|
|
@@ -0,0 +1,118 @@
|
|
|
+From 93d4579f90dd6ad26fd0dcda6420b3bb2fdcbc02 Mon Sep 17 00:00:00 2001
|
|
|
+From: Julien Olivain <ju.o@free.fr>
|
|
|
+Date: Mon, 20 Feb 2023 23:22:28 +0100
|
|
|
+Subject: [PATCH] Fix compilation for armv7 targets with vfp < v4 and gcc >= 8
|
|
|
+MIME-Version: 1.0
|
|
|
+Content-Type: text/plain; charset=UTF-8
|
|
|
+Content-Transfer-Encoding: 8bit
|
|
|
+
|
|
|
+When using a armv7 gcc >= 8 toolchain (like [1]) with Highway
|
|
|
+configured with -DHWY_CMAKE_ARM7=OFF and HWY_ENABLE_CONTRIB=ON,
|
|
|
+compilation fails with error:
|
|
|
+
|
|
|
+ In file included from /build/highway-1.0.3/hwy/ops/arm_neon-inl.h:33,
|
|
|
+ from /build/highway-1.0.3/hwy/highway.h:358,
|
|
|
+ from /build/highway-1.0.3/hwy/contrib/sort/shared-inl.h:104,
|
|
|
+ from /build/highway-1.0.3/hwy/contrib/sort/traits128-inl.h:27,
|
|
|
+ from /build/highway-1.0.3/hwy/contrib/sort/vqsort_128d.cc:23,
|
|
|
+ from /build/highway-1.0.3/hwy/foreach_target.h:81,
|
|
|
+ from /build/highway-1.0.3/hwy/contrib/sort/vqsort_128d.cc:20:
|
|
|
+ /toolchain/lib/gcc/arm-buildroot-linux-gnueabihf/12.2.0/include/arm_neon.h: In function 'void hwy::N_NEON::StoreU(Vec128<long long unsigned int, 2>, Full128<long long unsigned int>, uint64_t*)':
|
|
|
+ /toolchain/lib/gcc/arm-buildroot-linux-gnueabihf/12.2.0/include/arm_neon.h:11052:1: error: inlining failed in call to 'always_inline' 'void vst1q_u64(uint64_t*, uint64x2_t)': target specific option mismatch
|
|
|
+ 11052 | vst1q_u64 (uint64_t * __a, uint64x2_t __b)
|
|
|
+ | ^~~~~~~~~
|
|
|
+ /build/highway-1.0.3/hwy/ops/arm_neon-inl.h:2786:12: note: called from here
|
|
|
+ 2786 | vst1q_u64(unaligned, v.raw);
|
|
|
+ | ~~~~~~~~~^~~~~~~~~~~~~~~~~~
|
|
|
+
|
|
|
+The same errors happen when configured with HWY_ENABLE_EXAMPLES=ON,
|
|
|
+or from client libraries like libjxl (at other places).
|
|
|
+
|
|
|
+The issue is that Highway Arm NEON ops have a dependency on the
|
|
|
+Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions.
|
|
|
+The SIMD (Neon) v1 and VFPv3 instructions are not supported.
|
|
|
+
|
|
|
+There was several attempts to fix variants of this issues.
|
|
|
+See #834 and #1032.
|
|
|
+
|
|
|
+HWY_NEON target is selected only if __ARM_NEON is defined. See:
|
|
|
+https://github.com/google/highway/blob/1.0.3/hwy/detect_targets.h#L251
|
|
|
+
|
|
|
+This test is not sufficient since __ARM_NEON will be predefined in
|
|
|
+any cases when Neon is enabled (neon-vfpv3, neon-vfpv4).
|
|
|
+
|
|
|
+The issue is that HWY_CMAKE_ARM7=ON implies VFPv4 / NEON SIMD v2.
|
|
|
+When setting HWY_CMAKE_ARM7=OFF, "neon-vfpv4" will not be forced,
|
|
|
+but the code is still using intrinsics assuming VFPv4. Gcc will fail
|
|
|
+with error because code cannot be generated for the selected
|
|
|
+architecture.
|
|
|
+
|
|
|
+This issue can be avoided by adding "-DHWY_DISABLED_TARGETS=HWY_NEON" in
|
|
|
+CXXFLAGS. The problem with this solution is that every client program will
|
|
|
+also need to do the same. This goes against the very purpose of
|
|
|
+"hwy/detect_targets.h".
