From: Paolo Bonzini Date: Tue, 9 May 2023 14:17:15 +0000 (+0200) Subject: target/i386: fix operand size for VCOMI/VUCOMI instructions X-Git-Tag: qemu-xen-4.18.0-rc5^2~1^2~63 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=eee0666a501558d41b53a793fb0cfdc1e578294e;p=qemu-xen.git target/i386: fix operand size for VCOMI/VUCOMI instructions 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 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1637 Fixes: f8d19eec0d53 ("target/i386: reimplement 0x0f 0x28-0x2f, add AVX", 2022-10-18) Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini (cherry picked from commit 2b55e479e6fcbb466585fd25077a50c32e10dc3a) Signed-off-by: Michael Tokarev --- diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.c.inc index 80c579164f..c2ee712561 100644 --- a/target/i386/tcg/decode-new.c.inc +++ b/target/i386/tcg/decode-new.c.inc @@ -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),