From e9601584907fe238510f0d13de3ecdc263cd4b8d Mon Sep 17 00:00:00 2001
From: "Unknown W. Brackets" <checkins@unknownbrackets.org>
Date: Sun, 15 May 2016 14:03:45 -0700
Subject: [PATCH] jit-ir: Add notes and report about vrot prefixes.

---
 Core/MIPS/IR/IRCompVFPU.cpp | 15 +++++++++++++++
 Core/MIPS/MIPSIntVFPU.cpp   |  1 +
 Core/MIPS/x86/CompVFPU.cpp  |  8 ++++++++
 3 files changed, 24 insertions(+)

diff --git a/Core/MIPS/IR/IRCompVFPU.cpp b/Core/MIPS/IR/IRCompVFPU.cpp
index dab8e97e7a..a4c90ba784 100644
--- a/Core/MIPS/IR/IRCompVFPU.cpp
+++ b/Core/MIPS/IR/IRCompVFPU.cpp
@@ -1716,6 +1716,17 @@ namespace MIPSComp {
 	// calling the math library.
 	void IRFrontend::Comp_VRot(MIPSOpcode op) {
 		CONDITIONAL_DISABLE;
+		if (!js.HasNoPrefix()) {
+			// Prefixes work strangely for this:
+			//  * They never apply to cos (whether d or s prefixes.)
+			//  * They mostly apply to sin/0, e.g. 0:1, M, or |x|.
+			DISABLE;
+		}
+
+		// Vector rotation matrix (weird prefixes)
+		// d[N] = SINCOSVAL(s[0], imm[N])
+		// The imm selects: cos index, sin index, 0 or sin for others, sin sign flip.
+
 		int vd = _VD;
 		int vs = _VS;
 		int imm = (op >> 16) & 0x1f;
@@ -1844,6 +1855,10 @@ namespace MIPSComp {
 		if (js.HasUnknownPrefix())
 			DISABLE;
 
+		// Vector butterfly operation
+		// vbfy2: d[0] = s[0] + s[2], d[1] = s[1] + s[3], d[2] = s[0] - s[2], d[3] = s[1] - s[3]
+		// vbfy1: d[N*2] = s[N*2] + s[N*2+1], d[N*2+1] = s[N*2] - s[N*2+1]
+
 		VectorSize sz = GetVecSize(op);
 		int n = GetNumVectorElements(sz);
 		if (n != 2 && n != 4) {
diff --git a/Core/MIPS/MIPSIntVFPU.cpp b/Core/MIPS/MIPSIntVFPU.cpp
index 2d2c8f18f3..784cba75ca 100644
--- a/Core/MIPS/MIPSIntVFPU.cpp
+++ b/Core/MIPS/MIPSIntVFPU.cpp
@@ -1297,6 +1297,7 @@ namespace MIPSInt
 
 	// Generates one line of a rotation matrix around one of the three axes
 	void Int_Vrot(MIPSOpcode op) {
+		// Note: prefixes behave strangely for this.
 		int vd = _VD;
 		int vs = _VS;
 		int imm = (op >> 16) & 0x1f;
diff --git a/Core/MIPS/x86/CompVFPU.cpp b/Core/MIPS/x86/CompVFPU.cpp
index 50176066f6..33a74ccd01 100644
--- a/Core/MIPS/x86/CompVFPU.cpp
+++ b/Core/MIPS/x86/CompVFPU.cpp
@@ -3410,6 +3410,14 @@ void Jit::CompVrotShuffle(u8 *dregs, int imm, int n, bool negSin) {
 // Very heavily used by FF:CC
 void Jit::Comp_VRot(MIPSOpcode op) {
 	CONDITIONAL_DISABLE;
+	if (js.HasUnknownPrefix()) {
+		DISABLE;
+	}
+	if (!js.HasNoPrefix()) {
+		// Prefixes work strangely for this, see IRCompVFPU.
+		WARN_LOG_REPORT(JIT, "vrot instruction using prefixes at %08x", GetCompilerPC());
+		DISABLE;
+	}
 
 	int vd = _VD;
 	int vs = _VS;