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score: Clarify CPU port alignment requirements

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This commit is contained in:
Sebastian Huber
2014-04-07 14:50:24 +02:00
parent d507c03731
commit 57740ce8a1
2 changed files with 42 additions and 9 deletions
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16
cpukit/score/cpu/no_cpu/rtems/score/cpu.h
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@@ -733,7 +733,10 @@ SCORE_EXTERN Context_Control_fp _CPU_Null_fp_context;
/**
* CPU's worst alignment requirement for data types on a byte boundary. This
* alignment does not take into account the requirements for the stack.
* alignment does not take into account the requirements for the stack. It
* must be a power of two greater than or equal to two. The power of two
* requirement makes it possible to align values easily using simple bit
* operations.
*
* Port Specific Information:
*
@@ -749,12 +752,11 @@ SCORE_EXTERN Context_Control_fp _CPU_Null_fp_context;
* @ref CPU_ALIGNMENT. If the @ref CPU_ALIGNMENT is strict enough for
* the heap, then this should be set to @ref CPU_ALIGNMENT.
*
* NOTE: This does not have to be a power of 2 although it should be
* a multiple of 2 greater than or equal to 2. The requirement
* to be a multiple of 2 is because the heap uses the least
* significant field of the front and back flags to indicate
* that a block is in use or free. So you do not want any odd
* length blocks really putting length data in that bit.
* NOTE: It must be a power of two greater than or equal to two. The
* requirement to be a multiple of two is because the heap uses the
* least significant field of the front and back flags to indicate that
* a block is in use or free. So you do not want any odd length blocks
* really putting length data in that bit.
*
* On byte oriented architectures, @ref CPU_HEAP_ALIGNMENT normally will
* have to be greater or equal to than @ref CPU_ALIGNMENT to ensure that

35
cpukit/score/src/percpuasm.c
View File

@@ -1,8 +1,8 @@
/*
* Copyright (c) 2012 embedded brains GmbH. All rights reserved.
* Copyright (c) 2012-2014 embedded brains GmbH. All rights reserved.
*
* embedded brains GmbH
* Obere Lagerstr. 30
* Dornierstr. 4
* 82178 Puchheim
* Germany
* <rtems@embedded-brains.de>
@@ -21,6 +21,37 @@
#define _RTEMS_PERCPU_DEFINE_OFFSETS
#include <rtems/score/percpu.h>
/*
* In case a CPU port needs another alignment, then add this here and make sure
* it is a power of two greater than or equal to two.
*/
RTEMS_STATIC_ASSERT(
CPU_ALIGNMENT == 2
|| CPU_ALIGNMENT == 4
|| CPU_ALIGNMENT == 8
|| CPU_ALIGNMENT == 16
|| CPU_ALIGNMENT == 32,
CPU_ALIGNMENT
);
/*
* In case a CPU port needs another heap alignment, then add this here and make
* sure it is a power of two greater than or equal to two.
*/
RTEMS_STATIC_ASSERT(
CPU_HEAP_ALIGNMENT == 2
|| CPU_HEAP_ALIGNMENT == 4
|| CPU_HEAP_ALIGNMENT == 8
|| CPU_HEAP_ALIGNMENT == 16
|| CPU_HEAP_ALIGNMENT == 32,
CPU_HEAP_ALIGNMENT_0
);
RTEMS_STATIC_ASSERT(
CPU_HEAP_ALIGNMENT >= CPU_ALIGNMENT,
CPU_HEAP_ALIGNMENT_1
);
RTEMS_STATIC_ASSERT(
sizeof(void *) == CPU_SIZEOF_POINTER,
CPU_SIZEOF_POINTER