Cache tcp->u_nargs in a local variable for for() loops
Loops of the form "for (i = 0; i < tcp->u_nargs; i++) ..."
need to fetch tcp->u_nargs from memory on every iteration
if "..." part has a function call (gcc doesn't know that
tcp->u_nargs won't change). This can be sped up
by putting tcp->u_nargs in a local variable, which might
go into a CPU register.
* syscall.c (decode_subcall): Cache tcp->u_nargs in a local variable
as for() loop limit value.
(syscall_enter): Likewise.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/syscall.c b/syscall.c
index 85c8009..2af9085 100644
--- a/syscall.c
+++ b/syscall.c
@@ -570,7 +570,7 @@
decode_subcall(struct tcb *tcp, int subcall, int nsubcalls, enum subcall_style style)
{
unsigned long addr, mask;
- int i;
+ int i, n;
int size = personality_wordsize[current_personality];
switch (style) {
@@ -578,8 +578,8 @@
if (tcp->u_arg[0] < 0 || tcp->u_arg[0] >= nsubcalls)
return;
tcp->scno = subcall + tcp->u_arg[0];
- tcp->u_nargs = sysent[tcp->scno].nargs;
- for (i = 0; i < tcp->u_nargs; i++)
+ tcp->u_nargs = n = sysent[tcp->scno].nargs;
+ for (i = 0; i < n; i++)
tcp->u_arg[i] = tcp->u_arg[i + 1];
break;
case deref_style:
@@ -587,7 +587,8 @@
return;
tcp->scno = subcall + tcp->u_arg[0];
addr = tcp->u_arg[1];
- for (i = 0; i < sysent[tcp->scno].nargs; i++) {
+ tcp->u_nargs = n = sysent[tcp->scno].nargs;
+ for (i = 0; i < n; i++) {
if (size == sizeof(int)) {
unsigned int arg;
if (umove(tcp, addr, &arg) < 0)
@@ -604,7 +605,6 @@
abort();
addr += size;
}
- tcp->u_nargs = sysent[tcp->scno].nargs;
break;
case mask_style:
mask = (tcp->u_arg[0] >> 8) & 0xff;
@@ -2124,12 +2124,12 @@
# ifndef PT_ORIG_R3
# define PT_ORIG_R3 34
# endif
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, (i==0) ?
(sizeof(unsigned long) * PT_ORIG_R3) :
((i+PT_R3) * sizeof(unsigned long)),
@@ -2145,12 +2145,12 @@
for (i = 0; i < tcp->u_nargs; i++)
tcp->u_arg[i] = regs.u_regs[U_REG_O0 + i];
# elif defined(HPPA)
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, PT_GR26-4*i, &tcp->u_arg[i]) < 0)
return -1;
}
@@ -2171,26 +2171,26 @@
tcp->u_arg[4] = regs.r5;
tcp->u_arg[5] = regs.r3;
# elif defined(BFIN)
- int i;
+ int i, nargs;
static const int argreg[] = { PT_R0, PT_R1, PT_R2, PT_R3, PT_R4, PT_R5 };
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = ARRAY_SIZE(argreg);
+ nargs = tcp->u_nargs = ARRAY_SIZE(argreg);
- for (i = 0; i < tcp->u_nargs; ++i)
+ for (i = 0; i < nargs; ++i)
if (upeek(tcp, argreg[i], &tcp->u_arg[i]) < 0)
return -1;
# elif defined(SH)
- int i;
+ int i, nargs;
static const int syscall_regs[] = {
4 * (REG_REG0+4), 4 * (REG_REG0+5), 4 * (REG_REG0+6), 4 * (REG_REG0+7),
4 * (REG_REG0 ), 4 * (REG_REG0+1), 4 * (REG_REG0+2)
};
- tcp->u_nargs = sysent[tcp->scno].nargs;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, syscall_regs[i], &tcp->u_arg[i]) < 0)
return -1;
}
@@ -2207,90 +2207,90 @@
assert(sysent[tcp->scno].nargs < ARRAY_SIZE(syscall_regs));
*/
- tcp->u_nargs = sysent[tcp->scno].nargs;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, REG_GENERAL(syscall_regs[i]), &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(X86_64)
- int i;
+ int i, nargs;
static const int argreg[SUPPORTED_PERSONALITIES][MAX_ARGS] = {
{ 8 * RDI, 8 * RSI, 8 * RDX, 8 * R10, 8 * R8 , 8 * R9 }, /* x86-64 ABI */
{ 8 * RBX, 8 * RCX, 8 * RDX, 8 * RSI, 8 * RDI, 8 * RBP } /* i386 ABI */
};
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, argreg[current_personality][i], &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(MICROBLAZE)
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = 0;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = 0;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, (5 + i) * 4, &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(CRISV10) || defined(CRISV32)
- int i;
+ int i, nargs;
static const int crisregs[] = {
4*PT_ORIG_R10, 4*PT_R11, 4*PT_R12,
4*PT_R13 , 4*PT_MOF, 4*PT_SRP
};
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = 0;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = 0;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, crisregs[i], &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(TILE)
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; ++i) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; ++i) {
if (upeek(tcp, PTREGS_OFFSET_REG(i), &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(M68K)
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, (i < 5 ? i : i + 2)*4, &tcp->u_arg[i]) < 0)
return -1;
}
# else /* Other architecture (like i386) (32bits specific) */
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; i++) {
if (upeek(tcp, i*4, &tcp->u_arg[i]) < 0)
return -1;
}
# endif
#endif /* LINUX */
#ifdef SUNOS4
- int i;
+ int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
+ nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
- tcp->u_nargs = MAX_ARGS;
- for (i = 0; i < tcp->u_nargs; i++) {
+ nargs = tcp->u_nargs = MAX_ARGS;
+ for (i = 0; i < nargs; i++) {
struct user *u;
if (upeek(tcp, uoff(u_arg[0]) +