feat/arm7tdmi_dispatch_table: Done!

Moved away from using lazy_static for this one since every access to a
lazy_static reference adds a runtime check, Currently using a build.rs script to generate a const table instead.

Worked out the ARM decoding issues, seems to run fine now.

Though the dynamic decoding for ARM is broken now since I had to change things in Data Processing and MSR instructions

TODO use `const fn` when it becomes stable


Former-commit-id: ba09748ff74a403c7016adcbe0ca553b591f6855

Cargo.toml

@@ -12,7 +12,6 @@ members = [
 ]
 
 [dependencies]
-lazy_static = {version="1.4.0", optional = true}
 serde = {version = "1.0.104", features = ["derive"] }
 bincode = "1.2.1"
 byteorder = "1"
@@ -39,13 +38,16 @@ rustyline = {version = "6.0.0", optional = true}
 nom = {version = "5.0.0", optional = true}
 gdbstub = {git = "https://github.com/daniel5151/gdbstub.git", optional = true, features = ["std"], rev = "9686df6d74c4bf45cbc5746273b82640e8852b6d"}
 
+[build-dependencies]
+bit = "^0.1"
+
 [features]
+default = ["arm7tdmi_dispatch_table"]
 debugger = ["nom", "rustyline"]
 gdb = ["gdbstub"]
 # Uses lookup tables when executing instructions instead of `match` statements.
 # Faster, but consumes more memory.
-# Experimental and not thoroughly tested yet
-arm7tdmi_dispatch_table = ["lazy_static"]
+arm7tdmi_dispatch_table = []
 
