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From: Iain D Sandoe <iains@gcc.gnu.org>
To: gcc-cvs@gcc.gnu.org
Subject: [gcc/devel/c++-coroutines] [Ada] Add fallback on Integer_Arithmetic
Date: Thu, 11 Jun 2020 20:05:26 +0000 (GMT) [thread overview]
Message-ID: <20200611200526.4D7813949D96@sourceware.org> (raw)
https://gcc.gnu.org/g:f7823e6299fa49645b5ed20712a0272f1776cd5c
commit f7823e6299fa49645b5ed20712a0272f1776cd5c
Author: Arnaud Charlet <charlet@adacore.com>
Date: Thu Mar 12 13:16:05 2020 -0400
[Ada] Add fallback on Integer_Arithmetic
2020-06-11 Arnaud Charlet <charlet@adacore.com>
gcc/ada/
* libgnat/s-aoinar.adb (Atomic_Fetch_And_Add,
Atomic_Fetch_And_Subtract): Add fallback using
compare-and-exchange, in case the integer type does not map to a
machine type.
Diff:
---
gcc/ada/libgnat/s-aoinar.adb | 89 +++++++++++++++++++++++++++++++++++++-------
1 file changed, 75 insertions(+), 14 deletions(-)
diff --git a/gcc/ada/libgnat/s-aoinar.adb b/gcc/ada/libgnat/s-aoinar.adb
index 4cc6aa70314..b05134faa59 100644
--- a/gcc/ada/libgnat/s-aoinar.adb
+++ b/gcc/ada/libgnat/s-aoinar.adb
@@ -30,10 +30,13 @@
------------------------------------------------------------------------------
with System.Atomic_Primitives; use System.Atomic_Primitives;
+with System.Atomic_Operations.Exchange;
with Interfaces.C;
package body System.Atomic_Operations.Integer_Arithmetic is
+ package Exchange is new System.Atomic_Operations.Exchange (Atomic_Type);
+
----------------
-- Atomic_Add --
----------------
@@ -88,13 +91,42 @@ package body System.Atomic_Operations.Integer_Arithmetic is
pragma Warnings (On);
begin
- case Atomic_Type'Object_Size is
- when 8 => return Atomic_Fetch_Add_1 (Item'Address, Value);
- when 16 => return Atomic_Fetch_Add_2 (Item'Address, Value);
- when 32 => return Atomic_Fetch_Add_4 (Item'Address, Value);
- when 64 => return Atomic_Fetch_Add_8 (Item'Address, Value);
- when others => raise Program_Error;
- end case;
+ -- Use the direct intrinsics when possible, and fallback to
+ -- compare-and-exchange otherwise.
+
+ if Atomic_Type'Base'Last = Atomic_Type'Last
+ and then Atomic_Type'Base'First = Atomic_Type'First
+ and then Atomic_Type'Last
+ in 2 ** 7 - 1 | 2 ** 15 - 1 | 2 ** 31 - 1 | 2 ** 63 - 1
+ then
+ case Long_Long_Integer (Atomic_Type'Last) is
+ when 2 ** 7 - 1 =>
+ return Atomic_Fetch_Add_1 (Item'Address, Value);
+ when 2 ** 15 - 1 =>
+ return Atomic_Fetch_Add_2 (Item'Address, Value);
+ when 2 ** 31 - 1 =>
+ return Atomic_Fetch_Add_4 (Item'Address, Value);
+ when 2 ** 63 - 1 =>
+ return Atomic_Fetch_Add_8 (Item'Address, Value);
+ when others =>
+ raise Program_Error;
+ end case;
+ else
+ declare
+ Old_Value : aliased Atomic_Type := Item;
+ New_Value : Atomic_Type := Old_Value + Value;
+ begin
+ -- Keep iterating until the exchange succeeds
+
+ while not Exchange.Atomic_Compare_And_Exchange
+ (Item, Old_Value, New_Value)
+ loop
+ New_Value := Old_Value + Value;
+ end loop;
+
+ return Old_Value;
+ end;
+ end if;
end Atomic_Fetch_And_Add;
-------------------------------
@@ -125,13 +157,42 @@ package body System.Atomic_Operations.Integer_Arithmetic is
pragma Warnings (On);
begin
- case Atomic_Type'Object_Size is
- when 8 => return Atomic_Fetch_Sub_1 (Item'Address, Value);
- when 16 => return Atomic_Fetch_Sub_2 (Item'Address, Value);
- when 32 => return Atomic_Fetch_Sub_4 (Item'Address, Value);
- when 64 => return Atomic_Fetch_Sub_8 (Item'Address, Value);
- when others => raise Program_Error;
- end case;
+ -- Use the direct intrinsics when possible, and fallback to
+ -- compare-and-exchange otherwise.
+
+ if Atomic_Type'Base'Last = Atomic_Type'Last
+ and then Atomic_Type'Base'First = Atomic_Type'First
+ and then Atomic_Type'Last
+ in 2 ** 7 - 1 | 2 ** 15 - 1 | 2 ** 31 - 1 | 2 ** 63 - 1
+ then
+ case Long_Long_Integer (Atomic_Type'Last) is
+ when 2 ** 7 - 1 =>
+ return Atomic_Fetch_Sub_1 (Item'Address, Value);
+ when 2 ** 15 - 1 =>
+ return Atomic_Fetch_Sub_2 (Item'Address, Value);
+ when 2 ** 31 - 1 =>
+ return Atomic_Fetch_Sub_4 (Item'Address, Value);
+ when 2 ** 63 - 1 =>
+ return Atomic_Fetch_Sub_8 (Item'Address, Value);
+ when others =>
+ raise Program_Error;
+ end case;
+ else
+ declare
+ Old_Value : aliased Atomic_Type := Item;
+ New_Value : Atomic_Type := Old_Value - Value;
+ begin
+ -- Keep iterating until the exchange succeeds
+
+ while not Exchange.Atomic_Compare_And_Exchange
+ (Item, Old_Value, New_Value)
+ loop
+ New_Value := Old_Value - Value;
+ end loop;
+
+ return Old_Value;
+ end;
+ end if;
end Atomic_Fetch_And_Subtract;
------------------
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