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From: Bruce Richardson <bruce.richardson@intel.com>
To: dev@dpdk.org
Cc: bluca@debian.org, david.marchand@redhat.com, ian.stokes@intel.com,
Ilya Maximets <i.maximets@ovn.org>,
Bruce Richardson <bruce.richardson@intel.com>,
Jerin Jacob <jerinj@marvell.com>, Ruifeng Wang <ruifeng.wang@arm.com>,
Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
David Christensen <drc@linux.vnet.ibm.com>
Date: Fri, 11 Dec 2020 15:51:11 +0000
Message-Id: <20201211155111.145279-1-bruce.richardson@intel.com>
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Subject: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag
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Traditionally any apps built using DPDK had to support the same
instruction sets as supported when the DPDK SDK itself was built, since
that was "leaked" through to the end-app and DPDK headers via
RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
for app build correctness the "-march=" flag was included in the
pkg-config cflags output.
However, since the DPDK-specific CPU flags are now obsolete, and we
instead check directly for compiler-defined flags, we should no longer
need to force the exact same architecture match in all cases. To
faciliate such flexibility, a new pkg_config_machine_args array - which
defaults to the existing machine_args array has been defined. The
individual architectures - x86, arm and ppc - can choose if and how to
override this value themselves.
For x86, since SSE4.2 is the minimum instruction-set level needed to run
DPDK, and since some header files assume that minimum level of
instruction set support, we override the "-march=" value with "-msse4"
for the pkg-config file. This allows end applications to set their own
"march" value while still ensuring valid DPDK compilation.
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
CC: Jerin Jacob <jerinj@marvell.com>
CC: Ruifeng Wang <ruifeng.wang@arm.com>
CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
CC: David Christensen <drc@linux.vnet.ibm.com>
Feedback requested from ARM and PPC maintainers as to this change
and what flags, if any, need to be in the .pc file for DPDK on such
platforms. For example - is setting 'pkg_config_machine_args' to
'machine_args' by default necessary behaviour?
---
buildtools/pkg-config/meson.build | 2 +-
config/meson.build | 1 +
config/x86/meson.build | 3 +++
3 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/buildtools/pkg-config/meson.build b/buildtools/pkg-config/meson.build
index 5f1930428..8e2e24681 100644
--- a/buildtools/pkg-config/meson.build
+++ b/buildtools/pkg-config/meson.build
@@ -2,7 +2,7 @@
# Copyright(c) 2020 Intel Corporation
pkg = import('pkgconfig')
-pkg_extra_cflags = ['-include', 'rte_config.h'] + machine_args
+pkg_extra_cflags = ['-include', 'rte_config.h'] + pkg_config_machine_args
if is_freebsd
pkg_extra_cflags += ['-D__BSD_VISIBLE']
endif
diff --git a/config/meson.build b/config/meson.build
index 3ddcc3539..d58ff781d 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -100,6 +100,7 @@ if host_machine.cpu_family().startswith('ppc')
else
machine_args += '-march=' + machine
endif
+pkg_config_machine_args = machine_args # may be overriden late per arch
toolchain = cc.get_id()
dpdk_conf.set_quoted('RTE_TOOLCHAIN', toolchain)
diff --git a/config/x86/meson.build b/config/x86/meson.build
index 31bfa63b1..fcd75502e 100644
--- a/config/x86/meson.build
+++ b/config/x86/meson.build
@@ -16,6 +16,9 @@ if cc.get_define('__SSE4_2__', args: machine_args) == ''
machine_args += '-msse4'
endif
+# require SSE4.2 in pkg-config file - don't use -march
+pkg_config_machine_args = ['-msse4']
+
base_flags = ['SSE', 'SSE2', 'SSE3','SSSE3', 'SSE4_1', 'SSE4_2']
foreach f:base_flags
compile_time_cpuflags += ['RTE_CPUFLAG_' + f]
--
2.27.0