 [profile.dev]
 opt-level = 0

build.rs

@@ -0,0 +1,309 @@
+use std::env;
+use std::fs;
+use std::io::Write;
+use std::path::Path;
+
+extern crate bit;
+use bit::BitIndex;
+
+// copied and slightly adjusted from src/core/arm7tdmi/thumb/mod.rs
+fn thumb_decode(i: u16) -> &'static str {
+    if i & 0xf800 == 0x1800 {
+        "AddSub"
+    } else if i & 0xe000 == 0x0000 {
+        "MoveShiftedReg"
+    } else if i & 0xe000 == 0x2000 {
+        "DataProcessImm"
+    } else if i & 0xfc00 == 0x4000 {
+        "AluOps"
+    } else if i & 0xfc00 == 0x4400 {
+        "HiRegOpOrBranchExchange"
+    } else if i & 0xf800 == 0x4800 {
+        "LdrPc"
+    } else if i & 0xf200 == 0x5000 {
+        "LdrStrRegOffset"
+    } else if i & 0xf200 == 0x5200 {
+        "LdrStrSHB"
+    } else if i & 0xe000 == 0x6000 {
+        "LdrStrImmOffset"
+    } else if i & 0xf000 == 0x8000 {
+        "LdrStrHalfWord"
+    } else if i & 0xf000 == 0x9000 {
+        "LdrStrSp"
+    } else if i & 0xf000 == 0xa000 {
+        "LoadAddress"
+    } else if i & 0xff00 == 0xb000 {
+        "AddSp"
+    } else if i & 0xf600 == 0xb400 {
+        "PushPop"
+    } else if i & 0xf000 == 0xc000 {
+        "LdmStm"
+    } else if i & 0xff00 == 0xdf00 {
+        "Swi"
+    } else if i & 0xf000 == 0xd000 {
+        "BranchConditional"
+    } else if i & 0xf800 == 0xe000 {
+        "Branch"
+    } else if i & 0xf000 == 0xf000 {
+        "BranchLongWithLink"
+    } else {
+        "Undefined"
+    }
+}
+
+trait BitAsInt<T: From<bool>>: BitIndex {
+    fn ibit(&self, i: usize) -> T {
+        self.bit(i).into()
+    }
+}
+
+impl BitAsInt<u32> for u32 {}
+
+/// Returns a string representation of rustboyadvance_ng::core::arm7tdmi::arm::ArmFormat enum member
+/// # Arguments
+/// * `i` - A 32bit ARM instruction
+///
+/// Decoding is according to this table from http://problemkaputt.de/gbatek.htm#ARMBinaryOpcodeFormat
+/// ```
+/// |..3 ..................2 ..................1 ..................0|
+/// |1_0_9_8_7_6_5_4_3_2_1_0_9_8_7_6_5_4_3_2_1_0_9_8_7_6_5_4_3_2_1_0|
+/// |_Cond__|0_0_0|___Op__|S|__Rn___|__Rd___|__Shift__|Typ|0|__Rm___| DataProc
+/// |_Cond__|0_0_0|___Op__|S|__Rn___|__Rd___|__Rs___|0|Typ|1|__Rm___| DataProc
+/// |_Cond__|0_0_1|___Op__|S|__Rn___|__Rd___|_Shift_|___Immediate___| DataProc
+/// |_Cond__|0_0_1_1_0_0_1_0_0_0_0_0_1_1_1_1_0_0_0_0|_____Hint______| ARM11:Hint
+/// |_Cond__|0_0_1_1_0|P|1|0|_Field_|__Rd___|_Shift_|___Immediate___| PSR Imm
+/// |_Cond__|0_0_0_1_0|P|L|0|_Field_|__Rd___|0_0_0_0|0_0_0_0|__Rm___| PSR Reg
+/// |_Cond__|0_0_0_1_0_0_1_0_1_1_1_1_1_1_1_1_1_1_1_1|0_0|L|1|__Rn___| BX,BLX
+/// |1_1_1_0|0_0_0_1_0_0_1_0|_____immediate_________|0_1_1_1|_immed_| ARM9:BKPT
+/// |_Cond__|0_0_0_1_0_1_1_0_1_1_1_1|__Rd___|1_1_1_1|0_0_0_1|__Rm___| ARM9:CLZ
+/// |_Cond__|0_0_0_1_0|Op_|0|__Rn___|__Rd___|0_0_0_0|0_1_0_1|__Rm___| ARM9:QALU
+/// |_Cond__|0_0_0_0_0_0|A|S|__Rd___|__Rn___|__Rs___|1_0_0_1|__Rm___| Multiply
+/// |_Cond__|0_0_0_0_0_1_0_0|_RdHi__|_RdLo__|__Rs___|1_0_0_1|__Rm___| ARM11:UMAAL
+/// |_Cond__|0_0_0_0_1|U|A|S|_RdHi__|_RdLo__|__Rs___|1_0_0_1|__Rm___| MulLong
+/// |_Cond__|0_0_0_1_0|Op_|0|Rd/RdHi|Rn/RdLo|__Rs___|1|y|x|0|__Rm___| MulHalfARM9
+/// |_Cond__|0_0_0_1_0|B|0_0|__Rn___|__Rd___|0_0_0_0|1_0_0_1|__Rm___| TransSwp12
+/// |_Cond__|0_0_0_1_1|_Op__|__Rn___|__Rd___|1_1_1_1|1_0_0_1|__Rm___| ARM11:LDREX
+/// |_Cond__|0_0_0|P|U|0|W|L|__Rn___|__Rd___|0_0_0_0|1|S|H|1|__Rm___| TransReg10
+/// |_Cond__|0_0_0|P|U|1|W|L|__Rn___|__Rd___|OffsetH|1|S|H|1|OffsetL| TransImm10
+/// |_Cond__|0_1_0|P|U|B|W|L|__Rn___|__Rd___|_________Offset________| TransImm9
+/// |_Cond__|0_1_1|P|U|B|W|L|__Rn___|__Rd___|__Shift__|Typ|0|__Rm___| TransReg9
+/// |_Cond__|0_1_1|________________xxx____________________|1|__xxx__| Undefined
+/// |_Cond__|0_1_1|Op_|x_x_x_x_x_x_x_x_x_x_x_x_x_x_x_x_x_x|1|x_x_x_x| ARM11:Media
+/// |1_1_1_1_0_1_0_1_0_1_1_1_1_1_1_1_1_1_1_1_0_0_0_0_0_0_0_1_1_1_1_1| ARM11:CLREX
+/// |_Cond__|1_0_0|P|U|S|W|L|__Rn___|__________Register_List________| BlockTrans
+/// |_Cond__|1_0_1|L|___________________Offset______________________| B,BL,BLX
+/// |_Cond__|1_1_0|P|U|N|W|L|__Rn___|__CRd__|__CP#__|____Offset_____| CoDataTrans
+/// |_Cond__|1_1_0_0_0_1_0|L|__Rn___|__Rd___|__CP#__|_CPopc_|__CRm__| CoRR ARM9
+/// |_Cond__|1_1_1_0|_CPopc_|__CRn__|__CRd__|__CP#__|_CP__|0|__CRm__| CoDataOp
+/// |_Cond__|1_1_1_0|CPopc|L|__CRn__|__Rd___|__CP#__|_CP__|1|__CRm__| CoRegTrans
+/// |_Cond__|1_1_1_1|_____________Ignored_by_Processor______________| SWI
+/// ```
+fn arm_decode(i: u32) -> &'static str {
+    const T: bool = true;
+    const F: bool = false;
+
+    // First, decode the the top-most non-condition bits
+    match i.bit_range(26..28) {
+        0b00 => {
+            /* DataProcessing and friends */
+
+            let result: Option<&str> = match (i.bit_range(23..26), i.bit_range(4..8)) {
+                (0b000, 0b1001) => {
+                    if 0b0 == i.ibit(22) {
+                        Some("Multiply")
+                    } else {
+                        None
+                    }
+                }
+                (0b001, 0b1001) => Some("MultiplyLong"),
+                (0b010, 0b1001) => {
+                    if 0b00 == i.bit_range(20..22) {
+                        Some("SingleDataSwap")
+                    } else {
+                        None
+                    }
+                }
+                (0b010, 0b0001) => {
+                    if 0b010 == i.bit_range(20..23) {
+                        Some("BranchExchange")
+                    } else {
+                        None
+                    }
+                }
+                _ => None,
+            };
+
+            result.unwrap_or_else(|| {
+                match (i.ibit(25), i.ibit(22), i.ibit(7), i.ibit(4)) {
+                    (0, 0, 1, 1) => "HalfwordDataTransferRegOffset",
+                    (0, 1, 1, 1) => "HalfwordDataTransferImmediateOffset",
+                    _ => {
+                        let set_cond_flags = i.bit(20);
+                        // PSR Transfers are encoded as a subset of Data Processing,
+                        // with S bit OFF and the encode opcode is one of TEQ,CMN,TST,CMN
