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target/ppc: simplify bcdadd/sub functions

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After solving a corner case in bcdsub, this patch simplifies the logic
of both bcdadd/sub instructions by removing some unnecessary local flags.
This commit also rearranges some if-else conditions in bcdadd to make it
easier to read.

Signed-off-by: Yasmin Beatriz <yasmins@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Yasmin Beatriz 2018-07-30 17:09:17 +00:00 committed by David Gibson
parent 71c55a1eef
commit d03b174a83
1 changed files with 18 additions and 31 deletions
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49
target/ppc/int_helper.c
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@ -2671,16 +2671,14 @@ static int bcd_cmp_mag(ppc_avr_t *a, ppc_avr_t *b)
return 0;
}
static int bcd_add_mag(ppc_avr_t *t, ppc_avr_t *a, ppc_avr_t *b, int *invalid,
static void bcd_add_mag(ppc_avr_t *t, ppc_avr_t *a, ppc_avr_t *b, int *invalid,
int *overflow)
{
int carry = 0;
int i;
int is_zero = 1;
for (i = 1; i <= 31; i++) {
uint8_t digit = bcd_get_digit(a, i, invalid) +
bcd_get_digit(b, i, invalid) + carry;
is_zero &= (digit == 0);
if (digit > 9) {
carry = 1;
digit -= 10;
@ -2689,26 +2687,20 @@ static int bcd_add_mag(ppc_avr_t *t, ppc_avr_t *a, ppc_avr_t *b, int *invalid,
}
bcd_put_digit(t, digit, i);
if (unlikely(*invalid)) {
return -1;
}
}
*overflow = carry;
return is_zero;
}
static int bcd_sub_mag(ppc_avr_t *t, ppc_avr_t *a, ppc_avr_t *b, int *invalid,
static void bcd_sub_mag(ppc_avr_t *t, ppc_avr_t *a, ppc_avr_t *b, int *invalid,
int *overflow)
{
int carry = 0;
int i;
int is_zero = 1;
for (i = 1; i <= 31; i++) {
uint8_t digit = bcd_get_digit(a, i, invalid) -
bcd_get_digit(b, i, invalid) + carry;
is_zero &= (digit == 0);
if (digit & 0x80) {
carry = -1;
digit += 10;
@ -2717,14 +2709,9 @@ static int bcd_sub_mag(ppc_avr_t *t, ppc_avr_t *a, ppc_avr_t *b, int *invalid,
}
bcd_put_digit(t, digit, i);
if (unlikely(*invalid)) {
return -1;
}
}
*overflow = carry;
return is_zero;
}
uint32_t helper_bcdadd(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b, uint32_t ps)
@ -2734,26 +2721,28 @@ uint32_t helper_bcdadd(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b, uint32_t ps)
int sgnb = bcd_get_sgn(b);
int invalid = (sgna == 0) || (sgnb == 0);
int overflow = 0;
int zero = 0;
uint32_t cr = 0;
ppc_avr_t result = { .u64 = { 0, 0 } };
if (!invalid) {
if (sgna == sgnb) {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgna, ps);
zero = bcd_add_mag(&result, a, b, &invalid, &overflow);
cr = (sgna > 0) ? CRF_GT : CRF_LT;
} else if (bcd_cmp_mag(a, b) > 0) {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgna, ps);
zero = bcd_sub_mag(&result, a, b, &invalid, &overflow);
cr = (sgna > 0) ? CRF_GT : CRF_LT;
} else if (bcd_cmp_mag(a, b) == 0) {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(0, ps);
zero = bcd_sub_mag(&result, b, a, &invalid, &overflow);
bcd_add_mag(&result, a, b, &invalid, &overflow);
cr = bcd_cmp_zero(&result);
} else {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgnb, ps);
zero = bcd_sub_mag(&result, b, a, &invalid, &overflow);
cr = (sgnb > 0) ? CRF_GT : CRF_LT;
int magnitude = bcd_cmp_mag(a, b);
if (magnitude > 0) {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgna, ps);
bcd_sub_mag(&result, a, b, &invalid, &overflow);
cr = (sgna > 0) ? CRF_GT : CRF_LT;
} else if (magnitude < 0) {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgnb, ps);
bcd_sub_mag(&result, b, a, &invalid, &overflow);
cr = (sgnb > 0) ? CRF_GT : CRF_LT;
} else {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(0, ps);
cr = CRF_EQ;
}
}
}
@ -2762,8 +2751,6 @@ uint32_t helper_bcdadd(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b, uint32_t ps)
cr = CRF_SO;
} else if (overflow) {
cr |= CRF_SO;
} else if (zero) {
cr = CRF_EQ;
}
*r = result;