[PATCH 0/3] Claw back the IS_<platform> optimisation

[Tvrtko Ursulin <tursulin@ursulin.net>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Reorganise the IS_<platform> code a bit inspired by the pre-processor
code generation as used by Chris in the self test patches.

This avoids some source code duplication and makes maintenance easier.

In the last patch try to claw back the multiple IS_<platform> optimisation,
as the commit message says:

    If we use only power of two values for the platform enum
    values we can let the compiler optimize some common
    checks to a single conditional.

    For example code like this:

        if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))

    Goes from this:

       5c3c5:       8b 83 d8 06 00 00       mov    0x6d8(%rbx),%eax
       5c3cb:       83 f8 12                cmp    $0x12,%eax
       5c3ce:       0f 84 f3 00 00 00       je     5c4c7 <fw_domain_init+0x1a7>
       5c3d4:       83 f8 15                cmp    $0x15,%eax
       5c3d7:       0f 84 ea 00 00 00       je     5c4c7 <fw_domain_init+0x1a7>

    To this:

       5c1d5:       f7 83 d8 06 00 00 00    testl  $0x240000,0x6d8(%rbx)
       5c1dc:       00 24 00
       5c1df:       0f 85 da 00 00 00       jne    5c2bf <fw_domain_init+0x18f>

    It is not much but there is value in this that as long as we
    have to have conditions like the above sprinkled troughout the
    code, we can at least have the generate binary a bit smarter.

    Until we get to more than 32 platforms there is no downside
    to this approach.

Patch series saves 1890 bytes of binary:

   text    data     bss     dec     hex filename
1103970   26273     580 1130823  114147 i915.ko.0
1102080   26273     580 1128933  1139e5 i915.ko.1

Tvrtko Ursulin (3):
  drm/i915: Introduct i915_platforms.h
  drm/i915: Generate all IS_<platform> macros
  drm/i915: Number the platform enum strategically

 drivers/gpu/drm/i915/i915_drv.h          | 69 +++++++++-----------------------
 drivers/gpu/drm/i915/i915_platforms.h    | 34 ++++++++++++++++
 drivers/gpu/drm/i915/intel_device_info.c | 38 ++++--------------
 3 files changed, 61 insertions(+), 80 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/i915_platforms.h

-- 
2.7.4

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