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target-m68k: manage scaled index

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Scaled index is not supported by 68000, 68008, and 68010.

EA = (bd + PC) + Xn.SIZE*SCALE + od

Ignore it:

M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL
2.4 BRIEF EXTENSION WORD FORMAT COMPATIBILITY

"If the MC68000 were to execute an instruction that
encoded a scaling factor, the scaling factor would be
ignored and would not access the desired memory address.
The earlier microprocessors do not recognize the brief
extension word formats implemented by newer processors.
Although they can detect illegal instructions, they do not
decode invalid encodings of the brief extension word formats
as exceptions."

Backports commit d8633620a112296fcf6a6ae9a1cbba614c0ca502 from qemu
This commit is contained in:
Laurent Vivier 2018-02-27 08:27:14 -05:00 committed by Lioncash
parent fa4a71a1bf
commit d29cbb70b3
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 5 additions and 0 deletions
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qemu/target-m68k/translate.c
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@ -286,6 +286,11 @@ static TCGv gen_lea_indexed(CPUM68KState *env, DisasContext *s, TCGv base)
if ((ext & 0x800) == 0 && !m68k_feature(s->env, M68K_FEATURE_WORD_INDEX))
return tcg_ctx->NULL_QREG;
if (m68k_feature(s->env, M68K_FEATURE_M68000) &&
!m68k_feature(s->env, M68K_FEATURE_SCALED_INDEX)) {
ext &= ~(3 << 9);
}
if (ext & 0x100) {
/* full extension word format */
if (!m68k_feature(s->env, M68K_FEATURE_EXT_FULL))