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target/i386: fix operand size for VCOMI/VUCOMI instructions

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Compared to other SSE instructions, VUCOMISx and VCOMISx are different:
the single and double precision versions are distinguished through a
prefix, however they use no-prefix and 0x66 for SS and SD respectively.
Scalar values usually are associated with 0xF2 and 0xF3.

Because of these, they incorrectly perform a 128-bit memory load instead
of a 32- or 64-bit load.  Fix this by writing a custom decoding function.

I tested that the reproducer is fixed and the test-avx output does not
change.

Reported-by: Gabriele Svelto <gsvelto@mozilla.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1637
Fixes: f8d19eec0d ("target/i386: reimplement 0x0f 0x28-0x2f, add AVX", 2022-10-18)
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2023-05-09 16:17:15 +02:00 committed by Matt Borgerson
parent c37add4067
commit ff50379f74
1 changed files with 13 additions and 2 deletions
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15
target/i386/tcg/decode-new.c.inc
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@ -782,6 +782,17 @@ static void decode_0F2D(DisasContext *s, CPUX86State *env, X86OpEntry *entry, ui
*entry = *decode_by_prefix(s, opcodes_0F2D);
}
static void decode_VxCOMISx(DisasContext *s, CPUX86State *env, X86OpEntry *entry, uint8_t *b)
{
/*
* VUCOMISx and VCOMISx are different and use no-prefix and 0x66 for SS and SD
* respectively. Scalar values usually are associated with 0xF2 and 0xF3, for
* which X86_VEX_REPScalar exists, but here it has to be decoded by hand.
*/
entry->s1 = entry->s2 = (s->prefix & PREFIX_DATA ? X86_SIZE_sd : X86_SIZE_ss);
entry->gen = (*b == 0x2E ? gen_VUCOMI : gen_VCOMI);
}
static void decode_sse_unary(DisasContext *s, CPUX86State *env, X86OpEntry *entry, uint8_t *b)
{
if (!(s->prefix & (PREFIX_REPZ | PREFIX_REPNZ))) {
@ -870,8 +881,8 @@ static const X86OpEntry opcodes_0F[256] = {
[0x2B] = X86_OP_GROUP0(0F2B),
[0x2C] = X86_OP_GROUP0(0F2C),
[0x2D] = X86_OP_GROUP0(0F2D),
[0x2E] = X86_OP_ENTRY3(VUCOMI, None,None, V,x, W,x, vex4 p_00_66),
[0x2F] = X86_OP_ENTRY3(VCOMI, None,None, V,x, W,x, vex4 p_00_66),
[0x2E] = X86_OP_GROUP3(VxCOMISx, None,None, V,x, W,x, vex3 p_00_66), /* VUCOMISS/SD */
[0x2F] = X86_OP_GROUP3(VxCOMISx, None,None, V,x, W,x, vex3 p_00_66), /* VCOMISS/SD */
[0x38] = X86_OP_GROUP0(0F38),
[0x3a] = X86_OP_GROUP0(0F3A),