compiler: generate memmove for non-pointer slice copy

    
    The builtin copy function is lowered to runtime functions
    slicecopy, stringslicecopy, or typedslicecopy. The first two are
    basically thin wrappers of memmove. Instead of making a runtime
    call, we can just use __builtin_memmove. This gives the compiler
    backend opportunities for further optimizations.
    
    Move the lowering of builtin copy function to flatten phase for
    the ease of rewriting.
    
    Also do this optimization for the copy part of append(s1, s2...).
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/170005

From-SVN: r271017

1 files changed, 129 insertions, 55 deletions

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 402e8d3..707636a 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -7743,8 +7743,9 @@ Builtin_call_expression::do_lower(Gogo*, Named_object* function,
   return this;
 }
 
-// Flatten a builtin call expression.  This turns the arguments of copy and
-// append into temporary expressions.
+// Flatten a builtin call expression.  This turns the arguments of some
+// builtin calls into temporary expressions.  Also expand copy and append
+// to runtime calls.
 
 Expression*
 Builtin_call_expression::do_flatten(Gogo* gogo, Named_object* function,
@@ -7781,6 +7782,85 @@ Builtin_call_expression::do_flatten(Gogo* gogo, Named_object* function,
 		*pa = Expression::make_temporary_reference(temp, loc);
 	      }
 	  }
+
+        // Lower to runtime call.
+        const Expression_list* args = this->args();
+        go_assert(args != NULL && args->size() == 2);
+        Expression* arg1 = args->front();
+        Expression* arg2 = args->back();
+        go_assert(arg1->is_variable());
+        go_assert(arg2->is_variable());
+        bool arg2_is_string = arg2->type()->is_string_type();
+
+        Expression* ret;
+        Type* et = at->array_type()->element_type();
+        if (et->has_pointer())
+          {
+            Expression* td = Expression::make_type_descriptor(et, loc);
+            ret = Runtime::make_call(Runtime::TYPEDSLICECOPY, loc,
+                                     3, td, arg1, arg2);
+          }
+        else
+          {
+            Type* int_type = Type::lookup_integer_type("int");
+            Type* uintptr_type = Type::lookup_integer_type("uintptr");
+
+            // l1 = len(arg1)
+            Named_object* lenfn = gogo->lookup_global("len");
+            Expression* lenref = Expression::make_func_reference(lenfn, NULL, loc);
+            Expression_list* len_args = new Expression_list();
+            len_args->push_back(arg1->copy());
+            Expression* len1 = Expression::make_call(lenref, len_args, false, loc);
+            gogo->lower_expression(function, inserter, &len1);
+            gogo->flatten_expression(function, inserter, &len1);
+            Temporary_statement* l1tmp = Statement::make_temporary(int_type, len1, loc);
+            inserter->insert(l1tmp);
+
+            // l2 = len(arg2)
+            len_args = new Expression_list();
+            len_args->push_back(arg2->copy());
+            Expression* len2 = Expression::make_call(lenref, len_args, false, loc);
+            gogo->lower_expression(function, inserter, &len2);
+            gogo->flatten_expression(function, inserter, &len2);
+            Temporary_statement* l2tmp = Statement::make_temporary(int_type, len2, loc);
+            inserter->insert(l2tmp);
+
+            // n = (l1 < l2 ? l1 : l2)
+            Expression* l1ref = Expression::make_temporary_reference(l1tmp, loc);
+            Expression* l2ref = Expression::make_temporary_reference(l2tmp, loc);
+            Expression* cond = Expression::make_binary(OPERATOR_LT, l1ref, l2ref, loc);
+            Expression* n = Expression::make_conditional(cond,
+                                                         l1ref->copy(),
+                                                         l2ref->copy(),
+                                                         loc);
+            Temporary_statement* ntmp = Statement::make_temporary(NULL, n, loc);
+            inserter->insert(ntmp);
+
+            // sz = n * sizeof(elem_type)
+            Expression* nref = Expression::make_temporary_reference(ntmp, loc);
+            nref = Expression::make_cast(uintptr_type, nref, loc);
+            Expression* sz = Expression::make_type_info(et, TYPE_INFO_SIZE);
+            sz = Expression::make_binary(OPERATOR_MULT, sz, nref, loc);
+
+            // memmove(arg1.ptr, arg2.ptr, sz)
+            Expression* p1 = Expression::make_slice_info(arg1,
+                                                         SLICE_INFO_VALUE_POINTER,
+                                                         loc);
+            Expression* p2 = (arg2_is_string
+                              ? Expression::make_string_info(arg2,
+                                                             STRING_INFO_DATA,
+                                                             loc)
+                              : Expression::make_slice_info(arg2,
+                                                            SLICE_INFO_VALUE_POINTER,
+                                                            loc));
+            Expression* call = Runtime::make_call(Runtime::BUILTIN_MEMMOVE, loc, 3,
+                                                  p1, p2, sz);
+
+            // n is the return value of copy
+            nref = Expression::make_temporary_reference(ntmp, loc);
+            ret = Expression::make_compound(call, nref, loc);
+          }
+        return ret;
       }
       break;
 
