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target/i386: use TSTEQ/TSTNE to test low bits
When testing the sign bit or equality to zero of a partial register, it is useful to use a single TSTEQ or TSTNE operation. It can also be used to test the parity flag, using bit 0 of the population count. Do not do this for target_ulong-sized values however; the optimizer would produce a comparison against zero anyway, and it avoids shifts by 64 which are undefined behavior. Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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