Commit 8f6cad7c authored Aug 11, 2022 by David Gow Committed by Greg Kroah-Hartman Oct 26, 2022

drm/amd/display: fix overflow on MIN_I64 definition



[ Upstream commit 6ae0632d17759852c07e2d1e0a31c728eb6ba246 ]

The definition of MIN_I64 in bw_fixed.c can cause gcc to whinge about
integer overflow, because it is treated as a positive value, which is
then negated. The temporary positive value is not necessarily
representable.

This causes the following warning:
../drivers/gpu/drm/amd/amdgpu/../display/dc/dml/calcs/bw_fixed.c:30:19:
warning: integer overflow in expression ‘-9223372036854775808’ of type
‘long long int’ results in ‘-9223372036854775808’ [-Woverflow]
  30 |         (int64_t)(-(1LL << 63))
     |                   ^

Writing out (-MAX_I64 - 1) works instead.

Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Tales Aparecida <tales.aparecida@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent cdde55f9

drivers/gpu/drm/amd/display/dc/calcs/bw_fixed.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -26,12 +26,12 @@
		#include "bw_fixed.h"


		#define MIN_I64 \
		(int64_t)(-(1LL << 63))

		#define MAX_I64 \
		(int64_t)((1ULL << 63) - 1)

		#define MIN_I64 \
		(-MAX_I64 - 1)

		#define FRACTIONAL_PART_MASK \
		((1ULL << BW_FIXED_BITS_PER_FRACTIONAL_PART) - 1)