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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/loongarch/include/asm/alternative-asm.h
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/* SPDX-License-Identifier: GPL-2.0 */

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#ifndef _ASM_ALTERNATIVE_ASM_H

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#define _ASM_ALTERNATIVE_ASM_H

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#ifdef __ASSEMBLER__

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#include <asm/asm.h>

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/*

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 * Issue one struct alt_instr descriptor entry (need to put it into

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 * the section .altinstructions, see below). This entry contains

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 * enough information for the alternatives patching code to patch an

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 * instruction. See apply_alternatives().

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 */

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.macro altinstruction_entry orig alt feature orig_len alt_len

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	.long \orig - .

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	.long \alt - .

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	.short \feature

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	.byte \orig_len

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	.byte \alt_len

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.endm

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/*

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 * Define an alternative between two instructions. If @feature is

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 * present, early code in apply_alternatives() replaces @oldinstr with

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 * @newinstr. ".fill" directive takes care of proper instruction padding

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 * in case @newinstr is longer than @oldinstr.

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 */

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.macro ALTERNATIVE oldinstr, newinstr, feature

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140 :

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	\oldinstr

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141 :

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	.fill - (((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)) / 4, 4, 0x03400000

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142 :

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	.pushsection .altinstructions, "a"

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	altinstruction_entry 140b, 143f, \feature, 142b-140b, 144f-143f

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	.popsection

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	.subsection 1

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143 :

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	\newinstr

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144 :

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	.previous

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.endm

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#define old_len			(141b-140b)

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#define new_len1		(144f-143f)

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#define new_len2		(145f-144f)

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#define alt_max_short(a, b)	((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))

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/*

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 * Same as ALTERNATIVE macro above but for two alternatives. If CPU

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 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has

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 * @feature2, it replaces @oldinstr with @feature2.

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 */

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.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2

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140 :

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	\oldinstr

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141 :

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	.fill - ((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \

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		(alt_max_short(new_len1, new_len2) - (old_len)) / 4, 4, 0x03400000

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142 :

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	.pushsection .altinstructions, "a"

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	altinstruction_entry 140b, 143f, \feature1, 142b-140b, 144f-143f, 142b-141b

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	altinstruction_entry 140b, 144f, \feature2, 142b-140b, 145f-144f, 142b-141b

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	.popsection

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	.subsection 1

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143 :

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	\newinstr1

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	\newinstr2

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	.previous

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.endm

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#endif  /*  __ASSEMBLER__  */

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#endif /* _ASM_ALTERNATIVE_ASM_H */

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