ZJIT: Implement Polymorphic DefinedIvar (#16981)HEADmaster

* ZJIT: Implement Polymorphic Definedivar

Closes: https://github.com/Shopify/ruby/issues/980

Build polymorphic shape/type branches for definedivar in HIR. For each profiled T_OBJECT shape, specialize defined?(`@ivar`) to a constant pushval or nil based on the compile-time ivar index check.

DefinedIvar already profiles self on monomorphic shape guard failures for recompilation, so the recompiled HIR can use the collected polymorphic shapes while keeping a generic DefinedIvar fallback for misses and unsupported shapes.


## Benchmark
### lobsters
Summary:
```diff
- dynamic_definedivar_count:   1,294,854 ( 0.7%)
+ dynamic_definedivar_count:     503,058 ( 0.3%)

  ratio_in_zjit:                                     88.4%
```

```
zjit-master: ruby 4.1.0dev (2026-05-23T00:08:49Z master 5855d61ee4) +ZJIT stats +PRISM [arm64-darwin25]
zjit-polymorphic-definedivar: ruby 4.1.0dev (2026-05-23T07:11:22Z zjit-polymorphic-d.. f75a82e7f1) +ZJIT stats +PRISM [arm64-darwin25]
last_commit=ZJIT: Implement Polymorphic Definedivar

--------  ----------------  ---------------------------------  ------------------------------------  ----------------------------------------
bench     zjit-master (ms)  zjit-polymorphic-definedivar (ms)  zjit-polymorphic-definedivar 1st itr  zjit-master/zjit-polymorphic-definedivar
lobsters      529.9 ± 3.6%                       504.2 ± 7.7%                                 1.148                                     1.051
--------  ----------------  ---------------------------------  ------------------------------------  ----------------------------------------
```

