linux/arch/arm
Nathan Chancellor de9c0d49d8 ARM: 8833/1: Ensure that NEON code always compiles with Clang
While building arm32 allyesconfig, I ran into the following errors:

  arch/arm/lib/xor-neon.c:17:2: error: You should compile this file with
  '-mfloat-abi=softfp -mfpu=neon'

  In file included from lib/raid6/neon1.c:27:
  /home/nathan/cbl/prebuilt/lib/clang/8.0.0/include/arm_neon.h:28:2:
  error: "NEON support not enabled"

Building V=1 showed NEON_FLAGS getting passed along to Clang but
__ARM_NEON__ was not getting defined. Ultimately, it boils down to Clang
only defining __ARM_NEON__ when targeting armv7, rather than armv6k,
which is the '-march' value for allyesconfig.

>From lib/Basic/Targets/ARM.cpp in the Clang source:

  // This only gets set when Neon instructions are actually available, unlike
  // the VFP define, hence the soft float and arch check. This is subtly
  // different from gcc, we follow the intent which was that it should be set
  // when Neon instructions are actually available.
  if ((FPU & NeonFPU) && !SoftFloat && ArchVersion >= 7) {
    Builder.defineMacro("__ARM_NEON", "1");
    Builder.defineMacro("__ARM_NEON__");
    // current AArch32 NEON implementations do not support double-precision
    // floating-point even when it is present in VFP.
    Builder.defineMacro("__ARM_NEON_FP",
                        "0x" + Twine::utohexstr(HW_FP & ~HW_FP_DP));
  }

Ard Biesheuvel recommended explicitly adding '-march=armv7-a' at the
beginning of the NEON_FLAGS definitions so that __ARM_NEON__ always gets
definined by Clang. This doesn't functionally change anything because
that code will only run where NEON is supported, which is implicitly
armv7.

Link: https://github.com/ClangBuiltLinux/linux/issues/287

Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
2019-02-12 15:20:09 +00:00
..
boot ARM: 8819/1: Remove '-p' from LDFLAGS 2019-02-01 21:44:07 +00:00
common Included in this update: 2019-01-05 11:23:17 -08:00
configs ARM: SoC: late updates 2019-01-05 11:30:37 -08:00
crypto Kbuild updates for v4.21 2018-12-29 12:03:17 -08:00
firmware
include ARM: avoid Cortex-A9 livelock on tight dmb loops 2019-02-01 22:05:50 +00:00
kernel ARM: avoid Cortex-A9 livelock on tight dmb loops 2019-02-01 22:05:50 +00:00
kvm Kconfig updates for v4.21 2018-12-29 13:03:29 -08:00
lib ARM: 8833/1: Ensure that NEON code always compiles with Clang 2019-02-12 15:20:09 +00:00
mach-actions
mach-alpine
mach-artpec
mach-asm9260
mach-aspeed
mach-at91 treewide: add intermediate .s files to targets 2018-12-23 10:12:08 +09:00
mach-axxia
mach-bcm ARM: SoC platform updates 2018-12-31 17:27:54 -08:00
mach-berlin
mach-clps711x
mach-cns3xxx
mach-davinci ARM: SoC platform updates 2018-12-31 17:27:54 -08:00
mach-digicolor
mach-dove
mach-ebsa110
mach-efm32
mach-ep93xx mmc: spi: Convert to use GPIO descriptors 2018-12-17 08:26:24 +01:00
mach-exynos
mach-footbridge
mach-gemini
mach-highbank
mach-hisi
mach-imx ARM: SoC platform updates 2018-12-31 17:27:54 -08:00
mach-integrator
mach-iop13xx
mach-iop32x
mach-iop33x
mach-ixp4xx
mach-keystone
mach-ks8695 ARM: SoC platform updates 2018-12-31 17:27:54 -08:00
mach-lpc18xx
mach-lpc32xx
mach-mediatek
mach-meson ARM: meson: select HAVE_ARM_TWD and ARM_GLOBAL_TIMER 2018-12-10 12:43:40 -08:00
mach-mmp ARM: Device-tree updates 2018-12-31 17:36:02 -08:00
mach-moxart
mach-mv78xx0
mach-mvebu
mach-mxs
mach-netx
mach-nomadik
mach-npcm
mach-nspire
mach-omap1 ARM: SoC platform updates 2018-12-31 17:27:54 -08:00
mach-omap2 ARM: avoid Cortex-A9 livelock on tight dmb loops 2019-02-01 22:05:50 +00:00
mach-orion5x
mach-oxnas
mach-picoxcell
mach-prima2
mach-pxa Included in this update: 2019-01-05 11:23:17 -08:00
mach-qcom
mach-rda ARM: Prepare RDA8810PL SoC 2018-12-31 13:09:39 -08:00
mach-realview ARM: vexpress/realview: consolidate immitation CPU hotplug 2018-12-14 14:44:59 +00:00
mach-rockchip
mach-rpc
mach-s3c24xx mmc: s3cmci: Use the slot GPIO descriptor 2018-12-17 08:26:24 +01:00
mach-s3c64xx
mach-s5pv210
mach-sa1100 Included in this update: 2019-01-05 11:23:17 -08:00
mach-shmobile ARM: shmobile: R-Mobile: Move pm-rmobile to drivers/soc/renesas/ 2018-11-30 11:29:11 +01:00
mach-socfpga ARM: SoC platform updates 2018-12-31 17:27:54 -08:00
mach-spear
mach-sti ARM: sti: remove pen_release and boot_lock 2018-12-20 14:32:15 +01:00
mach-stm32
mach-sunxi ARM: sunxi: add Allwinner ARMv5 SoCs 2018-12-03 09:57:59 +01:00
mach-tango
mach-tegra ARM: tegra: avoid section mismatch warning 2018-12-12 13:57:55 -08:00
mach-u300
mach-uniphier
mach-ux500
mach-versatile
mach-vexpress ARM: vexpress/realview: consolidate immitation CPU hotplug 2018-12-14 14:44:59 +00:00
mach-vt8500
mach-w90x900
mach-zx
mach-zynq
mm ARM: 8831/1: NOMMU: pmsa-v8: remove unneeded semicolon 2019-02-01 21:44:45 +00:00
net
nwfpe
oprofile Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
plat-iop
plat-omap
plat-orion
plat-pxa
plat-samsung
plat-versatile ARM: versatile: rename and comment SMP implementation 2018-12-14 14:44:59 +00:00
probes
tools kbuild: remove redundant target cleaning on failure 2019-01-06 09:46:51 +09:00
vdso
vfp Merge branches 'misc', 'sa1100-for-next' and 'spectre' into for-linus 2019-01-02 10:37:05 +00:00
xen
Kconfig ARM: 8822/1: smp_twd: Remove legacy TWD registration 2019-02-01 21:44:10 +00:00
Kconfig-nommu ARM: 8832/1: NOMMU: Limit visibility for CONFIG_FLASH_{MEM_BASE,SIZE} 2019-02-01 21:44:46 +00:00
Kconfig.debug i.MX SoC changes for 4.21: 2018-12-12 13:52:48 -08:00
Makefile ARM: 8819/1: Remove '-p' from LDFLAGS 2019-02-01 21:44:07 +00:00