+                        let is_op_not_touching_rd = i.bit_range(21..25) & 0b1100 == 0b1000;
+                        if !set_cond_flags && is_op_not_touching_rd {
+                            if i.bit(21) {
+                                // Since bit-16 is ignored and we can't know statically if this is a MoveToStatus or MoveToFlags
+                                "MoveToStatus"
+                            } else {
+                                "MoveFromStatus"
+                            }
+                        } else {
+                            "DataProcessing"
+                        }
+                    }
+                }
+            })
+        }
+        0b01 => {
+            match (i.bit(25), i.bit(4)) {
+                (_, F) | (F, T) => "SingleDataTransfer",
+                (T, T) => "Undefined", /* Possible ARM11 but we don't implement these */
+            }
+        }
+        0b10 => match i.bit(25) {
+            F => "BlockDataTransfer",
+            T => "BranchLink",
+        },
+        0b11 => {
+            match (i.ibit(25), i.ibit(24), i.ibit(4)) {
+                (0b0, _, _) => "Undefined", /* CoprocessorDataTransfer not implemented */
+                (0b1, 0b0, 0b0) => "Undefined", /* CoprocessorDataOperation not implemented */
+                (0b1, 0b0, 0b1) => "Undefined", /* CoprocessorRegisterTransfer not implemented */
+                (0b1, 0b1, _) => "SoftwareInterrupt",
+                _ => "Undefined",
+            }
+        }
+        _ => unreachable!(),
+    }
+}
+
+fn thumb_format_to_handler(thumb_fmt: &str) -> &'static str {
+    match thumb_fmt {
+        "MoveShiftedReg" => "exec_thumb_move_shifted_reg",
+        "AddSub" => "exec_thumb_add_sub",
+        "DataProcessImm" => "exec_thumb_data_process_imm",
+        "AluOps" => "exec_thumb_alu_ops",
+        "HiRegOpOrBranchExchange" => "exec_thumb_hi_reg_op_or_bx",
+        "LdrPc" => "exec_thumb_ldr_pc",
+        "LdrStrRegOffset" => "exec_thumb_ldr_str_reg_offset",
+        "LdrStrSHB" => "exec_thumb_ldr_str_shb",
+        "LdrStrImmOffset" => "exec_thumb_ldr_str_imm_offset",
+        "LdrStrHalfWord" => "exec_thumb_ldr_str_halfword",
+        "LdrStrSp" => "exec_thumb_ldr_str_sp",
+        "LoadAddress" => "exec_thumb_load_address",
+        "AddSp" => "exec_thumb_add_sp",
+        "PushPop" => "exec_thumb_push_pop",
+        "LdmStm" => "exec_thumb_ldm_stm",
+        "BranchConditional" => "exec_thumb_branch_with_cond",
+        "Swi" => "exec_thumb_swi",
+        "Branch" => "exec_thumb_branch",
+        "BranchLongWithLink" => "exec_thumb_branch_long_with_link",
+        "Undefined" => "thumb_undefined",
+        _ => unreachable!(),
+    }
+}
+
+fn arm_format_to_handler(arm_fmt: &str) -> &'static str {
+    match arm_fmt {
+        "BranchExchange" => "exec_arm_bx",
+        "BranchLink" => "exec_arm_b_bl",
+        "DataProcessing" => "exec_arm_data_processing",
+        "SoftwareInterrupt" => "exec_arm_swi",
+        "SingleDataTransfer" => "exec_arm_ldr_str",
+        "HalfwordDataTransferImmediateOffset" => "exec_arm_ldr_str_hs",
+        "HalfwordDataTransferRegOffset" => "exec_arm_ldr_str_hs",
+        "BlockDataTransfer" => "exec_arm_ldm_stm",
+        "MoveFromStatus" => "exec_arm_mrs",
+        "MoveToStatus" => "exec_arm_transfer_to_status",
+        "MoveToFlags" => "exec_arm_transfer_to_status",
+        "Multiply" => "exec_arm_mul_mla",
+        "MultiplyLong" => "exec_arm_mull_mlal",
+        "SingleDataSwap" => "exec_arm_swp",
+        "Undefined" => "arm_undefined",
+        _ => unreachable!(),
+    }
+}
+
+fn generate_thumb_lut(file: &mut fs::File) -> Result<(), std::io::Error> {
+    writeln!(
+        file,
+        "use super::thumb::ThumbFormat;
+
+pub type ThumbInstructionHandler = fn(&mut Core, &mut SysBus, &ThumbInstruction) -> CpuAction;
+
+pub struct ThumbInstructionInfo {{
+    pub fmt: ThumbFormat,
+    pub handler_fn: ThumbInstructionHandler
+}}
+"
+    )?;
+
+    writeln!(
+        file,
+        "pub const THUMB_LUT: [ThumbInstructionInfo; 1024] = ["
+    )?;
+
+    for i in 0..1024 {
+        let thumb_fmt = thumb_decode(i << 6);
+        let handler_name = thumb_format_to_handler(thumb_fmt);
+        writeln!(
+            file,
+            "    /* {:#x} */ ThumbInstructionInfo {{ fmt: ThumbFormat::{}, handler_fn: Core::{} }},",
+            i, thumb_fmt, handler_name
+        )?;
+    }
+
+    writeln!(file, "];")?;
+
+    Ok(())
+}
+
+fn generate_arm_lut(file: &mut fs::File) -> Result<(), std::io::Error> {
+    writeln!(
+        file,
+        "use super::arm::ArmFormat;
+
+pub type ArmInstructionHandler = fn(&mut Core, &mut SysBus, &ArmInstruction) -> CpuAction;
+
+pub struct ArmInstructionInfo {{
+    pub fmt: ArmFormat,
+    pub handler_fn: ArmInstructionHandler
+}}
+"
+    )?;
+
+    writeln!(file, "pub const ARM_LUT: [ArmInstructionInfo; 4096] = [")?;
+    for i in 0..4096 {
+        let arm_fmt = arm_decode(((i & 0xff0) << 16) | ((i & 0x00f) << 4));
+        let handler_name = arm_format_to_handler(arm_fmt);
+        writeln!(
+            file,
+            "    /* {:#x} */ ArmInstructionInfo {{ fmt: ArmFormat::{}, handler_fn: Core::{} }},",
+            i, arm_fmt, handler_name
+        )?;
+    }
+    writeln!(file, "];")?;
+
+    Ok(())
+}
+
+fn main() {
+    let arm7tdmi_dispatch_table_enabled =
+        env::var_os("CARGO_FEATURE_ARM7TDMI_DISPATCH_TABLE").is_some();
+
+    if arm7tdmi_dispatch_table_enabled {
+        // TODO - don't do this in the build script and use `const fn` instead when it becomes stable
+        let out_dir = env::var_os("OUT_DIR").unwrap();
+        let thumb_lut_path = Path::new(&out_dir).join("thumb_lut.rs");
+        let mut thumb_lut_file = fs::File::create(&thumb_lut_path).expect("failed to create file");
+        generate_thumb_lut(&mut thumb_lut_file).expect("failed to generate thumb table");
+
+        let arm_lut_path = Path::new(&out_dir).join("arm_lut.rs");
+        let mut arm_lut_file = fs::File::create(&arm_lut_path).expect("failed to create file");
+        generate_arm_lut(&mut arm_lut_file).expect("failed to generate arm table");
+
+        println!("cargo:rerun-if-changed=build.rs");
+    }
+}

