[GH #837] Honor encoding in imcc optimizer

Context registers unfortunately do not store type information,
just the values. We would need at least type 'U" here.
So recreate an proper const'ed encoding string from the register
value.

compilers/imcc/optimizer.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2002-2010, Parrot Foundation.
+ * Copyright (C) 2002-2012, Parrot Foundation.
  */
 
 /*
@@ -1070,13 +1070,15 @@ IMCC_subst_constants(ARGMOD(imc_info_t *imcc), ARGMOD(IMC_Unit *unit),
           case 'S':
           {
             char * const cstr = Parrot_str_to_cstring(imcc->interp, REG_STR(imcc->interp, 0));
-
-            r[1] = mk_const(imcc, cstr, r[0]->set);
-
-            snprintf(b, sizeof (b), "%p", REG_STR(imcc->interp, 0));
+            const STR_VTABLE* encoding = REG_STR(imcc->interp, 0)->encoding;
+            if (encoding == Parrot_ascii_encoding_ptr) {
+                r[1] = mk_const(imcc, cstr, r[0]->set);
+            }
+            else {
+                snprintf(b, sizeof (b), "%s:\"%s\"", encoding->name, cstr);
+                r[1] = mk_const(imcc, b, 'U');
+            }
             Parrot_str_free_cstring(cstr);
-
-            break;
           }
           default:
             break;

src/string/api.c

@@ -700,7 +700,7 @@ STRING *encodingname)>
 Given a buffer and an encoding, creates and returns a new string. If buffer is
 NULL the result is a null string. Otherwise, the buffer should be a zero
 terminated c-style string and its content must be valid for the encoding
-specified. If encoding is null, assume plaftorm encoding.
+specified. If encoding is null, assume platform encoding.
 
 =cut
 

t/op/stringu.t

@@ -22,8 +22,11 @@ Tests Parrot unicode string system.
 
 =cut
 
-pir_output_is(<<'CODE',<<'OUTPUT', 'concat utf8 GH#837');
+pir_output_is(<<'CODE',<<'OUTPUT', 'non-ascii immc optimizer GH#837');
 .sub main
+    $S1 = utf8:"\x{a2}"
+    say $S1
+
     concat $S1, unicode:"\x{a2}", unicode:"\x{a2}"
     say $S1
 
@@ -34,6 +37,7 @@ pir_output_is(<<'CODE',<<'OUTPUT', 'concat utf8 GH#837');
     say $S3
 .end
 CODE
+¢
 ¢¢
 ¢c
 bb