cranelift: Add newtype wrappers for x64 register classes

This primary motivation of this large commit (apologies for its size!) is to
introduce `Gpr` and `Xmm` newtypes over `Reg`. This should help catch
difficult-to-diagnose register class mixup bugs in x64 lowerings.

But having a newtype for `Gpr` and `Xmm` themselves isn't enough to catch all of
our operand-with-wrong-register-class bugs, because about 50% of operands on x64
aren't just a register, but a register or memory address or even an
immediate! So we have `{Gpr,Xmm}Mem[Imm]` newtypes as well.

Unfortunately, `GprMem` et al can't be `enum`s and are therefore a little bit
noisier to work with from ISLE. They need to maintain the invariant that their
registers really are of the claimed register class, so they need to encapsulate
the inner data. If they exposed the underlying `enum` variants, then anyone
could just change register classes or construct a `GprMem` that holds an XMM
register, defeating the whole point of these newtypes. So when working with
these newtypes from ISLE, we rely on external constructors like `(gpr_to_gpr_mem
my_gpr)` instead of `(GprMem.Gpr my_gpr)`.

A bit of extra lines of code are included to add support for register mapping
for all of these newtypes as well. Ultimately this is all a bit wordier than I'd
hoped it would be when I first started authoring this commit, but I think it is
all worth it nonetheless!

In the process of adding these newtypes, I didn't want to have to update both
the ISLE `extern` type definition of `MInst` and the Rust definition, so I move
the definition fully into ISLE, similar as aarch64.

Finally, this process isn't complete. I've introduced the newtypes here, and
I've made most XMM-using instructions switch from `Reg` to `Xmm`, as well as
register class-converting instructions, but I haven't moved all of the GPR-using
instructions over to the newtypes yet. I figured this commit was big enough as
it was, and I can continue the adoption of these newtypes in follow up commits.

Part of #3685.

cranelift/codegen/src/isa/x64/inst/args.rs

@@ -13,6 +13,309 @@ use smallvec::{smallvec, SmallVec};
 use std::fmt;
 use std::string::String;
 
