The following example takes the "wrong_branch" when compiled with
gcc -O3 -fno-inline
gcc --version
gcc (GCC) 4.1.2
Copyright (C) 2006 Free Software Foundation, Inc.
===== example =====
#include <stdio.h>
static int get_kind(int v) {
volatile int k = v;
return k;
}
static int some_call(void)
{
return 0;
}
static void wrong_branch(void) {
printf("wrong_branch\n");
}
static int example(int arg)
{
int kind;
kind = get_kind(arg);
if (kind == 9 || kind == 10 || kind == 5) {
if (some_call() == 0) {
int tmp;
// kind = get_kind(arg); // ok if this call is inserted
if (kind == 9 || kind == 10) {
tmp = arg;
} else {
wrong_branch();
} /* if */
return 0;
}
}
return 0;
}
int main(void) {
int v = 10;
example(v);
return 0;
}
===================
The example prints "wrong_branch" when executed. If the second call to get_kind
is uncommented, nothing is printed (which is correct).
The generated assembly code is
===== example.s ======
example:
save %sp, -112, %sp
call get_kind, 0
mov %i0, %o0
add %o0, -9, %g1
subcc %g0, %g1, %g0
subx %g0, -1, %i0
cmp %g1, 1
bleu .LL11
cmp %o0, 5
be .LL11
nop
.LL9:
jmp %i7+8
restore %g0, 0, %o0
.LL11:
call some_call, 0
nop
cmp %o0, 0
bne .LL9
cmp %i0, 0
bne .LL9
nop
call wrong_branch, 0
mov 0, %i0
jmp %i7+8
restore
=======================
--
Summary: optimized code taking the wrong branch
Product: gcc
Version: 4.1.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: stephaniechc-gccbug at yahoo dot com
GCC build triplet: sparc-sun-solaris2.8
GCC host triplet: sparc-sun-solaris2.8+
GCC target triplet: sparc-sun-solaris2.8+
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31691
