.

	Looking at the assembler output, it seems clear what's going wrong:

	FuncB:
	        pushl %ebp
		movl %esp,%ebp
		subl $24,%esp
		pushl %edi
		pushl %esi
		pushl %ebx
		fldl 24(%ebp)
		fldl 40(%ebp)
		fldl 56(%ebp)
		fldl 72(%ebp)
		fldl 80(%ebp)
		fldl 96(%ebp)
		fldl 104(%ebp)
		movl 124(%ebp),%edi
		movl 128(%ebp),%esi
		movl 132(%ebp),%ebx
		movl 136(%ebp),%edx
		movl 140(%ebp),%ecx
		fldl 112(%ebp)
	#APP
		fldln2; fxch; fyl2x
	#NO_APP

	This piece of code loads nine values on the floating point stack,
which has
	only eight entries.
	This appears to be a bug in glibc-2.1.  Here's the log function
(after the
	preprocessor is done with it):

	extern __inline double 
	log (double __x)
	{
	  register double __result;
	  __asm __volatile__ ("fldln2; fxch; fyl2x":"=t" (__result):"0"
(__x));
	  return __result;
	}

	The asm statement is wrong, it doesn't tell the compiler that one
extra
	stack reg is needed.

	Bernd