compiler: revert `for package-scope "a = b; b = x" just set "a = x"`

Revert CL 245098.  It caused incorrect initialization ordering.

Adjust the runtime package to work even with the CL reverted.

Original description of CL 245098:

    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.

For golang/go#51913

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/395994

2 files changed, 8 insertions, 31 deletions

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 75ee2e3..bcb526c 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-323ab0e6fab89978bdbd83dca9c2ad9c5dcd690f
+62fc90f52da2f52cbe3b4f10e560dc6aa59baeb5
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/gogo.cc b/gcc/go/gofrontend/gogo.cc
index 30d5c9f..d35c6ba 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -1612,31 +1612,16 @@ Gogo::write_globals()
               // 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.
-	      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)
+              bool is_static_initializer = false;
+              if (var->init() == NULL)
                 is_static_initializer = true;
               else
                 {
                   Type* var_type = var->type();
-                  init = Expression::make_cast(var_type, init, var->location());
-                  is_static_initializer = init->is_static_initializer();
+                  Expression* init = var->init();
+                  Expression* init_cast =
+                      Expression::make_cast(var_type, init, var->location());
+                  is_static_initializer = init_cast->is_static_initializer();
                 }
 
 	      // Non-constant variable initializations might need to create
@@ -1655,15 +1640,7 @@ Gogo::write_globals()
                     }
 		  var_init_fn = init_fndecl;
 		}
-
-	      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);
-		}
+              Bexpression* var_binit = var->get_init(this, var_init_fn);
 
               if (var_binit == NULL)
 		;