Add a stack frame manager.

Use a new StackSlots struct to keep track of a function's stack slots
instead of just an entity map. This let's us build more internal data
structures for tracking the stack slots if necessary.

Start by adding a make_spill_slot() function that will be used by the
register allocator.

lib/cretonne/src/ir/function.rs

@@ -5,8 +5,8 @@
 
 use binemit::CodeOffset;
 use entity_map::{EntityMap, PrimaryEntityData};
-use ir::{FunctionName, Signature, Value, Inst, Ebb, StackSlot, StackSlotData, JumpTable,
-         JumpTableData, ValueLoc, DataFlowGraph, Layout};
+use ir::{FunctionName, Signature, Value, Inst, Ebb, StackSlots, JumpTable, JumpTableData,
+         ValueLoc, DataFlowGraph, Layout};
 use isa::{TargetIsa, Encoding};
 use std::fmt::{self, Display, Debug, Formatter};
 use write::write_function;
@@ -24,7 +24,7 @@ pub struct Function {
     pub signature: Signature,
 
     /// Stack slots allocated in this function.
-    pub stack_slots: EntityMap<StackSlot, StackSlotData>,
+    pub stack_slots: StackSlots,
 
     /// Jump tables used in this function.
     pub jump_tables: EntityMap<JumpTable, JumpTableData>,
@@ -50,7 +50,6 @@ pub struct Function {
     pub offsets: EntityMap<Ebb, CodeOffset>,
 }
 
-impl PrimaryEntityData for StackSlotData {}
 impl PrimaryEntityData for JumpTableData {}
 
 impl Function {
@@ -59,7 +58,7 @@ impl Function {
         Function {
             name,
             signature: sig,
-            stack_slots: EntityMap::new(),
+            stack_slots: StackSlots::new(),
             jump_tables: EntityMap::new(),
             dfg: DataFlowGraph::new(),
             layout: Layout::new(),

lib/cretonne/src/ir/mod.rs

@@ -22,7 +22,7 @@ pub use ir::extfunc::{Signature, ArgumentType, ArgumentExtension, ArgumentPurpos
 pub use ir::types::Type;
 pub use ir::entities::{Ebb, Inst, Value, StackSlot, JumpTable, FuncRef, SigRef};
 pub use ir::instructions::{Opcode, InstructionData, VariableArgs, ValueList, ValueListPool};
-pub use ir::stackslot::{StackSlotKind, StackSlotData};
+pub use ir::stackslot::{StackSlots, StackSlotKind, StackSlotData};
 pub use ir::jumptable::JumpTableData;
 pub use ir::valueloc::{ValueLoc, ArgumentLoc};
 pub use ir::dfg::{DataFlowGraph, ValueDef};

lib/cretonne/src/ir/stackslot.rs

@@ -3,7 +3,10 @@
 //! The `StackSlotData` struct keeps track of a single stack slot in a function.
 //!
 
+use entity_map::{EntityMap, PrimaryEntityData, Keys};
+use ir::{Type, StackSlot};
 use std::fmt;
+use std::ops::Index;
 use std::str::FromStr;
 
 /// The kind of a stack slot.
@@ -81,6 +84,71 @@ impl fmt::Display for StackSlotData {
     }
 }
 
+impl PrimaryEntityData for StackSlotData {}
+
+/// Stack frame manager.
+///
+/// Keep track of all the stack slots used by a function.
+#[derive(Clone, Debug)]
+pub struct StackSlots {
+    slots: EntityMap<StackSlot, StackSlotData>,
+}
+
+/// Stack slot manager functions that behave mostly like an entity map.
+impl StackSlots {
+    /// Create an empty stack slot manager.
+    pub fn new() -> StackSlots {
+        StackSlots { slots: EntityMap::new() }
+    }
+
+    /// Clear out everything.
+    pub fn clear(&mut self) {
+        self.slots.clear();
+    }
+
+    /// Allocate a new stack slot.
+    ///
+    /// This function should be primarily used by the text format parser. There are more convenient
+    /// functions for creating specific kinds of stack slots below.
+    pub fn push(&mut self, data: StackSlotData) -> StackSlot {
+        self.slots.push(data)
+    }
+
+    /// Check if `ss` is a valid stack slot reference.
+    pub fn is_valid(&self, ss: StackSlot) -> bool {
+        self.slots.is_valid(ss)
+    }
+
+    /// Get an iterator over all the stack slot keys.
+    pub fn keys(&self) -> Keys<StackSlot> {
+        self.slots.keys()
+    }
+
+    /// Get a reference to the next stack slot that would be created by `push()`.
+    ///
+    /// This should just be used by the parser.
+    pub fn next_key(&self) -> StackSlot {
+        self.slots.next_key()
+    }
+}
+
+/// Higher-level stack frame manipulation functions.
+impl StackSlots {
+    /// Create a new spill slot for spilling values of type `ty`.
+    pub fn make_spill_slot(&mut self, ty: Type) -> StackSlot {
+        let bytes = (ty.bits() as u32 + 7) / 8;
+        self.push(StackSlotData::new(StackSlotKind::SpillSlot, bytes))
+    }
+}
+
+impl Index<StackSlot> for StackSlots {
+    type Output = StackSlotData;
+
+    fn index(&self, ss: StackSlot) -> &StackSlotData {
+        &self.slots[ss]
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use ir::Function;