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Add GCC/Clang muladd assembly

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Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
This commit is contained in:
Kevin Bracey 2020-09-30 12:52:15 +03:00
parent 84f31d3eaa
commit e0f88d5140
1 changed files with 57 additions and 1 deletions
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58
tinycrypt/ecc.c
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@ -597,7 +597,63 @@ static __asm void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
STMIA r2!,{r0,r1,r3}
BX lr
#endif
}
#elif defined MBEDTLS_HAVE_ASM && (defined __GNUC__ || defined __clang__) && defined __arm__
static __attribute__((__naked__))
void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
{
asm(
#if defined __thumb__ && !defined(__thumb2__)
".syntax unified \n\t"
"PUSH {r4-r5} \n\t"
".cfi_remember_state \n\t"
".cfi_adjust_cfa_offset 8 \n\t"
".cfi_rel_offset r4,0 \n\t"
".cfi_rel_offset r5,4 \n\t"
// __ARM_common_mul_uu replacement - inline, faster, don't touch R2
// Separate operands into halfwords
"UXTH r3,r0 \n\t" // r3 := a.lo
"LSRS r4,r0,#16 \n\t" // r4 := a.hi
"UXTH r5,r1 \n\t" // r5 := b.lo
"LSRS r1,r1,#16 \n\t" // r1 := b.hi
// Multiply halfword pairs
"MOVS r0,r3 \n\t"
"MULS r0,r5,r0 \n\t" // r0 := a.lo * b.lo
"MULS r3,r1,r3 \n\t" // r3 := a.lo * b.hi
"MULS r5,r4,r5 \n\t" // r5 := a.hi * b.lo
"MULS r1,r4,r1 \n\t" // r1 := a.hi * b.hi
// Split, shift and add a.lo * b.hi
"LSRS r4,r3,#16 \n\t" // r4 := (a.lo * b.hi).hi
"LSLS r3,r3,#16 \n\t" // r3 := (a.lo * b.hi).lo
"ADDS r0,r0,r3 \n\t" // r0 := a.lo * b.lo + (a.lo * b.hi).lo
"ADCS r1,r4 \n\t" // r1 := a.hi * b.hi + (a.lo * b.hi).hi + carry
// Split, shift and add a.hi * b.lo
"LSRS r4,r5,#16 \n\t" // r4 := (a.hi * b.lo).hi
"LSLS r5,r5,#16 \n\t" // r5 := (a.hi * b.lo).lo
"ADDS r0,r0,r5 \n\t" // r0 := a.lo * b.lo + (a.lo * b.hi).lo + (a.hi * b.lo).lo
"ADCS r1,r4 \n\t" // r1 := a.hi * b.hi + (a.lo * b.hi).hi + (a.hi * b.lo).hi + carries
// Finally add r[]
"LDMIA r2!,{r3,r4,r5} \n\t"
"ADDS r3,r3,r0 \n\t"
"ADCS r4,r1 \n\t"
"MOVS r0,#0 \n\t"
"ADCS r5,r0 \n\t"
"SUBS r2,#12 \n\t"
"STMIA r2!,{r3,r4,r5} \n\t"
"POP {r4-r5} \n\t"
".cfi_restore_state \n\t"
"BX lr \n\t"
#else
"UMULL r3,ip,r0,r1 \n\t" // pre-ARMv6 requires Rd[Lo|Hi] != Rn
"LDMIA r2,{r0,r1} \n\t"
"ADDS r0,r0,r3 \n\t"
"LDR r3,[r2,#8] \n\t"
"ADCS r1,r1,ip \n\t"
"ADC r3,r3,#0 \n\t"
"STMIA r2!,{r0,r1,r3} \n\t"
"BX lr \n\t"
#endif
);
}
#else
static void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])