+/// An extenstion trait for converting `Writable{Xmm,Gpr}` to `Writable<Reg>`.
+pub trait ToWritableReg {
+    fn to_writable_reg(&self) -> Writable<Reg>;
+}
+
+/// An extension trait for converting `Writable<Reg>` to `Writable{Xmm,Gpr}`.
+pub trait FromWritableReg: Sized {
+    fn from_writable_reg(w: Writable<Reg>) -> Option<Self>;
+}
+
+/// An extension trait for mapping register uses on `{Xmm,Gpr}`.
+pub trait MapUseExt {
+    fn map_use<RM>(&mut self, mapper: &RM)
+    where
+        RM: RegMapper;
+}
+
+/// An extension trait for mapping register mods and defs on
+/// `Writable{Xmm,Gpr}`.
+pub trait MapDefModExt {
+    fn map_def<RM>(&mut self, mapper: &RM)
+    where
+        RM: RegMapper;
+
+    fn map_mod<RM>(&mut self, mapper: &RM)
+    where
+        RM: RegMapper;
+}
+
+/// A macro for defining a newtype of `Reg` that enforces some invariant about
+/// the wrapped `Reg` (such as that it is of a particular register class).
+macro_rules! newtype_of_reg {
+    (
+        $newtype_reg:ident,
+        $newtype_writable_reg:ident,
+        $newtype_reg_mem:ident,
+        $newtype_reg_mem_imm:ident,
+        |$check_reg:ident| $check:expr
+    ) => {
+        /// A newtype wrapper around `Reg`.
+        #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+        pub struct $newtype_reg(Reg);
+
+        impl PartialEq<Reg> for $newtype_reg {
+            fn eq(&self, other: &Reg) -> bool {
+                self.0 == *other
+            }
+        }
+
+        impl From<$newtype_reg> for Reg {
+            fn from(r: $newtype_reg) -> Self {
+                r.0
+            }
+        }
+
+        impl PrettyPrint for $newtype_reg {
+            fn show_rru(&self, mb_rru: Option<&RealRegUniverse>) -> String {
+                self.0.show_rru(mb_rru)
+            }
+        }
+
+        impl $newtype_reg {
+            /// Create this newtype from the given register, or return `None` if the register
+            /// is not a valid instance of this newtype.
+            pub fn new($check_reg: Reg) -> Option<Self> {
+                if $check {
+                    Some(Self($check_reg))
+                } else {
+                    None
+                }
+            }
+
+            /// Get this newtype's underlying `Reg`.
+            pub fn to_reg(self) -> Reg {
+                self.0
+            }
+        }
+
+        // Convenience impl so that people working with this newtype can use it
+        // "just like" a plain `Reg`.
+        //
+        // NB: We cannot implement `DerefMut` because that would let people do
+        // nasty stuff like `*my_gpr.deref_mut() = some_xmm_reg`, breaking the
+        // invariants that `Gpr` provides.
+        impl std::ops::Deref for $newtype_reg {
+            type Target = Reg;
+
+            fn deref(&self) -> &Reg {
+                &self.0
+            }
+        }
+
+        impl MapUseExt for $newtype_reg {
+            fn map_use<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                let mut reg = self.0;
+                mapper.map_use(&mut reg);
+                debug_assert!({
+                    let $check_reg = reg;
+                    $check
+                });
+                *self = $newtype_reg(reg);
+            }
+        }
+
+        pub type $newtype_writable_reg = Writable<$newtype_reg>;
+
+        impl ToWritableReg for $newtype_writable_reg {
+            fn to_writable_reg(&self) -> Writable<Reg> {
+                Writable::from_reg(self.to_reg().to_reg())
+            }
+        }
+
+        impl FromWritableReg for $newtype_writable_reg {
+            fn from_writable_reg(w: Writable<Reg>) -> Option<Self> {
+                Some(Writable::from_reg($newtype_reg::new(w.to_reg())?))
+            }
+        }
+
+        impl MapDefModExt for $newtype_writable_reg {
+            fn map_def<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                let mut reg = self.to_writable_reg();
+                mapper.map_def(&mut reg);
+                debug_assert!({
+                    let $check_reg = reg.to_reg();
+                    $check
+                });
+                *self = Writable::from_reg($newtype_reg(reg.to_reg()));
+            }
+
+            fn map_mod<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                let mut reg = self.to_writable_reg();
+                mapper.map_mod(&mut reg);
+                debug_assert!({
+                    let $check_reg = reg.to_reg();
+                    $check
+                });
+                *self = Writable::from_reg($newtype_reg(reg.to_reg()));
+            }
+        }
+
+        /// A newtype wrapper around `RegMem` for general-purpose registers.
+        #[derive(Clone, Debug)]
+        pub struct $newtype_reg_mem(RegMem);
+
+        impl From<$newtype_reg_mem> for RegMem {
+            fn from(rm: $newtype_reg_mem) -> Self {
+                rm.0
+            }
+        }
+
+        impl From<$newtype_reg> for $newtype_reg_mem {
+            fn from(r: $newtype_reg) -> Self {
+                $newtype_reg_mem(RegMem::reg(r.into()))
+            }
+        }
+
+        impl $newtype_reg_mem {
+            /// Construct a `RegMem` newtype from the given `RegMem`, or return
+            /// `None` if the `RegMem` is not a valid instance of this `RegMem`
+            /// newtype.
+            pub fn new(rm: RegMem) -> Option<Self> {
+                match rm {
+                    RegMem::Mem { addr: _ } => Some(Self(rm)),
+                    RegMem::Reg { reg: $check_reg } if $check => Some(Self(rm)),
+                    RegMem::Reg { reg: _ } => None,
+                }
+            }
+
+            /// Convert this newtype into its underlying `RegMem`.
+            pub fn to_reg_mem(self) -> RegMem {
+                self.0
+            }
+
+            #[allow(dead_code)] // Used by some newtypes and not others.
+            pub fn map_uses<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                self.0.map_uses(mapper);
+                debug_assert!(match self.0 {
+                    RegMem::Reg { reg: $check_reg } => $check,
+                    _ => true,
+                });
+            }
+
+            #[allow(dead_code)] // Used by some newtypes and not others.
+            pub fn map_as_def<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                self.0.map_as_def(mapper);
+                debug_assert!(match self.0 {
+                    RegMem::Reg { reg: $check_reg } => $check,
+                    _ => true,
+                });
+            }
+        }
+
+        impl PrettyPrint for $newtype_reg_mem {
+            fn show_rru(&self, mb_rru: Option<&RealRegUniverse>) -> String {
+                self.0.show_rru(mb_rru)
+            }
+        }
+
+        impl PrettyPrintSized for $newtype_reg_mem {
+            fn show_rru_sized(&self, mb_rru: Option<&RealRegUniverse>, size: u8) -> String {
+                self.0.show_rru_sized(mb_rru, size)
+            }
+        }
+
+        /// A newtype wrapper around `RegMemImm`.
+        #[derive(Clone, Debug)]
+        pub struct $newtype_reg_mem_imm(RegMemImm);
+
+        impl From<$newtype_reg_mem_imm> for RegMemImm {
+            fn from(rmi: $newtype_reg_mem_imm) -> RegMemImm {
+                rmi.0
+            }
+        }
+
+        impl From<$newtype_reg> for $newtype_reg_mem_imm {
+            fn from(r: $newtype_reg) -> Self {
+                $newtype_reg_mem_imm(RegMemImm::reg(r.into()))
+            }
+        }
+
+        impl $newtype_reg_mem_imm {
+            /// Construct this newtype from the given `RegMemImm`, or return
+            /// `None` if the `RegMemImm` is not a valid instance of this
+            /// newtype.
+            pub fn new(rmi: RegMemImm) -> Option<Self> {
+                match rmi {
+                    RegMemImm::Imm { .. } => Some(Self(rmi)),
+                    RegMemImm::Mem { addr: _ } => Some(Self(rmi)),
+                    RegMemImm::Reg { reg: $check_reg } if $check => Some(Self(rmi)),
+                    RegMemImm::Reg { reg: _ } => None,
+                }
+            }
+
+            /// Convert this newtype into its underlying `RegMemImm`.
+            #[allow(dead_code)] // Used by some newtypes and not others.
+            pub fn to_reg_mem_imm(self) -> RegMemImm {
+                self.0
+            }
+
+            #[allow(dead_code)] // Used by some newtypes and not others.
+            pub fn map_uses<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                self.0.map_uses(mapper);
+                debug_assert!(match self.0 {
+                    RegMemImm::Reg { reg: $check_reg } => $check,
+                    _ => true,
+                });
+            }
+
+            #[allow(dead_code)] // Used by some newtypes and not others.
+            pub fn map_as_def<RM>(&mut self, mapper: &RM)
+            where
+                RM: RegMapper,
+            {
+                self.0.map_as_def(mapper);
+                debug_assert!(match self.0 {
+                    RegMemImm::Reg { reg: $check_reg } => $check,
+                    _ => true,
+                });
+            }
+        }
+
+        impl PrettyPrint for $newtype_reg_mem_imm {
+            fn show_rru(&self, mb_rru: Option<&RealRegUniverse>) -> String {
+                self.0.show_rru(mb_rru)
+            }
+        }
+
+        impl PrettyPrintSized for $newtype_reg_mem_imm {
+            fn show_rru_sized(&self, mb_rru: Option<&RealRegUniverse>, size: u8) -> String {
+                self.0.show_rru_sized(mb_rru, size)
+            }
+        }
+    };
+}
+
+// Define a newtype of `Reg` for general-purpose registers.
+newtype_of_reg!(Gpr, WritableGpr, GprMem, GprMemImm, |reg| {
+    reg.get_class() == RegClass::I64
+});
+
+// Define a newtype of `Reg` for XMM registers.
+newtype_of_reg!(Xmm, WritableXmm, XmmMem, XmmMemImm, |reg| {
+    reg.get_class() == RegClass::V128
+});
+
 /// A possible addressing mode (amode) that can be used in instructions.
 /// These denote a 64-bit value only.
 #[derive(Clone, Debug)]
@@ -27,8 +330,8 @@ pub enum Amode {
     /// sign-extend-32-to-64(Immediate) + Register1 + (Register2 << Shift)
     ImmRegRegShift {
         simm32: u32,
-        base: Reg,
-        index: Reg,
+        base: Gpr,
+        index: Gpr,
         shift: u8, /* 0 .. 3 only */
         flags: MemFlags,
     },
@@ -48,7 +351,7 @@ impl Amode {
         }
     }
 
