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From: dillon@CORY (Matt Dillon)
Newsgroups: net.micro.amiga
Subject: LATTICE BUG (3.03)		-unsigned? short optimization bug
Message-ID: <8610020736.AA09001@cory.Berkeley.EDU>
Date: Thu, 2-Oct-86 03:36:22 EDT
Article-I.D.: cory.8610020736.AA09001
Posted: Thu Oct  2 03:36:22 1986
Date-Received: Sat, 4-Oct-86 05:20:18 EDT
Sender: uucp@ucbvax.BERKELEY.EDU
Organization: University of California at Berkeley
Lines: 86


	Here is an obscure lattice bug.   V3.03 (no suffix)  I'm
	probably the only one who has run into it.


CODE:

main()
{
   unsigned short x, xx;
   unsigned short y = 0xFFFF;
   unsigned short z = 2;

   x = (y + z) / 16;
   xx= ((y + z) / 16);
   printf ("x = %ld %ld\n", x, xx);
}


EXPECTED RESULT: (remember, y and z are supposed to be expanded to ints first)

   4096 4096

ACTUAL RESULT:

   1 1


SUSPECTED CAUSE:
	seems to be related to the fact that I'm assigning TO a short (x,xx)
	rather than an int.

BACKGROUND:
	This came up while I was programming some 3-D graphics routine.. It
	was a particulary tricky line which failed miserably when the 
	compiler failed to follow the standard C def.

	It's very obscure, but should be fixed.

					-Matt

----------------------------
OMD assembly:



LATTICE OBJECT MODULE DISASSEMBLER V2.00

Amiga Object File Loader V1.00
68000 Instruction Set

EXTERNAL DEFINITIONS

_main 0000-00

SECTION 00 "text" 00000050 BYTES
0000 4E56FFF8                   LINK      A6,FFF8
0004 48E72000                   MOVEM.L   D2,-(A7)
0008 70FF                       MOVEQ     #FF,D0
000A 7202                       MOVEQ     #02,D1
000C 3D40FFFA                   MOVE.W    D0,FFFA(A6)
0010 D041                       ADD.W     D1,D0
0012 243C00040000               MOVE.L    #00040000,D2		<----
0018 E468                       LSR.W     D2,D0			<----
001A 3D40FFFC                   MOVE.W    D0,FFFC(A6)		should be move
001E 3D40FFFE                   MOVE.W    D0,FFFE(A6)		imm #4 and 
0022 02800000FFFF               ANDI.L    #0000FFFF,D0		LSR.L 
0028 7400                       MOVEQ     #00,D2
002A 342EFFFC                   MOVE.W    FFFC(A6),D2
002E 2F02                       MOVE.L    D2,-(A7)
0030 2F00                       MOVE.L    D0,-(A7)
0032 4879 00000000-01           PEA       01.00000000
0038 3D41FFF8                   MOVE.W    D1,FFF8(A6)
003C 4EB9 00000000-XX           JSR       _printf
0042 4FEF000C                   LEA       000C(A7),A7
0046 4CDF0004                   MOVEM.L   (A7)+,D2
004A 4E5E                       UNLK      A6
004C 4E75                       RTS

SECTION 01 "data" 00000010 BYTES
0000 78 20 3D 20 25 6C 64 20 25 6C 64 0A 00 00 00 00 x = %ld %ld.....

SECTION 02 "udata" 00000000 BYTES


					-Matt