[builtins] Use __builtin_clzll for 64-bit types

This addresses the issue with __LP64__ not being defined for targets
with 32-bit pointers but 64-bit longs, resulting in worse codegen.

Author: s-barannikov

compiler-rt/lib/builtins/fp_extend.h

@@ -38,14 +38,7 @@ static const int srcSigFracBits = 52;
 static const int srcExpBits = 11;
 
 static inline int src_rep_t_clz_impl(src_rep_t a) {
-#if defined __LP64__
-  return __builtin_clzl(a);
-#else
-  if (a & REP_C(0xffffffff00000000))
-    return clzsi(a >> 32);
-  else
-    return 32 + clzsi(a & REP_C(0xffffffff));
-#endif
+  return __builtin_clzll(a);
 }
 #define src_rep_t_clz src_rep_t_clz_impl
 

compiler-rt/lib/builtins/fp_lib.h

@@ -58,15 +58,8 @@ typedef double fp_t;
 #define REP_C UINT64_C
 #define significandBits 52
 
-static __inline int rep_clz(rep_t a) {
-#if defined __LP64__
-  return __builtin_clzl(a);
-#else
-  if (a & REP_C(0xffffffff00000000))
-    return clzsi(a >> 32);
-  else
-    return 32 + clzsi(a & REP_C(0xffffffff));
-#endif
+static inline int rep_clz(rep_t a) {
+  return __builtin_clzll(a);
 }
 
 #define loWord(a) (a & 0xffffffffU)