From: Bernd Schmidt <crux@starsky.Informatik.RWTH-Aachen.DE>
To: Ulrich Drepper <drepper@ipd.info.uni-karlsruhe.de>
Cc: egcs@cygnus.com, kenner@vlsi1.ultra.nyu.edu
Subject: Re: another IEE related problem
Date: Wed, 10 Dec 1997 03:32:00 -0000 [thread overview]
Message-ID: <Pine.SOL.3.90.971210122825.25453C-100000@starsky.informatik.rwth-aachen.de> (raw)
In-Reply-To: <x7wwi4i73i.fsf@myware.rz.uni-karlsruhe.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
next prev parent reply other threads:[~1997-12-10 3:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-11-19 19:21 Ulrich Drepper
1997-12-10 3:32 ` Bernd Schmidt [this message]
1997-12-10 7:26 ` Ulrich Drepper
1997-12-10 10:58 ` Ulrich Drepper
1997-12-10 19:56 ` Jeffrey A Law
1997-12-10 19:28 ` Ulrich Drepper
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