From cb780cd6e6fe6e91f3971a052abb7aa4a09657b2 Mon Sep 17 00:00:00 2001
From: Ulf Wohlers <finsterr@users.sourceforge.net>
Date: Tue, 27 Aug 2002 10:15:38 +0000
Subject: [PATCH] Added instructions: BSF,BSR,BSWAP

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@227
---
 src/cpu/core_16/instructions.h |  3 +++
 src/cpu/core_16/prefix_of.h    | 44 +++++++++++++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/src/cpu/core_16/instructions.h b/src/cpu/core_16/instructions.h
index 9863b2e0..8bd1901c 100644
--- a/src/cpu/core_16/instructions.h
+++ b/src/cpu/core_16/instructions.h
@@ -649,3 +649,6 @@
 	flags.result.d=(flags.var1.d >> flags.var2.b) | (op2 << (32-flags.var2.b));	\
 	save(op1,flags.result.d);											\
 	flags.type=t_DSHRd;
+
+#define BSWAP(op1)														\
+	op1 = (op1>>24)|((op1>>8)&0xFF00)|((op1<<8)&0xFF0000)|((op1<<24)&0xFF000000);
diff --git a/src/cpu/core_16/prefix_of.h b/src/cpu/core_16/prefix_of.h
index 951ef21b..5d845201 100644
--- a/src/cpu/core_16/prefix_of.h
+++ b/src/cpu/core_16/prefix_of.h
@@ -350,7 +350,40 @@ switch(Fetchb()) {
 			if (flags.type!=t_CF)	{ flags.prev_type=flags.type;flags.type=t_CF;	}
 			break;
 		}
-	/* 0xbc BSF Gw,Ew */
+	case 0xbc:													/* 0xbc BSF Gw,Ew */
+		{
+			GetRMrw;
+			Bit16u result,value;
+			if (rm >= 0xc0) { GetEArw; value=*earw; } 
+			else			{ GetEAa; value=LoadMw(eaa); }
+			if (value==0) {
+				flags.zf = true;
+			} else {
+				result = 0;
+				while ((value & 0x01)==0) { result++; value>>=1; }
+				flags.zf = false;
+				*rmrw = result;
+			}
+			flags.type=t_UNKNOWN;
+			break;
+		}
+	case 0xbd:												/* 0xbd BSR Gw,Ew */
+		{
+			GetRMrw;
+			Bit16u result,value;
+			if (rm >= 0xc0) { GetEArw; value=*earw; } 
+			else			{ GetEAa; value=LoadMw(eaa); }
+			if (value==0) {
+				flags.zf = true;
+			} else {
+				result = 15;	// Operandsize-1
+				while ((value & 0x8000)==0) { result--; value<<=1; }
+				flags.zf = false;
+				*rmrw = result;
+			}
+			flags.type=t_UNKNOWN;
+			break;
+		}
 	/* 0xbd BSR Gw,Ew */
 	case 0xbe:												/* MOVSX Gw,Eb */
 		{
@@ -363,6 +396,15 @@ switch(Fetchb()) {
 	/* 0xc1 XADD Ew,Gw (486) */
 	/* 0xc7 CMPXCHG8B Mq (P5) */
 	/* 0xc8-cf BSWAP Rw (odd behavior,486) */
+	case 0xc8:	BSWAP(reg_eax);		break;
+	case 0xc9:	BSWAP(reg_ecx);		break;
+	case 0xca:	BSWAP(reg_edx);		break;
+	case 0xcb:	BSWAP(reg_ebx);		break;
+	case 0xcc:	BSWAP(reg_esp);		break;
+	case 0xcd:	BSWAP(reg_ebp);		break;
+	case 0xce:	BSWAP(reg_esi);		break;
+	case 0xcf:	BSWAP(reg_edi);		break;
+		
 	/* 0xd1 PSRLW Rq,Eq (MMX) */
 	/* 0xd2 PSRLD Rq,Eq (MMX) */
 	/* 0xd3 PSRLQ Rq,Eq (MMX) */