[PATCH] PPC JIT failure for t/pmc/threads_8.pasm

[Jeff Clites]

I was getting a failure under JIT on PPC for t/pmc/threads_8.pasm, and 
the problem turned out to be that emitting a restart op takes 26 
instructions, or 104 bytes, and we were hitting the grow-the-arena 
logic just shy of what would have triggered a resize, then running off 
the end.

The below patch fixes this; really that magic number (200, now) needs 
to be bigger than the amount of space we'd ever need to emit the JIT 
code for a single op (plus saving registers and such), but with the 
possibility of dynamically loadable op libs (with JIT?), it's hard to 
say what number is guaranteed to be large enough. Or, we can pick a 
reasonable, largish number that works for the built-in ops (empirically 
determined, as now), and document that loadable JITted ops which could 
take more than this, need to make sure to grow the arena as necessary. 
(And we could provide a utility function to make this easy.)

JEff
Index: src/jit.c
===================================================================
RCS file: /cvs/public/parrot/src/jit.c,v
retrieving revision 1.95
diff -u -b -r1.95 jit.c
--- src/jit.c   25 Oct 2004 10:24:14 -0000      1.95
+++ src/jit.c   29 Oct 2004 07:50:09 -0000
@@ -1395,7 +1395,7 @@
         while (cur_op <= cur_section->end) {
             /* Grow the arena early */
             if (jit_info->arena.size <
-                    (jit_info->arena.op_map[jit_info->op_i].offset + 
100)) {
+                    (jit_info->arena.op_map[jit_info->op_i].offset + 
200)) {
 #if REQUIRES_CONSTANT_POOL
                 Parrot_jit_extend_arena(jit_info);
 #else