This patch substantially improves the efficiency of copying large slices
of bit-packed arrays, by copying 32 bits at a time instead of 1 at a
time.
Tested on x86_64-pc-linux-gnu, committed on trunk
2019-09-18 Bob Duff <d...@adacore.com>
gcc/ada/
* exp_ch5.adb (Expand_Assign_Array_Loop_Or_Bitfield): The call
to Copy_Bitfield is now enabled.
(Expand_Assign_Array_Bitfield): Multiply 'Length times
'Component_Size "by hand" instead of using 'Size.--- gcc/ada/exp_ch5.adb
+++ gcc/ada/exp_ch5.adb
@@ -1411,12 +1411,21 @@ package body Exp_Ch5 is
-- Compute the Size of the bitfield
-- Note that the length check has already been done, so we can use the
- -- size of either L or R.
+ -- size of either L or R; they are equal. We can't use 'Size here,
+ -- because sometimes bit fields get copied into a temp, and the 'Size
+ -- ends up being the size of the temp (e.g. an 8-bit temp containing
+ -- a 4-bit bit field).
Size : constant Node_Id :=
- Make_Attribute_Reference (Loc,
- Prefix => Duplicate_Subexpr (Name (N), True),
- Attribute_Name => Name_Size);
+ Make_Op_Multiply (Loc,
+ Make_Attribute_Reference (Loc,
+ Prefix =>
+ Duplicate_Subexpr (Name (N), True),
+ Attribute_Name => Name_Length),
+ Make_Attribute_Reference (Loc,
+ Prefix =>
+ Duplicate_Subexpr (Name (N), True),
+ Attribute_Name => Name_Component_Size));
begin
return Make_Procedure_Call_Statement (Loc,
@@ -1466,10 +1475,7 @@ package body Exp_Ch5 is
-- optimization in that case as well. We could complicate this code by
-- actually looking for such volatile and independent components.
- -- Note that Expand_Assign_Array_Bitfield is disabled for now.
-
- if False and then -- ???
- RTE_Available (RE_Copy_Bitfield)
+ if RTE_Available (RE_Copy_Bitfield)
and then Is_Bit_Packed_Array (L_Type)
and then Is_Bit_Packed_Array (R_Type)
and then not Reverse_Storage_Order (L_Type)
