Path: utzoo!telly!ddsw1!lll-winken!uunet!tut.cis.ohio-state.edu!HARVARD.HARVARD.EDU!brad%cayman
From: brad%cayman@HARVARD.HARVARD.EDU (Brad Parker)
Newsgroups: gnu.gcc.bug
Subject: gcc 1.31 with -O generates bad compare
Message-ID: <8901020154.AA07897@cayman.Cayman.COM>
Date: 2 Jan 89 01:54:46 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 88


gcc 1.31 on a Sun 3/60 using SunOS 4.0; cross compiling for 68000 target.
I've been having fairly good luck with "-O" and "-O -fcombine-regs
-finline-functions -fstrength-reduce" (going for it ;-) except for the
following bug.

It seems that the branch type not correct;

----
func1()
{
}

typedef unsigned long ulong;

main()
{
	int high_addr = 0;

	/* generates wrong branch with -O */
	if ( (ulong)func1 > (ulong)0xfc0000 )
		high_addr = 1;

	printf("func1 = %lx, high_addr = %d\n", (ulong)func1, high_addr);
}
----
(gcc -c show.c)

#NO_APP
.text
	.even
.globl _func1
_func1:
	link a6,#0
L1:
	unlk a6
	rts
LC0:
	.ascii "func1 = %lx, high_addr = %d\12\0"
	.even
.globl _main
_main:
	link a6,#-4
	clrl a6@(-4)
	movel #16515072,d1
	cmpl #_func1,d1
	jcc L3				<--- correct, but not optimal
	moveq #1,d1
	movel d1,a6@(-4)
L3:
	movel a6@(-4),sp@-
	pea _func1
	pea LC0
	jbsr _printf
L2:
	unlk a6
	rts
-----
(gcc -c -O show.c)

#NO_APP
.text
	.even
.globl _func1
_func1:
	link a6,#0
	unlk a6
	rts
LC0:
	.ascii "func1 = %lx, high_addr = %d\12\0"
	.even
.globl _main
_main:
	link a6,#0
	clrl d0
	movel #_func1+-16515072,d1	<--- better, 
	jls L3				<--- but wrong branch type
	moveq #1,d0
L3:
	movel d0,sp@-
	pea _func1
	pea LC0
	jbsr _printf
	unlk a6
	rts
----

-brad