Merge pull request #3270 from 86Box/feature/checkio_optimize

386_common: Handle IOPB segment limit corner case more like the old code

src/cpu/386_common.c

@@ -1429,26 +1429,29 @@ x86illegal(void)
 int
 checkio(uint32_t port, int mask)
 {
-    uint16_t t;
+    uint32_t t;
 
     cpl_override = 1;
     t            = readmemw(tr.base, 0x66);
 
-    if (cpu_state.abrt) {
+    if (UNLIKELY(cpu_state.abrt)) {
         cpl_override = 0;
         return 0;
     }
 
-    if ((t + (port >> 3UL) + 1) > tr.limit) {
+    t += (port >> 3UL);
+    mask <<= (port & 7);
+    if (UNLIKELY(mask & 0xff00)) {
+        if (LIKELY(t < tr.limit))
+            mask &= readmemwl(tr.base + t);
+    } else {
+        if (LIKELY(t <= tr.limit))
+            mask &= readmembl(tr.base + t);
+    }
     cpl_override = 0;
     return mask;
 }
 
-    t            = readmemwl(tr.base + t + (port >> 3));
-    cpl_override = 0;
-    return (t >> (port & 7)) & mask;
-}
-
 #ifdef OLD_DIVEXCP
 #    define divexcp()                                                                       \
         {                                                                                   \

src/include/86box/86box.h

@@ -55,6 +55,14 @@
 #define BCD16(x)  ((((x) / 1000) << 12) | (((x) / 100) << 8) | BCD8(x))
 #define BCD32(x)  ((((x) / 10000000) << 28) | (((x) / 1000000) << 24) | (((x) / 100000) << 20) | (((x) / 10000) << 16) | BCD16(x))
 
+#if defined(__GNUC__) || defined(__clang__)
+#    define UNLIKELY(x) __builtin_expect((x), 0)
+#    define LIKELY(x)   __builtin_expect((x), 1)
+#else
+#    define UNLIKELY(x) (x)
+#    define LIKELY(x)   (x)
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif