[Bug 2025142] Re: SRU: build isl with the standard baseline

[Steve Langasek]

Test plan says:

> Hard to test, because we don't have older processors available. Just rely
> to the build logs, that no explicit -march option is passed in the compiler flags.

I think we can do better than this; it's possible with qemu to specify
what CPU we want to emulate and we should be able to reproduce this
SIGILL and confirm the fix.

What CPU does the current package's build log report that it's targeted
to?  Is this currently broken only on amd64 or also on other archs?

** Changed in: isl (Ubuntu Lunar)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/2025142

Title:
  SRU: build isl with the standard baseline

Status in isl package in Ubuntu:
  New
Status in isl source package in Jammy:
  New
Status in isl source package in Kinetic:
  New
Status in isl source package in Lunar:
  Incomplete

Bug description:
  by default, isl picks up the current processor and optimizes the build
  for that processor. That's not what we want. Configure isl --without-
  gcc-arch instead.

  [ Impact ]

  GCC (linked to libisl) aborts with an illegal instruction on older
  processors.

  Configuring --without-gcc-arch makes isl (and gcc) to work on all
  processors again.

  [ Test plan ]

  Hard to test, because we don't have older processors available. Just
  rely to the build logs, that no explicit -march option is passed in
  the compiler flags.

  [ Where problems could occur ]

  The regression potential is small, isl is only used for the graphite
  optimizations in GCC, which are not used by default.

  isl might become a bit slower when restricted to the standard
  baseline.

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