[SOFTX86]

Fix carry/overflow condition for the SUB instruction.

svn path=/branches/ntvdm/; revision=59490

diff --git a/lib/3rdparty/softx86/softx86/add.c b/lib/3rdparty/softx86/softx86/add.c
index 6279c8f..cf339d6 100644 (file)
--- a/lib/3rdparty/softx86/softx86/add.c
+++ b/lib/3rdparty/softx86/softx86/add.c
@@ -342,13 +342,16 @@ sx86_ubyte op_sub8(softx86_ctx* ctx,sx86_ubyte src,sx86_ubyte val)
 /* peform the addition */
        ret = src - val;
 
-/* if carry/overflow */
-       if (ret > src)
-               ctx->state->reg_flags.val |=
-                        (SX86_CPUFLAG_CARRY | SX86_CPUFLAG_OVERFLOW);
-       else
-               ctx->state->reg_flags.val &=
-                       ~(SX86_CPUFLAG_CARRY | SX86_CPUFLAG_OVERFLOW);
+/* if carry */
+        if (val > src) ctx->state->reg_flags.val |= SX86_CPUFLAG_CARRY;
+        else ctx->state->reg_flags.val &= ~SX86_CPUFLAG_CARRY;
+
+/* if overflow */
+       if (((src & 0x80) != (val & 0x80)) && ((src & 0x80) != (ret & 0x80)))
+        {
+            ctx->state->reg_flags.val |= SX86_CPUFLAG_OVERFLOW;
+        }
+       else ctx->state->reg_flags.val &= ~SX86_CPUFLAG_OVERFLOW;
 
 /* if result treated as signed value is negative */
        if (ret & 0x80) ctx->state->reg_flags.val |=  SX86_CPUFLAG_SIGN;
@@ -391,7 +394,10 @@ sx86_uword op_sub16(softx86_ctx* ctx,sx86_uword src,sx86_uword val)
         else ctx->state->reg_flags.val &= ~SX86_CPUFLAG_CARRY;
 
 /* if overflow */
-       if ((ret & 0x8000) != (src & 0x8000)) ctx->state->reg_flags.val |= SX86_CPUFLAG_OVERFLOW;
+       if (((src & 0x8000) != (val & 0x8000)) && ((src & 0x8000) != (ret & 0x8000)))
+        {
+            ctx->state->reg_flags.val |= SX86_CPUFLAG_OVERFLOW;
+        }
        else ctx->state->reg_flags.val &= ~SX86_CPUFLAG_OVERFLOW;
 
 /* if result treated as signed value is negative */
@@ -430,13 +436,17 @@ sx86_udword op_sub32(softx86_ctx* ctx,sx86_udword src,sx86_udword val)
 /* peform the addition */
        ret = src - val;
 
-/* if carry/overflow */
-       if (ret > src)
-               ctx->state->reg_flags.val |=
-                        (SX86_CPUFLAG_CARRY | SX86_CPUFLAG_OVERFLOW);
-       else
-               ctx->state->reg_flags.val &=
-                       ~(SX86_CPUFLAG_CARRY | SX86_CPUFLAG_OVERFLOW);
+/* if carry */
+        if (val > src) ctx->state->reg_flags.val |= SX86_CPUFLAG_CARRY;
+        else ctx->state->reg_flags.val &= ~SX86_CPUFLAG_CARRY;
+
+/* if overflow */
+       if (((src & 0x80000000) != (val & 0x80000000))
+            && ((src & 0x80000000) != (ret & 0x80000000)))
+        {
+            ctx->state->reg_flags.val |= SX86_CPUFLAG_OVERFLOW;
+        }
+       else ctx->state->reg_flags.val &= ~SX86_CPUFLAG_OVERFLOW;
 
 /* if result treated as signed value is negative */
        if (ret & 0x80000000)   ctx->state->reg_flags.val |=  SX86_CPUFLAG_SIGN;