From 196c1f56f7982d4558f4eff82394918ed96ccd98 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Wed, 18 Dec 2024 15:53:15 -0800
Subject: [PATCH] pulley: Remove unwind metadata from Cranelift backend

This is a copy/paste from the riscv64 backend originally but there's no
need to integrate with native unwinders on Pulley so there's no need to
track this information. This removes the `Unwind` pseudo-inst entirely.
---
 .../codegen/src/isa/pulley_shared/abi.rs      | 42 ++-----------------
 .../codegen/src/isa/pulley_shared/inst.isle   |  3 --
 .../src/isa/pulley_shared/inst/emit.rs        |  2 +-
 .../codegen/src/isa/pulley_shared/inst/mod.rs |  4 +-
 4 files changed, 5 insertions(+), 46 deletions(-)

diff --git a/cranelift/codegen/src/isa/pulley_shared/abi.rs b/cranelift/codegen/src/isa/pulley_shared/abi.rs
index 43a9ce7b789f..5893460461df 100644
--- a/cranelift/codegen/src/isa/pulley_shared/abi.rs
+++ b/cranelift/codegen/src/isa/pulley_shared/abi.rs
@@ -4,7 +4,7 @@ use super::{inst::*, PulleyFlags, PulleyTargetKind};
 use crate::isa::pulley_shared::{PointerWidth, PulleyBackend};
 use crate::{
     ir::{self, types::*, MemFlags, Signature},
-    isa::{self, unwind::UnwindInst},
+    isa::{self},
     machinst::*,
     settings, CodegenResult,
 };
@@ -290,7 +290,7 @@ where
 
     fn gen_prologue_frame_setup(
         _call_conv: isa::CallConv,
-        flags: &settings::Flags,
+        _flags: &settings::Flags,
         _isa_flags: &PulleyFlags,
         frame_layout: &FrameLayout,
     ) -> SmallInstVec<Self::I> {
@@ -298,16 +298,6 @@ where
 
         if frame_layout.setup_area_size > 0 {
             insts.push(RawInst::PushFrame.into());
-            if flags.unwind_info() {
-                insts.push(
-                    Inst::Unwind {
-                        inst: UnwindInst::PushFrameRegs {
-                            offset_upward_to_caller_sp: frame_layout.setup_area_size,
-                        },
-                    }
-                    .into(),
-                );
-            }
         }
 
         insts
@@ -350,7 +340,7 @@ where
 
     fn gen_clobber_save(
         _call_conv: isa::CallConv,
-        flags: &settings::Flags,
+        _flags: &settings::Flags,
         frame_layout: &FrameLayout,
     ) -> SmallVec<[Self::I; 16]> {
         let mut insts = SmallVec::new();
@@ -379,20 +369,6 @@ where
             }
         }
 
-        if flags.unwind_info() && setup_frame {
-            // The *unwind* frame (but not the actual frame) starts at the
-            // clobbers, just below the saved FP/LR pair.
-            insts.push(
-                Inst::Unwind {
-                    inst: UnwindInst::DefineNewFrame {
-                        offset_downward_to_clobbers: frame_layout.clobber_size,
-                        offset_upward_to_caller_sp: frame_layout.setup_area_size,
-                    },
-                }
-                .into(),
-            );
-        }
-
         // Adjust the stack pointer downward for clobbers, the function fixed
         // frame (spillslots and storage slots), and outgoing arguments.
         let stack_size = frame_layout.clobber_size
@@ -424,18 +400,6 @@ where
                     .into(),
                 );
 
-                if flags.unwind_info() {
-                    insts.push(
-                        Inst::Unwind {
-                            inst: UnwindInst::SaveReg {
-                                clobber_offset: frame_layout.clobber_size - cur_offset,
-                                reg: r_reg,
-                            },
-                        }
-                        .into(),
-                    );
-                }
-
                 cur_offset += 8
             }
         }
diff --git a/cranelift/codegen/src/isa/pulley_shared/inst.isle b/cranelift/codegen/src/isa/pulley_shared/inst.isle
index 2f2539917a92..5c2babb05270 100644
--- a/cranelift/codegen/src/isa/pulley_shared/inst.isle
+++ b/cranelift/codegen/src/isa/pulley_shared/inst.isle
@@ -18,9 +18,6 @@
     ;; A pseudo-instruction that moves vregs to return registers.
     (Rets (rets VecRetPair))
 
-    ;; A pseudo-instruction to update unwind info.
-    (Unwind (inst UnwindInst))
-
     ;; Implementation of `br_table`, uses `idx` to jump to one of `targets` or
     ;; jumps to `default` if it's out-of-bounds.
     (BrTable
diff --git a/cranelift/codegen/src/isa/pulley_shared/inst/emit.rs b/cranelift/codegen/src/isa/pulley_shared/inst/emit.rs
index 642662eb8e43..ce80539a1761 100644
--- a/cranelift/codegen/src/isa/pulley_shared/inst/emit.rs
+++ b/cranelift/codegen/src/isa/pulley_shared/inst/emit.rs
@@ -130,7 +130,7 @@ fn pulley_emit<P>(
 {
     match inst {
         // Pseduo-instructions that don't actually encode to anything.
-        Inst::Args { .. } | Inst::Rets { .. } | Inst::Unwind { .. } => {}
+        Inst::Args { .. } | Inst::Rets { .. } => {}
 
         Inst::TrapIf { cond, code } => {
             let trap = sink.defer_trap(*code);
diff --git a/cranelift/codegen/src/isa/pulley_shared/inst/mod.rs b/cranelift/codegen/src/isa/pulley_shared/inst/mod.rs
index e94df98065e9..ec95bdbe53e5 100644
--- a/cranelift/codegen/src/isa/pulley_shared/inst/mod.rs
+++ b/cranelift/codegen/src/isa/pulley_shared/inst/mod.rs
@@ -129,7 +129,7 @@ fn pulley_get_operands(inst: &mut Inst, collector: &mut impl OperandVisitor) {
             }
         }
 
-        Inst::Unwind { .. } | Inst::Nop => {}
+        Inst::Nop => {}
 
         Inst::TrapIf { cond, code: _ } => {
             cond.get_operands(collector);
@@ -578,8 +578,6 @@ impl Inst {
                 s
             }
 
-            Inst::Unwind { inst } => format!("unwind {inst:?}"),
-
             Inst::TrapIf { cond, code } => {
                 format!("trap_{cond} // code = {code:?}")
             }