-    pub(crate) fn imm_reg_reg_shift(simm32: u32, base: Reg, index: Reg, shift: u8) -> Self {
+    pub(crate) fn imm_reg_reg_shift(simm32: u32, base: Gpr, index: Gpr, shift: u8) -> Self {
         debug_assert!(base.get_class() == RegClass::I64);
         debug_assert!(index.get_class() == RegClass::I64);
         debug_assert!(shift <= 3);
@@ -96,8 +399,8 @@ impl Amode {
                 collector.add_use(*base);
             }
             Amode::ImmRegRegShift { base, index, .. } => {
-                collector.add_use(*base);
-                collector.add_use(*index);
+                collector.add_use(base.to_reg());
+                collector.add_use(index.to_reg());
             }
             Amode::RipRelative { .. } => {
                 // RIP isn't involved in regalloc.
@@ -225,7 +528,7 @@ impl PrettyPrint for SyntheticAmode {
 /// denote an 8, 16, 32 or 64 bit value.  For the Immediate form, in the 8- and 16-bit case, only
 /// the lower 8 or 16 bits of `simm32` is relevant.  In the 64-bit case, the value denoted by
 /// `simm32` is its sign-extension out to 64 bits.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub enum RegMemImm {
     Reg { reg: Reg },
     Mem { addr: SyntheticAmode },