This micro-optimizes again the implementation of a couple of hot functions
after recent changes. No functional changes.
Tested on x86_64-pc-linux-gnu, committed on trunk
2017-04-25 Eric Botcazou <ebotca...@adacore.com>
* fname.adb (Has_Internal_Extension): Add pragma Inline.
Use direct 4-character slice comparisons.
(Has_Prefix): Add
pragma Inline. (Has_Suffix): Delete.
(Is_Internal_File_Name):
Test Is_Predefined_File_Name first.
(Is_Predefined_File_Name):
Use direct slice comparisons as much as possible and limit all
comparisons to at most 8 characters.
Index: fname.adb
===================================================================
--- fname.adb (revision 247177)
+++ fname.adb (working copy)
@@ -58,27 +58,30 @@
Table_Name => "Fname_Dummy_Table");
function Has_Internal_Extension (Fname : String) return Boolean;
+ pragma Inline (Has_Internal_Extension);
-- True if the extension is appropriate for an internal/predefined
-- unit. That means ".ads" or ".adb" for source files, and ".ali" for
-- ALI files.
function Has_Prefix (X, Prefix : String) return Boolean;
+ pragma Inline (Has_Prefix);
-- True if Prefix is at the beginning of X. For example,
-- Has_Prefix("a-filename.ads", Prefix => "a-") is True.
- function Has_Suffix (X, Suffix : String) return Boolean;
- -- True if Suffix is at the end of X
-
----------------------------
-- Has_Internal_Extension --
----------------------------
function Has_Internal_Extension (Fname : String) return Boolean is
begin
- return
- Has_Suffix (Fname, Suffix => ".ads")
- or else Has_Suffix (Fname, Suffix => ".adb")
- or else Has_Suffix (Fname, Suffix => ".ali");
+ if Fname'Length >= 4 then
+ declare
+ S : String renames Fname (Fname'Last - 3 .. Fname'Last);
+ begin
+ return S = ".ads" or else S = ".adb" or else S = ".ali";
+ end;
+ end if;
+ return False;
end Has_Internal_Extension;
----------------
@@ -89,32 +92,14 @@
begin
if X'Length >= Prefix'Length then
declare
- Slice : String renames
- X (X'First .. X'First + Prefix'Length - 1);
+ S : String renames X (X'First .. X'First + Prefix'Length - 1);
begin
- return Slice = Prefix;
+ return S = Prefix;
end;
end if;
return False;
end Has_Prefix;
- ----------------
- -- Has_Suffix --
- ----------------
-
- function Has_Suffix (X, Suffix : String) return Boolean is
- begin
- if X'Length >= Suffix'Length then
- declare
- Slice : String renames
- X (X'Last - Suffix'Length + 1 .. X'Last);
- begin
- return Slice = Suffix;
- end;
- end if;
- return False;
- end Has_Suffix;
-
---------------------------
-- Is_Internal_File_Name --
---------------------------
@@ -124,6 +109,10 @@
Renamings_Included : Boolean := True) return Boolean
is
begin
+ if Is_Predefined_File_Name (Fname, Renamings_Included) then
+ return True;
+ end if;
+
-- Check for internal extensions first, so we don't think (e.g.)
-- "gnat.adc" is internal.
@@ -131,10 +120,7 @@
return False;
end if;
- return
- Is_Predefined_File_Name (Fname, Renamings_Included)
- or else Has_Prefix (Fname, Prefix => "g-")
- or else Has_Prefix (Fname, Prefix => "gnat.");
+ return Has_Prefix (Fname, "g-") or else Has_Prefix (Fname, "gnat.");
end Is_Internal_File_Name;
function Is_Internal_File_Name
@@ -156,16 +142,38 @@
(Fname : String;
Renamings_Included : Boolean := True) return Boolean
is
+ subtype Str8 is String (1 .. 8);
+
+ Renaming_Names : constant array (1 .. 8) of Str8 :=
+ ("calendar", -- Calendar
+ "machcode", -- Machine_Code
+ "unchconv", -- Unchecked_Conversion
+ "unchdeal", -- Unchecked_Deallocation
+ "directio", -- Direct_IO
+ "ioexcept", -- IO_Exceptions
+ "sequenio", -- Sequential_IO
+ "text_io."); -- Text_IO
+
+ -- Note: the implementation is optimized to perform uniform comparisons
+ -- on string slices whose length is known at compile time and at most 8
+ -- characters; the remaining calls to Has_Prefix must be inlined so as
+ -- to expose the compile-time known length.
+
begin
if not Has_Internal_Extension (Fname) then
return False;
end if;
- if Has_Prefix (Fname, "a-")
- or else Has_Prefix (Fname, "i-")
- or else Has_Prefix (Fname, "s-")
- then
- return True;
+ -- Definitely predefined if prefix is a- i- or s-
+
+ if Fname'Length >= 2 then
+ declare
+ S : String renames Fname (Fname'First .. Fname'First + 1);
+ begin
+ if S = "a-" or else S = "i-" or else S = "s-" then
+ return True;
+ end if;
+ end;
end if;
-- Definitely false if longer than 12 characters (8.3)
@@ -176,53 +184,30 @@
-- We include the "." in the prefixes below, so we don't match (e.g.)
-- adamant.ads. So the first line matches "ada.ads", "ada.adb", and
- -- "ada.ali".
+ -- "ada.ali". But that's not necessary if they have 8 characters.
- if Has_Prefix (Fname, Prefix => "ada.") -- Ada
- or else Has_Prefix (Fname, Prefix => "interfac.") -- Interfaces
- or else Has_Prefix (Fname, Prefix => "system.") -- System
+ if Has_Prefix (Fname, "ada.") -- Ada
+ or else Has_Prefix (Fname, "interfac") -- Interfaces
+ or else Has_Prefix (Fname, "system.") -- System
then
return True;
end if;
- if not Renamings_Included then
- return False;
+ -- If instructed and the name has 8+ characters, check for renamings
+
+ if Renamings_Included and then Fname'Length >= 8 then
+ declare
+ S : String renames Fname (Fname'First .. Fname'First + 7);
+ begin
+ for J in Renaming_Names'Range loop
+ if S = Renaming_Names (J) then
+ return True;
+ end if;
+ end loop;
+ end;
end if;
- -- The following are the predefined renamings
-
- return
- -- Calendar
-
- Has_Prefix (Fname, Prefix => "calendar.")
-
- -- Machine_Code
-
- or else Has_Prefix (Fname, Prefix => "machcode.")
-
- -- Unchecked_Conversion
-
- or else Has_Prefix (Fname, Prefix => "unchconv.")
-
- -- Unchecked_Deallocation
-
- or else Has_Prefix (Fname, Prefix => "unchdeal.")
-
- -- Direct_IO
-
- or else Has_Prefix (Fname, Prefix => "directio.")
-
- -- IO_Exceptions
-
- or else Has_Prefix (Fname, Prefix => "ioexcept.")
-
- -- Sequential_IO
-
- or else Has_Prefix (Fname, Prefix => "sequenio.")
-
- -- Text_IO
-
- or else Has_Prefix (Fname, Prefix => "text_io.");
+ return False;
end Is_Predefined_File_Name;
function Is_Predefined_File_Name
