ZJIT: Support invalidating constant patch points (ruby#13998)

Author: st0012

test/ruby/test_zjit.rb

@@ -889,6 +889,48 @@ def test = X
     end
   end
 
+  def test_constant_invalidation
+    assert_compiles '123', <<~RUBY, call_threshold: 2, insns: [:opt_getconstant_path]
+      class C; end
+      def test = C
+      test
+      test
+
+      C = 123
+      test
+    RUBY
+  end
+
+  def test_constant_path_invalidation
+    assert_compiles '["Foo::C", "Foo::C", "Bar::C"]', <<~RUBY, call_threshold: 2, insns: [:opt_getconstant_path]
+      module A
+        module B; end
+      end
+
+      module Foo
+        C = "Foo::C"
+      end
+
+      module Bar
+        C = "Bar::C"
+      end
+
+      A::B = Foo
+
+      def test = A::B::C
+
+      result = []
+
+      result << test
+      result << test
+
+      A::B = Bar
+
+      result << test
+      result
+    RUBY
+  end
+
   def test_dupn
     assert_compiles '[[1], [1, 1], :rhs, [nil, :rhs]]', <<~RUBY, insns: [:dupn]
       def test(array) = (array[1, 2] ||= :rhs)

vm_method.c

@@ -148,6 +148,7 @@ rb_clear_constant_cache_for_id(ID id)
     }
 
     rb_yjit_constant_state_changed(id);
+    rb_zjit_constant_state_changed(id);
 }
 
 static void

zjit.h

@@ -14,6 +14,7 @@ void rb_zjit_profile_enable(const rb_iseq_t *iseq);
 void rb_zjit_bop_redefined(int redefined_flag, enum ruby_basic_operators bop);
 void rb_zjit_cme_invalidate(const rb_callable_method_entry_t *cme);
 void rb_zjit_invalidate_ep_is_bp(const rb_iseq_t *iseq);
+void rb_zjit_constant_state_changed(ID id);
 void rb_zjit_iseq_mark(void *payload);
 void rb_zjit_iseq_update_references(void *payload);
 #else
@@ -24,6 +25,7 @@ static inline void rb_zjit_profile_enable(const rb_iseq_t *iseq) {}
 static inline void rb_zjit_bop_redefined(int redefined_flag, enum ruby_basic_operators bop) {}
 static inline void rb_zjit_cme_invalidate(const rb_callable_method_entry_t *cme) {}
 static inline void rb_zjit_invalidate_ep_is_bp(const rb_iseq_t *iseq) {}
+static inline void rb_zjit_constant_state_changed(ID id) {}
 #endif // #if USE_YJIT
 
 #endif // #ifndef ZJIT_H

zjit/src/codegen.rs

@@ -4,7 +4,7 @@ use std::ffi::{c_int};
 
 use crate::asm::Label;
 use crate::backend::current::{Reg, ALLOC_REGS};
-use crate::invariants::{track_bop_assumption, track_cme_assumption};
+use crate::invariants::{track_bop_assumption, track_cme_assumption, track_stable_constant_names_assumption};
 use crate::gc::{get_or_create_iseq_payload, append_gc_offsets};
 use crate::state::ZJITState;
 use crate::{asm::CodeBlock, cruby::*, options::debug, virtualmem::CodePtr};
@@ -505,6 +505,10 @@ fn gen_patch_point(jit: &mut JITState, asm: &mut Assembler, invariant: &Invarian
                 let side_exit_ptr = cb.resolve_label(label);
                 track_cme_assumption(cme, code_ptr, side_exit_ptr);
             }
+            Invariant::StableConstantNames { idlist } => {
+                let side_exit_ptr = cb.resolve_label(label);
+                track_stable_constant_names_assumption(idlist, code_ptr, side_exit_ptr);
+            }
             _ => {
                 debug!("ZJIT: gen_patch_point: unimplemented invariant {invariant:?}");
                 return;

zjit/src/cruby.rs

@@ -259,7 +259,7 @@ pub struct VALUE(pub usize);
 /// An interned string. See [ids] and methods this type.
 /// `0` is a sentinal value for IDs.
 #[repr(transparent)]
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 pub struct ID(pub ::std::os::raw::c_ulong);
 
