3 files changed, 18 insertions, 0 deletions
diff --git a/lib/ruby_vm/mjit/compiler.rb b/lib/ruby_vm/mjit/compiler.rb
index 892b250895..e6dde1d824 100644
--- a/lib/ruby_vm/mjit/compiler.rb
+++ b/lib/ruby_vm/mjit/compiler.rb
@@ -143,6 +143,9 @@ module RubyVM::MJIT
 
     def invalidate_block(block)
       iseq = block.iseq
+      # Avoid touching GCed ISEQs. We assume it won't be re-entered.
+      return if C.imemo_type(iseq) != C.imemo_iseq
+
       # Remove this block from the version array
       remove_block(iseq, block)
 
@@ -286,6 +289,11 @@ module RubyVM::MJIT
     end
 
     def mjit_blocks(iseq)
+      # Tolerate GC on any ISEQ
+      if C.imemo_type(iseq) != C.imemo_iseq
+        return Hash.new { |h, k| h[k] = {} }
+      end
+
       unless iseq.body.mjit_blocks
         iseq.body.mjit_blocks = Hash.new { |h, k| h[k] = {} }
         # For some reason, rb_mjit_iseq_mark didn't protect this Hash
diff --git a/mjit_c.rb b/mjit_c.rb
index c7525f3d98..3570d9bb8d 100644
--- a/mjit_c.rb
+++ b/mjit_c.rb
@@ -241,6 +241,11 @@ module RubyVM::MJIT # :nodoc: all
       }
     end
 
+    def imemo_type(ptr)
+      _ptr = ptr.to_i
+      Primitive.cexpr! 'UINT2NUM(imemo_type((VALUE)NUM2SIZET(_ptr)))'
+    end
+
     #========================================================================================
     #
     # Old stuff
@@ -670,6 +675,10 @@ module RubyVM::MJIT # :nodoc: all
     Primitive.cexpr! %q{ UINT2NUM(VM_METHOD_TYPE_ZSUPER) }
   end
 
+  def C.imemo_iseq
+    Primitive.cexpr! %q{ UINT2NUM(imemo_iseq) }
+  end
+
   def C.INVALID_SHAPE_ID
     Primitive.cexpr! %q{ ULONG2NUM(INVALID_SHAPE_ID) }
   end
diff --git a/tool/mjit/bindgen.rb b/tool/mjit/bindgen.rb
index 92b3ae1932..b8fd7308e9 100755
--- a/tool/mjit/bindgen.rb
+++ b/tool/mjit/bindgen.rb
@@ -420,6 +420,7 @@ generator = BindingGenerator.new(
       VM_METHOD_TYPE_UNDEF
       VM_METHOD_TYPE_ZSUPER
       VM_METHOD_TYPE_REFINED
+      imemo_iseq
     ],
     ULONG: %w[
       INVALID_SHAPE_ID