Use Standard'Maximum_Alignment * 2 unconditionally to accommodate
possible requirements by user code compiled with specific cpu/arch
options such as -mavx on x86 targets, which Gigi assumes the SS can
handle.
Such options influence what Standard'Maximum_Alignment returns and are
typically not used when s-secsta is compiled for the runtime.
Tested on x86_64-pc-linux-gnu, committed on trunk
2020-06-12 Olivier Hainque <hain...@adacore.com>
gcc/ada/
* libgnat/s-secsta.ads (Memory_Alignment): New constant, memory
alignment for chunks and allocated blocks. Initialize to
Standard'Maximum_Alignment * 2.
(Chunk_Memory): Use it.
* libgnat/s-secsta.adb (Round_Up): Likewise.--- gcc/ada/libgnat/s-secsta.adb
+++ gcc/ada/libgnat/s-secsta.adb
@@ -564,7 +564,7 @@ package body System.Secondary_Stack is
--------------
function Round_Up (Size : Storage_Count) return Memory_Size is
- Algn_MS : constant Memory_Size := Standard'Maximum_Alignment;
+ Algn_MS : constant Memory_Size := Memory_Alignment;
Size_MS : constant Memory_Size := Memory_Size (Size);
begin
--- gcc/ada/libgnat/s-secsta.ads
+++ gcc/ada/libgnat/s-secsta.ads
@@ -261,10 +261,23 @@ private
subtype Memory_Index is Memory_Size;
-- Index into the memory storage of a single chunk
+ Memory_Alignment : constant := Standard'Maximum_Alignment * 2;
+ -- The memory alignment we will want to honor on every allocation.
+ --
+ -- At this stage, gigi assumes we can accomodate any alignment requirement
+ -- there might be on the data type for which the memory gets allocated (see
+ -- build_call_alloc_dealloc).
+ --
+ -- The multiplication factor is intended to account for requirements
+ -- by user code compiled with specific arch/cpu options such as -mavx
+ -- on X86[_64] targets, which Standard'Maximum_Alignment doesn't convey
+ -- without such compilation options. * 4 would actually be needed to
+ -- support -mavx512f on X86, but this would incur more annoying memory
+ -- consumption overheads.
+
type Chunk_Memory is array (Memory_Size range <>) of SSE.Storage_Element;
- for Chunk_Memory'Alignment use Standard'Maximum_Alignment;
- -- The memory storage of a single chunk. It utilizes maximum alignment in
- -- order to guarantee efficient operations.
+ for Chunk_Memory'Alignment use Memory_Alignment;
+ -- The memory storage of a single chunk
--------------
-- SS_Chunk --
