diff mbox series

[RFC] build/pkg-config: remove machine arch flag

Message ID 20201211155111.145279-1-bruce.richardson@intel.com (mailing list archive)
State New
Delegated to: Thomas Monjalon
Headers show
Series [RFC] build/pkg-config: remove machine arch flag | expand

Checks

Context Check Description
ci/Intel-compilation success Compilation OK
ci/checkpatch warning coding style issues

Commit Message

Bruce Richardson Dec. 11, 2020, 3:51 p.m. UTC
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(-)

--
2.27.0

Comments

David Christensen Dec. 16, 2020, 6:45 p.m. UTC | #1
On 12/11/20 7:51 AM, Bruce Richardson wrote:
> 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?

Support for Altivec would be the equivalent here for PPC and I'm not 
aware of any additional flags required for supported POWER CPUs on DPDK. 
  I can't speak to P10 requirements yet but the proposed change is a 
don't care for me.

Dave
diff mbox series

Patch

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]