emu: INC/DEC opcodes. width={byte,word} argtypes for disambig

Also made all LValues also RValues for brevity (so INC/DEC don't have
to bound their destination arguments by both, but this is not required
if it causes problems for some reason down the road).

src/emu/i8088.rs

@@ -1,5 +1,6 @@
 use std::cell::Cell;
 use std::fmt::{Debug, Formatter};
+use std::marker::PhantomData;
 
 use super::byteorder::{ByteOrder, LittleEndian};
 
@@ -297,6 +298,14 @@ macro_rules! step {
     step!(@arg $cookie, $segment.unwrap())
   } };
 
+  (@width=byte $cookie:tt, $cpu:expr, $bus:expr, $prefix:tt, $modrm:tt) => {
+    step!(@arg $cookie, PhantomData::<u8>);
+  };
+
+  (@width=word $cookie:tt, $cpu:expr, $bus:expr, $prefix:tt, $modrm:tt) => {
+    step!(@arg $cookie, PhantomData::<u16>);
+  };
+
   // Group Decoder
   (@group $cpu:expr, $bus:expr, $prefix:tt,
           ($modrm_val:ident, $modrm:tt, $modrm16:tt, $modrm8:tt),
@@ -378,6 +387,22 @@ impl i8088 {
           0x3C => cmp[flags, reglo=a, d8] / "3/24+",
           0x3D => cmp[flags, reg=a, d16] / "3/24+",
           0x3E => nop[seg=ds, prefix] / 2,
+          0x40 => inc[width=word, flags, reg=a] / 3,
+          0x41 => inc[width=word, flags, reg=c] / 3,
+          0x42 => inc[width=word, flags, reg=d] / 3,
+          0x43 => inc[width=word, flags, reg=b] / 3,
+          0x44 => inc[width=word, flags, reg=sp] / 3,
+          0x45 => inc[width=word, flags, reg=bp] / 3,
+          0x46 => inc[width=word, flags, reg=si] / 3,
+          0x47 => inc[width=word, flags, reg=di] / 3,
+          0x48 => dec[width=word, flags, reg=a] / 3,
+          0x49 => dec[width=word, flags, reg=c] / 3,
+          0x4A => dec[width=word, flags, reg=d] / 3,
+          0x4B => dec[width=word, flags, reg=b] / 3,
+          0x4C => dec[width=word, flags, reg=sp] / 3,
+          0x4D => dec[width=word, flags, reg=bp] / 3,
+          0x4E => dec[width=word, flags, reg=si] / 3,
+          0x4F => dec[width=word, flags, reg=di] / 3,
           0x50 => push[bus, regval=ss, reg=sp, regval=a] / 15,
           0x51 => push[bus, regval=ss, reg=sp, regval=c] / 15,
           0x52 => push[bus, regval=ss, reg=sp, regval=d] / 15,
@@ -469,6 +494,10 @@ impl i8088 {
           0xE8 => call[reg=ip, bus, regval=ss, reg=sp, rel16] / 23,
           0xF2 => nop[rep=NotEqual, prefix] / 0,  // REPNE/REPNZ
           0xF3 => nop[rep=Equal, prefix] / 0,     // REP/REPE/REPZ
+          0xFE: { 00 => inc[width=byte, flags, modrm8] / "3/23+",      // INC r/m8
+                  08 => dec[width=byte, flags, modrm8] / "3/23+", },   // DEC r/m8
+          0xFF: { 00 => inc[width=word, flags, modrm16] / "3/23+",     // INC r/m16
+                  08 => dec[width=word, flags, modrm16] / "3/23+", },  // DEC r/m16
         },
         modrm: {
           0x00 => seg=ds, displace0=(b+si) / M 7,

src/emu/operands.rs

@@ -7,6 +7,7 @@ use emu::pc::Bus;
 
 pub trait Operand: Copy +
                nt::Num +
+               nt::ops::overflowing::OverflowingAdd +
                nt::ops::overflowing::OverflowingSub +
                std::ops::BitAnd<Output = Self> +
                std::ops::BitXor<Output = Self> {
@@ -28,7 +29,7 @@ impl Operand for u16 {
   }
 }
 
-pub trait LValue<T> {
+pub trait LValue<T>: RValue<T> {
   fn write(&mut self, val: T);
 }
 

src/emu/operations.rs

@@ -1,4 +1,5 @@
 use std::fmt::Debug;
+use std::marker::PhantomData;
 
 use emu::dos;
 use emu::i8088::{Flags, RepPrefix, i8088};
@@ -69,8 +70,8 @@ macro_rules! update_flags {
 
   // Entry Point
   ($flags:expr, $t:ty, $eval:expr $(, $flagnames:ident)* ) => { {
-    let (dst, carry) = $eval;
+    let (dst, _carry) = $eval;  // _carry used iff CF flag being updated
-    update_flags!(@recur $flags, $t, dst, carry $(, $flagnames)*);
+    update_flags!(@recur $flags, $t, dst, _carry $(, $flagnames)*);
     dst
   } }
 }
@@ -135,6 +136,22 @@ pub fn cmpsw(flags: &mut Flags,
   });
 }
 
+pub fn dec<T: Operand>(_width: PhantomData<T>,  // Needed to disambiguate when dst is a FarPtr
+                       flags: &mut Flags,
+                       dst: &mut impl LValue<T>) {
+  let res = update_flags!(flags, T, dst.read().overflowing_sub(&T::one()), sf, zf, af, pf);
+  flags.of = res == T::HI_BIT_MASK - T::one();
+  dst.write(res);
+}
+
+pub fn inc<T: Operand>(_width: PhantomData<T>,  // Needed to disambiguate when dst is a FarPtr
+                       flags: &mut Flags,
+                       dst: &mut impl LValue<T>) {
+  let res = update_flags!(flags, T, dst.read().overflowing_add(&T::one()), sf, zf, af, pf);
+  flags.of = res == T::HI_BIT_MASK;
+  dst.write(res);
+}
+
 pub fn int(cpu: &mut i8088, bus: &mut Bus, num: &u8) {
   match num {
     0x21 => dos::interrupt(cpu, bus),