src/core/arm7tdmi/arm/display.rs

@@ -289,15 +289,16 @@ impl ArmInstruction {
         )
     }
 
-    /// MSR - transfer register contents to PSR
-    fn fmt_msr_reg(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    /// MSR - transfer register/immediate contents to PSR
+    fn fmt_msr(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "msr{cond}\t{psr}, {Rm}",
+            "msr{cond}\t{psr}, ",
             cond = self.cond(),
             psr = if self.spsr_flag() { "SPSR" } else { "CPSR" },
-            Rm = reg_string(self.rm()),
-        )
+        )?;
+        self.fmt_operand2(f).unwrap();
+        Ok(())
     }
 
     fn fmt_msr_flags(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -422,7 +423,7 @@ impl fmt::Display for ArmInstruction {
             SingleDataTransfer => self.fmt_ldr_str(f),
             BlockDataTransfer => self.fmt_ldm_stm(f),
             MoveFromStatus => self.fmt_mrs(f),
-            MoveToStatus => self.fmt_msr_reg(f),
+            MoveToStatus => self.fmt_msr(f),
             MoveToFlags => self.fmt_msr_flags(f),
             Multiply => self.fmt_mul_mla(f),
             MultiplyLong => self.fmt_mull_mlal(f),

src/core/arm7tdmi/arm/exec.rs

@@ -21,8 +21,8 @@ impl Core {
             ArmFormat::HalfwordDataTransferRegOffset => self.exec_arm_ldr_str_hs(bus, insn),
             ArmFormat::BlockDataTransfer => self.exec_arm_ldm_stm(bus, insn),
             ArmFormat::MoveFromStatus => self.exec_arm_mrs(bus, insn),
-            ArmFormat::MoveToStatus => self.exec_arm_msr_reg(bus, insn),
-            ArmFormat::MoveToFlags => self.exec_arm_msr_flags(bus, insn),
+            ArmFormat::MoveToStatus => self.exec_arm_transfer_to_status(bus, insn),
+            ArmFormat::MoveToFlags => self.exec_arm_transfer_to_status(bus, insn),
             ArmFormat::Multiply => self.exec_arm_mul_mla(bus, insn),
             ArmFormat::MultiplyLong => self.exec_arm_mull_mlal(bus, insn),
             ArmFormat::SingleDataSwap => self.exec_arm_swp(bus, insn),
@@ -96,12 +96,46 @@ impl Core {
         self.move_from_status_register(sb, insn.rd(), insn.spsr_flag())
     }
 
