Method spill_impl

winch/codegen/src/codegen/context.rs:834–862

Spill locals and registers to memory. TODO: optimize the spill range; At any point in the program, the stack might already contain memory entries; we could effectively ignore that range; only focusing on the range that contains spillable values.

(
        stack: &mut Stack,
        regalloc: &mut RegAlloc,
        frame: &Frame<Emission>,
        masm: &mut M,
    )

    // entries; we could effectively ignore that range; only focusing on the
    // range that contains spillable values.
    fn spill_impl<M: MacroAssembler>(
        stack: &mut Stack,
        regalloc: &mut RegAlloc,
        frame: &Frame<Emission>,
        masm: &mut M,
    ) -> Result<()> {
        for v in stack.inner_mut() {
            match v {
                Val::Reg(r) => {
                    let slot = masm.push(r.reg, r.ty.try_into()?)?;
                    regalloc.free(r.reg);
                    *v = Val::mem(r.ty, slot);
                }
                Val::Local(local) => {
                    let slot = frame.get_wasm_local(local.index);
                    let addr = masm.local_address(&slot)?;
                    masm.with_scratch_for(slot.ty, |masm, scratch| {
                        masm.load(addr, scratch.writable(), slot.ty.try_into()?)?;
                        let stack_slot = masm.push(scratch.inner(), slot.ty.try_into()?)?;
                        *v = Val::mem(slot.ty, stack_slot);
                        wasmtime_environ::error::Ok(())
                    })?;
                }
                _ => {}
            }
        }

        Ok(())
    }

    /// Prepares for emitting a binary operation where four 64-bit operands are
    /// used to produce two 64-bit operands, e.g. a 128-bit binop.