Files
linux/lib
Nathan Chancellor d93fe5e6c9 ARM: 8833/1: Ensure that NEON code always compiles with Clang
[ Upstream commit de9c0d49d8 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-04-05 22:33:08 +02:00
..
2018-07-10 15:00:52 -06:00
2018-08-22 10:52:48 -07:00
2017-12-01 13:09:40 -08:00
2017-12-01 13:09:40 -08:00
2018-10-12 09:17:46 +02:00
2018-08-16 12:14:42 -07:00
2017-12-01 13:09:40 -08:00
2011-10-29 21:20:22 +02:00
2018-02-06 18:32:44 -08:00
2018-08-22 10:52:48 -07:00
2018-07-23 15:22:39 +10:00
2014-04-30 19:49:37 +01:00
2018-02-06 18:32:44 -08:00
2017-10-07 10:45:14 -06:00
2017-02-24 17:46:57 -08:00
2018-06-12 16:19:22 -07:00
2018-05-01 10:22:41 -04:00
2018-04-12 09:41:19 -07:00
2018-06-12 16:19:22 -07:00
2017-12-01 13:09:40 -08:00
2018-10-12 09:17:46 +02:00
2017-12-01 13:09:40 -08:00
2016-12-06 10:17:03 +02:00
2018-08-21 23:54:21 -04:00
2018-06-27 18:58:49 +03:00
2018-10-15 16:31:29 -04:00
2018-04-23 16:39:35 +01:00
2017-08-15 09:02:07 -07:00