-    pub fn exec_arm_msr_reg(&mut self, sb: &mut SysBus, insn: &ArmInstruction) -> CpuAction {
-        self.write_status_register(sb, insn.spsr_flag(), self.get_reg(insn.rm()))
+    #[inline(always)]
+    fn decode_msr_param(&mut self, insn: &ArmInstruction) -> u32 {
+        if insn.raw.bit(25) {
+            let immediate = insn.raw & 0xff;
+            let rotate = 2 * insn.raw.bit_range(8..12);
+            self.ror(immediate, rotate, self.cpsr.C(), false, true)
+        } else {
+            self.get_reg((insn.raw & 0b1111) as usize)
+        }
     }
 
-    fn write_status_register(&mut self, sb: &mut SysBus, is_spsr: bool, value: u32) -> CpuAction {
-        let new_status_reg = RegPSR::new(value);
+    // #[cfg(feature = "arm7tdmi_dispatch_table")]
+    pub fn exec_arm_transfer_to_status(
+        &mut self,
+        sb: &mut SysBus,
+        insn: &ArmInstruction,
+    ) -> CpuAction {
+        let value = self.decode_msr_param(insn);
+
+        let f = insn.raw.bit(19);
+        let s = insn.raw.bit(18);
+        let x = insn.raw.bit(17);
+        let c = insn.raw.bit(16);
+
+        let mut mask = 0;
+        if f {
+            mask |= 0xff << 24;
+        }
+        if s {
+            mask |= 0xff << 16;
+        }
+        if x {
+            mask |= 0xff << 8;
+        }
+        if c {
+            mask |= 0xff << 0;
+        }
+
+        let is_spsr = insn.spsr_flag();
+
         match self.cpsr.mode() {
             CpuMode::User => {
                 if is_spsr {
@@ -113,16 +147,13 @@ impl Core {
                 if is_spsr {
                     self.spsr.set(value);
                 } else {
-                    let t_bit = self.cpsr.state();
                     let old_mode = self.cpsr.mode();
-                    self.cpsr.set(value);
-                    if t_bit != self.cpsr.state() {
-                        panic!("T bit changed from MSR");
-                    }
-                    let new_mode = new_status_reg.mode();
+                    let new_psr = RegPSR::new((self.cpsr.get() & !mask) | (value & mask));
+                    let new_mode = new_psr.mode();
                     if old_mode != new_mode {
                         self.change_mode(old_mode, new_mode);
                     }
+                    self.cpsr = new_psr;
                 }
             }
         }
@@ -131,19 +162,6 @@ impl Core {
         CpuAction::AdvancePC
     }
 
-    pub fn exec_arm_msr_flags(&mut self, sb: &mut SysBus, insn: &ArmInstruction) -> CpuAction {
-        self.S_cycle32(sb, self.pc);
-        let op = insn.operand2();
-        let op = self.decode_operand2(&op);
-
-        if insn.spsr_flag() {
-            self.spsr.set_flag_bits(op);
-        } else {
-            self.cpsr.set_flag_bits(op);
-        }
-        CpuAction::AdvancePC
-    }
-
     fn decode_operand2(&mut self, op2: &BarrelShifterValue) -> u32 {
         match op2 {
             BarrelShifterValue::RotatedImmediate(val, amount) => {
@@ -195,19 +213,6 @@ impl Core {
         let op2 = self.decode_operand2(&op2);
 
         let reg_rd = insn.rd();
-        if !s_flag {
-            match opcode {
-                TEQ => {
-                    return self.write_status_register(sb, false, op2);
-                }
-                CMN => {
-                    return self.write_status_register(sb, true, op2);
-                }
-                TST => return self.move_from_status_register(sb, reg_rd, false),
-                CMP => return self.move_from_status_register(sb, reg_rd, true),
-                _ => (),
-            }
-        }
 
         if reg_rd == REG_PC && s_flag {
             self.transfer_spsr_mode();

