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authorVineet Gupta <Vineet.Gupta1@synopsys.com>2021-08-05 12:14:08 -0700
committerArnd Bergmann <arnd@arndb.de>2021-08-14 13:07:42 +0200
commit8f76f9c46952659dd925c21c3f62a0d05a3f3e71 (patch)
tree804e531533b24f68c2841facdd8a6aef88997b19 /lib/Kconfig
parenta71bfc0079762b4d3cb36dcc5fe6c23c806cfc8c (diff)
bitops/non-atomic: make @nr unsigned to avoid any DIV
signed math causes generation of costlier instructions such as DIV when they could be done by barrerl shifter. Worse part is this is not caught by things like bloat-o-meter since instruction length / symbols are typically same size. e.g. stock (signed math) __________________ 919b4614 <test_taint>: 919b4614: div r2,r0,0x20 ^^^ 919b4618: add2 r2,0x920f6050,r2 919b4620: ld_s r2,[r2,0] 919b4622: lsr r0,r2,r0 919b4626: j_s.d [blink] 919b4628: bmsk_s r0,r0,0 919b462a: nop_s (patched) unsigned math __________________ 919b4614 <test_taint>: 919b4614: lsr r2,r0,0x5 @nr/32 ^^^ 919b4618: add2 r2,0x920f6050,r2 919b4620: ld_s r2,[r2,0] 919b4622: lsr r0,r2,r0 #test_bit() 919b4626: j_s.d [blink] 919b4628: bmsk_s r0,r0,0 919b462a: nop_s Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'lib/Kconfig')
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