compiler: introduce size threshold for nil checks

    
    Add a new control variable to the Gogo class that stores the size
    threshold for nil checks. This value can be used to control the
    policy for deciding when a given deference operation needs a check and
    when it does not. A size threshold of -1 means that every potentially
    faulting dereference needs an explicit check (and branch to error
    call). A size threshold of K (where K > 0) means that if the size of
    the object being dereferenced is >= K, then we need a check.
    
    Reviewed-on: https://go-review.googlesource.com/80996

	* go-c.h (go_create_gogo_args): Add nil_check_size_threshold
	field.
	* go-lang.c (go_langhook_init): Set nil_check_size_threshold.

From-SVN: r255340

1 files changed, 5 insertions, 2 deletions

diff --git a/gcc/go/gofrontend/parse.cc b/gcc/go/gofrontend/parse.cc
index f7d53af..be6f3f1 100644
--- a/gcc/go/gofrontend/parse.cc
+++ b/gcc/go/gofrontend/parse.cc
@@ -2745,14 +2745,17 @@ Parse::enclosing_var_reference(Named_object* in_function, Named_object* var,
 
   Expression* closure_ref = Expression::make_var_reference(closure,
 							   location);
-  closure_ref = Expression::make_unary(OPERATOR_MULT, closure_ref, location);
+  closure_ref =
+      Expression::make_dereference(closure_ref,
+                                   Expression::NIL_CHECK_DEFAULT,
+                                   location);
 
   // The closure structure holds pointers to the variables, so we need
   // to introduce an indirection.
   Expression* e = Expression::make_field_reference(closure_ref,
 						   ins.first->index(),
 						   location);
-  e = Expression::make_unary(OPERATOR_MULT, e, location);
+  e = Expression::make_dereference(e, Expression::NIL_CHECK_DEFAULT, location);
   return Expression::make_enclosing_var_reference(e, var, location);
 }