From 131085be803138c30884f3785fad7d2f2b49da14 Mon Sep 17 00:00:00 2001
From: SChernykh <sergey.v.chernykh@gmail.com>
Date: Fri, 21 Feb 2020 19:00:58 +0100
Subject: [PATCH] Optimized CFROUND

Shorter version using BMI2 instructionns
---
 src/crypto/randomx/jit_compiler_x86.cpp | 23 +++++++++++++++++++++++
 src/crypto/randomx/jit_compiler_x86.hpp |  1 +
 src/crypto/randomx/randomx.cpp          | 12 +++++++++++-
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/crypto/randomx/jit_compiler_x86.cpp b/src/crypto/randomx/jit_compiler_x86.cpp
index 1307c9a59..83bb87ad3 100644
--- a/src/crypto/randomx/jit_compiler_x86.cpp
+++ b/src/crypto/randomx/jit_compiler_x86.cpp
@@ -1118,6 +1118,29 @@ namespace randomx {
 		codePos = pos;
 	}
 
+	void JitCompilerX86::h_CFROUND_BMI2(const Instruction& instr) {
+		uint8_t* const p = code;
+		int pos = codePos;
+
+		const uint64_t src = instr.src;
+
+		const uint64_t rotate = (static_cast<int>(instr.getImm32() & 63) - 2) & 63;
+		*(uint64_t*)(p + pos) = 0xC0F0FBC3C4ULL | (src << 32) | (rotate << 40);
+
+		if (vm_flags & RANDOMX_FLAG_AMD) {
+			*(uint64_t*)(p + pos + 6) = 0x742024443B0CE083ULL;
+			*(uint8_t*)(p + pos + 14) = 8;
+			*(uint64_t*)(p + pos + 15) = 0x202444890414AE0FULL;
+			pos += 23;
+		}
+		else {
+			*(uint64_t*)(p + pos + 6) = 0x0414AE0F0CE083ULL;
+			pos += 13;
+		}
+
+		codePos = pos;
+	}
+
 	void JitCompilerX86::h_CBRANCH(const Instruction& instr) {
 		uint8_t* const p = code;
 		int pos = codePos;
diff --git a/src/crypto/randomx/jit_compiler_x86.hpp b/src/crypto/randomx/jit_compiler_x86.hpp
index c1a05c873..c37890ad5 100644
--- a/src/crypto/randomx/jit_compiler_x86.hpp
+++ b/src/crypto/randomx/jit_compiler_x86.hpp
@@ -147,6 +147,7 @@ namespace randomx {
 		void h_FSQRT_R(const Instruction&);
 		void h_CBRANCH(const Instruction&);
 		void h_CFROUND(const Instruction&);
+		void h_CFROUND_BMI2(const Instruction&);
 		void h_ISTORE(const Instruction&);
 		void h_NOP(const Instruction&);
 	};
diff --git a/src/crypto/randomx/randomx.cpp b/src/crypto/randomx/randomx.cpp
index 9fcaec925..b283a6c23 100644
--- a/src/crypto/randomx/randomx.cpp
+++ b/src/crypto/randomx/randomx.cpp
@@ -279,7 +279,17 @@ void RandomX_ConfigurationBase::Apply()
 	INST_HANDLE(FDIV_M, FMUL_R);
 	INST_HANDLE(FSQRT_R, FDIV_M);
 	INST_HANDLE(CBRANCH, FSQRT_R);
-	INST_HANDLE(CFROUND, CBRANCH);
+
+#if defined(_M_X64) || defined(__x86_64__)
+	if (xmrig::Cpu::info()->hasBMI2()) {
+		INST_HANDLE2(CFROUND, CFROUND_BMI2, CBRANCH);
+	}
+	else
+#endif
+	{
+		INST_HANDLE(CFROUND, CBRANCH);
+	}
+
 	INST_HANDLE(ISTORE, CFROUND);
 	INST_HANDLE(NOP, ISTORE);
 #undef INST_HANDLE