From 51489d031ceb729d9a2c38744eb02befc94ec254 Mon Sep 17 00:00:00 2001
From: TomW <TomW@localhost>
Date: Wed, 8 Jul 2015 20:40:37 +0100
Subject: [PATCH] Reduced number of segment/selector checks in recompiler -
 minor speedup.

---
 src/codegen_ops_x86.h | 22 ++++++++++++++++++++++
 src/codegen_x86.c     |  2 ++
 src/ibm.h             |  3 +++
 src/x86seg.c          |  6 ++++++
 4 files changed, 33 insertions(+)

diff --git a/src/codegen_ops_x86.h b/src/codegen_ops_x86.h
index 3ba492b..8a136c2 100644
--- a/src/codegen_ops_x86.h
+++ b/src/codegen_ops_x86.h
@@ -462,6 +462,15 @@ static void SAR_L_IMM(int reg, int count)
 
 static void CHECK_SEG_READ(x86seg *seg)
 {
+        /*Segments always valid in real/V86 mode*/
+        if (!(cr0 & 1) || (eflags & VM_FLAG))
+                return;
+        /*CS and SS must always be valid*/
+        if (seg == &_cs || seg == &_ss)
+                return;
+        if (seg->checked)
+                return;
+
         addbyte(0x83); /*CMP seg->base, -1*/
         addbyte(0x05|0x38);
         addlong((uint32_t)&seg->base);
@@ -469,9 +478,20 @@ static void CHECK_SEG_READ(x86seg *seg)
         addbyte(0x0f);
         addbyte(0x84); /*JE end*/
         addlong(BLOCK_EXIT_OFFSET - (block_pos + 4));
+        
+        seg->checked = 1;
 }
 static void CHECK_SEG_WRITE(x86seg *seg)
 {
+        /*Segments always valid in real/V86 mode*/
+        if (!(cr0 & 1) || (eflags & VM_FLAG))
+                return;
+        /*CS and SS must always be valid*/
+        if (seg == &_cs || seg == &_ss)
+                return;
+        if (seg->checked)
+                return;
+                
         addbyte(0x83); /*CMP seg->base, -1*/
         addbyte(0x05|0x38);
         addlong((uint32_t)&seg->base);
@@ -479,6 +499,8 @@ static void CHECK_SEG_WRITE(x86seg *seg)
         addbyte(0x0f);
         addbyte(0x84); /*JE end*/
         addlong(BLOCK_EXIT_OFFSET - (block_pos + 4));
+
+        seg->checked = 1;
 }
 static void CHECK_SEG_LIMITS(x86seg *seg, int end_offset)
 {
diff --git a/src/codegen_x86.c b/src/codegen_x86.c
index 1528590..b06859e 100644
--- a/src/codegen_x86.c
+++ b/src/codegen_x86.c
@@ -261,6 +261,8 @@ void codegen_block_init(uint32_t phys_addr)
 
         codegen_fpu_loaded_iq[0] = codegen_fpu_loaded_iq[1] = codegen_fpu_loaded_iq[2] = codegen_fpu_loaded_iq[3] =
         codegen_fpu_loaded_iq[4] = codegen_fpu_loaded_iq[5] = codegen_fpu_loaded_iq[6] = codegen_fpu_loaded_iq[7] = 0;
+        
+        _ds.checked = _es.checked = _fs.checked = _gs.checked = (cr0 & 1) ? 0 : 1;
 }
 
 void codegen_block_remove()
diff --git a/src/ibm.h b/src/ibm.h
index 4c5cd67..85e11d2 100644
--- a/src/ibm.h
+++ b/src/ibm.h
@@ -114,6 +114,9 @@ typedef struct
         uint8_t access;
         uint16_t seg;
         uint32_t limit_low, limit_high;
+#ifdef DYNAREC
+        int checked; /*Non-zero if selector is known to be valid*/
+#endif
 } x86seg;
 
 x86seg gdt,ldt,idt,tr;
diff --git a/src/x86seg.c b/src/x86seg.c
index 0355b03..8de8923 100644
--- a/src/x86seg.c
+++ b/src/x86seg.c
@@ -395,6 +395,9 @@ void loadseg(uint16_t seg, x86seg *s)
 #endif
 #ifndef CS_ACCESSED
                 }
+#endif
+#ifdef DYNAREC
+                s->checked = 0;
 #endif
         }
         else
@@ -404,6 +407,9 @@ void loadseg(uint16_t seg, x86seg *s)
                 s->seg = seg;
                 if (s == &_ss)
                         stack32 = 0;
+#ifdef DYNAREC
+                s->checked = 1;
+#endif
         }
 }