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[#6] (Try to) generalise dealing with flags.
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@kosarev
kosarev committed Jun 24, 2021
1 parent b4cb5df commit 9c8ed3c
Showing 1 changed file with 76 additions and 40 deletions.
116 changes: 76 additions & 40 deletions z80.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2418,7 +2418,7 @@ class i8080_executor : public internals::executor_base<B> {
fast_u8 hfb(fast_u8 ops12) {
return (ops12 << (base::hf_bit - 3)) & hf_mask; }

enum class flag_op { adc, sbc, bitwise, set_cf, daa };
enum class flag_op { adc, sbc, bitwise, daa };

enum class flag_set : fast_u8 {
cf = cf_mask,
Expand All @@ -2432,7 +2432,7 @@ class i8080_executor : public internals::executor_base<B> {
// core code executing instructions as possible, leaving there
// only those operations that can be performed very fast.
// TODO: Provide a way to control CF separately.
fast_u8 flags(flag_op fop, fast_u8 b, fast_u16 w) {
fast_u8 eval_flags(flag_op fop, fast_u8 b, fast_u16 w) {
switch(fop) {
case flag_op::adc:
case flag_op::sbc: {
Expand All @@ -2446,8 +2446,6 @@ class i8080_executor : public internals::executor_base<B> {
fast_u8 res = mask8(w); // TODO: Can be just a cast?
fast_u8 ops12 = b;
return sf(res) | zf(res) | pf(res) | hfb(ops12); }
case flag_op::set_cf:
return (b & ~cf_mask) | cfa(w);
case flag_op::daa: {
fast_u8 t = b;
fast_u8 hf = static_cast<fast_u8>(w & hf_mask);
Expand All @@ -2456,39 +2454,77 @@ class i8080_executor : public internals::executor_base<B> {
unreachable("Unknown flag set!");
}

// TODO: Make this public once lazy flags are fully supported.
// TODO: Test calls to this function.
fast_u8 on_flags_read(flag_set fs) {
return self().on_get_f() & static_cast<fast_u8>(fs);
fast_u32 eval_adc_flags(fast_u8 ops12, fast_u16 res) {
return eval_flags(flag_op::adc, ops12, res);
}

fast_u32 eval_sbc_flags(fast_u8 ops12, fast_u16 res) {
return eval_flags(flag_op::sbc, ops12, res);
}

fast_u32 eval_bitwise_flags(fast_u8 ops12, fast_u16 res) {
return eval_flags(flag_op::bitwise, ops12, res);
}

fast_u32 eval_daa_flags(fast_u8 b, fast_u16 w) {
return eval_flags(flag_op::daa, b, w);
}

void unpack_flags(fast_u32 flags, flag_op &fop, fast_u8 &b, fast_u16 &w) {
fop = static_cast<flag_op>(flags >> 24);
b = mask8(flags >> 16);
w = mask16(flags);
}

// TODO: Make this public once lazy flags are fully supported.
// TODO: Test calls to this function.
void on_flags_update(flag_op fop, fast_u8 b, fast_u16 w) {
self().on_set_f(flags(fop, b, w));
fast_u32 on_get_flags() {
return self().on_get_f();
}

void on_set_flags(fast_u32 flags) {
#if 0 // TODO
flag_op fop;
fast_u8 b;
fast_u16 w;
unpack_flags(flags, fop, b, w);
self().on_set_f(eval_flags(fop, b, w));
#endif
self().on_set_f(static_cast<fast_u8>(flags));
}

static fast_u8 get_cf(fast_u32 flags) {
return flags & cf_mask;
}

static fast_u32 set_cf(fast_u32 flags, fast_u32 cf) {
return (flags & ~cf_mask) | cf;
}

static fast_u8 get_hf_cf(fast_u32 flags) {
return flags & (hf_mask | cf_mask);
}

public:
void do_alu(alu k, fast_u8 n) {
fast_u8 a = self().on_get_a();
flag_op fop;
fast_u16 t;
fast_u8 b;
fast_u32 flags;
if(((static_cast<unsigned>(k) + 1) & 0x7) < 5) {
// ADD, ADC, SUB, SBC, CP
fast_u8 cfv = (k == alu::adc || k == alu::sbc) ?
self().on_flags_read(flag_set::cf) : 0;
get_cf(self().on_get_flags()) : 0;
b = a ^ n;
if(k <= alu::adc) {
t = a + n + cfv;
fop = flag_op::adc;
flags = eval_adc_flags(b, t);
} else {
t = a - n - cfv;
fop = flag_op::sbc;
flags = eval_sbc_flags(b, t);
}
b = a ^ n;
} else {
// AND, XOR, OR
fop = flag_op::bitwise;
if(k == alu::and_a) {
// Alexander Demin notes that the half-carry flag has
// its own special logic for the ANA and ANI
Expand All @@ -2502,10 +2538,11 @@ class i8080_executor : public internals::executor_base<B> {
t = (k == alu::xor_a) ? a ^ n : a | n;
b = 0;
}
flags = eval_bitwise_flags(b, t);
}
if(k != alu::cp)
self().on_set_a(mask8(t));
self().on_flags_update(fop, b, t);
self().on_set_flags(flags);
}

void on_add_irp_rp(regp rp) {
Expand All @@ -2514,12 +2551,11 @@ class i8080_executor : public internals::executor_base<B> {

