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    Subject[patch 07/10] Immediate Value - PowerPC Optimization
    PowerPC optimization of the immediate values which uses a li instruction,
    patched with an immediate value 0 or 1 to set the immediate value.

    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    ---
    arch/powerpc/kernel/Makefile | 1
    arch/powerpc/kernel/immediate.c | 29 ++++++++++++++++
    include/asm-powerpc/immediate.h | 69 +++++++++++++++++++++++++++++++++++++++-
    3 files changed, 98 insertions(+), 1 deletion(-)

    Index: linux-2.6-lttng/include/asm-powerpc/immediate.h
    ===================================================================
    --- linux-2.6-lttng.orig/include/asm-powerpc/immediate.h 2007-06-18 19:15:39.000000000 -0400
    +++ linux-2.6-lttng/include/asm-powerpc/immediate.h 2007-06-18 19:15:46.000000000 -0400
    @@ -1 +1,68 @@
    -#include <asm-generic/immediate.h>
    +#ifndef _ASM_POWERPC_IMMEDIATE_H
    +#define _ASM_POWERPC_IMMEDIATE_H
    +
    +/*
    + * Immediate values. PowerPC architecture optimizations.
    + *
    + * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    + *
    + * This file is released under the GPLv2.
    + * See the file COPYING for more details.
    + */
    +
    +#include <asm/asm-compat.h>
    +
    +#define IF_DEFAULT (IF_OPTIMIZED | IF_LOCKDEP)
    +
    +/* Optimized version of the immediate */
    +#define immediate_optimized(flags, var) \
    + ({ \
    + char condition; \
    + asm ( ".section __immediate, \"a\", @progbits;\n\t" \
    + PPC_LONG "%1, 0f, %2;\n\t" \
    + ".previous;\n\t" \
    + ".align 4\n\t" \
    + "0:\n\t" \
    + "li %0,%3;\n\t" \
    + : "=r" (condition) \
    + : "i" (&var), \
    + "i" (flags), \
    + "i" (0)); \
    + condition; \
    + })
    +
    +/*
    + * immediate macro selecting the generic or optimized version of immediate,
    + * depending on the flags specified. It is a macro because we need to pass the
    + * name to immediate_optimized() and immediate_generic() so they can declare a
    + * static variable with it.
    + */
    +#define _immediate(flags, var) \
    +({ \
    + ((flags) & IF_OPTIMIZED) ? \
    + immediate_optimized(flags, var) : \
    + immediate_generic(flags, var); \
    +})
    +
    +/* immediate with default behavior */
    +#define immediate(var) _immediate(IF_DEFAULT, var)
    +
    +/*
    + * Architecture dependant immediate information, used internally for immediate
    + * activation.
    + */
    +
    +/*
    + * Offset of the immediate value from the start of the addi instruction (result
    + * of the li mnemonic), in bytes.
    + */
    +#define IMMEDIATE_OPTIMIZED_ENABLE_IMMEDIATE_OFFSET 2
    +#define IMMEDIATE_OPTIMIZED_ENABLE_TYPE unsigned short
    +/* Dereference enable as lvalue from a pointer to its instruction */
    +#define IMMEDIATE_OPTIMIZED_ENABLE(a) \
    + (*(IMMEDIATE_OPTIMIZED_ENABLE_TYPE*) \
    + ((char*)(a)+IMMEDIATE_OPTIMIZED_ENABLE_IMMEDIATE_OFFSET))
    +
    +extern int immediate_optimized_set_enable(void *address, char enable);
    +
    +#endif /* _ASM_POWERPC_IMMEDIATE_H */
    Index: linux-2.6-lttng/arch/powerpc/kernel/Makefile
    ===================================================================
    --- linux-2.6-lttng.orig/arch/powerpc/kernel/Makefile 2007-06-18 19:15:39.000000000 -0400
    +++ linux-2.6-lttng/arch/powerpc/kernel/Makefile 2007-06-18 19:15:46.000000000 -0400
    @@ -96,3 +96,4 @@

    extra-$(CONFIG_PPC_FPU) += fpu.o
    extra-$(CONFIG_PPC64) += entry_64.o
    +obj-$(CONFIG_IMMEDIATE) += immediate.o
    Index: linux-2.6-lttng/arch/powerpc/kernel/immediate.c
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-2.6-lttng/arch/powerpc/kernel/immediate.c 2007-06-18 19:27:52.000000000 -0400
    @@ -0,0 +1,29 @@
    +/*
    + * Powerpc optimized immediate values enabling/disabling.
    + *
    + * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    + */
    +
    +#include <linux/module.h>
    +#include <linux/immediate.h>
    +#include <linux/string.h>
    +#include <asm/cacheflush.h>
    +#include <asm/page.h>
    +
    +/*
    + * The address is aligned on 4 bytes boundary: the 4 bytes instruction we are
    + * changing fits within one page.
    + */
    +int immediate_optimized_set_enable(void *address, char enable)
    +{
    + char newi[IMMEDIATE_OPTIMIZED_ENABLE_IMMEDIATE_OFFSET+1];
    + int size = IMMEDIATE_OPTIMIZED_ENABLE_IMMEDIATE_OFFSET
    + + sizeof(IMMEDIATE_OPTIMIZED_ENABLE_TYPE);
    +
    + memcpy(newi, address, size);
    + IMMEDIATE_OPTIMIZED_ENABLE(&newi[0]) = enable;
    + memcpy(address, newi, size);
    + flush_icache_range((unsigned long)address, size);
    + return 0;
    +}
    +EXPORT_SYMBOL_GPL(immediate_optimized_set_enable);
    --
    Mathieu Desnoyers
    Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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