archiel@hercules.UUCP (Archie Lachner) (10/02/84)
Several people have asked for copies of the program that exercises the cc
optimizer bug that I reported recently. One suggested that I submit it
to this news group. Though a fix for the bug has already been posted, I'm
happy to comply.
-------
#include <stdio.h>
main()
{
union {
int one_word; /* one-word form */
struct {
unsigned int type:7; /* type */
unsigned int flag_1:1; /* flag no 1 */
unsigned int flag_2:1; /* flag no 2 */
unsigned int count:7; /* count of whatever */
unsigned int number:16; /* number of "things" */
} split; /* split form */
} field_union;
int type;
int flag_1;
int flag_2;
int count;
int number;
field_union.one_word = 0x300;
fprintf(stdout, "foobar: field_union = %d (%x hex)\n",
field_union.one_word, field_union.one_word);
type = field_union.split.type;
fprintf(stdout, "foobar: type = %d\n", type);
flag_1 = field_union.split.flag_1;
fprintf(stdout, "foobar: flag_1 = %d\n", flag_1);
flag_2 = field_union.split.flag_2;
fprintf(stdout, "foobar: flag_2 = %d\n", flag_2);
count = field_union.split.count;
fprintf(stdout, "foobar: count = %d\n", count);
/*
* when this is compiled with optimization, "number" will be 3
*
* it should be 0
*
* the error can be traced to line 54 of the assembler output
* produced using "cc -O -S"
*
* the source address in a "movzwl" instruction is incorrect
*/
number = field_union.split.number;
fprintf(stdout, "foobar: number = %d\n", number);
exit(0);
}
--
Archie Lachner
Logic Design Systems Division
Tektronix, Inc.
uucp: {ucbvax,decvax,pur-ee,cbosg,ihnss}!tektronix!teklds!archiel
CSnet: archiel@tek
ARPAnet: archiel.tek@csnet-relay