target/arm: Vectorize USHL and SSHL
These instructions shift left or right depending on the sign of the input, and 7 bits are significant to the shift. This requires several masks and selects in addition to the actual shifts to form the complete answer. That said, the operation is still a small improvement even for two 64-bit elements -- 13 vector operations instead of 2 * 7 integer operations. Reviewed-by: NAlex Bennée <alex.bennee@linaro.org> Signed-off-by: NRichard Henderson <richard.henderson@linaro.org> Message-id: 20200216214232.4230-2-richard.henderson@linaro.org Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
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