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g-altive.ads (VECTOR_ALIGNMENT): Set to Min (16...

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2006-02-13  Olivier Hainque  <hainque@adacore.com>

	* g-altive.ads (VECTOR_ALIGNMENT): Set to Min (16, Max_Alignment),
	to avoid useless and space inefficient overalignments on targets where
	Max_Alignment is larger than 16.

From-SVN: r111071
This commit is contained in:
Olivier Hainque 2006-02-15 10:40:32 +01:00 committed by Arnaud Charlet
parent add9f797fa
commit 0c52d1f344
1 changed files with 18 additions and 2 deletions
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gcc/ada/g-altive.ads
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@ -6,7 +6,7 @@
-- --
-- S p e c --
-- --
-- Copyright (C) 2004-2005, Free Software Foundation, Inc. --
-- Copyright (C) 2004-2006, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
@ -236,7 +236,23 @@ package GNAT.Altivec is
-- points to a 16-byte boundary. The compiler is responsible for aligning
-- vector data types on 16-byte boundaries."
VECTOR_ALIGNMENT : constant := 16;
VECTOR_ALIGNMENT : constant := Natural'Min (16, Standard'Maximum_Alignment);
-- This value is used to set the alignment of vector datatypes in both the
-- hard and the soft binding implementations.
--
-- We want this value to never be greater than 16, because none of the
-- binding implementations requires larger alignments and such a value
-- would cause useless space to be allocated/wasted for vector objects.
-- Furthermore, the alignment of 16 matches the hard binding leading to
-- a more faithful emulation.
--
-- It needs to be exactly 16 for the hard binding, and the initializing
-- expression is just right for this purpose since Maximum_Alignment is
-- expected to be 16 for the real Altivec ABI.
--
-- The soft binding doesn't rely on strict 16byte alignment, and we want
-- the value to be no greater than Standard'Maximum_Alignment in this case
-- to ensure it is supported on every possible target.
-------------------------------------------------------
-- [PIM-2.1] Data Types - Interpretation of contents --