Optimize setivar for known ivar index

Merged: https://github.com/ruby/ruby/pull/7448

lib/ruby_vm/mjit/assembler.rb

@@ -370,6 +370,10 @@ module RubyVM::MJIT
 
     def jbe(dst)
       case dst
+      # JBE rel8
+      in Label => dst_label
+        # 76 cb
+        insn(opcode: 0x76, imm: dst_label)
       # JBE rel32
       in Integer => dst_addr
         # 0F 86 cd
@@ -441,6 +445,10 @@ module RubyVM::MJIT
 
     def jnz(dst)
       case dst
+      # JE rel8
+      in Label => dst_label
+        # 75 cb
+        insn(opcode: 0x75, imm: dst_label)
       # JNZ rel32
       in Integer => dst_addr
         # 0F 85 cd

lib/ruby_vm/mjit/insn_compiler.rb

@@ -183,25 +183,122 @@ module RubyVM::MJIT
       jit_getivar(jit, ctx, asm, comptime_obj, id)
     end
 
+      #id = jit.operand(0)
+      #ivc = jit.operand(1)
+
+      ## rb_vm_setinstancevariable could raise exceptions
+      #jit_prepare_routine_call(jit, ctx, asm)
+
+      #val_opnd = ctx.stack_pop
+
+      #asm.comment('rb_vm_setinstancevariable')
+      #asm.mov(:rdi, jit.iseq.to_i)
+      #asm.mov(:rsi, [CFP, C.rb_control_frame_t.offsetof(:self)])
+      #asm.mov(:rdx, id)
+      #asm.mov(:rcx, val_opnd)
+      #asm.mov(:r8, ivc)
+      #asm.call(C.rb_vm_setinstancevariable)
+
+      #KeepCompiling
+
     # @param jit [RubyVM::MJIT::JITState]
     # @param ctx [RubyVM::MJIT::Context]
     # @param asm [RubyVM::MJIT::Assembler]
     def setinstancevariable(jit, ctx, asm)
-      id = jit.operand(0)
+      starting_context = ctx.dup # make a copy for use with jit_chain_guard
-      ivc = jit.operand(1)
 
-      # rb_vm_setinstancevariable could raise exceptions
+      # Defer compilation so we can specialize on a runtime `self`
+      unless jit.at_current_insn?
+        defer_compilation(jit, ctx, asm)
+        return EndBlock
+      end
+
+      ivar_name = jit.operand(0)
+      comptime_receiver = jit.peek_at_self
+      comptime_val_klass = C.rb_class_of(comptime_receiver)
+
+      # If the comptime receiver is frozen, writing an IV will raise an exception
+      # and we don't want to JIT code to deal with that situation.
+      if C.rb_obj_frozen_p(comptime_receiver)
+        asm.incr_counter(:setivar_frozen)
+        return CantCompile
+      end
+
+      # Check if the comptime receiver is a T_OBJECT
+      receiver_t_object = C.BUILTIN_TYPE(comptime_receiver) == C.T_OBJECT
+
+      # If the receiver isn't a T_OBJECT, or uses a custom allocator,
+      # then just write out the IV write as a function call.
+      # too-complex shapes can't use index access, so we use rb_ivar_get for them too.
+      if !receiver_t_object || shape_too_complex?(comptime_receiver) || ctx.chain_depth >= 10
+        asm.comment('call rb_vm_setinstancevariable')
+
+        ic = jit.operand(1)
+
+        # The function could raise exceptions.
+        # Note that this modifies REG_SP, which is why we do it first
         jit_prepare_routine_call(jit, ctx, asm)
 
-      val_opnd = ctx.stack_pop
+        # Get the operands from the stack
+        val_opnd = ctx.stack_pop(1)
 
-      asm.comment('rb_vm_setinstancevariable')
+        # Call rb_vm_setinstancevariable(iseq, obj, id, val, ic);
         asm.mov(:rdi, jit.iseq.to_i)
         asm.mov(:rsi, [CFP, C.rb_control_frame_t.offsetof(:self)])
-      asm.mov(:rdx, id)
+        asm.mov(:rdx, ivar_name)
         asm.mov(:rcx, val_opnd)
-      asm.mov(:r8, ivc)
+        asm.mov(:r8, ic)
         asm.call(C.rb_vm_setinstancevariable)
+      else
+        # Get the iv index
+        shape_id = C.rb_shape_get_shape_id(comptime_receiver)
+        ivar_index = C.rb_shape_get_iv_index(shape_id, ivar_name)
+
+        # Get the receiver
+        asm.mov(:rax, [CFP, C.rb_control_frame_t.offsetof(:self)])
+
+        # Generate a side exit
+        side_exit = side_exit(jit, ctx)
+
+        # Upgrade type
+        guard_object_is_heap(asm, :rax, counted_exit(side_exit, :setivar_not_heap))
+
+        asm.comment('guard shape')
+        asm.cmp(DwordPtr[:rax, C.rb_shape_id_offset], shape_id)
+        megamorphic_side_exit = counted_exit(side_exit, :setivar_megamorphic)
+        jit_chain_guard(:jne, jit, starting_context, asm, megamorphic_side_exit)
+
+        # If we don't have an instance variable index, then we need to
+        # transition out of the current shape.
+        if ivar_index.nil?
+          asm.incr_counter(:setivar_no_index)
+          return CantCompile
+        else
+          # If the iv index already exists, then we don't need to
+          # transition to a new shape.  The reason is because we find
+          # the iv index by searching up the shape tree.  If we've
+          # made the transition already, then there's no reason to
+          # update the shape on the object.  Just set the IV.
+          write_val = ctx.stack_pop(1)
+          jit_write_iv(asm, comptime_receiver, :rax, :rcx, ivar_index, write_val)
+        end
+
+        skip_wb = asm.new_label('skip_wb')
+        # If the value we're writing is an immediate, we don't need to WB
+        asm.test(write_val, C.RUBY_IMMEDIATE_MASK)
+        asm.jnz(skip_wb)
+
+        # If the value we're writing is nil or false, we don't need to WB
+        asm.cmp(write_val, Qnil)
+        asm.jbe(skip_wb)
+
+        asm.comment('write barrier')
+        asm.mov(C_ARGS[0], [CFP, C.rb_control_frame_t.offsetof(:self)])
+        asm.mov(C_ARGS[1], write_val)
+        asm.call(C.rb_gc_writebarrier)
+
+        asm.write_label(skip_wb)
+      end
 
