Rename the 'cretonne' crate to 'cretonne-codegen'.

This fixes the next part of #287.

lib/codegen/src/isa/encoding.rs

@@ -0,0 +1,137 @@
+//! The `Encoding` struct.
+
+use binemit::CodeOffset;
+use isa::constraints::{BranchRange, RecipeConstraints};
+use std::fmt;
+
+/// Bits needed to encode an instruction as binary machine code.
+///
+/// The encoding consists of two parts, both specific to the target ISA: An encoding *recipe*, and
+/// encoding *bits*. The recipe determines the native instruction format and the mapping of
+/// operands to encoded bits. The encoding bits provide additional information to the recipe,
+/// typically parts of the opcode.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Encoding {
+    recipe: u16,
+    bits: u16,
+}
+
+impl Encoding {
+    /// Create a new `Encoding` containing `(recipe, bits)`.
+    pub fn new(recipe: u16, bits: u16) -> Encoding {
+        Encoding { recipe, bits }
+    }
+
+    /// Get the recipe number in this encoding.
+    pub fn recipe(self) -> usize {
+        self.recipe as usize
+    }
+
+    /// Get the recipe-specific encoding bits.
+    pub fn bits(self) -> u16 {
+        self.bits
+    }
+
+    /// Is this a legal encoding, or the default placeholder?
+    pub fn is_legal(self) -> bool {
+        self != Self::default()
+    }
+}
+
+/// The default encoding is the illegal one.
+impl Default for Encoding {
+    fn default() -> Self {
+        Self::new(0xffff, 0xffff)
+    }
+}
+
+/// ISA-independent display of an encoding.
+impl fmt::Display for Encoding {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.is_legal() {
+            write!(f, "{}#{:02x}", self.recipe, self.bits)
+        } else {
+            write!(f, "-")
+        }
+    }
+}
+
+/// Temporary object that holds enough context to properly display an encoding.
+/// This is meant to be created by `EncInfo::display()`.
+pub struct DisplayEncoding {
+    pub encoding: Encoding,
+    pub recipe_names: &'static [&'static str],
+}
+
+impl fmt::Display for DisplayEncoding {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.encoding.is_legal() {
+            write!(
+                f,
+                "{}#{:02x}",
+                self.recipe_names[self.encoding.recipe()],
+                self.encoding.bits
+            )
+        } else {
+            write!(f, "-")
+        }
+    }
+}
+
+/// Code size information for an encoding recipe.
+///
+/// All encoding recipes correspond to an exact instruction size.
+pub struct RecipeSizing {
+    /// Size in bytes of instructions encoded with this recipe.
+    pub bytes: u8,
+
+    /// Allowed branch range in this recipe, if any.
+    ///
+    /// All encoding recipes for branches have exact branch range information.
+    pub branch_range: Option<BranchRange>,
+}
+
+/// Information about all the encodings in this ISA.
+#[derive(Clone)]
+pub struct EncInfo {
+    /// Constraints on value operands per recipe.
+    pub constraints: &'static [RecipeConstraints],
+
+    /// Code size information per recipe.
+    pub sizing: &'static [RecipeSizing],
+
+    /// Names of encoding recipes.
+    pub names: &'static [&'static str],
+}
+
+impl EncInfo {
+    /// Get the value operand constraints for `enc` if it is a legal encoding.
+    pub fn operand_constraints(&self, enc: Encoding) -> Option<&'static RecipeConstraints> {
+        self.constraints.get(enc.recipe())
+    }
+
+    /// Create an object that can display an ISA-dependent encoding properly.
+    pub fn display(&self, enc: Encoding) -> DisplayEncoding {
+        DisplayEncoding {
+            encoding: enc,
+            recipe_names: self.names,
+        }
+    }
+
+    /// Get the exact size in bytes of instructions encoded with `enc`.
+    ///
+    /// Returns 0 for illegal encodings.
+    pub fn bytes(&self, enc: Encoding) -> CodeOffset {
+        self.sizing
+            .get(enc.recipe())
+            .map(|s| CodeOffset::from(s.bytes))
+            .unwrap_or(0)
+    }
+
+    /// Get the branch range that is supported by `enc`, if any.
+    ///
+    /// This will never return `None` for a legal branch encoding.
+    pub fn branch_range(&self, enc: Encoding) -> Option<BranchRange> {
+        self.sizing.get(enc.recipe()).and_then(|s| s.branch_range)
+    }
+}