|
|
|
+
|
|
|
+Technically, Armv7-a processors with VFPv4 can be detected using some
|
|
|
+ACLE (Arm C Language Extensions [2]) predefined macros:
|
|
|
+
|
|
|
+Basically, we want Highway to define HWY_NEON only when the target
|
|
|
+supports SIMDv2/VFPv4 or higher. An older target with vfpv3 only
|
|
|
+(e.g. Cortex-A8, A9, ...) would NOT define HWY_NEON, and therefore
|
|
|
+would fallback on HWY_SCALAR implementation.
|
|
|
+
|
|
|
+However, not all compiler completely support ACLE. There is also
|
|
|
+several versions too. So we cannot easily rely on macros like
|
|
|
+"__ARM_VFPV4__" (which clang predefine, but not gcc).
|
|
|
+
|
|
|
+The alternative solution proposed in this patch, is to declare the
|
|
|
+HWY_NEON target architecture as broken, when we detect the target is
|
|
|
+Armv7-A, but mandatory features for vfpv4 (namely half-float, FMA)
|
|
|
+are missing. Half-floats are tested using the macro __ARM_NEON_FP,
|
|
|
+and the FMA with the macro __ARM_FEATURE_FMA. See ACLE [2]. The
|
|
|
+intent of declaring the target as broken, rather than selecting
|
|
|
+HWY_NEON only if vfpv4 features are detected is to remain a bit
|
|
|
+conservative, since the detection is slithly inaccurate.
|
|
|
+
|
|
|
+For a given compiler/cflags, predefined macros for Arm/ACLE can be
|
|
|
+reviewed with commands like:
|
|
|
+
|
|
|
+ arm-linux-gnueabihf-gcc -mcpu=cortex-a9 -mfpu=neon-vfpv3 -Wp,-dM -E -c - < /dev/null | grep -Fi arm | sort
|
|
|
+ arm-linux-gnueabihf-gcc -mcpu=cortex-a7 -mfpu=neon-vfpv4 -Wp,-dM -E -c - < /dev/null | grep -Fi arm | sort
|
|
|
+ clang -target armv7a -mcpu=cortex-a9 -mfpu=neon-vfpv3 -mfloat-abi=hard -Wp,-dM -E -c - < /dev/null | grep -Fi arm | sort
|
|
|
+ clang -target armv7a -mcpu=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard -Wp,-dM -E -c - < /dev/null | grep -Fi arm | sort
|
|
|
+
|
|
|
+The different values of __ARM_NEON_FP can be seen, depending which
|
|
|
+"-mfpu" is passed. Same for __ARM_FEATURE_FMA.
|
|
|
+
|
|
|
+[1] https://toolchains.bootlin.com/downloads/releases/toolchains/armv7-eabihf/tarballs/armv7-eabihf--glibc--bleeding-edge-2022.08-1.tar.bz2
|
|
|
+[2] https://github.com/ARM-software/acle/
|
|
|
+
|
|
|
+Signed-off-by: Julien Olivain <ju.o@free.fr>
|
|
|
+---
|
|
|
+ hwy/detect_targets.h | 10 ++++++++++
|
|
|
+ 1 file changed, 10 insertions(+)
|
|
|
+
|
|
|
+diff --git a/hwy/detect_targets.h b/hwy/detect_targets.h
|
|
|
+index 2beca95..40ae7fe 100644
|
|
|
+--- a/hwy/detect_targets.h
|
|
|
++++ b/hwy/detect_targets.h
|
|
|
+@@ -154,6 +154,16 @@
|
|
|
+ (defined(__BYTE_ORDER) && __BYTE_ORDER == __BIG_ENDIAN))
|
|
|
+ #define HWY_BROKEN_TARGETS (HWY_NEON)
|
|
|
+
|
|
|
++// armv7-a without a detected vfpv4 is not supported
|
|
|
++// (for example Cortex-A8, Cortex-A9)
|
|
|
++// vfpv4 always have neon half-float _and_ FMA.
|
|
|
++#elif HWY_ARCH_ARM_V7 && \
|
|
|
++ (__ARM_ARCH_PROFILE == 'A') && \
|
|
|
++ !defined(__ARM_VFPV4__) && \
|
|
|
++ !((__ARM_NEON_FP & 0x2 /* half-float */) && \
|
|
|
++ (__ARM_FEATURE_FMA == 1))
|
|
|
++#define HWY_BROKEN_TARGETS (HWY_NEON)
|
|
|
++
|
|
|
+ // SVE[2] require recent clang or gcc versions.
|
|
|
+ #elif (HWY_COMPILER_CLANG && HWY_COMPILER_CLANG < 1100) || \
|
|
|
+ (HWY_COMPILER_GCC_ACTUAL && HWY_COMPILER_GCC_ACTUAL < 1000)
|
|
|
+--
|
|
|
+2.39.2
|
|
|
+
|
Julien Olivain