@@ -8209,21 +8289,51 @@ Builtin_call_expression::flatten_append(Gogo* gogo, Named_object* function,
 
   if (this->is_varargs())
     {
-      // copy(s1tmp[l1tmp:], s2tmp)
-      a1 = Expression::make_temporary_reference(s1tmp, loc);
-      ref = Expression::make_temporary_reference(l1tmp, loc);
-      Expression* nil = Expression::make_nil(loc);
-      a1 = Expression::make_array_index(a1, ref, nil, NULL, loc);
-      a1->array_index_expression()->set_needs_bounds_check(false);
-
-      a2 = Expression::make_temporary_reference(s2tmp, loc);
-
-      Named_object* copyfn = gogo->lookup_global("copy");
-      Expression* copyref = Expression::make_func_reference(copyfn, NULL, loc);
-      call_args = new Expression_list();
-      call_args->push_back(a1);
-      call_args->push_back(a2);
-      call = Expression::make_call(copyref, call_args, false, loc);
+      if (element_type->has_pointer())
+        {
+          // copy(s1tmp[l1tmp:], s2tmp)
+          a1 = Expression::make_temporary_reference(s1tmp, loc);
+          ref = Expression::make_temporary_reference(l1tmp, loc);
+          Expression* nil = Expression::make_nil(loc);
+          a1 = Expression::make_array_index(a1, ref, nil, NULL, loc);
+          a1->array_index_expression()->set_needs_bounds_check(false);
+
+          a2 = Expression::make_temporary_reference(s2tmp, loc);
+
+          Named_object* copyfn = gogo->lookup_global("copy");
+          Expression* copyref = Expression::make_func_reference(copyfn, NULL, loc);
+          call_args = new Expression_list();
+          call_args->push_back(a1);
+          call_args->push_back(a2);
+          call = Expression::make_call(copyref, call_args, false, loc);
+        }
+      else
+        {
+          // memmove(&s1tmp[l1tmp], s2tmp.ptr, l2tmp*sizeof(elem))
+          a1 = Expression::make_temporary_reference(s1tmp, loc);
+          ref = Expression::make_temporary_reference(l1tmp, loc);
+          a1 = Expression::make_array_index(a1, ref, NULL, NULL, loc);
+          a1->array_index_expression()->set_needs_bounds_check(false);
+          a1 = Expression::make_unary(OPERATOR_AND, a1, loc);
+
+          a2 = Expression::make_temporary_reference(s2tmp, loc);
+          a2 = (a2->type()->is_string_type()
+                ? Expression::make_string_info(a2,
+                                               STRING_INFO_DATA,
+                                               loc)
+                : Expression::make_slice_info(a2,
+                                              SLICE_INFO_VALUE_POINTER,
+                                              loc));
+
+          Type* uintptr_type = Type::lookup_integer_type("uintptr");
+          ref = Expression::make_temporary_reference(l2tmp, loc);
+          ref = Expression::make_cast(uintptr_type, ref, loc);
+          a3 = Expression::make_type_info(element_type, TYPE_INFO_SIZE);
+          a3 = Expression::make_binary(OPERATOR_MULT, a3, ref, loc);
+
+          call = Runtime::make_call(Runtime::BUILTIN_MEMMOVE, loc, 3,
+                                    a1, a2, a3);
+        }
       gogo->lower_expression(function, inserter, &call);
       gogo->flatten_expression(function, inserter, &call);
       inserter->insert(Statement::make_statement(call, false));
@@ -9666,44 +9776,8 @@ Builtin_call_expression::do_get_backend(Translate_context* context)
       }
 
     case BUILTIN_COPY:
-      {
-	const Expression_list* args = this->args();
-	go_assert(args != NULL && args->size() == 2);
-	Expression* arg1 = args->front();
-	Expression* arg2 = args->back();
-
-	Type* arg1_type = arg1->type();
-	Array_type* at = arg1_type->array_type();
-	go_assert(arg1->is_variable());
-
-	Expression* call;
-
-	Type* arg2_type = arg2->type();
-        go_assert(arg2->is_variable());
-	if (arg2_type->is_string_type())
-	  call = Runtime::make_call(Runtime::SLICESTRINGCOPY, location,
-				    2, arg1, arg2);
-	else
-	  {
-	    Type* et = at->element_type();
-	    if (et->has_pointer())
-	      {
-		Expression* td = Expression::make_type_descriptor(et,
-								  location);
-		call = Runtime::make_call(Runtime::TYPEDSLICECOPY, location,
-					  3, td, arg1, arg2);
-	      }
-	    else
-	      {
-		Expression* sz = Expression::make_type_info(et,
-							    TYPE_INFO_SIZE);
-		call = Runtime::make_call(Runtime::SLICECOPY, location, 3,
-					  arg1, arg2, sz);
-	      }
-	  }
-
-	return call->get_backend(context);
-      }
+      // Handled in Builtin_call_expression::do_flatten.
+      go_unreachable();
 
     case BUILTIN_APPEND:
       // Handled in Builtin_call_expression::flatten_append.