From 27d0ba8c7e68344bddc16ea304ed0c7ba8817e6d Mon Sep 17 00:00:00 2001 From: Rekai Musuka Date: Fri, 4 Feb 2022 15:50:58 -0400 Subject: [PATCH] chore: clean up THUMB instruction decoding --- src/cpu.zig | 171 ++++++++++++++++++++++++++-------------------------- 1 file changed, 86 insertions(+), 85 deletions(-) diff --git a/src/cpu.zig b/src/cpu.zig index 6e7b025..7f07bfb 100644 --- a/src/cpu.zig +++ b/src/cpu.zig @@ -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] = 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; + break :blk format2(I, is_sub, rn); + } else blk: { + const op = i >> 5 & 0x3; + const offset = i & 0x1F; + break :blk format1(op, offset); + }, + 0b001 => blk: { + const op = i >> 5 & 0x3; + const rd = i >> 2 & 0x7; + 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; + 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; + break :blk format10(L, offset); + }, + 0b001 => blk: { + const L = i >> 5 & 1 == 1; + const rd = i >> 2 & 0x3; + break :blk format11(L, rd); + }, + 0b010 => blk: { + const isSP = i >> 5 & 1 == 1; + const rd = i >> 2 & 0x7; + break :blk format12(isSP, rd); + }, + 0b011 => if (i >> 4 & 1 == 1) blk: { + const L = i >> 5 & 1 == 1; + const R = i >> 2 & 1 == 1; + 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] = 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) { - 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) { - const op = i >> 5 & 0x3; - const offset = i & 0x1F; - - lut[i] = format1(op, offset); - } else if (i >> 7 & 0x7 == 0b001) { - const op = i >> 5 & 0x3; - const rd = i >> 2 & 0x7; - - lut[i] = format3(op, rd); - } else if (i >> 7 & 0x7 == 0b011) { - 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) { - const L = i >> 5 & 1 == 1; - const offset = i & 0x1F; - - lut[i] = format10(L, offset); - } else if (i >> 6 & 0xF == 0b1001) { - const L = i >> 5 & 1 == 1; - const rd = i >> 2 & 0x3; - - lut[i] = format11(L, rd); - } else if (i >> 6 & 0xF == 0b1010) { - 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) { - const L = i >> 5 & 1 == 1; - const R = i >> 2 & 1 == 1; - - lut[i] = format14(L, R); - } else if (i >> 6 & 0xF == 0b1100) { - const L = i >> 5 & 1 == 1; - const rb = i >> 2 & 0x7; - - lut[i] = format15(L, rb); - } else if (i >> 6 & 0xF == 0b1101) { - const cond = i >> 2 & 0xF; - - lut[i] = format16(cond); - } else if (i >> 5 & 0x1F == 0b11100) { - lut[i] = format18(); - } else if (i >> 6 & 0xF == 0b1111) { - const is_low = i >> 5 & 1 == 1; - - lut[i] = format19(is_low); - } + break :blk format15(L, rb); + }, + 0b101 => if (i >> 2 & 0xF == 0b1111) blk: { + break :blk thumbSoftwareInterrupt(); + } else blk: { + const cond = i >> 2 & 0xF; + break :blk format16(cond); + }, + 0b110 => format18(), + 0b111 => blk: { + const is_low = i >> 5 & 1 == 1; + break :blk format19(is_low); + }, + }, + }; } return lut;