compiler: for package-scope "a = b; b = x" just set "a = x"
This avoids requiring an init function to initialize the variable.
This can only be done if x is a static initializer.
The go1.15rc1 runtime package relies on this optimization.
The package has a variable "var maxSearchAddr = maxOffAddr".
The maxSearchAddr variable is used by code that runs before package
initialization is complete.
Change-Id: Ied19a6d06f44c0c3e69632960a85f8d32139095c
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/245098
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/go/gogo.cc b/go/gogo.cc
index c1021e5..4c8c55f 100644
--- a/go/gogo.cc
+++ b/go/gogo.cc
@@ -1622,16 +1622,31 @@
// The initializer is constant if it is the zero-value of the
// variable's type or if the initial value is an immutable value
// that is not copied to the heap.
- bool is_static_initializer = false;
- if (var->init() == NULL)
+ Expression* init = var->init();
+
+ // If we see "a = b; b = x", and x is a static
+ // initializer, just set a to x.
+ while (init != NULL && init->var_expression() != NULL)
+ {
+ Named_object* ino = init->var_expression()->named_object();
+ if (!ino->is_variable() || ino->package() != NULL)
+ break;
+ Expression* ino_init = ino->var_value()->init();
+ if (ino->var_value()->has_pre_init()
+ || ino_init == NULL
+ || !ino_init->is_static_initializer())
+ break;
+ init = ino_init;
+ }
+
+ bool is_static_initializer;
+ if (init == NULL)
is_static_initializer = true;
else
{
Type* var_type = var->type();
- Expression* init = var->init();
- Expression* init_cast =
- Expression::make_cast(var_type, init, var->location());
- is_static_initializer = init_cast->is_static_initializer();
+ init = Expression::make_cast(var_type, init, var->location());
+ is_static_initializer = init->is_static_initializer();
}
// Non-constant variable initializations might need to create
@@ -1650,7 +1665,15 @@
}
var_init_fn = init_fndecl;
}
- Bexpression* var_binit = var->get_init(this, var_init_fn);
+
+ Bexpression* var_binit;
+ if (init == NULL)
+ var_binit = NULL;
+ else
+ {
+ Translate_context context(this, var_init_fn, NULL, NULL);
+ var_binit = init->get_backend(&context);
+ }
if (var_binit == NULL)
;
