machinst aarch64: New backend unwind (#2313)

* Unwind information for aarch64 backend.

cranelift/codegen/src/isa/aarch64/inst/unwind.rs

@@ -1,14 +1,194 @@
 use super::*;
-use crate::isa::unwind::input::UnwindInfo;
+use crate::isa::aarch64::inst::{args::PairAMode, imms::Imm12, regs, ALUOp, Inst};
+use crate::isa::unwind::input::{UnwindCode, UnwindInfo};
+use crate::machinst::UnwindInfoContext;
 use crate::result::CodegenResult;
+use alloc::vec::Vec;
+use regalloc::Reg;
+
+#[cfg(feature = "unwind")]
+pub(crate) mod systemv;
 
 pub struct AArch64UnwindInfo;
 
 impl UnwindInfoGenerator<Inst> for AArch64UnwindInfo {
     fn create_unwind_info(
-        _context: UnwindInfoContext<Inst>,
+        context: UnwindInfoContext<Inst>,
     ) -> CodegenResult<Option<UnwindInfo<Reg>>> {
-        // TODO
-        Ok(None)
+        let word_size = 8u8;
+        let pair_size = word_size * 2;
+        let mut codes = Vec::new();
+
+        for i in context.prologue.clone() {
+            let i = i as usize;
+            let inst = &context.insts[i];
+            let offset = context.insts_layout[i];
+
+            match inst {
+                Inst::StoreP64 {
+                    rt,
+                    rt2,
+                    mem: PairAMode::PreIndexed(rn, imm7),
+                } if *rt == regs::fp_reg()
+                    && *rt2 == regs::link_reg()
+                    && *rn == regs::writable_stack_reg()
+                    && imm7.value == -(pair_size as i16) =>
+                {
+                    // stp fp (x29), lr (x30), [sp, #-16]!
+                    codes.push((
+                        offset,
+                        UnwindCode::StackAlloc {
+                            size: pair_size as u32,
+                        },
+                    ));
+                    codes.push((
+                        offset,
+                        UnwindCode::SaveRegister {
+                            reg: *rt,
+                            stack_offset: 0,
+                        },
+                    ));
+                    codes.push((
+                        offset,
+                        UnwindCode::SaveRegister {
+                            reg: *rt2,
+                            stack_offset: word_size as u32,
+                        },
+                    ));
+                }
+                Inst::StoreP64 {
+                    rt,
+                    rt2,
+                    mem: PairAMode::PreIndexed(rn, imm7),
+                } if rn.to_reg() == regs::stack_reg() && imm7.value % (pair_size as i16) == 0 => {
+                    // stp r1, r2, [sp, #(i * #16)]
+                    let stack_offset = imm7.value as u32;
+                    codes.push((
+                        offset,
+                        UnwindCode::SaveRegister {
+                            reg: *rt,
+                            stack_offset,
+                        },
+                    ));
+                    if *rt2 != regs::zero_reg() {
+                        codes.push((
+                            offset,
+                            UnwindCode::SaveRegister {
+                                reg: *rt2,
+                                stack_offset: stack_offset + word_size as u32,
+                            },
+                        ));
+                    }
+                }
+                Inst::AluRRImm12 {
+                    alu_op: ALUOp::Add64,
+                    rd,
+                    rn,
+                    imm12:
+                        Imm12 {
+                            bits: 0,
+                            shift12: false,
+                        },
+                } if *rd == regs::writable_fp_reg() && *rn == regs::stack_reg() => {
+                    // mov fp (x29), sp.
+                    codes.push((offset, UnwindCode::SetFramePointer { reg: rd.to_reg() }));
+                }
+                Inst::VirtualSPOffsetAdj { offset: adj } if offset > 0 => {
+                    codes.push((offset, UnwindCode::StackAlloc { size: *adj as u32 }));
+                }
+                _ => {}
+            }
+        }
+
+        // TODO epilogues
+
+        let prologue_size = context.insts_layout[context.prologue.end as usize - 1];
+        Ok(Some(UnwindInfo {
+            prologue_size,
+            prologue_unwind_codes: codes,
+            epilogues_unwind_codes: vec![],
+            function_size: context.len,
+            word_size,
+            initial_sp_offset: 0,
+        }))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::cursor::{Cursor, FuncCursor};
+    use crate::ir::{ExternalName, Function, InstBuilder, Signature, StackSlotData, StackSlotKind};
+    use crate::isa::{lookup, CallConv};
+    use crate::settings::{builder, Flags};
+    use crate::Context;
+    use std::str::FromStr;
+    use target_lexicon::triple;
+
+    #[test]
+    fn test_simple_func() {
+        let isa = lookup(triple!("aarch64"))
+            .expect("expect aarch64 ISA")
+            .finish(Flags::new(builder()));
+
+        let mut context = Context::for_function(create_function(
+            CallConv::SystemV,
+            Some(StackSlotData::new(StackSlotKind::ExplicitSlot, 64)),
+        ));
+
+        context.compile(&*isa).expect("expected compilation");
+
+        let result = context.mach_compile_result.unwrap();
+        let unwind_info = result.unwind_info.unwrap();
+
+        assert_eq!(
+            unwind_info,
+            UnwindInfo {
+                prologue_size: 12,
+                prologue_unwind_codes: vec![
+                    (4, UnwindCode::StackAlloc { size: 16 }),
+                    (
+                        4,
+                        UnwindCode::SaveRegister {
+                            reg: regs::fp_reg(),
+                            stack_offset: 0
+                        }
+                    ),
+                    (
+                        4,
+                        UnwindCode::SaveRegister {
+                            reg: regs::link_reg(),
+                            stack_offset: 8
+                        }
+                    ),
+                    (
+                        8,
+                        UnwindCode::SetFramePointer {
+                            reg: regs::fp_reg()
+                        }
+                    )
+                ],
+                epilogues_unwind_codes: vec![],
+                function_size: 24,
+                word_size: 8,
+                initial_sp_offset: 0,
+            }
+        );
+    }
+
+    fn create_function(call_conv: CallConv, stack_slot: Option<StackSlotData>) -> Function {
+        let mut func =
+            Function::with_name_signature(ExternalName::user(0, 0), Signature::new(call_conv));
+
+        let block0 = func.dfg.make_block();
+        let mut pos = FuncCursor::new(&mut func);
+        pos.insert_block(block0);
+        pos.ins().return_(&[]);
+
+        if let Some(stack_slot) = stack_slot {
+            func.stack_slots.push(stack_slot);
+        }
+
+        func
     }
 }