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From: Nathan Chancellor <natechancellor@gmail.com>
To: Jani Nikula <jani.nikula@linux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
	Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH] drm/i915: Disable -Wtautological-constant-out-of-range-compare
Date: Mon, 10 Feb 2020 22:08:08 -0700	[thread overview]
Message-ID: <20200211050808.29463-1-natechancellor@gmail.com> (raw)

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@gmail.com>
---
 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 38df01c23176..55dbcca179c7 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -21,6 +21,7 @@ subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
 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 += $(call cc-disable-warning, tautological-constant-out-of-range-compare)
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
 
 # Fine grained warnings disable
-- 
2.25.0


             reply	other threads:[~2020-02-11  5:08 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11  5:08 Nathan Chancellor [this message]
2020-02-11  6:13 ` [PATCH v2] " Nathan Chancellor
2020-02-11  9:41   ` Michel Dänzer
2020-02-11 20:39     ` Nathan Chancellor
2020-02-12  8:52       ` Michel Dänzer
2020-02-12 17:07         ` Nathan Chancellor
2020-02-12 17:17           ` Michel Dänzer
2020-02-13 14:37             ` [Intel-gfx] " Jani Nikula
2020-02-13 21:48               ` Nathan Chancellor
2020-02-13 22:05                 ` Jani Nikula
2020-02-13 22:43             ` Nick Desaulniers
2020-02-13 23:27               ` Nathan Chancellor

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