* [Qemu-devel] [PATCH v2] target/ppc: simplify bcdadd/sub functions
@ 2018-07-30 17:09 Yasmin Beatriz
2018-08-01 4:26 ` David Gibson
0 siblings, 1 reply; 2+ messages in thread
From: Yasmin Beatriz @ 2018-07-30 17:09 UTC (permalink / raw)
To: qemu-ppc; +Cc: qemu-devel, david, rth
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>
---
target/ppc/int_helper.c | 49 ++++++++++++++++++-------------------------------
1 file changed, 18 insertions(+), 31 deletions(-)
diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
index fa18e6e..1906f22 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)
@@ -2734,26 +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;
--
1.8.3.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [PATCH v2] target/ppc: simplify bcdadd/sub functions
2018-07-30 17:09 [Qemu-devel] [PATCH v2] target/ppc: simplify bcdadd/sub functions Yasmin Beatriz
@ 2018-08-01 4:26 ` David Gibson
0 siblings, 0 replies; 2+ messages in thread
From: David Gibson @ 2018-08-01 4:26 UTC (permalink / raw)
To: Yasmin Beatriz; +Cc: qemu-ppc, qemu-devel, rth
[-- Attachment #1: Type: text/plain, Size: 5214 bytes --]
On Mon, Jul 30, 2018 at 05:09:17PM +0000, Yasmin Beatriz wrote:
> 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>
Applied to ppc-for-3.1, thanks.
> ---
> target/ppc/int_helper.c | 49 ++++++++++++++++++-------------------------------
> 1 file changed, 18 insertions(+), 31 deletions(-)
>
> diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
> index fa18e6e..1906f22 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)
> @@ -2734,26 +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;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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