Implement if, for (modulo ranges), break, continue, increment,

and decrement.  blockCompilers now form a tree the mimics the
nesting of scopes and provide convenient ways to enter and
exit scopes.  blockCompilers also track the break and continue
PC for the current block.  The statement testing interface now
works in lists of statements, which simplifies a bunch of
things.

R=rsc
APPROVED=rsc
DELTA=401  (335 added, 44 deleted, 22 changed)
OCL=32308
CL=32317

1 files changed, 4 insertions, 0 deletions

diff --git a/usr/austin/eval/func.go b/usr/austin/eval/func.go
index 29bc05b22..cc790452b 100644
--- a/usr/austin/eval/func.go
+++ b/usr/austin/eval/func.go
@@ -62,6 +62,10 @@ func (b *codeBuf) push(instr func(*vm)) {
 	b.instrs[n] = instr;
 }
 
+func (b *codeBuf) nextPC() uint {
+	return uint(len(b.instrs));
+}
+
 func (b *codeBuf) get() code {
 	// Freeze this buffer into an array of exactly the right size
 	a := make(code, len(b.instrs));