par-ch4.adb (P_Simple_Expression): Fold long sequences of concatenations of string literals into a single literal...

2007-08-31  Bob Duff  <duff@adacore.com>

	* par-ch4.adb (P_Simple_Expression): Fold long sequences of
	concatenations of string literals into a single literal, in order to
	avoid very deep recursion in the front end, which was causing stack
	overflow.

	* sem_eval.adb (Eval_Concatenation): If the left operand is the empty
	string, and the right operand is a string literal (the case of "" &
	"..."), optimize by avoiding copying the right operand -- just use the
	value of the right operand directly.

	* stringt.adb (Store_String_Chars): Optimize by growing the
	String_Chars table all at once, rather than appending characters one by
	one.
	(Write_String_Table_Entry): If the string to be printed is very long,
	just print the first few characters, followed by the length. Otherwise,
	doing "pn(n)" in the debugger can take an extremely long time.

	* sem_prag.adb (Process_Interface_Name): Replace loop doing
	Store_String_Char with Store_String_Chars.

From-SVN: r127977

1 files changed, 29 insertions, 3 deletions

diff --git a/gcc/ada/stringt.adb b/gcc/ada/stringt.adb
index e272009..88b72e05 100644
--- a/gcc/ada/stringt.adb
+++ b/gcc/ada/stringt.adb
@@ -202,10 +202,27 @@ package body Stringt is
    end Store_String_Chars;
 
    procedure Store_String_Chars (S : String_Id) is
+
+      --  We are essentially doing this:
+
+      --   for J in 1 .. String_Length (S) loop
+      --      Store_String_Char (Get_String_Char (S, J));
+      --   end loop;
+
+      --  but when the string is long it's more efficient to grow the
+      --  String_Chars table all at once.
+
+      S_First  : constant Int := Strings.Table (S).String_Index;
+      S_Len    : constant Int := String_Length (S);
+      Old_Last : constant Int := String_Chars.Last;
+      New_Last : constant Int := Old_Last + S_Len;
+
    begin
-      for J in 1 .. String_Length (S) loop
-         Store_String_Char (Get_String_Char (S, J));
-      end loop;
+      String_Chars.Set_Last (New_Last);
+      String_Chars.Table (Old_Last + 1 .. New_Last) :=
+        String_Chars.Table (S_First .. S_First + S_Len - 1);
+      Strings.Table (Strings.Last).Length :=
+        Strings.Table (Strings.Last).Length + S_Len;
    end Store_String_Chars;
 
    ----------------------
@@ -417,6 +434,15 @@ package body Stringt is
             else
                Write_Char_Code (C);
             end if;
+
+            --  If string is very long, quit
+
+            if J >= 1000 then  --  arbitrary limit
+               Write_Str ("""...etc (length = ");
+               Write_Int (String_Length (Id));
+               Write_Str (")");
+               return;
+            end if;
          end loop;
 
          Write_Char ('"');