src/core/arm7tdmi/arm/lut.rs

@@ -1,161 +0,0 @@
-use super::super::super::SysBus;
-use super::super::Core;
-use super::super::CpuAction;
-use super::{ArmFormat, ArmInstruction};
-
-use bit::BitIndex;
-
-pub type ArmInstructionHandler = fn(&mut Core, &mut SysBus, &ArmInstruction) -> CpuAction;
-
-impl From<ArmFormat> for ArmInstructionHandler {
-    fn from(arm_fmt: ArmFormat) -> ArmInstructionHandler {
-        match arm_fmt {
-            ArmFormat::BranchExchange => Core::exec_arm_bx,
-            ArmFormat::BranchLink => Core::exec_arm_b_bl,
-            ArmFormat::DataProcessing => Core::exec_arm_data_processing,
-            ArmFormat::SoftwareInterrupt => Core::exec_arm_swi,
-            ArmFormat::SingleDataTransfer => Core::exec_arm_ldr_str,
-            ArmFormat::HalfwordDataTransferImmediateOffset => Core::exec_arm_ldr_str_hs,
-            ArmFormat::HalfwordDataTransferRegOffset => Core::exec_arm_ldr_str_hs,
-            ArmFormat::BlockDataTransfer => Core::exec_arm_ldm_stm,
-            ArmFormat::Multiply => Core::exec_arm_mul_mla,
-            ArmFormat::MultiplyLong => Core::exec_arm_mull_mlal,
-            ArmFormat::SingleDataSwap => Core::exec_arm_swp,
-            _ => Core::arm_undefined,
-        }
-    }
-}
-
-pub struct ArmInstructionInfo {
-    pub fmt: ArmFormat,
-    pub handler_fn: ArmInstructionHandler,
-}
-
-impl ArmInstructionInfo {
-    fn new(fmt: ArmFormat, handler_fn: ArmInstructionHandler) -> ArmInstructionInfo {
-        ArmInstructionInfo { fmt, handler_fn }
-    }
-}
-
-#[inline(always)]
-pub fn arm_insn_hash(insn: u32) -> usize {
-    (((insn >> 16) & 0xff0) | ((insn >> 4) & 0x00f)) as usize
-}
-
-impl From<u32> for ArmFormat {
-    fn from(i: u32) -> ArmFormat {
-        use ArmFormat::*;
-
-        // match i.bit_range(26..28) {
-        //     0b00 => {
-        //         match (i.bit_range(23..26), i.bit(22) as u32, i.bit_range(20..22), i.bit_range(4..8)) {
-        //             (0b000, 0b0, , _, 0b1001) => Multiply,
-        //             (0b001, _,  _, 0b1001) => MultiplyLong,
-        //             (0b010, _,  0b00, 0b1001) => SingleDataSwap,
-        //             (0b010, 0b0, 0b10, 0b0001) => BranchExchange,
-
-        //             _ => DataProcessing
-        //         }
-        //     }
-        //     0b01 => {
-        //         if i.bit(4) {
-        //             Undefined
-        //         } else {
-        //             SingleDataTransfer
-        //         }
-        //     }
-        //     0b10 => {
-
-        //     }
-        //     0b11 {
-
-        //     }
-        // }
-
-        if (0x0ff0_00f0 & i) == 0x0120_0010 {
-            BranchExchange
-        } else if (0x0e00_0000 & i) == 0x0a00_0000 {
-            BranchLink
-        } else if (0xe000_0010 & i) == 0x0600_0000 {
-            Undefined
-        } else if (0x0fb0_0ff0 & i) == 0x0100_0090 {
-            SingleDataSwap
-        } else if (0x0fc0_00f0 & i) == 0x0000_0090 {
-            Multiply
-        } else if (0x0f80_00f0 & i) == 0x0080_0090 {
-            MultiplyLong
-        } else if (0x0c00_0000 & i) == 0x0400_0000 {
-            SingleDataTransfer
-        } else if (0x0e40_0F90 & i) == 0x0000_0090 {
-            HalfwordDataTransferRegOffset
-        } else if (0x0e40_0090 & i) == 0x0040_0090 {
-            HalfwordDataTransferImmediateOffset
-        } else if (0x0e00_0000 & i) == 0x0800_0000 {
-            BlockDataTransfer
-        } else if (0x0f00_0000 & i) == 0x0f00_0000 {
-            SoftwareInterrupt
-        } else if (0x0c00_0000 & i) == 0x0000_0000 {
-            DataProcessing
-        } else {
-            Undefined
-        }
-    }
-}
-
-lazy_static! {
-
-    pub static ref ARM_FN_LUT: [ArmInstructionHandler; 256] = {
-
-        use std::mem::{self, MaybeUninit};
-
-        let mut lut: [MaybeUninit<ArmInstructionHandler>; 256] = unsafe {
-            MaybeUninit::uninit().assume_init()
-        };
-
-        for i in 0..256 {
-            lut[i] = MaybeUninit::new(Core::arm_undefined);
-        }
-
-        lut[ArmFormat::BranchExchange as usize] = MaybeUninit::new(Core::exec_arm_bx);
-        lut[ArmFormat::BranchLink as usize] = MaybeUninit::new(Core::exec_arm_b_bl);
-        lut[ArmFormat::DataProcessing as usize] = MaybeUninit::new(Core::exec_arm_data_processing);
-        lut[ArmFormat::SoftwareInterrupt as usize] = MaybeUninit::new(Core::exec_arm_swi);
-        lut[ArmFormat::SingleDataTransfer as usize] = MaybeUninit::new(Core::exec_arm_ldr_str);
-        lut[ArmFormat::HalfwordDataTransferImmediateOffset as usize] = MaybeUninit::new(Core::exec_arm_ldr_str_hs);
-        lut[ArmFormat::HalfwordDataTransferRegOffset as usize] = MaybeUninit::new(Core::exec_arm_ldr_str_hs);
-        lut[ArmFormat::BlockDataTransfer as usize] = MaybeUninit::new(Core::exec_arm_ldm_stm);
-        lut[ArmFormat::MoveFromStatus as usize] = MaybeUninit::new(Core::exec_arm_mrs);
-        lut[ArmFormat::MoveToStatus as usize] = MaybeUninit::new(Core::exec_arm_msr_reg);
-        lut[ArmFormat::MoveToFlags as usize] = MaybeUninit::new(Core::exec_arm_msr_flags);
-        lut[ArmFormat::Multiply as usize] = MaybeUninit::new(Core::exec_arm_mul_mla);
-        lut[ArmFormat::MultiplyLong as usize] = MaybeUninit::new(Core::exec_arm_mull_mlal);
-        lut[ArmFormat::SingleDataSwap as usize] = MaybeUninit::new(Core::exec_arm_swp);
-        lut[ArmFormat::Undefined as usize] = MaybeUninit::new(Core::arm_undefined);
-
-        // Everything is initialized. Transmute the array to the
-        // initialized type.
-        unsafe { mem::transmute::<_, [ArmInstructionHandler; 256]>(lut) }
-    };
-
-    // there are 0xfff different hashes
-    pub static ref ARM_LUT: [u8; 4096] = {
-
-        debug!("generating ARM lookup table");
-
-        use std::mem::{self, MaybeUninit};
-
-        let mut lut: [MaybeUninit<u8>; 4096] = unsafe {
-            MaybeUninit::uninit().assume_init()
-        };
-
-        for i in 0..4096 {
-            let x = ((i & 0xff0) << 16) | ((i & 0x00f) << 4);
-            let fmt = ArmFormat::from(x);
-            lut[i as usize] = MaybeUninit::new(fmt as u8);
-        }
-
-        // Everything is initialized. Transmute the array to the
-        // initialized type.
-        unsafe { mem::transmute::<_, [u8; 4096]>(lut) }
-    };
-}

