Go patch committed: More lvalue marking fixes

[Ian Lance Taylor]

This patch to the Go frontend by Than McIntosh fixes an lvalue/rvalue
context mixup Set_and_use_temporary_expression's do_get_backend()
method, and enhances Mark_lvalue_varexprs to handle conversions and
temporary reference expressions, since occasionally the front end
emits code such as "deref(conv(tempref)) = ...".  Bootstrapped and ran
Go testsuite on x86_64-pc-linux-gnu.  Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 249033)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-82961ce59e8bb02598d963d2a05b3acca860d9dd
+d4875b19266d5f726e0e32843b903075f5c50b4c
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/expressions.cc
===================================================================
--- gcc/go/gofrontend/expressions.cc    (revision 249029)
+++ gcc/go/gofrontend/expressions.cc    (working copy)
@@ -962,7 +962,7 @@ Set_and_use_temporary_expression::do_get
   Location loc = this->location();
   Gogo* gogo = context->gogo();
   Bvariable* bvar = this->statement_->get_backend_variable(context);
-  Bexpression* lvar_ref = gogo->backend()->var_expression(bvar, VE_rvalue, 
loc);
+  Bexpression* lvar_ref = gogo->backend()->var_expression(bvar, VE_lvalue, 
loc);
 
   Named_object* fn = context->function();
   go_assert(fn != NULL);
@@ -970,7 +970,7 @@ Set_and_use_temporary_expression::do_get
   Bexpression* bexpr = this->expr_->get_backend(context);
   Bstatement* set = gogo->backend()->assignment_statement(bfn, lvar_ref,
                                                           bexpr, loc);
-  Bexpression* var_ref = gogo->backend()->var_expression(bvar, VE_lvalue, loc);
+  Bexpression* var_ref = gogo->backend()->var_expression(bvar, VE_rvalue, loc);
   Bexpression* ret = gogo->backend()->compound_expression(set, var_ref, loc);
   return ret;
 }
Index: gcc/go/gofrontend/statements.cc
===================================================================
--- gcc/go/gofrontend/statements.cc     (revision 249028)
+++ gcc/go/gofrontend/statements.cc     (working copy)
@@ -912,6 +912,21 @@ int Mark_lvalue_varexprs::expression(Exp
   if (ue && ue->op() == OPERATOR_MULT)
     return TRAVERSE_CONTINUE;
 
+  Type_conversion_expression* ce = e->conversion_expression();
+  if (ce)
+    return TRAVERSE_CONTINUE;
+
+  Temporary_reference_expression* tre =
+      e->temporary_reference_expression();
+  if (tre)
+    {
+      tre = new Temporary_reference_expression(tre->statement(),
+                                               tre->location());
+      *ppexpr = tre;
+      tre->set_is_lvalue();
+      return TRAVERSE_EXIT;
+    }
+
   return TRAVERSE_EXIT;
 }