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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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