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s390x/tcg: Fix VECTOR SUBTRACT COMPUTE BORROW INDICATION

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Looks like my idea of what a "borrow" is was wrong. The PoP says:

 "If the resulting subtraction results in a carry out of bit zero, a value
 of one is placed in the corresponding element of the first operand;
 otherwise, a value of zero is placed in the corresponding element"

As clarified by Richard, all we have to do is invert the result.

Fixes: 1ee2d7ba72 ("s390x/tcg: Implement VECTOR SUBTRACT COMPUTE BORROW INDICATION")
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20191021085715.3797-5-david@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
David Hildenbrand 2019-10-21 10:57:13 +02:00 committed by Cornelia Huck
parent b57b336876
commit 23e797749f
2 changed files with 5 additions and 4 deletions
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7
target/s390x/translate_vx.inc.c
View File

@ -2132,12 +2132,12 @@ static DisasJumpType op_vs(DisasContext *s, DisasOps *o)
static void gen_scbi_i32(TCGv_i32 d, TCGv_i32 a, TCGv_i32 b)
{
tcg_gen_setcond_i32(TCG_COND_LTU, d, a, b);
tcg_gen_setcond_i32(TCG_COND_GEU, d, a, b);
}
static void gen_scbi_i64(TCGv_i64 d, TCGv_i64 a, TCGv_i64 b)
{
tcg_gen_setcond_i64(TCG_COND_LTU, d, a, b);
tcg_gen_setcond_i64(TCG_COND_GEU, d, a, b);
}
static void gen_scbi2_i64(TCGv_i64 dl, TCGv_i64 dh, TCGv_i64 al,
@ -2151,7 +2151,8 @@ static void gen_scbi2_i64(TCGv_i64 dl, TCGv_i64 dh, TCGv_i64 al,
tcg_gen_andi_i64(th, th, 1);
tcg_gen_sub2_i64(tl, th, ah, zero, th, zero);
tcg_gen_sub2_i64(tl, th, tl, th, bh, zero);
tcg_gen_andi_i64(dl, th, 1);
/* "invert" the result: -1 -> 0; 0 -> 1 */
tcg_gen_addi_i64(dl, th, 1);
tcg_gen_mov_i64(dh, zero);
tcg_temp_free_i64(th);

2
target/s390x/vec_int_helper.c
View File

@ -593,7 +593,7 @@ void HELPER(gvec_vscbi##BITS)(void *v1, const void *v2, const void *v3, \
const uint##BITS##_t a = s390_vec_read_element##BITS(v2, i); \
const uint##BITS##_t b = s390_vec_read_element##BITS(v3, i); \
\
s390_vec_write_element##BITS(v1, i, a < b); \
s390_vec_write_element##BITS(v1, i, a >= b); \
} \
}
DEF_VSCBI(8)