Explain what commute-flonum-predicate is doing.

diff --git a/src/compiler/machines/x86-64/rulflo.scm b/src/compiler/machines/x86-64/rulflo.scm
index 3cdebd19676eb5da6f4134642a7b4a75fe8023f8..c0ad9be809b73959cd12f2c5ee751ee57db8d1ab 100644 (file)
--- a/src/compiler/machines/x86-64/rulflo.scm
+++ b/src/compiler/machines/x86-64/rulflo.scm
@@ -318,6 +318,10 @@ USA.
                       (flonum-source-reference! source)
                       operand))))
 
+;;; For predicate giving (if (predicate x y) a b), return the
+;;; equivalent (if (predicate* y x) a b).  The unary predicates are
+;;; treated as if y = 0.  (XXX Separate this into another function.)
+
 (define (commute-flonum-predicate predicate)
   (case predicate
     ((FLONUM-EQUAL? FLONUM-ZERO?) 'FLONUM-EQUAL?)