From: Glen Nakamura <glen@imodulo.com> To: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org Cc: Subject: Re: other/7814: incorrect scheduling for glibc-2.2.92 stpcpy test Date: Mon, 2 Sep 2002 09:36:09 -1000 --J2SCkAp4GZ/dPZZf Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hmm, I intended to file this under optimization, but I must have selected other by mistake... *grr* Anyway, here is the C source for the uploaded testcase. http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7814 --J2SCkAp4GZ/dPZZf Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="stpcpy.c" #define _GNU_SOURCE #include <stdio.h> #include <string.h> const char *it = "<UNSET>"; /* Routine name for message routines. */ size_t errors = 0; /* Complain if condition is not true. */ static void check (int thing, int number) { if (!thing) { printf("%s flunked test %d\n", it, number); ++errors; } } /* Complain if first two args don't strcmp as equal. */ static void equal (const char *a, const char *b, int number) { check(a != NULL && b != NULL && (strcmp (a, b) == 0), number); } char one[50]; char two[50]; char *cp; #undef __stpcpy # define __stpcpy(dest, src) \ (__extension__ (__builtin_constant_p (src) \ ? (__string2_1bptr_p (src) && strlen (src) + 1 <= 8 \ ? __builtin_strcpy (dest, src) + strlen (src) \ : ((char *) (__mempcpy) (dest, src, strlen (src) + 1) \ - 1)) \ : __stpcpy (dest, src))) static void test_stpcpy (void) { it = "stpcpy"; check ((stpcpy (one, "a") - one) == 1, 1); equal (one, "a", 2); check ((stpcpy (one, "ab") - one) == 2, 3); equal (one, "ab", 4); check ((stpcpy (one, "abc") - one) == 3, 5); equal (one, "abc", 6); check ((stpcpy (one, "abcd") - one) == 4, 7); equal (one, "abcd", 8); check ((stpcpy (one, "abcde") - one) == 5, 9); equal (one, "abcde", 10); check ((stpcpy (one, "abcdef") - one) == 6, 11); equal (one, "abcdef", 12); check ((stpcpy (one, "abcdefg") - one) == 7, 13); equal (one, "abcdefg", 14); check ((stpcpy (one, "abcdefgh") - one) == 8, 15); equal (one, "abcdefgh", 16); check ((stpcpy (one, "abcdefghi") - one) == 9, 17); equal (one, "abcdefghi", 18); check ((stpcpy (one, "x") - one) == 1, 19); equal (one, "x", 20); /* Writeover. */ equal (one+2, "cdefghi", 21); /* Wrote too much? */ check ((stpcpy (one, "xx") - one) == 2, 22); equal (one, "xx", 23); /* Writeover. */ equal (one+3, "defghi", 24); /* Wrote too much? */ check ((stpcpy (one, "xxx") - one) == 3, 25); equal (one, "xxx", 26); /* Writeover. */ equal (one+4, "efghi", 27); /* Wrote too much? */ check ((stpcpy (one, "xxxx") - one) == 4, 28); equal (one, "xxxx", 29); /* Writeover. */ equal (one+5, "fghi", 30); /* Wrote too much? */ check ((stpcpy (one, "xxxxx") - one) == 5, 31); equal (one, "xxxxx", 32); /* Writeover. */ equal (one+6, "ghi", 33); /* Wrote too much? */ check ((stpcpy (one, "xxxxxx") - one) == 6, 34); equal (one, "xxxxxx", 35); /* Writeover. */ equal (one+7, "hi", 36); /* Wrote too much? */ check ((stpcpy (one, "xxxxxxx") - one) == 7, 37); equal (one, "xxxxxxx", 38); /* Writeover. */ equal (one+8, "i", 39); /* Wrote too much? */ check ((stpcpy (stpcpy (stpcpy (one, "a"), "b"), "c") - one) == 3, 40); equal (one, "abc", 41); equal (one + 4, "xxx", 42); } int main (void) { int status; /* A closely related function is stpcpy. */ test_stpcpy (); if (errors == 0) { status = 0; puts("No errors."); } else { status = 1; printf("%Zd errors.\n", errors); } return status; } --J2SCkAp4GZ/dPZZf--
From: Glen Nakamura <glen@imodulo.com> To: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org Cc: Subject: Re: other/7814: incorrect scheduling for glibc-2.2.92 stpcpy test Date: Mon, 2 Sep 2002 10:24:48 -1000 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7814 Okay, I think the problem is that when we flush the dependency lists (e.g. when ?_length > MAX_PENDING_LIST_LENGTH), we end up with a single insn in the 'clobbers' list while the 'sets' and 'uses' lists are empty. Now, if there is another clobber insn before any set or use insn, it won't be dependent on any previous insn because the 'sets' and 'uses' lists are empty... The problem is fixed by adding the last insn to the 'sets' list after flushing. - glen Here is the patch: ChangeLog =================================================================== 2002-09-02 Glen Nakamura <glen@imodulo.com> * sched-deps.c (sched_analyze_insn): Make sure to add insn to reg_last->sets after flushing the dependency lists to guarantee that subsequent clobbers will be dependent on it. Index: sched-deps.c =================================================================== RCS file: /cvsroot/gcc/gcc/gcc/sched-deps.c,v retrieving revision 1.34.6.1 diff -c -3 -p -u -r1.34.6.1 sched-deps.c --- sched-deps.c 19 Aug 2002 18:59:31 -0000 1.34.6.1 +++ sched-deps.c 2 Sep 2002 06:35:15 -0000 @@ -1118,8 +1118,6 @@ sched_analyze_insn (deps, x, insn, loop_ EXECUTE_IF_SET_IN_REG_SET (reg_pending_clobbers, 0, i, { struct deps_reg *reg_last = &deps->reg_last[i]; - add_dependence_list (insn, reg_last->sets, REG_DEP_OUTPUT); - add_dependence_list (insn, reg_last->uses, REG_DEP_ANTI); if (reg_last->uses_length > MAX_PENDING_LIST_LENGTH || reg_last->clobbers_length > MAX_PENDING_LIST_LENGTH) { @@ -1129,6 +1127,7 @@ sched_analyze_insn (deps, x, insn, loop_ REG_DEP_ANTI); add_dependence_list_and_free (insn, ®_last->clobbers, REG_DEP_OUTPUT); + reg_last->sets = alloc_INSN_LIST (insn, reg_last->sets); reg_last->clobbers_length = 0; reg_last->uses_length = 0; }
GCC incorrectly generates scheduling dependencies... test_stpcpy: pushl %ebp movl %esp, %ebp pushl %edi pushl %esi movl $1, %esi pushl %ebx movl $one, %ebx subl %ebx, %esi subl $20, %esp movl $.LC2, it leal (%ebx,%esi), %edi pushl $1 cmpl $1, %edi addl $one+2, %esi << incorrectly clobbers CC sete %al andl $255, %eax pushl %eax movw $97, one call check addl $12, %esp Release: gcc 3.2 Environment: i586-pc-linux-gnu How-To-Repeat: bash:~# gcc -O2 -mcpu=i586 stpcpy.i bash:~# ./a.out stpcpy flunked test 1 1 errors.
Fix: I'm testing a patch to sched-deps.c which I'll post soon.
State-Changed-From-To: open->closed State-Changed-Why: Fixed.