qemu-ppc
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## [Qemu-ppc] [PATCH] target/ppc: simplify bcdadd/sub functions

 From: Yasmin Beatriz Subject: [Qemu-ppc] [PATCH] target/ppc: simplify bcdadd/sub functions Date: Tue, 24 Jul 2018 12:13:04 +0000

```After solving a corner case in bcdsub, this patch simplifies the logic
of both bcdadd/sub instructions by removing some unnecessary local flags.

---
target/ppc/int_helper.c | 33 +++++++++------------------------
1 file changed, 9 insertions(+), 24 deletions(-)

diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
index fa18e6e..b8ac4bb 100644
--- a/target/ppc/int_helper.c
+++ b/target/ppc/int_helper.c
@@ -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)
@@ -2734,25 +2721,25 @@ 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;
+            bcd_add_mag(&result, a, b, &invalid, &overflow);
+            cr = bcd_cmp_zero(&result);
} 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);
+            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_sub_mag(&result, b, a, &invalid, &overflow);
+            cr = CRF_EQ;
} else {
result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgnb, ps);
-            zero = bcd_sub_mag(&result, b, a, &invalid, &overflow);
+            bcd_sub_mag(&result, b, a, &invalid, &overflow);
cr = (sgnb > 0) ? CRF_GT : CRF_LT;
}
}
@@ -2762,8 +2749,6 @@ 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;
--
1.8.3.1

```