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SubGhz: faster mess_with_iv (#845)

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* subghz_keystore_mess_with_iv shortened
- less instructions
- less registers used (no need for r3 anymore)
* subghz_keystore_mess_with_iv shortened (again)
* 7b46c12e408cdc541e9e91c0392365bb4960fabd reduced instructions count from 4+16x8=132 to 3+16x7=115
* here loop is removed and reduces all to only 15 instructions
* branch label is kept to preserve original intent and for historical record
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ImprovingRigmarole 2021-11-26 12:47:17 +01:00 committed by GitHub
parent 2db5eee03b
commit 6857b98ecd
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1 changed files with 16 additions and 13 deletions
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lib/subghz/subghz_keystore.c
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@ -81,19 +81,22 @@ static void subghz_keystore_mess_with_iv(uint8_t* iv) {
// Sharing them will bring some discomfort to legal owners // Sharing them will bring some discomfort to legal owners
// And potential legal action against you // And potential legal action against you
// While you reading this code think about your own personal responsibility // While you reading this code think about your own personal responsibility
asm volatile("movs r0, #0x0 \n" asm volatile("nani: \n"
"movs r1, #0x0 \n" "ldrd r0, r2, [%0, #0x0] \n"
"movs r2, #0x0 \n" "lsl r1, r0, #8 \n"
"movs r3, #0x0 \n" "lsl r3, r2, #8 \n"
"nani: \n" "orr r3, r3, r0, lsr #24\n"
"ldrb r1, [r0, %0]\n" "uadd8 r1, r1, r0 \n"
"mov r2, r1 \n" "uadd8 r3, r3, r2 \n"
"add r1, r3 \n" "strd r1, r3, [%0, #0x0] \n"
"mov r3, r2 \n" "ldrd r1, r3, [%0, #0x8] \n"
"strb r1, [r0, %0]\n" "lsl r0, r1, #8 \n"
"adds r0, #0x1 \n" "orr r0, r0, r2, lsr #24\n"
"cmp r0, #0xF \n" "lsl r2, r3, #8 \n"
"bls nani \n" "orr r2, r2, r1, lsr #24\n"
"uadd8 r1, r1, r0 \n"
"uadd8 r3, r3, r2 \n"
"strd r1, r3, [%0, #0x8] \n"
: :
: "r"(iv) : "r"(iv)
: "r0", "r1", "r2", "r3", "memory"); : "r0", "r1", "r2", "r3", "memory");