src/core/arm7tdmi/arm/mod.rs

@@ -1,11 +1,6 @@
 pub mod display;
 pub mod exec;
 
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-mod lut;
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-pub use lut::*;
-
 use serde::{Deserialize, Serialize};
 
 use super::alu::*;

src/core/arm7tdmi/cpu.rs

@@ -7,28 +7,30 @@ use serde::{Deserialize, Serialize};
 use std::fmt;
 
 use super::arm::ArmCond;
+
+// Include files that are auto-generated by the build script
+// See `build.rs`
 #[cfg(feature = "arm7tdmi_dispatch_table")]
-use super::arm::{arm_insn_hash, ARM_LUT};
+include!(concat!(env!("OUT_DIR"), "/arm_lut.rs"));
+#[cfg(feature = "arm7tdmi_dispatch_table")]
+include!(concat!(env!("OUT_DIR"), "/thumb_lut.rs"));
+
+#[cfg(not(feature = "arm7tdmi_dispatch_table"))]
+use super::InstructionDecoder;
+
 pub use super::exception::Exception;
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-use super::thumb::THUMB_LUT;
+
 use super::CpuAction;
 #[cfg(feature = "debugger")]
 use super::DecodedInstruction;
 use super::{arm::*, psr::RegPSR, thumb::ThumbInstruction, Addr, CpuMode, CpuState};
 
-#[cfg(not(feature = "arm7tdmi_dispatch_table"))]
-use super::InstructionDecoder;
-
 use crate::core::bus::Bus;
 use crate::core::sysbus::{MemoryAccessType::*, MemoryAccessWidth::*, SysBus};
 
 use bit::BitIndex;
 use num::FromPrimitive;
 
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-use lazy_static;
-
 #[derive(Serialize, Deserialize, Clone, Debug, Default)]
 pub struct Core {
     pub pc: u32,
@@ -68,13 +70,6 @@ pub struct Core {
 
 impl Core {
     pub fn new() -> Core {
-        #[cfg(feature = "arm7tdmi_dispatch_table")]
-        {
-            lazy_static::initialize(&ARM_LUT);
-            lazy_static::initialize(&ARM_FN_LUT);
-            lazy_static::initialize(&THUMB_LUT);
-        }
-
         let cpsr = RegPSR::new(0x0000_00D3);
         Core {
             memreq: 0xffff_0000, // set memreq to an invalid addr so the first load cycle will be non-sequential
@@ -322,17 +317,14 @@ impl Core {
 
