Improve performance of float overflow checks in btree_gist

The current code could do unnecessary calls to isinf() (two for the
argument values all the time while one could be sufficient in some
cases).  zero_is_valid was never used but the result value was still
checked on 0 in the first position of the check.

This is similar to 607f8ce.  btree_gist has just copy-pasted the code
doing those checks from the backend float4/8 code, as of the macro
CHECKFLOATVAL(), to do the work.

Author: Haiying Tang
Discussion: https://postgr.es/m/OS0PR01MB611358E3A7BC3C2F874AC36BFBF39@OS0PR01MB6113.jpnprd01.prod.outlook.com

contrib/btree_gist/btree_float4.c

@@ -5,6 +5,7 @@
 
 #include "btree_gist.h"
 #include "btree_utils_num.h"
+#include "utils/float.h"
 
 typedef struct float4key
 {
@@ -98,7 +99,8 @@ float4_dist(PG_FUNCTION_ARGS)
 	float4		r;
 
 	r = a - b;
-	CHECKFLOATVAL(r, isinf(a) || isinf(b), true);
+	if (unlikely(isinf(r)) && !isinf(a) && !isinf(b))
+		float_overflow_error();
 
 	PG_RETURN_FLOAT4(Abs(r));
 }

contrib/btree_gist/btree_float8.c

@@ -5,6 +5,7 @@
 
 #include "btree_gist.h"
 #include "btree_utils_num.h"
+#include "utils/float.h"
 
 typedef struct float8key
 {
@@ -76,8 +77,8 @@ gbt_float8_dist(const void *a, const void *b, FmgrInfo *flinfo)
 	float8		r;
 
 	r = arg1 - arg2;
-	CHECKFLOATVAL(r, isinf(arg1) || isinf(arg2), true);
-
+	if (unlikely(isinf(r)) && !isinf(arg1) && !isinf(arg2))
+		float_overflow_error();
 	return Abs(r);
 }
 
@@ -106,7 +107,8 @@ float8_dist(PG_FUNCTION_ARGS)
 	float8		r;
 
 	r = a - b;
-	CHECKFLOATVAL(r, isinf(a) || isinf(b), true);
+	if (unlikely(isinf(r)) && !isinf(a) && !isinf(b))
+		float_overflow_error();
 
 	PG_RETURN_FLOAT8(Abs(r));
 }

contrib/btree_gist/btree_utils_num.h

@@ -89,23 +89,6 @@ typedef struct
 
 #define GET_FLOAT_DISTANCE(t, arg1, arg2)	Abs( ((float8) *((const t *) (arg1))) - ((float8) *((const t *) (arg2))) )
 
-/*
- * check to see if a float4/8 val has underflowed or overflowed
- * borrowed from src/backend/utils/adt/float.c
- */
-#define CHECKFLOATVAL(val, inf_is_valid, zero_is_valid)			\
-do {															\
-	if (isinf(val) && !(inf_is_valid))							\
-		ereport(ERROR,											\
-				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),	\
-		  errmsg("value out of range: overflow")));				\
-																\
-	if ((val) == 0.0 && !(zero_is_valid))						\
-		ereport(ERROR,											\
-				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),	\
-		 errmsg("value out of range: underflow")));				\
-} while(0)
-
 
 extern Interval *abs_interval(Interval *a);