[gcc r12-1918] compiler: don't generate temporaries for composite literals

[gcc r12-1918] compiler: don't generate temporaries for composite literals

[Ian Lance Taylor]

https://gcc.gnu.org/g:13c906f43f473ee9ff16d80590789d719f2190a4

commit r12-1918-g13c906f43f473ee9ff16d80590789d719f2190a4
Author: Ian Lance Taylor <iant@golang.org>
Date:   Tue Jun 29 12:53:02 2021 -0700

    compiler: don't generate temporaries for composite literals
    
    We were generating temporaries for composite literals when a
    conversion to interface type was required.  However, Cherry's
    https://golang.org/cl/176459 changed the compiler to insert explicit
    type conversions.  And those explicit type conversions insert the
    required temporaries in Type_conversion_expression::do_flatten.
    So in practice the composite literal do_flatten methods would never
    insert temporaries, as the values they see would always be multi_eval_safe.
    So just remove the unnecessary do_flatten methods.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/331691

Diff:
---
 gcc/go/gofrontend/MERGE          |   2 +-
 gcc/go/gofrontend/expressions.cc | 103 +++------------------------------------
 gcc/go/gofrontend/expressions.h  |   6 ---
 3 files changed, 7 insertions(+), 104 deletions(-)

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index f7bcc8c484a..ab1384d698b 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-cad187fe3aceb2a7d964b64c70dfa8c8ad24ce65
+01cb2b5e69a2d08ef3cc1ea023c22ed9b79f5114
 
 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/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 94342b2f9b8..a0472acc209 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -15147,48 +15147,6 @@ Struct_construction_expression::do_copy()
   return ret;
 }
 
-// Flatten a struct construction expression.  Store the values into
-// temporaries if they may need interface conversion.
-
-Expression*
-Struct_construction_expression::do_flatten(Gogo*, Named_object*,
-					   Statement_inserter* inserter)
-{
-  if (this->vals() == NULL)
-    return this;
-
-  // If this is a constant struct, we don't need temporaries.
-  if (this->is_constant_struct() || this->is_static_initializer())
-    return this;
-
-  Location loc = this->location();
-  const Struct_field_list* fields = this->type_->struct_type()->fields();
-  Struct_field_list::const_iterator pf = fields->begin();
-  for (Expression_list::iterator pv = this->vals()->begin();
-       pv != this->vals()->end();
-       ++pv, ++pf)
-    {
-      go_assert(pf != fields->end());
-      if (*pv != NULL)
-	{
-          if ((*pv)->is_error_expression() || (*pv)->type()->is_error_type())
-            {
-              go_assert(saw_errors());
-              return Expression::make_error(loc);
-            }
-	  if (pf->type()->interface_type() != NULL
-	      && !(*pv)->is_multi_eval_safe())
-	    {
-	      Temporary_statement* temp =
-		Statement::make_temporary(NULL, *pv, loc);
-	      inserter->insert(temp);
-	      *pv = Expression::make_temporary_reference(temp, loc);
-	    }
-	}
-    }
-  return this;
-}
-
 // Make implicit type conversions explicit.
 
 void
@@ -15451,55 +15409,6 @@ Array_construction_expression::do_check_types(Gogo*)
     }
 }
 
-// Flatten an array construction expression.  Store the values into
-// temporaries if they may need interface conversion.
-
-Expression*
-Array_construction_expression::do_flatten(Gogo*, Named_object*,
-					   Statement_inserter* inserter)
-{
-  if (this->is_error_expression())
-    {
-      go_assert(saw_errors());
-      return this;
-    }
-
-  if (this->vals() == NULL)
-    return this;
-
-  // If this is a constant array, we don't need temporaries.
-  if (this->is_constant_array() || this->is_static_initializer())
-    return this;
-
-  // If the array element type is not an interface type, we don't need
-  // temporaries.
-  if (this->type_->array_type()->element_type()->interface_type() == NULL)
-    return this;
-
-  Location loc = this->location();
-  for (Expression_list::iterator pv = this->vals()->begin();
-       pv != this->vals()->end();
-       ++pv)
-    {
-      if (*pv != NULL)
-	{
-          if ((*pv)->is_error_expression() || (*pv)->type()->is_error_type())
-            {
-              go_assert(saw_errors());
-              return Expression::make_error(loc);
-            }
-	  if (!(*pv)->is_multi_eval_safe())
-	    {
-	      Temporary_statement* temp =
-		Statement::make_temporary(NULL, *pv, loc);
-	      inserter->insert(temp);
-	      *pv = Expression::make_temporary_reference(temp, loc);
-	    }
-	}
-    }
-  return this;
-}
-
 // Make implicit type conversions explicit.
 
 void
@@ -15768,14 +15677,14 @@ Slice_construction_expression::create_array_val()
 // the new temp statement.
 
 Expression*
-Slice_construction_expression::do_flatten(Gogo* gogo, Named_object* no,
+Slice_construction_expression::do_flatten(Gogo*, Named_object*,
                                           Statement_inserter* inserter)
 {
   if (this->type()->array_type() == NULL)
-    return NULL;
-
-  // Base class flattening first
-  this->Array_construction_expression::do_flatten(gogo, no, inserter);
+    {
+      go_assert(saw_errors());
+      return Expression::make_error(this->location());
+    }
 
   // Create a stack-allocated storage temp if storage won't escape
   if (!this->storage_escapes_
@@ -15784,7 +15693,7 @@ Slice_construction_expression::do_flatten(Gogo* gogo, Named_object* no,
     {
       Location loc = this->location();
       this->array_val_ = this->create_array_val();
-      go_assert(this->array_val_);
+      go_assert(this->array_val_ != NULL);
       Temporary_statement* temp =
           Statement::make_temporary(this->valtype_, this->array_val_, loc);
       inserter->insert(temp);
diff --git a/gcc/go/gofrontend/expressions.h b/gcc/go/gofrontend/expressions.h
index e3747cc65d7..57c974d3c70 100644
--- a/gcc/go/gofrontend/expressions.h
+++ b/gcc/go/gofrontend/expressions.h
@@ -3806,9 +3806,6 @@ class Struct_construction_expression : public Expression,
   Expression*
   do_copy();
 
-  Expression*
-  do_flatten(Gogo*, Named_object*, Statement_inserter*);
-
   Bexpression*
   do_get_backend(Translate_context*);
 
@@ -3881,9 +3878,6 @@ protected:
   indexes()
   { return this->indexes_; }
 
-  Expression*
-  do_flatten(Gogo*, Named_object*, Statement_inserter*);
-
   // Get the backend constructor for the array values.
   Bexpression*
   get_constructor(Translate_context* context, Btype* btype);