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target/i386: implement CMPccXADD

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The main difficulty here is that a page fault when writing to the destination
must not overwrite the flags.  Therefore, the flags computation must be
inlined instead of using gen_jcc1*.

For simplicity, I am using an unconditional cmpxchg operation, that becomes
a NOP if the comparison fails.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2023-10-10 10:31:39 +02:00
parent e7bbb7cb71
commit 405c7c0708
5 changed files with 133 additions and 1 deletions
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2
target/i386/cpu.c
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@ -738,7 +738,7 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
#define TCG_7_0_EDX_FEATURES (CPUID_7_0_EDX_FSRM | CPUID_7_0_EDX_KERNEL_FEATURES)
#define TCG_7_1_EAX_FEATURES (CPUID_7_1_EAX_FZRM | CPUID_7_1_EAX_FSRS | \
CPUID_7_1_EAX_FSRC)
CPUID_7_1_EAX_FSRC | CPUID_7_1_EAX_CMPCCXADD)
#define TCG_7_1_EDX_FEATURES 0
#define TCG_7_2_EDX_FEATURES 0
#define TCG_APM_FEATURES 0

25
target/i386/tcg/decode-new.c.inc
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@ -538,6 +538,28 @@ static const X86OpEntry opcodes_0F38_00toEF[240] = {
[0xdd] = X86_OP_ENTRY3(VAESENCLAST, V,x, H,x, W,x, vex4 cpuid(AES) p_66),
[0xde] = X86_OP_ENTRY3(VAESDEC, V,x, H,x, W,x, vex4 cpuid(AES) p_66),
[0xdf] = X86_OP_ENTRY3(VAESDECLAST, V,x, H,x, W,x, vex4 cpuid(AES) p_66),
/*
* REG selects srcdest2 operand, VEX.vvvv selects src3. VEX class not found
* in manual, assumed to be 13 from the VEX.L0 constraint.
*/
[0xe0] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe1] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe2] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe3] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe4] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe5] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe6] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe7] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe8] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xe9] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xea] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xeb] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xec] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xed] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xee] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
[0xef] = X86_OP_ENTRY3(CMPccXADD, M,y, G,y, B,y, vex13 xchg chk(o64) cpuid(CMPCCXADD) p_66),
};
/* five rows for no prefix, 66, F3, F2, 66+F2 */
@ -1503,6 +1525,9 @@ static bool has_cpuid_feature(DisasContext *s, X86CPUIDFeature cpuid)
return (s->cpuid_7_0_ebx_features & CPUID_7_0_EBX_AVX2);
case X86_FEAT_SHA_NI:
return (s->cpuid_7_0_ebx_features & CPUID_7_0_EBX_SHA_NI);
case X86_FEAT_CMPCCXADD:
return (s->cpuid_7_1_eax_features & CPUID_7_1_EAX_CMPCCXADD);
}
g_assert_not_reached();
}

1
target/i386/tcg/decode-new.h
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@ -104,6 +104,7 @@ typedef enum X86CPUIDFeature {
X86_FEAT_AVX2,
X86_FEAT_BMI1,
X86_FEAT_BMI2,
X86_FEAT_CMPCCXADD,
X86_FEAT_F16C,
X86_FEAT_FMA,
X86_FEAT_MOVBE,