     #[cfg(feature = "arm7tdmi_dispatch_table")]
     fn step_arm_exec(&mut self, insn: u32, sb: &mut SysBus) -> CpuAction {
-        let l1_index = ARM_LUT[arm_insn_hash(insn)] as usize;
-        let handler_fn = ARM_FN_LUT[l1_index];
-
-        // This is safe because the table can't hold invalid indices
-        let arm_format: ArmFormat = unsafe { std::mem::transmute(l1_index as u8) };
-        let arm_insn = ArmInstruction::new(insn, self.pc.wrapping_sub(8), arm_format);
+        let hash = (((insn >> 16) & 0xff0) | ((insn >> 4) & 0x00f)) as usize;
+        let arm_info = &ARM_LUT[hash];
+        let arm_insn = ArmInstruction::new(insn, self.pc.wrapping_sub(8), arm_info.fmt);
 
         #[cfg(feature = "debugger")]
         self.debugger_record_step(DecodedInstruction::Arm(arm_insn.clone()));
 
-        (handler_fn)(self, sb, &arm_insn)
+        (arm_info.handler_fn)(self, sb, &arm_insn)
     }
 
     #[cfg(feature = "arm7tdmi_dispatch_table")]

src/core/arm7tdmi/thumb/lut.rs

@@ -1,65 +0,0 @@
-use super::super::super::SysBus;
-use super::super::Core;
-use super::super::CpuAction;
-use super::super::InstructionDecoder;
-use super::{ThumbFormat, ThumbInstruction};
-
-pub type ThumbInstructionHandler = fn(&mut Core, &mut SysBus, &ThumbInstruction) -> CpuAction;
-
-impl From<ThumbFormat> for ThumbInstructionHandler {
-    fn from(thumb_fmt: ThumbFormat) -> ThumbInstructionHandler {
-        match thumb_fmt {
-            ThumbFormat::MoveShiftedReg => Core::exec_thumb_move_shifted_reg,
-            ThumbFormat::AddSub => Core::exec_thumb_add_sub,
-            ThumbFormat::DataProcessImm => Core::exec_thumb_data_process_imm,
-            ThumbFormat::AluOps => Core::exec_thumb_alu_ops,
-            ThumbFormat::HiRegOpOrBranchExchange => Core::exec_thumb_hi_reg_op_or_bx,
-            ThumbFormat::LdrPc => Core::exec_thumb_ldr_pc,
-            ThumbFormat::LdrStrRegOffset => Core::exec_thumb_ldr_str_reg_offset,
-            ThumbFormat::LdrStrSHB => Core::exec_thumb_ldr_str_shb,
-            ThumbFormat::LdrStrImmOffset => Core::exec_thumb_ldr_str_imm_offset,
-            ThumbFormat::LdrStrHalfWord => Core::exec_thumb_ldr_str_halfword,
-            ThumbFormat::LdrStrSp => Core::exec_thumb_ldr_str_sp,
-            ThumbFormat::LoadAddress => Core::exec_thumb_load_address,
-            ThumbFormat::AddSp => Core::exec_thumb_add_sp,
-            ThumbFormat::PushPop => Core::exec_thumb_push_pop,
-            ThumbFormat::LdmStm => Core::exec_thumb_ldm_stm,
-            ThumbFormat::BranchConditional => Core::exec_thumb_branch_with_cond,
-            ThumbFormat::Swi => Core::exec_thumb_swi,
-            ThumbFormat::Branch => Core::exec_thumb_branch,
-            ThumbFormat::BranchLongWithLink => Core::exec_thumb_branch_long_with_link,
-            ThumbFormat::Undefined => Core::thumb_undefined,
-        }
-    }
-}
-
-pub struct ThumbInstructionInfo {
-    pub fmt: ThumbFormat,
-    pub handler_fn: ThumbInstructionHandler,
-}
-
-lazy_static! {
-    pub static ref THUMB_LUT: [ThumbInstructionInfo; 1024] = {
-
-        debug!("generating THUMB lookup table");
-
-        use std::mem::{self, MaybeUninit};
-
-        let mut lut: [MaybeUninit<ThumbInstructionInfo>; 1024] = unsafe {
-            MaybeUninit::uninit().assume_init()
-        };
-
-        for i in 0..1024 {
-            let insn = ThumbInstruction::decode(i << 6, 0);
-            let info = ThumbInstructionInfo {
-                fmt: insn.fmt,
-                handler_fn: insn.fmt.into()
-            };
-            lut[i as usize] = MaybeUninit::new(info);
-        }
-
-        // Everything is initialized. Transmute the array to the
-        // initialized type.
-        unsafe { mem::transmute::<_, [ThumbInstructionInfo; 1024]>(lut) }
-    };
-}

src/core/arm7tdmi/thumb/mod.rs

@@ -7,10 +7,6 @@ use crate::num::FromPrimitive;
 
 pub mod display;
 pub mod exec;
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-mod lut;
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-pub use lut::*;
 
 #[derive(Serialize, Deserialize, Debug, Copy, Clone, PartialEq)]
 pub enum ThumbFormat {

src/lib.rs

@@ -1,7 +1,3 @@
-#[cfg(feature = "arm7tdmi_dispatch_table")]
-#[macro_use]
-extern crate lazy_static;
-
 #[macro_use]
 extern crate serde;