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Remove unnecessary zero test for a slight speed improvement.

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This commit is contained in:
Ken MacKay
2014-05-17 22:29:32 -07:00
parent 58610ddcec
commit 5b6724c5f1
2 changed files with 9 additions and 50 deletions
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asm_avr.inc
+6 -44
View File
@@ -15571,26 +15571,10 @@ static void vli_mmod_fast(uint8_t *RESTRICT p_result, uint8_t *RESTRICT p_produc
"adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */ "adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */
/* at this point x is at the end of p_product, y is at the end of p_result, z is 20 bytes into tmp */ /* at this point x is at the end of p_product, y is at the end of p_result, z is 20 bytes into tmp */
"sbiw r28, 20 \n\t" /* move y back to point at p_result */ "sbiw r28, 20 \n\t" /* move y back to point at p_result */
"adiw r30, 4 \n\t" /* move z to point to the end of tmp */
"eor r19, r19 \n\t" /* do omega_mult again with the 4 relevant bytes */
"ld r18, z+ \n\t" /* z points to the end of tmp, x points to the end of p_product */
"add r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
/* now z points to the end of tmp */
"brcs mmod_remult \n\t" /* carry was set, so something was not zero (need to mult again) */
"cp r19, __zero_reg__ \n\t"
"brne mmod_remult \n\t" /* sum was not equal to zero (need to mult again) */
"rjmp mmod_after_remult \n\t"
"mmod_remult: \n\t" /* do omega_mult with the 4 relevant bytes */
/* z already points to the end of tmp, x points to the end of p_product */
"ld r18, -z \n\t" /* Load word. */ "ld r18, -z \n\t" /* Load word. */
"lsr r18 \n\t" /* Shift. */ "lsr r18 \n\t" /* Shift. */
"st -x, r18 \n\t" /* Store the first result word. */ "st -x, r18 \n\t" /* Store the first result word. */
@@ -15660,8 +15644,6 @@ static void vli_mmod_fast(uint8_t *RESTRICT p_result, uint8_t *RESTRICT p_produc
"adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */ "adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */
"sbiw r28, 20 \n\t" /* move y back to point at p_result */ "sbiw r28, 20 \n\t" /* move y back to point at p_result */
"mmod_after_remult: \n\t"
"sbiw r30, 1 \n\t" /* fix stack pointer */ "sbiw r30, 1 \n\t" /* fix stack pointer */
"in r0, __SREG__ \n\t" "in r0, __SREG__ \n\t"
"cli \n\t" "cli \n\t"
@@ -15886,27 +15868,9 @@ static void vli_mmod_fast(uint8_t *RESTRICT p_result, uint8_t *RESTRICT p_produc
"adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */ "adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */
/* at this point x is at the end of p_product, y is at the end of p_result, z is 32 bytes into tmp */ /* at this point x is at the end of p_product, y is at the end of p_result, z is 32 bytes into tmp */
"sbiw r28, 32 \n\t" /* move y back to point at p_result */ "sbiw r28, 32 \n\t" /* move y back to point at p_result */
"eor r19, r19 \n\t" /* do omega_mult again with the 5 relevant bytes */
"ld r18, z+ \n\t" /* z points to l_tmp + uECC_WORDS, x points to the end of p_product */
"add r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
"ld r18, z+ \n\t"
"adc r19, r18 \n\t"
/* now z points to the end of tmp */
"brcs mmod_remult \n\t" /* carry was set, so something was not zero (need to mult again) */
"cp r19, __zero_reg__ \n\t"
"brne mmod_remult \n\t" /* sum was not equal to zero (need to mult again) */
"rjmp mmod_after_remult \n\t"
"mmod_remult: \n\t" /* do omega_mult with the 5 relevant bytes */
/* z points to the end of tmp, x points to the end of p_product */
"sbiw r30, 5 \n\t" /* move z back to point at l_tmp + uECC_WORDS */
"sbiw r26, 32 \n\t" /* shift x back to point into the p_product buffer (we can overwrite it now) */ "sbiw r26, 32 \n\t" /* shift x back to point into the p_product buffer (we can overwrite it now) */
"ld r18, z+ \n\t" "ld r18, z+ \n\t"
@@ -16003,8 +15967,6 @@ static void vli_mmod_fast(uint8_t *RESTRICT p_result, uint8_t *RESTRICT p_produc
"adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */ "adc %[carry], __zero_reg__ \n\t" /* Store carry bit (carry flag is cleared). */
"sbiw r28, 32 \n\t" /* move y back to point at p_result */ "sbiw r28, 32 \n\t" /* move y back to point at p_result */
"mmod_after_remult: \n\t"
"sbiw r30, 1 \n\t" /* fix stack pointer */ "sbiw r30, 1 \n\t" /* fix stack pointer */
"in r0, __SREG__ \n\t" "in r0, __SREG__ \n\t"
"cli \n\t" "cli \n\t"
uECC.c
+3 -6
View File
@@ -785,12 +785,9 @@ static void vli_mmod_fast(uECC_word_t *RESTRICT p_result, uECC_word_t *RESTRICT
omega_mult(l_tmp, p_product + uECC_WORDS); /* (Rq, q) = q * c */ omega_mult(l_tmp, p_product + uECC_WORDS); /* (Rq, q) = q * c */
l_carry = vli_add(p_result, p_product, l_tmp); /* (C, r) = r + q */ l_carry = vli_add(p_result, p_product, l_tmp); /* (C, r) = r + q */
if(!vli_isZero(l_tmp + uECC_WORDS)) /* if Rq > 0 */ vli_clear(p_product);
{ omega_mult(p_product, l_tmp + uECC_WORDS); /* Rq*c */
vli_clear(p_product); l_carry += vli_add(p_result, p_result, p_product); /* (C1, r) = r + Rq*c */
omega_mult(p_product, l_tmp + uECC_WORDS); /* Rq*c */
l_carry += vli_add(p_result, p_result, p_product); /* (C1, r) = r + Rq*c */
}
while(l_carry > 0) while(l_carry > 0)
{ {