104
target/i386/tcg/emit.c.inc
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@ -1190,6 +1190,110 @@ static void gen_BZHI(DisasContext *s, CPUX86State *env, X86DecodedInsn *decode)
prepare_update2_cc(decode, s, CC_OP_BMILGB + ot);
}
static void gen_CMPccXADD(DisasContext *s, CPUX86State *env, X86DecodedInsn *decode)
{
TCGLabel *label_top = gen_new_label();
TCGLabel *label_bottom = gen_new_label();
TCGv oldv = tcg_temp_new();
TCGv newv = tcg_temp_new();
TCGv cmpv = tcg_temp_new();
TCGCond cond;
TCGv cmp_lhs, cmp_rhs;
MemOp ot, ot_full;
int jcc_op = (decode->b >> 1) & 7;
static const TCGCond cond_table[8] = {
[JCC_O] = TCG_COND_LT, /* test sign bit by comparing against 0 */
[JCC_B] = TCG_COND_LTU,
[JCC_Z] = TCG_COND_EQ,
[JCC_BE] = TCG_COND_LEU,
[JCC_S] = TCG_COND_LT, /* test sign bit by comparing against 0 */
[JCC_P] = TCG_COND_EQ, /* even parity - tests low bit of popcount */
[JCC_L] = TCG_COND_LT,
[JCC_LE] = TCG_COND_LE,
};
cond = cond_table[jcc_op];
if (decode->b & 1) {
cond = tcg_invert_cond(cond);
}
ot = decode->op[0].ot;
ot_full = ot | MO_LE;
if (jcc_op >= JCC_S) {
/*
* Sign-extend values before subtracting for S, P (zero/sign extension
* does not matter there) L, LE and their inverses.
*/
ot_full |= MO_SIGN;
}
/*
* cmpv will be moved to cc_src *after* cpu_regs[] is written back, so use
* tcg_gen_ext_tl instead of gen_ext_tl.
*/
tcg_gen_ext_tl(cmpv, cpu_regs[decode->op[1].n], ot_full);
/*
* Cmpxchg loop starts here.
* - s->T1: addition operand (from decoder)
* - s->A0: dest address (from decoder)
* - s->cc_srcT: memory operand (lhs for comparison)
* - cmpv: rhs for comparison
*/
gen_set_label(label_top);
gen_op_ld_v(s, ot_full, s->cc_srcT, s->A0);
tcg_gen_sub_tl(s->T0, s->cc_srcT, cmpv);
/* Compute the comparison result by hand, to avoid clobbering cc_*. */
switch (jcc_op) {
case JCC_O:
/* (src1 ^ src2) & (src1 ^ dst). newv is only used here for a moment */
tcg_gen_xor_tl(newv, s->cc_srcT, s->T0);
tcg_gen_xor_tl(s->tmp0, s->cc_srcT, cmpv);
tcg_gen_and_tl(s->tmp0, s->tmp0, newv);
tcg_gen_sextract_tl(s->tmp0, s->tmp0, 0, 8 << ot);
cmp_lhs = s->tmp0, cmp_rhs = tcg_constant_tl(0);
break;
case JCC_P:
tcg_gen_ext8u_tl(s->tmp0, s->T0);
tcg_gen_ctpop_tl(s->tmp0, s->tmp0);
tcg_gen_andi_tl(s->tmp0, s->tmp0, 1);
cmp_lhs = s->tmp0, cmp_rhs = tcg_constant_tl(0);
break;
case JCC_S:
tcg_gen_sextract_tl(s->tmp0, s->T0, 0, 8 << ot);
cmp_lhs = s->tmp0, cmp_rhs = tcg_constant_tl(0);
break;
default:
cmp_lhs = s->cc_srcT, cmp_rhs = cmpv;
break;
}
/* Compute new value: if condition does not hold, just store back s->cc_srcT */
tcg_gen_add_tl(newv, s->cc_srcT, s->T1);
tcg_gen_movcond_tl(cond, newv, cmp_lhs, cmp_rhs, newv, s->cc_srcT);
tcg_gen_atomic_cmpxchg_tl(oldv, s->A0, s->cc_srcT, newv, s->mem_index, ot_full);
/* Exit unconditionally if cmpxchg succeeded. */
tcg_gen_brcond_tl(TCG_COND_EQ, oldv, s->cc_srcT, label_bottom);
/* Try again if there was actually a store to make. */
tcg_gen_brcond_tl(cond, cmp_lhs, cmp_rhs, label_top);
gen_set_label(label_bottom);
/* Store old value to registers only after a successful store. */
gen_writeback(s, decode, 1, s->cc_srcT);
decode->cc_dst = s->T0;
decode->cc_src = cmpv;
decode->cc_op = CC_OP_SUBB + ot;
}
static void gen_CRC32(DisasContext *s, CPUX86State *env, X86DecodedInsn *decode)
{
MemOp ot = decode->op[2].ot;

2
target/i386/tcg/translate.c
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@ -122,6 +122,7 @@ typedef struct DisasContext {
int cpuid_ext3_features;
int cpuid_7_0_ebx_features;
int cpuid_7_0_ecx_features;
int cpuid_7_1_eax_features;
int cpuid_xsave_features;
/* TCG local temps */
@ -6963,6 +6964,7 @@ static void i386_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cpu)
dc->cpuid_ext3_features = env->features[FEAT_8000_0001_ECX];
dc->cpuid_7_0_ebx_features = env->features[FEAT_7_0_EBX];
dc->cpuid_7_0_ecx_features = env->features[FEAT_7_0_ECX];
dc->cpuid_7_1_eax_features = env->features[FEAT_7_1_EAX];
dc->cpuid_xsave_features = env->features[FEAT_XSAVE];
dc->jmp_opt = !((cflags & CF_NO_GOTO_TB) ||
(flags & (HF_TF_MASK | HF_INHIBIT_IRQ_MASK)));