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| H A D | jit.c | 9a90c83c Mon Oct 23 13:58:10 CDT 2017 Jakub Kicinski <jakub.kicinski@netronome.com> nfp: bpf: optimize the RMW for stack accesses
When we are performing unaligned stack accesses in the 32-64B window
we have to do a read-modify-write cycle. E.g. for reading 8 bytes
from address 17:
0: tmp = stack[16]
1: gprLo = tmp >> 8
2: tmp = stack[20]
3: gprLo |= tmp << 24
4: tmp = stack[20]
5: gprHi = tmp >> 8
6: tmp = stack[24]
7: gprHi |= tmp << 24
The load on line 4 is unnecessary, because tmp already contains data
from stack[20].
For write we can optimize both loads and writebacks away.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
9a90c83c Mon Oct 23 13:58:10 CDT 2017 Jakub Kicinski <jakub.kicinski@netronome.com> nfp: bpf: optimize the RMW for stack accesses
When we are performing unaligned stack accesses in the 32-64B window
we have to do a read-modify-write cycle. E.g. for reading 8 bytes
from address 17:
0: tmp = stack[16]
1: gprLo = tmp >> 8
2: tmp = stack[20]
3: gprLo |= tmp << 24
4: tmp = stack[20]
5: gprHi = tmp >> 8
6: tmp = stack[24]
7: gprHi |= tmp << 24
The load on line 4 is unnecessary, because tmp already contains data
from stack[20].
For write we can optimize both loads and writebacks away.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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