Merge remote-tracking branch 'drm/drm-next' into msm-next

Back-merge drm-next to (indirectly) get arm-smmu updates for making
stall-on-fault more reliable.

Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 9c05a59f0184..d627e66a04a6 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -81,6 +81,28 @@
 #define __is_constexpr(x) \
 	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
 
+/*
+ * Similar to statically_true() but produces a constant expression
+ *
+ * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(),
+ * which require their input to be a constant expression and for which
+ * statically_true() would otherwise fail.
+ *
+ * This is a trade-off: const_true() requires all its operands to be
+ * compile time constants. Else, it would always returns false even on
+ * the most trivial cases like:
+ *
+ *   true || non_const_var
+ *
+ * On the opposite, statically_true() is able to fold more complex
+ * tautologies and will return true on expressions such as:
+ *
+ *   !(non_const_var * 8 % 4)
+ *
+ * For the general case, statically_true() is better.
+ */
+#define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false)
+
 #ifdef __ANDROID__
 /*
  * FIXME: Big hammer to get rid of tons of: