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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Sat, 7 Nov 2020 09:29:23 +0100
Message-ID: <CAMj1kXG+qb267Hig6zoO=y6_BVsKsqHikvbJ83YsBD8SBaZ1xw@mail.gmail.com>
Subject: Re: [PATCH v2] Make iwmmxt.S support Clang's integrated assembler
To:     Jian Cai <jiancai@google.com>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Manoj Gupta <manojgupta@google.com>,
        Luis Lozano <llozano@google.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Russell King <linux@armlinux.org.uk>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Sat, 7 Nov 2020 at 01:11, Jian Cai <jiancai@google.com> wrote:
>
> This patch replaces 6 IWMMXT instructions Clang's integrated assembler
> does not support in iwmmxt.S using macros, while making sure GNU
> assembler still emit the same instructions. This should be easier than
> providing full IWMMXT support in Clang.
>
> "Intel Wireless MMX Technology - Developer Guide - August, 2002" should
> be referenced for the encoding schemes of these extensions.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/975
>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Jian Cai <jiancai@google.com>

Please make sure you test this carefully on BE32, as the instruction
byte order used by .inst is LE IIRC

> ---
>  arch/arm/kernel/iwmmxt.S | 89 ++++++++++++++++++++--------------------
>  arch/arm/kernel/iwmmxt.h | 47 +++++++++++++++++++++
>  2 files changed, 92 insertions(+), 44 deletions(-)
>  create mode 100644 arch/arm/kernel/iwmmxt.h
>
> diff --git a/arch/arm/kernel/iwmmxt.S b/arch/arm/kernel/iwmmxt.S
> index 0dcae787b004..d2b4ac06e4ed 100644
> --- a/arch/arm/kernel/iwmmxt.S
> +++ b/arch/arm/kernel/iwmmxt.S
> @@ -16,6 +16,7 @@
>  #include <asm/thread_info.h>
>  #include <asm/asm-offsets.h>
>  #include <asm/assembler.h>
> +#include "iwmmxt.h"
>
>  #if defined(CONFIG_CPU_PJ4) || defined(CONFIG_CPU_PJ4B)
>  #define PJ4(code...)           code
> @@ -113,33 +114,33 @@ concan_save:
>
>  concan_dump:
>
> -       wstrw   wCSSF, [r1, #MMX_WCSSF]
> -       wstrw   wCASF, [r1, #MMX_WCASF]
> -       wstrw   wCGR0, [r1, #MMX_WCGR0]
> -       wstrw   wCGR1, [r1, #MMX_WCGR1]
> -       wstrw   wCGR2, [r1, #MMX_WCGR2]
> -       wstrw   wCGR3, [r1, #MMX_WCGR3]
> +       wstrw   wCSSF, r1, MMX_WCSSF
> +       wstrw   wCASF, r1, MMX_WCASF
> +       wstrw   wCGR0, r1, MMX_WCGR0
> +       wstrw   wCGR1, r1, MMX_WCGR1
> +       wstrw   wCGR2, r1, MMX_WCGR2
> +       wstrw   wCGR3, r1, MMX_WCGR3
>
>  1:     @ MUP? wRn
>         tst     r2, #0x2
>         beq     2f
>
> -       wstrd   wR0,  [r1, #MMX_WR0]
> -       wstrd   wR1,  [r1, #MMX_WR1]
> -       wstrd   wR2,  [r1, #MMX_WR2]
> -       wstrd   wR3,  [r1, #MMX_WR3]
> -       wstrd   wR4,  [r1, #MMX_WR4]
> -       wstrd   wR5,  [r1, #MMX_WR5]
> -       wstrd   wR6,  [r1, #MMX_WR6]
> -       wstrd   wR7,  [r1, #MMX_WR7]
> -       wstrd   wR8,  [r1, #MMX_WR8]
> -       wstrd   wR9,  [r1, #MMX_WR9]
> -       wstrd   wR10, [r1, #MMX_WR10]
> -       wstrd   wR11, [r1, #MMX_WR11]
> -       wstrd   wR12, [r1, #MMX_WR12]
> -       wstrd   wR13, [r1, #MMX_WR13]
> -       wstrd   wR14, [r1, #MMX_WR14]
> -       wstrd   wR15, [r1, #MMX_WR15]
> +       wstrd   wR0,  r1, MMX_WR0
> +       wstrd   wR1,  r1, MMX_WR1
> +       wstrd   wR2,  r1, MMX_WR2
> +       wstrd   wR3,  r1, MMX_WR3
> +       wstrd   wR4,  r1, MMX_WR4
> +       wstrd   wR5,  r1, MMX_WR5
> +       wstrd   wR6,  r1, MMX_WR6
> +       wstrd   wR7,  r1, MMX_WR7
> +       wstrd   wR8,  r1, MMX_WR8
> +       wstrd   wR9,  r1, MMX_WR9
> +       wstrd   wR10, r1, MMX_WR10
> +       wstrd   wR11, r1, MMX_WR11
> +       wstrd   wR12, r1, MMX_WR12
> +       wstrd   wR13, r1, MMX_WR13
> +       wstrd   wR14, r1, MMX_WR14
> +       wstrd   wR15, r1, MMX_WR15
>
>  2:     teq     r0, #0                          @ anything to load?
