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target/mips: Make the results of MOD_<U|S>.<B|H|W|D> the same as on hardware

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MSA instructions MOD_<U|S>.<B|H|W|D> when dividing by zero,
didn't return the same value when executed on a referent hardware
(FPGA MIPS 64 r6, little endian) and when executed on QEMU, which
is not a real bug, because the result when dividing by zero is
UNPREDICTABLE [1] (page 255, 256).

[1] MIPS Architecture for Programmers
Volume IV-j: The MIPS64 SIMD
Architecture Module, Revision 1.12

Backports commit cf122bf8d2732d5d8647901ebaea596668aaaa3a from qemu
This commit is contained in:
Mateja Marjanovic 2019-05-28 19:24:58 -04:00 committed by Lioncash
parent d712d3f226
commit 1527b25428
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 2 additions and 2 deletions
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4
qemu/target/mips/msa_helper.c
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@ -657,14 +657,14 @@ static inline int64_t msa_mod_s_df(uint32_t df, int64_t arg1, int64_t arg2)
if (arg1 == DF_MIN_INT(df) && arg2 == -1) {
return 0;
}
return arg2 ? arg1 % arg2 : 0;
return arg2 ? arg1 % arg2 : arg1;
}
static inline int64_t msa_mod_u_df(uint32_t df, int64_t arg1, int64_t arg2)
{
uint64_t u_arg1 = UNSIGNED(arg1, df);
uint64_t u_arg2 = UNSIGNED(arg2, df);
return u_arg2 ? u_arg1 % u_arg2 : 0;
return u_arg2 ? u_arg1 % u_arg2 : u_arg1;
}
#define SIGNED_EVEN(a, df) \