Use new overflow aware integer operations.

A previous commit added inline functions that provide fast(er) and
correct overflow checks for signed integer math. Use them in a
significant portion of backend code.  There's more to touch in both
backend and frontend code, but these were the easily identifiable
cases.

The old overflow checks are noticeable in integer heavy workloads.

A secondary benefit is that getting rid of overflow checks that rely
on signed integer overflow wrapping around, will allow us to get rid
of -fwrapv in the future. Which in turn slows down other code.

Author: Andres Freund
Discussion: https://postgr.es/m/20171024103954.ztmatprlglz3rwke@alap3.anarazel.de

1 files changed, 19 insertions, 20 deletions

diff --git a/src/backend/utils/adt/cash.c b/src/backend/utils/adt/cash.c
index 7bbc634bd2b..c787dd34191 100644
--- a/src/backend/utils/adt/cash.c
+++ b/src/backend/utils/adt/cash.c
@@ -22,6 +22,7 @@
 #include <ctype.h>
 #include <math.h>
 
+#include "common/int.h"
 #include "libpq/pqformat.h"
 #include "utils/builtins.h"
 #include "utils/cash.h"
@@ -199,20 +200,21 @@ cash_in(PG_FUNCTION_ARGS)
 
 	for (; *s; s++)
 	{
-		/* we look for digits as long as we have found less */
-		/* than the required number of decimal places */
+		/*
+		 * We look for digits as long as we have found less than the required
+		 * number of decimal places.
+		 */
 		if (isdigit((unsigned char) *s) && (!seen_dot || dec < fpoint))
 		{
-			Cash		newvalue = (value * 10) - (*s - '0');
+			int8		digit = *s - '0';
 
-			if (newvalue / 10 != value)
+			if (pg_mul_s64_overflow(value, 10, &value) ||
+				pg_sub_s64_overflow(value, digit, &value))
 				ereport(ERROR,
 						(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 						 errmsg("value \"%s\" is out of range for type %s",
 								str, "money")));
 
-			value = newvalue;
-
 			if (seen_dot)
 				dec++;
 		}
@@ -230,26 +232,23 @@ cash_in(PG_FUNCTION_ARGS)
 
 	/* round off if there's another digit */
 	if (isdigit((unsigned char) *s) && *s >= '5')
-		value--;				/* remember we build the value in the negative */
-
-	if (value > 0)
-		ereport(ERROR,
-				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
-				 errmsg("value \"%s\" is out of range for type %s",
-						str, "money")));
+	{
+		/* remember we build the value in the negative */
+		if (pg_sub_s64_overflow(value, 1, &value))
+			ereport(ERROR,
+					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+					 errmsg("value \"%s\" is out of range for type %s",
+							str, "money")));
+	}
 
 	/* adjust for less than required decimal places */
 	for (; dec < fpoint; dec++)
 	{
-		Cash		newvalue = value * 10;
-
-		if (newvalue / 10 != value)
+		if (pg_mul_s64_overflow(value, 10, &value))
 			ereport(ERROR,
 					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 					 errmsg("value \"%s\" is out of range for type %s",
 							str, "money")));
-
-		value = newvalue;
 	}
 
 	/*
@@ -285,12 +284,12 @@ cash_in(PG_FUNCTION_ARGS)
 	 */
 	if (sgn > 0)
 	{
-		result = -value;
-		if (result < 0)
+		if (value == PG_INT64_MIN)
 			ereport(ERROR,
 					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 					 errmsg("value \"%s\" is out of range for type %s",
 							str, "money")));
+		result = -value;
 	}
 	else
 		result = value;