build: check AVX512 rather than binutils version

Rather than checking the binutils version number, which can lead to
unnecessary disabling of AVX512 if fixes have been backported to distro
versions, we can instead check the output of "as" from binutils to see if
it is correct.

The check in the script uses the minimal assembly reproduction code posted
to the public bug tracker for gcc/binutils for those issues [1]. If the
binutils bug is present, the instruction parameters - specifically the
displacement parameter - will be different in the disassembled output
compared to the input. Therefore the check involves assembling a single
instruction and disassembling it again, checking that the two match.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90028

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Tested-by: Harry van Haaren <harry.van.haaren@intel.com>

MAINTAINERS

@@ -123,6 +123,7 @@ M: Bruce Richardson <bruce.richardson@intel.com>
 F: meson.build
 F: meson_options.txt
 F: config/rte_config.h
+F: buildtools/binutils-avx512-check.sh
 F: buildtools/call-sphinx-build.py
 F: buildtools/gen-pmdinfo-cfile.sh
 F: buildtools/list-dir-globs.py

buildtools/binutils-avx512-check.sh

@@ -0,0 +1,16 @@
+#! /bin/sh
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2020 Intel Corporation
+
+AS=${AS:-as}
+OBJFILE=$(mktemp -t dpdk.binutils-check.XXXXXX.o)
+trap 'rm -f "$OBJFILE"' EXIT
+# from https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90028
+GATHER_PARAMS='0x8(,%ymm1,1),%ymm0{%k2}'
+
+# assemble vpgather to file and similarly check
+echo "vpgatherqq $GATHER_PARAMS" | $AS --64 -o $OBJFILE -
+objdump -d  --no-show-raw-insn $OBJFILE | grep -q $GATHER_PARAMS || {
+	echo "vpgatherqq displacement error with as"
+	exit 1
+}

buildtools/meson.build

@@ -1,13 +1,12 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2017-2019 Intel Corporation
 
-subdir('pmdinfogen')
-
 pkgconf = find_program('pkg-config', 'pkgconf', required: false)
 pmdinfo = find_program('gen-pmdinfo-cfile.sh')
 list_dir_globs = find_program('list-dir-globs.py')
 check_symbols = find_program('check-symbols.sh')
 ldflags_ibverbs_static = find_program('options-ibverbs-static.sh')
+binutils_avx512_check = find_program('binutils-avx512-check.sh')
 
 # set up map-to-win script using python, either built-in or external
 python3 = import('python').find_installation(required: false)

config/x86/meson.build

@@ -3,14 +3,10 @@
 
 # get binutils version for the workaround of Bug 97
 if not is_windows
-	ldver = run_command('ld', '-v').stdout().strip()
-	if ldver.contains('2.30') and cc.has_argument('-mno-avx512f')
+	binutils_ok = run_command(binutils_avx512_check)
+	if binutils_ok.returncode() != 0 and cc.has_argument('-mno-avx512f')
 		machine_args += '-mno-avx512f'
-		message('Binutils 2.30 detected, disabling AVX512 support as workaround for bug #97')
-	endif
-	if ldver.contains('2.31') and cc.has_argument('-mno-avx512f')
-		machine_args += '-mno-avx512f'
-		message('Binutils 2.31 detected, disabling AVX512 support as workaround for bug #249')
+		warning('Binutils error with AVX512 assembly, disabling AVX512 support')
 	endif
 endif
 

meson.build

@@ -39,10 +39,13 @@ global_inc = include_directories('.', 'config',
 	'lib/librte_eal/@0@/include'.format(host_machine.system()),
 	'lib/librte_eal/@0@/include'.format(arch_subdir),
 )
+
+# do configuration and get tool paths
+subdir('buildtools')
 subdir('config')
 
 # build libs and drivers
-subdir('buildtools')
+subdir('buildtools/pmdinfogen')
 subdir('lib')
 subdir('drivers')