       KeepCompiling
     end
@@ -2079,6 +2176,31 @@ module RubyVM::MJIT
       EndBlock
     end
 
+    def jit_write_iv(asm, comptime_receiver, recv_reg, temp_reg, ivar_index, set_value)
+      # Compile time self is embedded and the ivar index lands within the object
+      embed_test_result = C.FL_TEST_RAW(comptime_receiver, C.ROBJECT_EMBED)
+
+      if embed_test_result
+        # Find the IV offset
+        offs = C.RObject.offsetof(:as, :ary) + ivar_index * C.VALUE.size
+
+        # Write the IV
+        asm.comment('write IV')
+        asm.mov(temp_reg, set_value)
+        asm.mov([recv_reg, offs], temp_reg)
+      else
+        # Compile time value is *not* embedded.
+
+        # Get a pointer to the extended table
+        asm.mov(recv_reg, [recv_reg, C.RObject.offsetof(:as, :heap, :ivptr)])
+
+        # Write the ivar in to the extended table
+        asm.comment("write IV");
+        asm.mov(temp_reg, set_value)
+        asm.mov([recv_reg, C.VALUE.size * ivar_index], temp_reg)
+      end
+    end
+
     # vm_caller_setup_arg_block
     # @param jit [RubyVM::MJIT::JITState]
     # @param ctx [RubyVM::MJIT::Context]
@@ -2835,6 +2957,10 @@ module RubyVM::MJIT
       (C.to_value(obj) & 0xff) == C.RUBY_SYMBOL_FLAG
     end
 
+    def shape_too_complex?(obj)
+      C.rb_shape_get_shape_id(obj) == C.OBJ_TOO_COMPLEX_SHAPE_ID
+    end
+
     # @param jit [RubyVM::MJIT::JITState]
     # @param ctx [RubyVM::MJIT::Context]
     # @param asm [RubyVM::MJIT::Assembler]

lib/ruby_vm/mjit/stats.rb

@@ -37,6 +37,7 @@ module RubyVM::MJIT
       print_counters(stats, prefix: 'send_', prompt: 'method call exit reasons')
       print_counters(stats, prefix: 'invokesuper_', prompt: 'invokesuper exit reasons')
       print_counters(stats, prefix: 'getivar_', prompt: 'getinstancevariable exit reasons')
+      print_counters(stats, prefix: 'setivar_', prompt: 'setinstancevariable exit reasons')
       print_counters(stats, prefix: 'optaref_', prompt: 'opt_aref exit reasons')
       print_counters(stats, prefix: 'optgetconst_', prompt: 'opt_getconstant_path exit reasons')
       print_counters(stats, prefix: 'expandarray_', prompt: 'expandarray exit reasons')

mjit_c.h

@@ -180,6 +180,11 @@ MJIT_RUNTIME_COUNTERS(
     optgetconst_not_cached,
     optgetconst_cref,
 
+    setivar_frozen,
+    setivar_not_heap,
+    setivar_megamorphic,
+    setivar_no_index,
+
     expandarray_splat,
     expandarray_postarg,
     expandarray_not_array,

mjit_c.rb

@@ -261,6 +261,14 @@ module RubyVM::MJIT # :nodoc: all
       }
     end
 
+    def rb_gc_writebarrier
+      Primitive.cexpr! 'SIZET2NUM((size_t)rb_gc_writebarrier)'
+    end
+
+    def rb_obj_frozen_p(obj)
+      Primitive.cexpr! 'rb_obj_frozen_p(obj)'
+    end
+
     #========================================================================================
     #
     # Old stuff
@@ -1322,6 +1330,10 @@ module RubyVM::MJIT # :nodoc: all
       optaref_send: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), optaref_send)")],
       optgetconst_not_cached: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), optgetconst_not_cached)")],
       optgetconst_cref: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), optgetconst_cref)")],
+      setivar_frozen: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), setivar_frozen)")],
+      setivar_not_heap: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), setivar_not_heap)")],
+      setivar_megamorphic: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), setivar_megamorphic)")],
+      setivar_no_index: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), setivar_no_index)")],
       expandarray_splat: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), expandarray_splat)")],
       expandarray_postarg: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), expandarray_postarg)")],
       expandarray_not_array: [CType::Immediate.parse("size_t"), Primitive.cexpr!("OFFSETOF((*((struct rb_mjit_runtime_counters *)NULL)), expandarray_not_array)")],