From 1dff9897c9a0ba6a0ed7a4db5ec9106fe0a3d169 Mon Sep 17 00:00:00 2001
From: Stenzek <stenzek@gmail.com>
Date: Sun, 1 Jan 2023 16:16:27 +1000
Subject: [PATCH] x86/microVU: Only update MXCSR when it's different

Saves reloading it when the EE and VU0 rounding modes are the same.
---
 pcsx2/x86/microVU_Execute.inl | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/pcsx2/x86/microVU_Execute.inl b/pcsx2/x86/microVU_Execute.inl
index 3910dad5ab..9c98eeef6f 100644
--- a/pcsx2/x86/microVU_Execute.inl
+++ b/pcsx2/x86/microVU_Execute.inl
@@ -18,6 +18,15 @@
 //------------------------------------------------------------------
 // Dispatcher Functions
 //------------------------------------------------------------------
+static bool mvuNeedsFPCRUpdate(mV)
+{
+	// always update on the vu1 thread
+	if (isVU1 && THREAD_VU1)
+		return true;
+
+	// otherwise only emit when it's different to the EE
+	return g_sseMXCSR.bitmask != (isVU0 ? g_sseVU0MXCSR.bitmask : g_sseVU1MXCSR.bitmask);
+}
 
 // Generates the code for entering/exit recompiled blocks
 void mVUdispatcherAB(mV)
@@ -32,7 +41,8 @@ void mVUdispatcherAB(mV)
 		else        xFastCall((void*)mVUexecuteVU1, arg1reg, arg2reg);
 
 		// Load VU's MXCSR state
-		xLDMXCSR(isVU0 ? g_sseVU0MXCSR : g_sseVU1MXCSR);
+		if (mvuNeedsFPCRUpdate(mVU))
+			xLDMXCSR(isVU0 ? g_sseVU0MXCSR : g_sseVU1MXCSR);
 
 		// Load Regs
 		xMOVAPS (xmmT1, ptr128[&mVU.regs().VI[REG_P].UL]);
@@ -71,7 +81,8 @@ void mVUdispatcherAB(mV)
 		mVU.exitFunct = x86Ptr;
 
 		// Load EE's MXCSR state
-		xLDMXCSR(g_sseMXCSR);
+		if (mvuNeedsFPCRUpdate(mVU))
+			xLDMXCSR(g_sseMXCSR);
 
 		// = The first two DWORD or smaller arguments are passed in ECX and EDX registers;
 		//              all other arguments are passed right to left.
@@ -94,7 +105,8 @@ void mVUdispatcherCD(mV)
 		xScopedStackFrame frame(false, true);
 
 		// Load VU's MXCSR state
-		xLDMXCSR(isVU0 ? g_sseVU0MXCSR : g_sseVU1MXCSR);
+		if (mvuNeedsFPCRUpdate(mVU))
+			xLDMXCSR(isVU0 ? g_sseVU0MXCSR : g_sseVU1MXCSR);
 
 		mVUrestoreRegs(mVU);
 		xMOV(gprF0, ptr32[&mVU.regs().micro_statusflags[0]]);
@@ -114,7 +126,8 @@ void mVUdispatcherCD(mV)
 		xMOV(ptr32[&mVU.regs().micro_statusflags[3]], gprF3);
 
 		// Load EE's MXCSR state
-		xLDMXCSR(g_sseMXCSR);
+		if (mvuNeedsFPCRUpdate(mVU))
+			xLDMXCSR(g_sseMXCSR);
 	}
 
 	xRET();