[perl #16308] [PATCH] logical right shift

[via RT]

# New Ticket Created by  Jason Gloudon 
# Please include the string:  [perl #16308]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=16308 >



This adds logical shift right opcodes. They are essential for bit shifting
negative values without sign extension getting in the way.

-- 
Jason


-- attachment  1 ------------------------------------------------------
url: http://rt.perl.org/rt2/attach/34429/28142/d00f4b/lsr.diff


Index: core.ops
===================================================================
RCS file: /cvs/public/parrot/core.ops,v
retrieving revision 1.199
diff -u -r1.199 core.ops
--- core.ops    18 Aug 2002 23:57:37 -0000      1.199
+++ core.ops    19 Aug 2002 21:12:45 -0000
@@ -2854,6 +2854,19 @@
 
 ########################################
 
+=item B<lsr>(out INT, in INT, in INT)
+
+Set $1 to the value of $2 logically shifted right by $3 bits.
+
+=cut
+
+inline op lsr(out INT, in INT, in INT) {
+  $1 = (INTVAL)((UINTVAL)$2 >> $3);
+  goto NEXT();
+}
+
+########################################
+
 =item B<bxor>(inout INT, in INT)
 
 =item B<bxor>(inout PMC, in INT)
Index: t/op/bitwise.t
===================================================================
RCS file: /cvs/public/parrot/t/op/bitwise.t,v
retrieving revision 1.5
diff -u -r1.5 bitwise.t
--- t/op/bitwise.t      27 Jul 2002 20:18:12 -0000      1.5
+++ t/op/bitwise.t      19 Aug 2002 21:12:46 -0000
@@ -1,6 +1,6 @@
 #perl -w
 
-use Parrot::Test tests => 18;
+use Parrot::Test tests => 20;
 
 output_is(<<'CODE', <<'OUTPUT', "shr_i_i (>>)");
        set I0, 0b001100
@@ -70,6 +70,37 @@
 CODE
 6
 5
+OUTPUT
+
+# The crux of this test is that a proper logical right shift 
+# will clear the most significant bit, so the shifted value 
+# will be a positive value on any 2's or 1's complement CPU
+output_is(<<'CODE', <<'OUTPUT', "lsr_ic_ic (<<)");
+       lsr I2, -40, 1
+       lt I2, 0, BAD
+       print "OK\n"
+       end
+BAD:
+       print "Not OK"
+       print "\n"
+       end
+CODE
+OK
+OUTPUT
+
+output_is(<<'CODE', <<'OUTPUT', "lsr_i_i (<<)");
+       set I0, -40
+       set I1, 1
+       lsr I2, I0, I1
+       lt I2, 0, BAD
+       print "OK\n"
+       end
+BAD:
+       print "Not OK"
+       print "\n"
+       end
+CODE
+OK
 OUTPUT
 
 output_is(<<'CODE', <<'OUTPUT', "shl_i_i (<<)");