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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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118c40b7b5
Commit a3e8fe814a ("x86/build: Raise the minimum GCC version to 8.1")
raised the minimum compiler version as enforced by Kbuild to gcc-8.1
and clang-15 for x86.
This is actually the same gcc version that has been discussed as the
minimum for all architectures several times in the past, with little
objection. A previous concern was the kernel for SLE15-SP7 needing to
be built with gcc-7. As this ended up still using linux-6.4 and there
is no plan for an SP8, this is no longer a problem.
Change it for all architectures and adjust the documentation accordingly.
A few version checks can be removed in the process. The binutils
version 2.30 is the lowest version used in combination with gcc-8 on
common distros, so use that as the corresponding minimum.
Link: https://lore.kernel.org/lkml/20240925150059.3955569-32-ardb+git@google.com/
Link: https://lore.kernel.org/lkml/871q7yxrgv.wl-tiwai@suse.de/
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
79 lines
3.0 KiB
C
79 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2023 Google LLC.
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*/
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#ifndef __UNROLL_H
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#define __UNROLL_H
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#include <linux/args.h>
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#ifdef CONFIG_CC_IS_CLANG
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#define __pick_unrolled(x, y) _Pragma(#x)
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#else
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#define __pick_unrolled(x, y) _Pragma(#y)
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#endif
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/**
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* unrolled - loop attributes to ask the compiler to unroll it
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*
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* Usage:
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*
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* #define BATCH 8
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*
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* unrolled_count(BATCH)
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* for (u32 i = 0; i < BATCH; i++)
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* // loop body without cross-iteration dependencies
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*
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* This is only a hint and the compiler is free to disable unrolling if it
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* thinks the count is suboptimal and may hurt performance and/or hugely
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* increase object code size.
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* Not having any cross-iteration dependencies (i.e. when iter x + 1 depends
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* on what iter x will do with variables) is not a strict requirement, but
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* provides best performance and object code size.
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* Available only on Clang and GCC 8.x onwards.
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*/
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/* Ask the compiler to pick an optimal unroll count, Clang only */
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#define unrolled \
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__pick_unrolled(clang loop unroll(enable), /* nothing */)
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/* Unroll each @n iterations of the loop */
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#define unrolled_count(n) \
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__pick_unrolled(clang loop unroll_count(n), GCC unroll n)
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/* Unroll the whole loop */
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#define unrolled_full \
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__pick_unrolled(clang loop unroll(full), GCC unroll 65534)
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/* Never unroll the loop */
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#define unrolled_none \
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__pick_unrolled(clang loop unroll(disable), GCC unroll 1)
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#define UNROLL(N, MACRO, args...) CONCATENATE(__UNROLL_, N)(MACRO, args)
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#define __UNROLL_0(MACRO, args...)
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#define __UNROLL_1(MACRO, args...) __UNROLL_0(MACRO, args) MACRO(0, args)
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#define __UNROLL_2(MACRO, args...) __UNROLL_1(MACRO, args) MACRO(1, args)
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#define __UNROLL_3(MACRO, args...) __UNROLL_2(MACRO, args) MACRO(2, args)
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#define __UNROLL_4(MACRO, args...) __UNROLL_3(MACRO, args) MACRO(3, args)
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#define __UNROLL_5(MACRO, args...) __UNROLL_4(MACRO, args) MACRO(4, args)
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#define __UNROLL_6(MACRO, args...) __UNROLL_5(MACRO, args) MACRO(5, args)
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#define __UNROLL_7(MACRO, args...) __UNROLL_6(MACRO, args) MACRO(6, args)
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#define __UNROLL_8(MACRO, args...) __UNROLL_7(MACRO, args) MACRO(7, args)
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#define __UNROLL_9(MACRO, args...) __UNROLL_8(MACRO, args) MACRO(8, args)
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#define __UNROLL_10(MACRO, args...) __UNROLL_9(MACRO, args) MACRO(9, args)
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#define __UNROLL_11(MACRO, args...) __UNROLL_10(MACRO, args) MACRO(10, args)
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#define __UNROLL_12(MACRO, args...) __UNROLL_11(MACRO, args) MACRO(11, args)
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#define __UNROLL_13(MACRO, args...) __UNROLL_12(MACRO, args) MACRO(12, args)
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#define __UNROLL_14(MACRO, args...) __UNROLL_13(MACRO, args) MACRO(13, args)
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#define __UNROLL_15(MACRO, args...) __UNROLL_14(MACRO, args) MACRO(14, args)
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#define __UNROLL_16(MACRO, args...) __UNROLL_15(MACRO, args) MACRO(15, args)
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#define __UNROLL_17(MACRO, args...) __UNROLL_16(MACRO, args) MACRO(16, args)
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#define __UNROLL_18(MACRO, args...) __UNROLL_17(MACRO, args) MACRO(17, args)
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#define __UNROLL_19(MACRO, args...) __UNROLL_18(MACRO, args) MACRO(18, args)
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#define __UNROLL_20(MACRO, args...) __UNROLL_19(MACRO, args) MACRO(19, args)
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#endif /* __UNROLL_H */
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