compiler: ensure evaluation order in type hash/eq functions

    
    The type hash and equality functions are generated after the
    order_evaluations pass. They may contain shortcut operators and
    Set_and_use_temporary_expressions (e.g. from lowering a
    Binary_exprssion) that need to be ordered. Run order_evaluations
    and remove_shortcuts on these functions. (The hash functions
    may be fine, but to be on the safe side we run on them anyway.
    We do need to run on the equality functions.)
    
    A Set_and_use_temporary_expression is effectively an assignment,
    so it needs to be ordered. Otherwise if we insert a temporary
    statement before it, we may get wrong evaluation order.
    
    A test case is CL 185818.
    
    Fixes golang/go#33062.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/185817

From-SVN: r273425

gcc/go/gofrontend/MERGE

-ec754ff4617d564d3dc377121ea9ac5e55f6535a
+70ceba5e95716653b9f829a457a44a829175d4da
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.h

@@ -1628,6 +1628,10 @@ class Set_and_use_temporary_expression : public Expression
   }
 
   bool
+  do_must_eval_in_order() const
+  { return true; }
+
+  bool
   do_is_addressable() const
   { return true; }
 

gcc/go/gofrontend/gogo.cc

@@ -4097,6 +4097,15 @@ Gogo::order_evaluations()
   this->traverse(&order_eval);
 }
 
+// Order evaluations in a block.
+
+void
+Gogo::order_block(Block* block)
+{
+  Order_eval order_eval(this);
+  block->traverse(&order_eval);
+}
+
 // A traversal class used to find a single shortcut operator within an
 // expression.
 
@@ -4306,6 +4315,15 @@ Gogo::remove_shortcuts()
   this->traverse(&shortcuts);
 }
 
+// Turn shortcut operators into explicit if statements in a block.
+
+void
+Gogo::remove_shortcuts_in_block(Block* block)
+{
+  Shortcuts shortcuts(this);
+  block->traverse(&shortcuts);
+}
+
 // Traversal to flatten parse tree after order of evaluation rules are applied.
 
 class Flatten : public Traverse

gcc/go/gofrontend/gogo.h

@@ -749,10 +749,18 @@ class Gogo
   void
   remove_shortcuts();
 
+  // Turn short-cut operators into explicit if statements in a block.
+  void
+  remove_shortcuts_in_block(Block*);
+
   // Use temporary variables to force order of evaluation.
   void
   order_evaluations();
 
+  // Order evaluations in a block.
+  void
+  order_block(Block*);
+
   // Add write barriers as needed.
   void
   add_write_barriers();

gcc/go/gofrontend/types.cc

@@ -2098,6 +2098,8 @@ Type::write_specific_type_functions(Gogo* gogo, Named_type* name, int64_t size,
   Block* b = gogo->finish_block(bloc);
   gogo->add_block(b, bloc);
   gogo->lower_block(hash_fn, b);
+  gogo->order_block(b);
+  gogo->remove_shortcuts_in_block(b);
   gogo->finish_function(bloc);
 
   Named_object *equal_fn = gogo->start_function(equal_name, equal_fntype,
@@ -2119,6 +2121,8 @@ Type::write_specific_type_functions(Gogo* gogo, Named_type* name, int64_t size,
   b = gogo->finish_block(bloc);
   gogo->add_block(b, bloc);
   gogo->lower_block(equal_fn, b);
+  gogo->order_block(b);
+  gogo->remove_shortcuts_in_block(b);
   gogo->finish_function(bloc);
 
   // Build the function descriptors for the type descriptor to refer to.