A recent commit in clang added -Wtautological-compare to -Wall, which is
enabled for i915 so we see the following warning:
../drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:1485:22: warning:
result of comparison of constant 576460752303423487 with expression of
type 'unsigned int' is always false
[-Wtautological-constant-out-of-range-compare]
if (unlikely(remain > N_RELOC(ULONG_MAX)))
~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
This warning only happens on x86_64 but that check is relevant for
32-bit x86 so we cannot remove it. -Wtautological-compare on a whole has
good warnings but this one is not really relevant for the kernel because
of all of the different configurations that are used to build the
kernel. When -Wtautological-compare is enabled for the kernel, this
option will remain disabled so do that for i915 now.
Link: https://github.com/ClangBuiltLinux/linux/issues/778
Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
---
v1 -> v2: https://lore.kernel.org/lkml/20200211050808.29463-1-natechancellor@xxxxxxxxx/
* Fix patch application due to basing on a local tree that had
-Wuninitialized turned on. Can confirm that patch applies on
latest -next now.
drivers/gpu/drm/i915/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index b8c5f8934dbd..159355eb43a9 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -22,6 +22,7 @@ subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
subdir-ccflags-y += $(call cc-disable-warning, sometimes-uninitialized)
subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides)
subdir-ccflags-y += $(call cc-disable-warning, uninitialized)
+subdir-ccflags-y += $(call cc-disable-warning, tautological-constant-out-of-range-compare)
subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
# Fine grained warnings disable
--
2.25.0
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