Smaller and faster sqlite3IsNaN() implementation makes deserialization of

floating point values much faster.

FossilOrigin-Name: ea748edecb261f2b862d542daff6e99a6fd8879a8ace94b440d99e110577d1c1

3 files changed, 9 insertions, 41 deletions

diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 24fabe627..542200795 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3802,8 +3802,12 @@ void sqlite3MutexWarnOnContention(sqlite3_mutex*);
 #endif
 
 #ifndef SQLITE_OMIT_FLOATING_POINT
+# define EXP754 (((u64)0x7ff)<<52)
+# define MAN754 ((((u64)1)<<52)-1)
+# define IsNaN(X) (((X)&EXP754)==EXP754 && ((X)&MAN754)!=0)
   int sqlite3IsNaN(double);
 #else
+# define IsNaN(X)         0
 # define sqlite3IsNaN(X)  0
 #endif
 
diff --git a/src/util.c b/src/util.c
index 938b6a9fb..31c88046e 100644
--- a/src/util.c
+++ b/src/util.c
@@ -58,47 +58,11 @@ int sqlite3FaultSim(int iTest){
 #ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Return true if the floating point value is Not a Number (NaN).
-**
-** Use the math library isnan() function if compiled with SQLITE_HAVE_ISNAN.
-** Otherwise, we have our own implementation that works on most systems.
 */
 int sqlite3IsNaN(double x){
-  int rc;   /* The value return */
-#if !SQLITE_HAVE_ISNAN && !HAVE_ISNAN
-  /*
-  ** Systems that support the isnan() library function should probably
-  ** make use of it by compiling with -DSQLITE_HAVE_ISNAN.  But we have
-  ** found that many systems do not have a working isnan() function so
-  ** this implementation is provided as an alternative.
-  **
-  ** This NaN test sometimes fails if compiled on GCC with -ffast-math.
-  ** On the other hand, the use of -ffast-math comes with the following
-  ** warning:
-  **
-  **      This option [-ffast-math] should never be turned on by any
-  **      -O option since it can result in incorrect output for programs
-  **      which depend on an exact implementation of IEEE or ISO 
-  **      rules/specifications for math functions.
-  **
-  ** Under MSVC, this NaN test may fail if compiled with a floating-
-  ** point precision mode other than /fp:precise.  From the MSDN 
-  ** documentation:
-  **
-  **      The compiler [with /fp:precise] will properly handle comparisons 
-  **      involving NaN. For example, x != x evaluates to true if x is NaN 
-  **      ...
-  */
-#ifdef __FAST_MATH__
-# error SQLite will not work correctly with the -ffast-math option of GCC.
-#endif
-  volatile double y = x;
-  volatile double z = y;
-  rc = (y!=z);
-#else  /* if HAVE_ISNAN */
-  rc = isnan(x);
-#endif /* HAVE_ISNAN */
-  testcase( rc );
-  return rc;
+  u64 y;
+  memcpy(&y,&x,sizeof(y));
+  return IsNaN(y);
 }
 #endif /* SQLITE_OMIT_FLOATING_POINT */
 
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 98c50f362..8dd2b421a 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -3652,7 +3652,7 @@ u32 sqlite3VdbeSerialPut(u8 *buf, Mem *pMem, u32 serial_type){
 ** routine so that in most cases the overhead of moving the stack pointer
 ** is avoided.
 */ 
-static u32 SQLITE_NOINLINE serialGet(
+static u32 serialGet(
   const unsigned char *buf,     /* Buffer to deserialize from */
   u32 serial_type,              /* Serial type to deserialize */
   Mem *pMem                     /* Memory cell to write value into */
@@ -3684,7 +3684,7 @@ static u32 SQLITE_NOINLINE serialGet(
     assert( sizeof(x)==8 && sizeof(pMem->u.r)==8 );
     swapMixedEndianFloat(x);
     memcpy(&pMem->u.r, &x, sizeof(x));
-    pMem->flags = sqlite3IsNaN(pMem->u.r) ? MEM_Null : MEM_Real;
+    pMem->flags = IsNaN(x) ? MEM_Null : MEM_Real;
   }
   return 8;
 }