From: Jani Nikula <jani.nikula@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH] drm/i915: Use __is_constexpr()
Date: Thu, 21 Mar 2019 11:50:25 +0200 [thread overview]
Message-ID: <87o964eeu6.fsf@intel.com> (raw)
In-Reply-To: <20190320154021.5244-1-chris@chris-wilson.co.uk>
On Wed, 20 Mar 2019, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> gcc-4.8 and older dislike the use of __builtin_constant_p() within a
> constant expression context, and so we must use the magical
> __is_constexpr() instead.
>
> For example, with gcc-4.8.5:
> ../drivers/gpu/drm/i915/i915_reg.h:167:27: error: first argument to ‘__builtin_choose_expr’ not a constant
> ../include/linux/build_bug.h:16:45: error: bit-field ‘<anonymous>’ width not an integer constant
>
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Fixes: baa09e7d2f42 ("drm/i915: use REG_FIELD_PREP() to define register bitfield values")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
Thanks, Uma reported this too and confirmed __is_constexpr works.
Reported-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 85e8d1a1f70b..50d0b2ae89eb 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -161,10 +161,10 @@
> */
> #define REG_FIELD_PREP(__mask, __val) \
> ((u32)((((typeof(__mask))(__val) << __bf_shf(__mask)) & (__mask)) + \
> - BUILD_BUG_ON_ZERO(!__builtin_constant_p(__mask)) + \
> + BUILD_BUG_ON_ZERO(!__is_constexpr(__mask)) + \
> BUILD_BUG_ON_ZERO((__mask) == 0 || (__mask) > U32_MAX) + \
> BUILD_BUG_ON_ZERO(!IS_POWER_OF_2((__mask) + (1ULL << __bf_shf(__mask)))) + \
> - BUILD_BUG_ON_ZERO(__builtin_choose_expr(__builtin_constant_p(__val), (~((__mask) >> __bf_shf(__mask)) & (__val)), 0))))
> + BUILD_BUG_ON_ZERO(__builtin_choose_expr(__is_constexpr(__val), (~((__mask) >> __bf_shf(__mask)) & (__val)), 0))))
>
> /**
> * REG_FIELD_GET() - Extract a u32 bitfield value
--
Jani Nikula, Intel Open Source Graphics Center
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next prev parent reply other threads:[~2019-03-21 9:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-20 15:40 [PATCH] drm/i915: Use __is_constexpr() Chris Wilson
2019-03-20 16:05 ` Randy Dunlap
2019-03-20 17:20 ` ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2019-03-21 9:50 ` Jani Nikula [this message]
2019-03-21 10:00 ` [PATCH] " Chris Wilson
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