Try to optimize takedispatcher to cleardispatcher.

The latter is cheaper and simpler code. In many of the simple ops,
we do not make any kind of call, and thus could never call one of
the defering things (nextsame, etc.)

src/Perl6/Optimizer.nqp

@@ -414,6 +414,9 @@ my class BlockVarOptimizer {
     has @!autoslurpy_setups;
     has @!autoslurpy_binds;
 
+    # The takedispatcher operation.
+    has $!takedispatcher;
+
     # If lowering is, for some reason, poisoned.
     has $!poisoned;
 
@@ -449,6 +452,10 @@ my class BlockVarOptimizer {
         nqp::push(@!autoslurpy_binds, $node);
     }
 
+    method register_takedispatcher($node) {
+        $!takedispatcher := $node;
+    }
+
     method poison_lowering() { $!poisoned := 1; }
 
     method get_decls() { %!decls }
@@ -568,6 +575,15 @@ my class BlockVarOptimizer {
         }
     }
 
+    method simplify_takedispatcher() {
+        unless $!calls {
+            if $!takedispatcher {
+                $!takedispatcher.op('cleardispatcher');
+                $!takedispatcher.shift();
+            }
+        }
+    }
+
     method lexicals_to_locals() {
         return 0 if $!poisoned;
         for %!decls {
@@ -841,9 +857,10 @@ class Perl6::Optimizer {
         my $vars_info := @!block_var_stack.pop();
 
         # We might be able to delete some of the magical variables when they
-        # are trivially unused.
+        # are trivially unused, and also simplify takedispatcher.
         $vars_info.delete_unused_magicals($block);
         $vars_info.delete_unused_autoslurpy();
+        $vars_info.simplify_takedispatcher();
 
         # If the block is immediate, we may be able to inline it.
         my int $flattened := 0;
@@ -1031,6 +1048,11 @@ class Perl6::Optimizer {
             }
         }
 
+        # Make be able to simplify takedispatcher ops.
+        elsif $optype eq 'takedispatcher' {
+            @!block_var_stack[nqp::elems(@!block_var_stack) - 1].register_takedispatcher($op);
+        }
+
         # Calls are especially interesting as we may wish to do some
         # kind of inlining.
         elsif $optype eq 'call' && $op.name ne '' {

tools/build/NQP_REVISION

@@ -1 +1 @@
-2014.06-9-gd7f23d9
+2014.06-16-g32ddb22