>         reteq   lr                              @ if not, return
> @@ -147,30 +148,30 @@ concan_dump:
>  concan_load:
>
>         @ Load wRn
> -       wldrd   wR0,  [r0, #MMX_WR0]
> -       wldrd   wR1,  [r0, #MMX_WR1]
> -       wldrd   wR2,  [r0, #MMX_WR2]
> -       wldrd   wR3,  [r0, #MMX_WR3]
> -       wldrd   wR4,  [r0, #MMX_WR4]
> -       wldrd   wR5,  [r0, #MMX_WR5]
> -       wldrd   wR6,  [r0, #MMX_WR6]
> -       wldrd   wR7,  [r0, #MMX_WR7]
> -       wldrd   wR8,  [r0, #MMX_WR8]
> -       wldrd   wR9,  [r0, #MMX_WR9]
> -       wldrd   wR10, [r0, #MMX_WR10]
> -       wldrd   wR11, [r0, #MMX_WR11]
> -       wldrd   wR12, [r0, #MMX_WR12]
> -       wldrd   wR13, [r0, #MMX_WR13]
> -       wldrd   wR14, [r0, #MMX_WR14]
> -       wldrd   wR15, [r0, #MMX_WR15]
> +       wldrd   wR0,  r0, MMX_WR0
> +       wldrd   wR1,  r0, MMX_WR1
> +       wldrd   wR2,  r0, MMX_WR2
> +       wldrd   wR3,  r0, MMX_WR3
> +       wldrd   wR4,  r0, MMX_WR4
> +       wldrd   wR5,  r0, MMX_WR5
> +       wldrd   wR6,  r0, MMX_WR6
> +       wldrd   wR7,  r0, MMX_WR7
> +       wldrd   wR8,  r0, MMX_WR8
> +       wldrd   wR9,  r0, MMX_WR9
> +       wldrd   wR10, r0, MMX_WR10
> +       wldrd   wR11, r0, MMX_WR11
> +       wldrd   wR12, r0, MMX_WR12
> +       wldrd   wR13, r0, MMX_WR13
> +       wldrd   wR14, r0, MMX_WR14
> +       wldrd   wR15, r0, MMX_WR15
>
>         @ Load wCx
> -       wldrw   wCSSF, [r0, #MMX_WCSSF]
> -       wldrw   wCASF, [r0, #MMX_WCASF]
> -       wldrw   wCGR0, [r0, #MMX_WCGR0]
> -       wldrw   wCGR1, [r0, #MMX_WCGR1]
> -       wldrw   wCGR2, [r0, #MMX_WCGR2]
> -       wldrw   wCGR3, [r0, #MMX_WCGR3]
> +       wldrw   wCSSF, r0, MMX_WCSSF
> +       wldrw   wCASF, r0, MMX_WCASF
> +       wldrw   wCGR0, r0, MMX_WCGR0
> +       wldrw   wCGR1, r0, MMX_WCGR1
> +       wldrw   wCGR2, r0, MMX_WCGR2
> +       wldrw   wCGR3, r0, MMX_WCGR3
>
>         @ clear CUP/MUP (only if r1 != 0)
>         teq     r1, #0
> diff --git a/arch/arm/kernel/iwmmxt.h b/arch/arm/kernel/iwmmxt.h
> new file mode 100644
> index 000000000000..fb627286f5bb
> --- /dev/null
> +++ b/arch/arm/kernel/iwmmxt.h
> @@ -0,0 +1,47 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __IWMMXT_H__
> +#define __IWMMXT_H__
> +
> +.irp b, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
> +.set .LwR\b, \b
> +.set .Lr\b, \b
> +.endr
> +
> +.set .LwCSSF, 0x2
> +.set .LwCASF, 0x3
> +.set .LwCGR0, 0x8
> +.set .LwCGR1, 0x9
> +.set .LwCGR2, 0xa
> +.set .LwCGR3, 0xb
> +
> +.macro wldrd, reg:req, base:req, offset:req
> +.inst 0xedd00100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
> +.endm
> +
> +.macro wldrw, reg:req, base:req, offset:req
> +.inst 0xfd900100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
> +.endm
> +
> +.macro wstrd, reg:req, base:req, offset:req
> +.inst 0xedc00100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
> +.endm
> +
> +.macro wstrw, reg:req, base:req, offset:req
> +.inst 0xfd800100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
> +.endm
> +
> +#ifdef __clang__
> +
> +#define wCon c1
> +
> +.macro tmrc, dest:req, control:req
> +mrc p1, 0, \dest, \control, c0, 0
> +.endm
> +
> +.macro tmcr, control:req, src:req
> +mcr p1, 0, \src, \control, c0, 0
> +.endm
> +#endif
> +
> +#endif
> --
> 2.29.1.341.ge80a0c044ae-goog
>