[v2] build: check functionality 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>

---
V2:
- Renamed "as_ok" variable to "binutils_ok" for readability
- Removed one test case from the script because even though two DPDK bugs
  were filed, the one binutils bug is the root cause, and a single commit
  fixes them both
- Changed message() to warning() in the printout
---
 buildtools/binutils-avx512-check.sh | 16 ++++++++++++++++
 buildtools/meson.build              |  3 +--
 config/x86/meson.build              | 10 +++-------
 meson.build                         |  5 ++++-
 4 files changed, 24 insertions(+), 10 deletions(-)
 create mode 100755 buildtools/binutils-avx512-check.sh
  

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Bruce Richardson
> Sent: Thursday, June 18, 2020 12:57 PM
> To: dev@dpdk.org
> Cc: Yigit, Ferruh <ferruh.yigit@intel.com>; thomas@monjalon.net; Richardson,
> Bruce <bruce.richardson@intel.com>
> Subject: [dpdk-dev] [PATCH v2] build: check functionality 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 on binutils 2.30 without backported fixes, can confirm that __AVX512F__ define is
not present at meson configure time.

Tested-by: Harry van Haaren <harry.van.haaren@intel.com>
  

18/06/2020 13:56, Bruce Richardson:
> 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.
[...]
> --- /dev/null
> +++ b/buildtools/binutils-avx512-check.sh
> +MESON_BUILD_ROOT=${MESON_BUILD_ROOT:-/tmp}
> +OBJFILE=$MESON_BUILD_ROOT/binutils-avx512-check.o
> +# 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
> +}

For the temporary OBJFILE, please use mktemp and trap for cleanup.
If you grep "mktemp" in DPDK, you will see the filename is pretty well
standardized with "dpdk." as prefix.
Thanks
  

On Thu, Jul 02, 2020 at 11:28:51PM +0200, Thomas Monjalon wrote:
> 18/06/2020 13:56, Bruce Richardson:
> > 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.
> [...]
> > --- /dev/null
> > +++ b/buildtools/binutils-avx512-check.sh
> > +MESON_BUILD_ROOT=${MESON_BUILD_ROOT:-/tmp}
> > +OBJFILE=$MESON_BUILD_ROOT/binutils-avx512-check.o
> > +# 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
> > +}
> 
> For the temporary OBJFILE, please use mktemp and trap for cleanup.
> If you grep "mktemp" in DPDK, you will see the filename is pretty well
> standardized with "dpdk." as prefix.
> Thanks
>
Will change for v3