lzms_common.h: add cast needed if sizeof(int) > sizeof(u32)

[wimlib] / include / wimlib / lzms_common.h

diff --git a/include/wimlib/lzms_common.h b/include/wimlib/lzms_common.h
index 69b6e67b4dbbeebd76463be5a39e4322a838ca53..6db35b77fcbad1cc432fa8165545589d6b3b155d 100644 (file)
--- a/include/wimlib/lzms_common.h
+++ b/include/wimlib/lzms_common.h
@@ -74,13 +74,36 @@ lzms_init_probabilities(struct lzms_probabilites *probs);
 static inline void
 lzms_update_probability_entry(struct lzms_probability_entry *entry, int bit)
 {
-       BUILD_BUG_ON(LZMS_PROBABILITY_DENOMINATOR != sizeof(entry->recent_bits) * 8);
-
-       s32 delta_zero_bits = (s32)(entry->recent_bits >>
-                                   (LZMS_PROBABILITY_DENOMINATOR - 1)) - bit;
-
-       entry->num_recent_zero_bits += delta_zero_bits;
-       entry->recent_bits = (entry->recent_bits << 1) | bit;
+       STATIC_ASSERT(LZMS_PROBABILITY_DENOMINATOR == sizeof(entry->recent_bits) * 8);
+
+#ifdef __x86_64__
+       if (__builtin_constant_p(bit)) {
+               /* Optimized implementation for x86_64 using carry flag  */
+               if (bit) {
+                      __asm__("shlq %[recent_bits]                          \n"
+                              "adcl $0xffffffff, %[num_recent_zero_bits]    \n"
+                              "orq $0x1, %[recent_bits]                     \n"
+                              : [recent_bits] "+r" (entry->recent_bits),
+                                [num_recent_zero_bits] "+mr" (entry->num_recent_zero_bits)
+                              :
+                              : "cc");
+               } else {
+                      __asm__("shlq %[recent_bits]                          \n"
+                              "adcl $0x0, %[num_recent_zero_bits]           \n"
+                              : [recent_bits] "+m" (entry->recent_bits),
+                                [num_recent_zero_bits] "+mr" (entry->num_recent_zero_bits)
+                              :
+                              : "cc");
+               }
+       } else
+#endif
+       {
+               s32 delta_zero_bits = (s32)(entry->recent_bits >>
+                                           (LZMS_PROBABILITY_DENOMINATOR - 1)) - bit;
+
+               entry->num_recent_zero_bits += delta_zero_bits;
+               entry->recent_bits = (entry->recent_bits << 1) | bit;
+       }
 }
 
 /* Given a probability entry, return the chance out of
@@ -91,10 +114,19 @@ lzms_get_probability(const struct lzms_probability_entry *prob_entry)
        u32 prob = prob_entry->num_recent_zero_bits;
 
        /* 0% and 100% probabilities aren't allowed.  */
-       if (prob == 0)
-               prob++;
-       else if (prob == LZMS_PROBABILITY_DENOMINATOR)
-               prob--;
+
+       /*
+        *      if (prob == 0)
+        *              prob++;
+        */
+       prob += (u32)(prob - 1) >> 31;
+
+       /*
+        *      if (prob == LZMS_PROBABILITY_DENOMINATOR)
+        *              prob--;
+        */
+       prob -= (prob >> LZMS_PROBABILITY_BITS);
+
        return prob;
 }