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chore: clean up THUMB instruction decoding

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-02-04 15:50:58 -04:00
parent 2f74b61f2e
commit 27d0ba8c7e
1 changed files with 86 additions and 85 deletions
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127
src/cpu.zig
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@ -432,96 +432,97 @@ pub fn checkCond(cpsr: PSR, cond: u4) bool {
fn thumbPopulate() [0x400]ThumbInstrFn {
return comptime {
@setEvalBranchQuota(0x5000);
@setEvalBranchQuota(5025); // This is exact
var lut = [_]ThumbInstrFn{thumbUndefined} ** 0x400;
var i: usize = 0;
while (i < lut.len) : (i += 1) {
if (i >> 4 & 0x3F == 0b010000) {
const op = i & 0xF;
lut[i] = format4(op);
} else if (i >> 4 & 0x3F == 0b010001) {
const op = i >> 2 & 0x3;
const h1 = i >> 1 & 1;
const h2 = i & 1;
lut[i] = format5(op, h1, h2);
} else if (i >> 5 & 0x1F == 0b00011) {
lut[i] = switch (@as(u3, i >> 7 & 0x7)) {
0b000 => if (i >> 5 & 0x3 == 0b11) blk: {
const I = i >> 4 & 1 == 1;
const is_sub = i >> 3 & 1 == 1;
const rn = i & 0x7;
lut[i] = format2(I, is_sub, rn);
} else if (i >> 5 & 0x1F == 0b01001) {
const rd = i >> 2 & 0x7;
lut[i] = format6(rd);
} else if (i >> 6 & 0xF == 0b0101) {
const op = i >> 4 & 0x3;
const T = i >> 3 & 1 == 1;
lut[i] = format78(op, T);
} else if (i >> 7 & 0x7 == 0b000) {
break :blk format2(I, is_sub, rn);
} else blk: {
const op = i >> 5 & 0x3;
const offset = i & 0x1F;
lut[i] = format1(op, offset);
} else if (i >> 7 & 0x7 == 0b001) {
break :blk format1(op, offset);
},
0b001 => blk: {
const op = i >> 5 & 0x3;
const rd = i >> 2 & 0x7;
lut[i] = format3(op, rd);
} else if (i >> 7 & 0x7 == 0b011) {
break :blk format3(op, rd);
},
0b010 => switch (@as(u2, i >> 5 & 0x3)) {
0b00 => if (i >> 4 & 1 == 1) blk: {
const op = i >> 2 & 0x3;
const h1 = i >> 1 & 1;
const h2 = i & 1;
break :blk format5(op, h1, h2);
} else blk: {
const op = i & 0xF;
break :blk format4(op);
},
0b01 => blk: {
const rd = i >> 2 & 0x7;
break :blk format6(rd);
},
else => blk: {
const op = i >> 4 & 0x3;
const T = i >> 3 & 1 == 1;
break :blk format78(op, T);
},
},
0b011 => blk: {
const B = i >> 6 & 1 == 1;
const L = i >> 5 & 1 == 1;
const offset = i & 0x1F;
lut[i] = format9(B, L, offset);
}
if (i >> 2 & 0xFF == 0xB0) {
const S = i >> 1 & 1 == 1;
lut[i] = format13(S);
} else if (i >> 2 & 0xFF == 0xDF) {
lut[i] = thumbSoftwareInterrupt();
} else if (i >> 6 & 0xF == 0b1000) {
break :blk format9(B, L, offset);
},
else => switch (@as(u3, i >> 6 & 0x7)) {
// MSB is guaranteed to be 1
0b000 => blk: {
const L = i >> 5 & 1 == 1;
const offset = i & 0x1F;
lut[i] = format10(L, offset);
} else if (i >> 6 & 0xF == 0b1001) {
break :blk format10(L, offset);
},
0b001 => blk: {
const L = i >> 5 & 1 == 1;
const rd = i >> 2 & 0x3;
lut[i] = format11(L, rd);
} else if (i >> 6 & 0xF == 0b1010) {
break :blk format11(L, rd);
},
0b010 => blk: {
const isSP = i >> 5 & 1 == 1;
const rd = i >> 2 & 0x7;
lut[i] = format12(isSP, rd);
} else if (i >> 6 & 0xF == 0b1011 and i >> 3 & 0x3 == 0b10) {
break :blk format12(isSP, rd);
},
0b011 => if (i >> 4 & 1 == 1) blk: {
const L = i >> 5 & 1 == 1;
const R = i >> 2 & 1 == 1;
lut[i] = format14(L, R);
} else if (i >> 6 & 0xF == 0b1100) {
break :blk format14(L, R);
} else blk: {
const S = i >> 1 & 1 == 1;
break :blk format13(S);
},
0b100 => blk: {
const L = i >> 5 & 1 == 1;
const rb = i >> 2 & 0x7;
lut[i] = format15(L, rb);
} else if (i >> 6 & 0xF == 0b1101) {
break :blk format15(L, rb);
},
0b101 => if (i >> 2 & 0xF == 0b1111) blk: {
break :blk thumbSoftwareInterrupt();
} else blk: {
const cond = i >> 2 & 0xF;
lut[i] = format16(cond);
} else if (i >> 5 & 0x1F == 0b11100) {
lut[i] = format18();
} else if (i >> 6 & 0xF == 0b1111) {
break :blk format16(cond);
},
0b110 => format18(),
0b111 => blk: {
const is_low = i >> 5 & 1 == 1;
lut[i] = format19(is_low);
}
break :blk format19(is_low);
},
},
};
}
return lut;