 /// Pointer to an ISEQ

zjit/src/invariants.rs

@@ -1,6 +1,6 @@
 use std::{collections::{HashMap, HashSet}};
 
-use crate::{backend::lir::{asm_comment, Assembler}, cruby::{rb_callable_method_entry_t, ruby_basic_operators, src_loc, with_vm_lock, IseqPtr, RedefinitionFlag}, hir::Invariant, options::debug, state::{zjit_enabled_p, ZJITState}, virtualmem::CodePtr};
+use crate::{backend::lir::{asm_comment, Assembler}, cruby::{rb_callable_method_entry_t, ruby_basic_operators, src_loc, with_vm_lock, IseqPtr, RedefinitionFlag, ID}, hir::Invariant, options::debug, state::{zjit_enabled_p, ZJITState}, virtualmem::CodePtr};
 
 #[derive(Debug, Eq, Hash, PartialEq)]
 struct Jump {
@@ -23,6 +23,9 @@ pub struct Invariants {
 
     /// Map from CME to patch points that assume the method hasn't been redefined
     cme_patch_points: HashMap<*const rb_callable_method_entry_t, HashSet<Jump>>,
+
+    /// Map from constant ID to patch points that assume the constant hasn't been redefined
+    constant_state_patch_points: HashMap<ID, HashSet<Jump>>,
 }
 
 /// Called when a basic operator is redefined. Note that all the blocks assuming
@@ -116,6 +119,30 @@ pub fn track_cme_assumption(
     });
 }
 
+/// Track a patch point for each constant name in a constant path assumption.
+pub fn track_stable_constant_names_assumption(
+    idlist: *const ID,
+    patch_point_ptr: CodePtr,
+    side_exit_ptr: CodePtr
+) {
+    let invariants = ZJITState::get_invariants();
+
+    let mut idx = 0;
+    loop {
+        let id = unsafe { *idlist.wrapping_add(idx) };
+        if id.0 == 0 {
+            break;
+        }
+
+        invariants.constant_state_patch_points.entry(id).or_default().insert(Jump {
+            from: patch_point_ptr,
+            to: side_exit_ptr,
+        });
+
+        idx += 1;
+    }
+}
+
 /// Called when a method is redefined. Invalidates all JIT code that depends on the CME.
 #[unsafe(no_mangle)]
 pub extern "C" fn rb_zjit_cme_invalidate(cme: *const rb_callable_method_entry_t) {
@@ -144,3 +171,32 @@ pub extern "C" fn rb_zjit_cme_invalidate(cme: *const rb_callable_method_entry_t)
         }
     });
 }
+
+/// Called when a constant is redefined. Invalidates all JIT code that depends on the constant.
+#[unsafe(no_mangle)]
+pub extern "C" fn rb_zjit_constant_state_changed(id: ID) {
+    // If ZJIT isn't enabled, do nothing
+    if !zjit_enabled_p() {
+        return;
+    }
+
+    with_vm_lock(src_loc!(), || {
+        let invariants = ZJITState::get_invariants();
+        if let Some(jumps) = invariants.constant_state_patch_points.get(&id) {
+            let cb = ZJITState::get_code_block();
+            debug!("Constant state changed: {:?}", id);
+
+            // Invalidate all patch points for this constant ID
+            for jump in jumps {
+                cb.with_write_ptr(jump.from, |cb| {
+                    let mut asm = Assembler::new();
+                    asm_comment!(asm, "Constant state changed: {:?}", id);
+                    asm.jmp(jump.to.into());
+                    asm.compile(cb).expect("can write existing code");
+                });
+            }
+
+            cb.mark_all_executable();
+        }
+    });
+}