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RandomX: optimized IMUL_RCP instruction

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+0.4% on AMD Zen2
+0.3% on AMD Zen3
+0.1% on Intel SandyBridge
+0.3% on rx/wow on Intel SandyBridge
This commit is contained in:
SChernykh 2021-04-19 17:43:58 +02:00
parent 61d165a314
commit 3477f9fbc1
6 changed files with 55 additions and 9 deletions
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28
src/crypto/randomx/jit_compiler_x86.cpp
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@ -428,7 +428,10 @@ namespace randomx {
xmrig::RxFix::setMainLoopBounds(mainLoopBounds);
# endif
memcpy(code + prologueSize - 48, &pcfg.eMask, sizeof(pcfg.eMask));
imul_rcp_storage = code + (ADDR(randomx_program_imul_rcp_store) - codePrologue) + 2;
imul_rcp_storage_used = 0;
memcpy(imul_rcp_storage - 34, &pcfg.eMask, sizeof(pcfg.eMask));
codePos = codePosFirst;
prevCFROUND = 0;
@ -1012,13 +1015,24 @@ namespace randomx {
uint64_t divisor = instr.getImm32();
if (!isZeroOrPowerOf2(divisor)) {
*(uint32_t*)(p + pos) = 0xb848;
pos += 2;
emit64(randomx_reciprocal_fast(divisor), p, pos);
const uint32_t dst = instr.dst % RegistersCount;
emit32(0xc0af0f4c + (dst << 27), p, pos);
const uint64_t reciprocal = randomx_reciprocal_fast(divisor);
if (imul_rcp_storage_used < 16) {
*(uint64_t*)(imul_rcp_storage) = reciprocal;
*(uint64_t*)(p + pos) = 0x2444AF0F4Cull + (dst << 27) + (static_cast<uint64_t>(248 - imul_rcp_storage_used * 8) << 40);
++imul_rcp_storage_used;
imul_rcp_storage += 11;
pos += 6;
}
else {
*(uint32_t*)(p + pos) = 0xb848;
pos += 2;
emit64(reciprocal, p, pos);
emit32(0xc0af0f4c + (dst << 27), p, pos);
}
registerUsage[dst] = pos;
}