Factor out the common subexpression month_remainder * DAYS_PER_MONTH

in interval_mul and interval_div.  This avoids an optimization bug
in A Certain Company's compiler (and given their explanation, I wouldn't
be surprised if other compilers blow it too).  Besides the code seems
more clear this way --- in the original formulation, you had to mentally
recognize the common subexpression in order to understand what was going
on.

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index c218422a79799311fdefea3bb020b233cbc79cde..2b15e64e06172a6c0b21b4bc379b67baab3dd86d 100644 (file)
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.150 2005/08/25 03:53:22 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.151 2005/08/25 05:01:43 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2262,7 +2262,7 @@ interval_mul(PG_FUNCTION_ARGS)
 {
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    float8      factor = PG_GETARG_FLOAT8(1);
-   double      month_remainder, day_remainder;
+   double      month_remainder, day_remainder, month_remainder_days;
    Interval   *result;
 
    result = (Interval *) palloc(sizeof(Interval));
@@ -2276,17 +2276,15 @@ interval_mul(PG_FUNCTION_ARGS)
 
    /* Cascade fractions to lower units */
    /* fractional months full days into days */
-   result->day += month_remainder * DAYS_PER_MONTH;
+   month_remainder_days = month_remainder * DAYS_PER_MONTH;
+   result->day += month_remainder_days;
    /* fractional months partial days into time */
-   day_remainder += (month_remainder * DAYS_PER_MONTH) -
-                    (int)(month_remainder * DAYS_PER_MONTH);
+   day_remainder += month_remainder_days - (int) month_remainder_days;
 
 #ifdef HAVE_INT64_TIMESTAMP
-   result->time = rint(span->time * factor +
-                   day_remainder * USECS_PER_DAY);
+   result->time = rint(span->time * factor + day_remainder * USECS_PER_DAY);
 #else
-   result->time = JROUND(span->time * factor +
-                   day_remainder * SECS_PER_DAY);
+   result->time = JROUND(span->time * factor + day_remainder * SECS_PER_DAY);
 #endif
 
    result = DatumGetIntervalP(DirectFunctionCall1(interval_justify_hours,
@@ -2309,7 +2307,7 @@ interval_div(PG_FUNCTION_ARGS)
 {
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    float8      factor = PG_GETARG_FLOAT8(1);
-   double      month_remainder, day_remainder;
+   double      month_remainder, day_remainder, month_remainder_days;
    Interval   *result;
 
    result = (Interval *) palloc(sizeof(Interval));
@@ -2329,10 +2327,10 @@ interval_div(PG_FUNCTION_ARGS)
 
    /* Cascade fractions to lower units */
    /* fractional months full days into days */
-   result->day += month_remainder * DAYS_PER_MONTH;
+   month_remainder_days = month_remainder * DAYS_PER_MONTH;
+   result->day += month_remainder_days;
    /* fractional months partial days into time */
-   day_remainder += (month_remainder * DAYS_PER_MONTH) -
-                    (int)(month_remainder * DAYS_PER_MONTH);
+   day_remainder += month_remainder_days - (int) month_remainder_days;
 
 #ifdef HAVE_INT64_TIMESTAMP
    result->time += rint(day_remainder * USECS_PER_DAY);