Track frame layout changes. (#1204)

* Track frame layout changes.

cranelift/codegen/src/ir/framelayout.rs

@@ -0,0 +1,70 @@
+//! Frame layout item changes.
+
+use crate::ir::entities::Inst;
+use crate::isa::RegUnit;
+use std::boxed::Box;
+
+use crate::HashMap;
+
+/// Change in the frame layout information.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub enum FrameLayoutChange {
+    /// Base CallFrameAddress (CFA) pointer moved to different register/offset.
+    CallFrameAddressAt {
+        /// CFA register.
+        reg: RegUnit,
+        /// CFA offset.
+        offset: isize,
+    },
+    /// Register saved at.
+    RegAt {
+        /// Saved register.
+        reg: RegUnit,
+        /// Offset in the frame (offset from CFA).
+        cfa_offset: isize,
+    },
+    /// Return address saved at.
+    ReturnAddressAt {
+        /// Offset in the frame (offset from CFA).
+        cfa_offset: isize,
+    },
+    /// The entire frame layout must be preserved somewhere to be restored at a corresponding
+    /// `Restore` change.
+    ///
+    /// This likely maps to the DWARF call frame instruction `.cfa_remember_state`.
+    Preserve,
+    /// Restore the entire frame layout from a corresponding prior `Preserve` frame change.
+    ///
+    /// This likely maps to the DWARF call frame instruction `.cfa_restore_state`.
+    Restore,
+}
+
+/// Set of frame layout changes.
+pub type FrameLayoutChanges = Box<[FrameLayoutChange]>;
+
+/// Frame items layout for (prologue/epilogue) instructions.
+#[derive(Debug, Clone)]
+pub struct FrameLayout {
+    /// Initial frame layout.
+    pub initial: FrameLayoutChanges,
+
+    /// Instruction frame layout (changes). Because the map will not be dense,
+    /// a HashMap is used instead of a SecondaryMap.
+    pub instructions: HashMap<Inst, FrameLayoutChanges>,
+}
+
+impl FrameLayout {
+    /// Create instance of FrameLayout.
+    pub fn new() -> Self {
+        FrameLayout {
+            initial: vec![].into_boxed_slice(),
+            instructions: HashMap::new(),
+        }
+    }
+
+    /// Clear the structure.
+    pub fn clear(&mut self) {
+        self.initial = vec![].into_boxed_slice();
+        self.instructions.clear();
+    }
+}

cranelift/codegen/src/ir/function.rs

@@ -11,7 +11,7 @@ use crate::ir::{
     Ebb, ExtFuncData, FuncRef, GlobalValue, GlobalValueData, Heap, HeapData, Inst, JumpTable,
     JumpTableData, SigRef, StackSlot, StackSlotData, Table, TableData,
 };
-use crate::ir::{EbbOffsets, InstEncodings, SourceLocs, StackSlots, ValueLocations};
+use crate::ir::{EbbOffsets, FrameLayout, InstEncodings, SourceLocs, StackSlots, ValueLocations};
 use crate::ir::{JumpTableOffsets, JumpTables};
 use crate::isa::{CallConv, EncInfo, Encoding, Legalize, TargetIsa};
 use crate::regalloc::{EntryRegDiversions, RegDiversions};
@@ -92,6 +92,13 @@ pub struct Function {
     ///
     /// This is used for some calling conventions to track the end of unwind information.
     pub prologue_end: Option<Inst>,
+
+    /// Frame layout for the instructions.
+    ///
+    /// The stack unwinding requires to have information about which registers and where they
+    /// are saved in the frame. This information is created during the prologue and epilogue
+    /// passes.
+    pub frame_layout: Option<FrameLayout>,
 }
 
 impl Function {
@@ -115,6 +122,7 @@ impl Function {
             jt_offsets: SecondaryMap::new(),
             srclocs: SecondaryMap::new(),
             prologue_end: None,
+            frame_layout: None,
         }
     }
 
@@ -135,6 +143,7 @@ impl Function {
         self.jt_offsets.clear();
         self.srclocs.clear();
         self.prologue_end = None;
+        self.frame_layout = None;
     }
 
     /// Create a new empty, anonymous function with a Fast calling convention.
@@ -244,6 +253,7 @@ impl Function {
     /// Starts collection of debug information.
     pub fn collect_debug_info(&mut self) {
         self.dfg.collect_debug_info();
+        self.frame_layout = Some(FrameLayout::new());
     }
 
     /// Changes the destination of a jump or branch instruction.

cranelift/codegen/src/ir/mod.rs

@@ -6,6 +6,7 @@ pub mod dfg;
 pub mod entities;
 mod extfunc;
 mod extname;
+mod framelayout;
 pub mod function;
 mod globalvalue;
 mod heap;
@@ -39,6 +40,7 @@ pub use crate::ir::extfunc::{
     AbiParam, ArgumentExtension, ArgumentPurpose, ExtFuncData, Signature,
 };
 pub use crate::ir::extname::ExternalName;
+pub use crate::ir::framelayout::{FrameLayout, FrameLayoutChange, FrameLayoutChanges};
 pub use crate::ir::function::{DisplayFunctionAnnotations, Function};
 pub use crate::ir::globalvalue::GlobalValueData;
 pub use crate::ir::heap::{HeapData, HeapStyle};