fast_u16 i = self().on_get_hl();
fast_u16 n = self().on_get_regp(rp);
fast_u8 f = self().on_flags_read(flag_set::sf_zf_hf_pf);
fast_u32 flags = self().on_get_flags();
fast_u32 r32 = i + n;
self().on_set_wz(inc16(i));
self().on_set_hl(mask16(r32));
self().on_flags_update(flag_op::set_cf, f,
static_cast<fast_u16>(r32 >> 8)); }
self().on_set_flags(set_cf(flags, r32 >> 16)); }
void on_alu_r(alu k, reg r) {
do_alu(k, self().on_get_reg(r)); }
void on_call_cc_nn(condition cc, fast_u16 nn) {
Expand All @@ -2529,13 +2565,13 @@ class i8080_executor : public internals::executor_base<B> {
self().on_set_wz(nn);
}
void on_ccf() {
fast_u8 f = self().on_flags_read(flag_set::all);
self().on_flags_update(flag_op::set_cf, f, (f ^ cf_mask) << 8); }
fast_u32 flags = self().on_get_flags();
self().on_set_flags(set_cf(flags, get_cf(flags) ^ 1)); }
void on_cpl() {
self().on_set_a(self().on_get_a() ^ 0xff); }
void on_daa() {
fast_u8 a = self().on_get_a();
fast_u8 f = self().on_flags_read(flag_set::hf_cf);
fast_u8 f = get_hf_cf(self().on_get_flags());

fast_u8 r = a;
fast_u8 t = r + 6;
Expand All @@ -2549,13 +2585,13 @@ class i8080_executor : public internals::executor_base<B> {
r = mask8(t2);

self().on_set_a(r);
self().on_flags_update(flag_op::daa, r, w | hfv); }
self().on_set_flags(eval_daa_flags(r, w | hfv)); }
void on_dec_r(reg r) {
fast_u8 n = self().on_get_reg(r);
fast_u8 f = self().on_flags_read(flag_set::cf);
fast_u32 flags = self().on_get_flags();
fast_u8 t = mask8(n - 1);
self().on_set_reg(r, t);
self().on_flags_update(flag_op::sbc, n ^ 1, (f << 8) | t); }
self().on_set_flags(eval_sbc_flags(n ^ 1, (get_cf(flags) << 8) | t)); }
void on_di() {
self().set_iff_on_di(false); }
void on_ei() {
Expand All @@ -2581,10 +2617,10 @@ class i8080_executor : public internals::executor_base<B> {
self().on_set_a(self().on_input_cycle(n)); }
void on_inc_r(reg r) {
fast_u8 n = self().on_get_reg(r);
fast_u8 f = self().on_flags_read(flag_set::cf);
fast_u32 flags = self().on_get_flags();
fast_u8 t = mask8(n + 1);
self().on_set_reg(r, t);
self().on_flags_update(flag_op::adc, n ^ 1, (f << 8) | t); }
self().on_set_flags(eval_adc_flags(n ^ 1, (get_cf(flags) << 8) | t)); }
void on_ld_r_n(reg r, fast_u8 n) {
self().on_set_reg(r, n); }
void on_ld_r_r(reg rd, reg rs) {
Expand Down Expand Up @@ -2622,31 +2658,31 @@ class i8080_executor : public internals::executor_base<B> {
self().on_set_regp2(rp, nn); }
void on_rla() {
fast_u8 a = self().on_get_a();
fast_u8 f = self().on_flags_read(flag_set::all);
fast_u16 t = (a << 1) | (f & cf_mask);
fast_u32 flags = self().on_get_flags();
fast_u16 t = (a << 1) | get_cf(flags);
self().on_set_a(mask8(t));
self().on_flags_update(flag_op::set_cf, f, t); }
self().on_set_flags(set_cf(flags, t >> 8)); }
void on_rra() {
fast_u8 a = self().on_get_a();
fast_u8 f = self().on_flags_read(flag_set::all);
fast_u8 r = (a >> 1) | ((f & cf_mask) << 7);
fast_u32 flags = self().on_get_flags();
fast_u8 r = (a >> 1) | (get_cf(flags) << 7);
self().on_set_a(r);
self().on_flags_update(flag_op::set_cf, f, a << 8); }
self().on_set_flags(set_cf(flags, a & 1)); }
void on_rlca() {
fast_u8 a = self().on_get_a();
fast_u8 f = self().on_flags_read(flag_set::all);
fast_u32 flags = self().on_get_flags();
a = rol8(a);
self().on_set_a(a);
self().on_flags_update(flag_op::set_cf, f, a << 8); }
self().on_set_flags(set_cf(flags, a & 1)); }
void on_rrca() {
fast_u8 a = self().on_get_a();
fast_u8 f = self().on_flags_read(flag_set::all);
fast_u32 flags = self().on_get_flags();
a = ror8(a);
self().on_set_a(a);
self().on_flags_update(flag_op::set_cf, f, a << 1); }
self().on_set_flags(set_cf(flags, a >> 7)); }
void on_scf() {
fast_u8 f = self().on_flags_read(flag_set::sf_zf_hf_pf);
self().on_flags_update(flag_op::set_cf, f, 0x100); }
fast_u32 flags = self().on_get_flags();
self().on_set_flags(set_cf(flags, 1)); }

protected:
using base::self;
Expand Down

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