qemu /
qemu /
35020629914b4d3af6195d33e1a68e8b1c8c2fa3 tcg/optimize: optimize TSTNE using smask and zmask
Generalize the existing optimization of "TSTNE x,sign" and "TSTNE x,-1".
This can be useful for example in the i386 frontend, which will generate
tests of zero-extended registers against 0xffffffff.
Ironically, on x86 hosts this is a very slight pessimization in the very
case it's meant to optimize because
brcond_i64 cc_dst,$0xffffffff,tsteq,$L1
(test %ebx, %ebx) is 1 byte smaller than
brcond_i64 cc_dst,$0x0,eq,$L1
(test %rbx, %rbx). However, in general it is an improvement, especially
if it avoids placing a large immediate in the constant pool.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed
