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tcg: Fix tcg gen for vectorized absolute value 

The fallback inline expansion for vectorized absolute value,
when the host doesn't support such an insn was flawed.

E.g. when a vector of bytes has all elements negative, mask
will be 0xffff_ffff_ffff_ffff.  Subtracting mask only adds 1
to the low element instead of all elements becase -mask is 1
and not 0x0101_0101_0101_0101.

Signed-off-by: Stephen Long <steplong@quicinc.com>
Message-Id: <20200813161818.190-1-steplong@quicinc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Stephen Long 2020-08-13 09:18:18 -07:00 committed by Richard Henderson
parent 6b8b622e87
commit e7e8f33fb6
1 changed files with 3 additions and 2 deletions
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5
tcg/tcg-op-gvec.c
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@ -2264,12 +2264,13 @@ static void gen_absv_mask(TCGv_i64 d, TCGv_i64 b, unsigned vece)
tcg_gen_muli_i64(t, t, (1 << nbit) - 1);
/*
* Invert (via xor -1) and add one (via sub -1).
* Invert (via xor -1) and add one.
* Because of the ordering the msb is cleared,
* so we never have carry into the next element.
*/
tcg_gen_xor_i64(d, b, t);
tcg_gen_sub_i64(d, d, t);
tcg_gen_andi_i64(t, t, dup_const(vece, 1));
tcg_gen_add_i64(d, d, t);
tcg_temp_free_i64(t);
}