pulley: Refactor register restores on tail-calls (bytecodealliance#10022)

* pulley: Refactor register restores on tail-calls

Use helpers from `abi.rs` where possible to avoid duplicating logic.

* Shuffle where stack increments from tail args happens

Author: alexcrichton

cranelift/codegen/src/isa/pulley_shared/abi.rs

@@ -360,16 +360,6 @@ where
         _call_conv: isa::CallConv,
         _flags: &settings::Flags,
         _isa_flags: &PulleyFlags,
-        _frame_layout: &FrameLayout,
-    ) -> SmallInstVec<Self::I> {
-        // Note that this is intentionally empty as `gen_return` does
-        // everything.
-        SmallVec::new()
-    }
-
-    fn gen_return(
-        _call_conv: isa::CallConv,
-        _isa_flags: &PulleyFlags,
         frame_layout: &FrameLayout,
     ) -> SmallInstVec<Self::I> {
         let mut insts = SmallVec::new();
@@ -411,20 +401,24 @@ where
             }
         }
 
+        insts
+    }
+
+    fn gen_return(
+        _call_conv: isa::CallConv,
+        _isa_flags: &PulleyFlags,
+        frame_layout: &FrameLayout,
+    ) -> SmallInstVec<Self::I> {
+        let mut insts = SmallVec::new();
+
         // Handle final stack adjustments for the tail-call ABI.
         if frame_layout.tail_args_size > 0 {
             insts.extend(Self::gen_sp_reg_adjust(
                 frame_layout.tail_args_size.try_into().unwrap(),
             ));
         }
-
-        // And finally, return.
-        //
-        // FIXME: if `frame_layout.tail_args_size` is zero this instruction
-        // should get folded into the macro-instructions above. No need to have
-        // all functions do `pop_frame; ret`, that could be `pop_frame_and_ret`.
-        // Should benchmark whether this is worth it though.
         insts.push(RawInst::Ret {}.into());
+
         insts
     }
 

cranelift/codegen/src/isa/pulley_shared/inst/emit.rs

@@ -2,6 +2,7 @@
 
 use super::*;
 use crate::ir::{self, Endianness};
+use crate::isa;
 use crate::isa::pulley_shared::abi::PulleyMachineDeps;
 use crate::isa::pulley_shared::PointerWidth;
 use core::marker::PhantomData;
@@ -10,19 +11,19 @@ use pulley_interpreter::encode as enc;
 use pulley_interpreter::regs::BinaryOperands;
 
 pub struct EmitInfo {
-    #[allow(dead_code)] // Will get used as we fill out this backend.
+    call_conv: isa::CallConv,
     shared_flags: settings::Flags,
-
-    #[allow(dead_code)] // Will get used as we fill out this backend.
     isa_flags: crate::isa::pulley_shared::settings::Flags,
 }
 
 impl EmitInfo {
     pub(crate) fn new(
+        call_conv: isa::CallConv,
         shared_flags: settings::Flags,
         isa_flags: crate::isa::pulley_shared::settings::Flags,
     ) -> Self {
         Self {
+            call_conv,
             shared_flags,
             isa_flags,
         }
@@ -644,46 +645,17 @@ fn return_call_emit_impl<T, P>(
 ) where
     P: PulleyTargetKind,
 {
-    let sp_to_fp_offset = {
-        let frame_layout = state.frame_layout();
-        i64::from(
-            frame_layout.clobber_size
-                + frame_layout.fixed_frame_storage_size
-                + frame_layout.outgoing_args_size,
-        )
-    };
-
-    // Restore all clobbered registers before leaving the function.
-    let mut clobber_offset = sp_to_fp_offset - 8;
-    for reg in state.frame_layout().clobbered_callee_saves.clone() {
-        let rreg = reg.to_reg();
-        let ty = match rreg.class() {
-            RegClass::Int => I64,
-            RegClass::Float => F64,
-            RegClass::Vector => unimplemented!("Vector Clobber Restores"),
-        };
-
-        <InstAndKind<P>>::from(Inst::gen_load(
-            reg.map(Reg::from),
-            Amode::SpOffset {
-                offset: clobber_offset.try_into().unwrap(),
-            },
-            ty,
-            MemFlags::trusted(),
-        ))
-        .emit(sink, emit_info, state);
-
-        clobber_offset -= 8
+    let epilogue = <PulleyMachineDeps<P>>::gen_epilogue_frame_restore(
+        emit_info.call_conv,
+        &emit_info.shared_flags,
+        &emit_info.isa_flags,
+        &state.frame_layout,
+    );
+
+    for inst in epilogue {
+        inst.emit(sink, emit_info, state);
     }
 
-    // Restore the link register and frame pointer using a `pop_frame`
-    // instruction. This will move `sp` to the current frame pointer and then
-    // restore the old lr/fp, so this restores all of sp/fp/lr in one
-    // instruction.
-    let setup_area_size = i64::from(state.frame_layout().setup_area_size);
-    assert!(setup_area_size > 0, "must have frame pointers enabled");
-    <InstAndKind<P>>::from(RawInst::PopFrame).emit(sink, emit_info, state);
-
     // Now that `sp` is restored to what it was on function entry it may need to
     // be adjusted if the stack arguments of our own function differ from the
     // stack arguments of the callee. Perform any necessary adjustment here.

cranelift/codegen/src/isa/pulley_shared/mod.rs

@@ -124,7 +124,11 @@ where
         domtree: &DominatorTree,
         ctrl_plane: &mut ControlPlane,
     ) -> CodegenResult<(VCode<inst::InstAndKind<P>>, regalloc2::Output)> {
-        let emit_info = EmitInfo::new(self.flags.clone(), self.isa_flags.clone());
+        let emit_info = EmitInfo::new(
+            func.signature.call_conv,
+            self.flags.clone(),
+            self.isa_flags.clone(),
+        );
         let sigs = SigSet::new::<abi::PulleyMachineDeps<P>>(func, &self.flags)?;
         let abi = abi::PulleyCallee::new(func, self, &self.isa_flags, &sigs)?;
         machinst::compile::<Self>(func, domtree, self, abi, emit_info, sigs, ctrl_plane)