Go patch committed: Don't make temporaries for constant operands

[Ian Lance Taylor]

This patch by Chris Manghane changes the Go frontend to not make
temporaries for constant operands in binary expressions.  This fixes
https://golang.org/issue/12616 .  Bootstrapped and ran Go testsuite on
x86_64-unknown-linux-gnu.  Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 228576)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-651e71a729e5dcbd9dc14c1b59b6eff05bfe3d26
+a4bcd319d98ddc52b3e7d16ec87d92aad868ab05
 
 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 228306)
+++ gcc/go/gofrontend/expressions.cc    (working copy)
@@ -5200,13 +5200,13 @@ Binary_expression::do_flatten(Gogo* gogo
       || (is_idiv_op
          && (gogo->check_divide_by_zero() || gogo->check_divide_overflow())))
     {
-      if (!this->left_->is_variable())
+      if (!this->left_->is_variable() && !this->left_->is_constant())
         {
           temp = Statement::make_temporary(NULL, this->left_, loc);
           inserter->insert(temp);
           this->left_ = Expression::make_temporary_reference(temp, loc);
         }
-      if (!this->right_->is_variable())
+      if (!this->right_->is_variable() && !this->right_->is_constant())
         {
           temp =
               Statement::make_temporary(NULL, this->right_, loc);