Replace RAPIDJSON_CLZLL with internal clzll (Tencent#1660)

RAPIDJSON_CLZLL is defined as macro of __builtin_clzll when
using gcc to compile. This introduces two issues:
1. in gcc __builtin_clzll returns int, not uint32_t.
2. __builtin_clzll return is undefined when input x is 0
See: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html

This patch removes RAPIDJSON_CLZLL, merges __builtin_clzll to
internal clzll with input check and return value explicit cast.

Change-Id: Iac4b355dc5e5b4ed9b3f35a640b6b5537e76f22c
Signed-off-by: Jun He <[email protected]>

Co-authored-by: Jun He <[email protected]>

Author: JunHe77

include/rapidjson/internal/clzll.h

@@ -29,10 +29,6 @@
 RAPIDJSON_NAMESPACE_BEGIN
 namespace internal {
 
-#if (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll)
-#define RAPIDJSON_CLZLL __builtin_clzll
-#else
-
 inline uint32_t clzll(uint64_t x) {
     // Passing 0 to __builtin_clzll is UB in GCC and results in an
     // infinite loop in the software implementation.
@@ -52,7 +48,11 @@ inline uint32_t clzll(uint64_t x) {
 #endif // _WIN64
 
     return 63 - r;
+#elif (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll)
+    // __builtin_clzll wrapper
+    return static_cast<uint32_t>(__builtin_clzll(x));
 #else
+    // naive version
     uint32_t r;
     while (!(x & (static_cast<uint64_t>(1) << 63))) {
         x <<= 1;
@@ -64,9 +64,8 @@ inline uint32_t clzll(uint64_t x) {
 }
 
 #define RAPIDJSON_CLZLL RAPIDJSON_NAMESPACE::internal::clzll
-#endif // (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll)
 
 } // namespace internal
 RAPIDJSON_NAMESPACE_END
 
-#endif // RAPIDJSON_CLZLL_H_
+#endif // RAPIDJSON_CLZLL_H_

include/rapidjson/internal/diyfp.h

@@ -100,7 +100,7 @@ struct DiyFp {
     }
 
     DiyFp Normalize() const {
-        int s = static_cast<int>(RAPIDJSON_CLZLL(f));
+        int s = static_cast<int>(clzll(f));
         return DiyFp(f << s, e - s);
     }
 

include/rapidjson/reader.h

@@ -450,11 +450,11 @@ inline const char *SkipWhitespace_SIMD(const char* p) {
 
         if (low == 0) {
             if (high != 0) {
-                uint32_t lz = RAPIDJSON_CLZLL(high);
+                uint32_t lz = internal::clzll(high);
                 return p + 8 + (lz >> 3);
             }
         } else {
-            uint32_t lz = RAPIDJSON_CLZLL(low);
+            uint32_t lz = internal::clzll(low);
             return p + (lz >> 3);
         }
     }
@@ -486,11 +486,11 @@ inline const char *SkipWhitespace_SIMD(const char* p, const char* end) {
 
         if (low == 0) {
             if (high != 0) {
-                uint32_t lz = RAPIDJSON_CLZLL(high);
+                uint32_t lz = internal::clzll(high);
                 return p + 8 + (lz >> 3);
             }
         } else {
-            uint32_t lz = RAPIDJSON_CLZLL(low);
+            uint32_t lz = internal::clzll(low);
             return p + (lz >> 3);
         }
     }
@@ -1257,12 +1257,12 @@ class GenericReader {
             bool escaped = false;
             if (low == 0) {
                 if (high != 0) {
-                    uint32_t lz = RAPIDJSON_CLZLL(high);
+                    uint32_t lz = internal::clzll(high);
                     length = 8 + (lz >> 3);
                     escaped = true;
                 }
             } else {
-                uint32_t lz = RAPIDJSON_CLZLL(low);
+                uint32_t lz = internal::clzll(low);
                 length = lz >> 3;
                 escaped = true;
             }
@@ -1327,12 +1327,12 @@ class GenericReader {
             bool escaped = false;
             if (low == 0) {
                 if (high != 0) {
-                    uint32_t lz = RAPIDJSON_CLZLL(high);
+                    uint32_t lz = internal::clzll(high);
                     length = 8 + (lz >> 3);
                     escaped = true;
                 }
             } else {
-                uint32_t lz = RAPIDJSON_CLZLL(low);
+                uint32_t lz = internal::clzll(low);
                 length = lz >> 3;
                 escaped = true;
             }
@@ -1381,12 +1381,12 @@ class GenericReader {
 
             if (low == 0) {
                 if (high != 0) {
-                    uint32_t lz = RAPIDJSON_CLZLL(high);
+                    uint32_t lz = internal::clzll(high);
                     p += 8 + (lz >> 3);
                     break;
                 }
             } else {
-                uint32_t lz = RAPIDJSON_CLZLL(low);
+                uint32_t lz = internal::clzll(low);
                 p += lz >> 3;
                 break;
             }

include/rapidjson/writer.h

@@ -676,12 +676,12 @@ inline bool Writer<StringBuffer>::ScanWriteUnescapedString(StringStream& is, siz
         bool escaped = false;
         if (low == 0) {
             if (high != 0) {
-                uint32_t lz = RAPIDJSON_CLZLL(high);
+                uint32_t lz = internal::clzll(high);
                 len = 8 + (lz >> 3);
                 escaped = true;
             }
         } else {
-            uint32_t lz = RAPIDJSON_CLZLL(low);
+            uint32_t lz = internal::clzll(low);
             len = lz >> 3;
             escaped = true;
         }