From: Dan Nicolaescu <dann@godzilla.ICS.UCI.EDU>
To: gcc@gcc.gnu.org
Subject: g++ and aliasing bools
Date: Wed, 23 Jan 2002 17:56:00 -0000 [thread overview]
Message-ID: <200201231638.aa22100@gremlin-relay.ics.uci.edu> (raw)
It looks like g++ has some problems with aliasing bools, and gcc
doesn't.
The following program:
#ifdef __cplusplus
struct bool_struct
{
bool f0;
bool f1;
bool f2;
bool f3;
};
#else
struct bool_struct
{
_Bool f0;
_Bool f1;
_Bool f2;
_Bool f3;
};
#endif
struct bool_struct *str;
void
g (void)
{
str->f0 = 1;
str->f1 = 0;
str->f2 = 1;
str->f3 = 0;
}
compiles to:
_Z1gv:
.LLFB1:
!#PROLOGUE# 0
!#PROLOGUE# 1
sethi %hi(str), %o2
ld [%o2+%lo(str)], %o1
mov 1, %o3
stb %o3, [%o1]
ld [%o2+%lo(str)], %o0 <- this load is not needed
stb %g0, [%o0+1]
ld [%o2+%lo(str)], %o1 <- this load is not needed
stb %o3, [%o1+2]
ld [%o2+%lo(str)], %o0 <- this load is not needed
retl
stb %g0, [%o0+3]
when compiled with g++ -O2 on sparc-sun-solaris2.8 using a GCC from
CVS as of this morning.
but the code is much better when compiling with gcc -O2
g:
!#PROLOGUE# 0
!#PROLOGUE# 1
sethi %hi(str), %o0
ld [%o0+%lo(str)], %o1
mov 1, %o2
stb %o2, [%o1+2]
stb %g0, [%o1+3]
stb %o2, [%o1]
retl
stb %g0, [%o1+1]
so it looks like g++ has some issues with aliasing bools.
Any idea what is wrong?
next reply other threads:[~2002-01-24 0:38 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-23 17:56 Dan Nicolaescu [this message]
2002-01-23 18:27 ` Daniel Berlin
2002-01-23 18:48 ` Dan Nicolaescu
2002-01-23 19:16 ` Daniel Berlin
2002-01-24 14:15 ` Mark Mitchell
2002-01-24 14:16 ` Daniel Berlin
2002-01-24 14:27 ` Mark Mitchell
2002-01-24 14:35 ` Daniel Berlin
2002-01-24 15:06 ` Mark Mitchell
2002-01-24 15:08 ` Paolo Carlini
2002-01-24 15:18 ` Dan Nicolaescu
2002-01-24 15:36 ` Mark Mitchell
2002-01-25 2:25 ` Daniel Berlin
2002-01-25 15:48 ` Dan Nicolaescu
2002-01-25 20:22 ` Joe Buck
2002-01-25 23:59 ` Daniel Berlin
2002-01-27 17:04 ` Dan Nicolaescu
2002-01-27 17:59 ` Paolo Carlini
2002-03-04 16:20 ` improving g++ alias analysis (was: Re: g++ and aliasing bools) Dan Nicolaescu
2002-01-24 15:30 g++ and aliasing bools Richard Kenner
2002-01-25 2:16 ` Gabriel Dos Reis
2002-01-25 3:04 ` Paolo Carlini
2002-01-25 4:17 ` Gabriel Dos Reis
2002-01-25 4:35 ` Paolo Carlini
2002-01-25 6:34 ` Daniel Berlin
2002-01-25 7:17 ` Daniel Berlin
2002-01-25 13:57 ` Gabriel Dos Reis
2002-01-25 14:47 ` Tim Hollebeek
2002-01-24 16:09 Richard Kenner
2002-01-25 7:05 Richard Kenner
2002-01-25 8:59 ` Paolo Carlini
2002-01-25 7:23 Richard Kenner
2002-01-25 7:24 ` Daniel Berlin
2002-01-25 7:30 Richard Kenner
2002-01-25 7:33 ` Daniel Berlin
2002-01-25 15:43 ` Daniel Berlin
2002-01-25 7:30 Richard Kenner
2002-01-25 7:38 Robert Dewar
2002-01-25 8:11 ` Daniel Berlin
2002-01-25 14:09 ` Gabriel Dos Reis
2002-01-25 7:51 Robert Dewar
2002-01-25 8:18 ` Daniel Berlin
2002-01-25 8:20 ` Daniel Berlin
2002-01-25 8:28 Robert Dewar
2002-01-25 8:49 ` Daniel Berlin
2002-01-25 8:32 Robert Dewar
2002-01-25 8:53 ` Daniel Berlin
2002-01-25 9:39 ` Joe Buck
2002-01-25 8:33 Richard Kenner
2002-01-25 8:35 Robert Dewar
2002-01-25 8:54 ` Daniel Berlin
2002-01-25 8:55 Robert Dewar
2002-01-25 9:21 ` Daniel Berlin
2002-01-25 10:00 ` Daniel Berlin
2002-01-25 10:54 ` Paolo Carlini
2002-01-25 11:37 ` Daniel Berlin
2002-01-25 11:45 ` David Edelsohn
2002-01-25 11:53 ` Joe Buck
2002-01-25 12:09 ` Mark Mitchell
2002-01-25 12:28 ` Paolo Carlini
2002-01-25 13:49 ` Mark Mitchell
2002-01-25 14:19 ` Joe Buck
2002-01-25 14:21 ` Mark Mitchell
2002-01-25 15:41 ` Neil Booth
2002-01-25 16:04 ` Joe Buck
2002-01-25 17:37 ` Paolo Carlini
2002-01-25 18:10 ` Daniel Berlin
2002-01-27 5:11 ` Mark Mitchell
2002-01-27 5:34 ` Daniel Berlin
2002-01-28 10:39 ` Joe Buck
2002-01-28 10:51 ` Joe Buck
2002-01-28 15:59 ` Mark Mitchell
2002-01-28 17:11 ` Daniel Berlin
2002-01-28 17:28 ` Joe Buck
2002-01-28 18:14 ` Daniel Berlin
2002-01-28 17:18 ` Joe Buck
2002-01-28 18:05 ` Mark Mitchell
2002-01-28 18:50 ` Joe Buck
2002-01-28 19:33 ` Mark Mitchell
2002-01-28 17:40 ` Daniel Berlin
2002-01-28 21:55 ` Daniel Berlin
2002-01-28 22:02 ` Alexandre Oliva
2002-01-28 22:12 ` Mark Mitchell
2002-01-25 13:07 ` Joe Buck
2002-01-25 15:43 ` Daniel Berlin
2002-01-25 16:03 ` Joe Buck
2002-01-25 15:13 ` Daniel Berlin
2002-01-25 12:10 ` Paolo Carlini
2002-01-25 13:16 ` Joe Buck
2002-01-25 15:23 ` Daniel Berlin
2002-01-25 12:05 ` Mark Mitchell
2002-01-25 22:14 ` Daniel Berlin
2002-01-26 3:46 ` Mark Mitchell
2002-01-25 9:13 Robert Dewar
2002-01-25 12:06 mike stump
2002-01-25 12:23 Robert Dewar
2002-01-25 13:29 ` Joe Buck
2002-01-25 14:49 mike stump
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