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@xxxxxxxxxxxxx>
Fixes: baa09e7d2f42 ("drm/i915: use REG_FIELD_PREP() to define register bitfield values")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Imre Deak <imre.deak@xxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
---
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
--
2.20.1
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