Full stats details below:
<details>

<summary>before patch</summary>

```
Top-2 not optimized method types for send (100.0% of total 65,120):
       null: 44,877 (68.9%)
  optimized: 20,243 (31.1%)
Top-3 not optimized method types for send_without_block (100.0% of total 716,678):
        optimized_send: 711,905 (99.3%)
  optimized_block_call:   4,299 ( 0.6%)
                zsuper:     474 ( 0.1%)
Top-1 not optimized method types for super (100.0% of total 3,678):
  attrset: 3,678 (100.0%)
Top-1 instructions with uncategorized fallback reason (100.0% of total 65,868):
  opt_send_without_block: 65,868 (100.0%)
Top-20 send fallback reasons (99.5% of total 22,386,632):
                             invokeblock_not_specialized: 5,946,612 (26.6%)
                            one_or_more_complex_arg_pass: 4,376,419 (19.5%)
                          send_without_block_polymorphic: 3,748,855 (16.7%)
                          send_without_block_no_profiles: 2,830,116 (12.6%)
                          send_without_block_megamorphic: 1,108,467 ( 5.0%)
                             sendforward_not_specialized:   971,957 ( 4.3%)
                                        send_polymorphic:   806,862 ( 3.6%)
  send_without_block_not_optimized_method_type_optimized:   716,204 ( 3.2%)
                                       super_polymorphic:   337,181 ( 1.5%)
                                   too_many_args_for_lir:   333,633 ( 1.5%)
                      send_not_optimized_need_permission:   238,842 ( 1.1%)
        send_without_block_not_optimized_need_permission:   180,946 ( 0.8%)
                                        send_no_profiles:   177,008 ( 0.8%)
                                     argc_param_mismatch:   124,061 ( 0.6%)
                                 super_complex_args_pass:    89,280 ( 0.4%)
                      invokesuperforward_not_specialized:    80,729 ( 0.4%)
                                           uncategorized:    65,868 ( 0.3%)
                          send_not_optimized_method_type:    65,120 ( 0.3%)
                                        super_from_block:    43,185 ( 0.2%)
                                obj_to_string_not_string:    42,731 ( 0.2%)
Top-4 setivar fallback reasons (100.0% of total 4,182,333):
            not_monomorphic: 3,969,254 (94.9%)
               not_t_object:   119,505 ( 2.9%)
                    complex:    93,131 ( 2.2%)
  new_shape_needs_extension:       443 ( 0.0%)
Top-2 getivar fallback reasons (100.0% of total 11,716,846):
  not_monomorphic: 11,537,525 (98.5%)
          complex:    179,321 ( 1.5%)
Top-3 definedivar fallback reasons (100.0% of total 1,294,854):
  not_monomorphic: 1,289,423 (99.6%)
          complex:     5,122 ( 0.4%)
     not_t_object:       309 ( 0.0%)
Top-5 invokeblock handler (100.0% of total 6,968,323):
  monomorphic_ifunc: 4,143,418 (59.5%)
  monomorphic_other: 1,444,525 (20.7%)
   monomorphic_iseq:   865,749 (12.4%)
        polymorphic:   508,677 ( 7.3%)
        megamorphic:     5,954 ( 0.1%)
Top-6 getblockparamproxy handler (100.0% of total 3,321,873):
  polymorphic: 2,370,458 (71.4%)
          nil:   492,185 (14.8%)
         iseq:   242,627 ( 7.3%)
  no_profiles:   168,826 ( 5.1%)
         proc:    40,245 ( 1.2%)
  megamorphic:     7,532 ( 0.2%)
Top-7 popular complex argument-parameter features not optimized (100.0% of total 4,677,994):
    caller_blockarg: 3,092,361 (66.1%)
  param_forwardable:   697,044 (14.9%)
         param_rest:   409,311 ( 8.7%)
       caller_kwarg:   193,462 ( 4.1%)
       param_kwrest:   143,181 ( 3.1%)
    caller_kw_splat:    85,992 ( 1.8%)
       caller_splat:    56,643 ( 1.2%)
Top-3 compile error reasons (100.0% of total 196,397):
                  exception_handler: 192,000 (97.8%)
             native_stack_too_large:   4,342 ( 2.2%)
  validation_mismatched_block_arity:      55 ( 0.0%)
Top-2 unhandled HIR insns (100.0% of total 229,881):
          throw: 194,104 (84.4%)
  invokebuiltin:  35,777 (15.6%)
Top-19 side exit reasons (100.0% of total 8,637,525):
                   guard_type_failure: 7,692,359 (89.1%)
                   unhandled_hir_insn:   229,881 ( 2.7%)
                        compile_error:   196,397 ( 2.3%)
          patchpoint_method_redefined:   118,680 ( 1.4%)
      block_param_proxy_fallback_miss:   112,551 ( 1.3%)
                      no_profile_send:    93,334 ( 1.1%)
            block_param_proxy_not_nil:    75,195 ( 0.9%)
     patchpoint_stable_constant_names:    55,819 ( 0.6%)
        patchpoint_no_singleton_class:    19,352 ( 0.2%)
                  unhandled_block_arg:    14,541 ( 0.2%)
  block_param_proxy_not_iseq_or_ifunc:    13,401 ( 0.2%)
               fixnum_lshift_overflow:    10,165 ( 0.1%)
                   guard_less_failure:     3,120 ( 0.0%)
                  guard_shape_failure:     1,302 ( 0.0%)
             guard_greater_eq_failure:       941 ( 0.0%)
             guard_super_method_entry:       407 ( 0.0%)
                            interrupt:        49 ( 0.0%)
               obj_to_string_fallback:        30 ( 0.0%)
             guard_not_shared_failure:         1 ( 0.0%)
                             send_count: 182,469,185
                     dynamic_send_count:  22,386,632 (12.3%)
                   optimized_send_count: 160,082,553 (87.7%)
                  dynamic_setivar_count:   4,182,333 ( 2.3%)
                  dynamic_getivar_count:  11,716,846 ( 6.4%)
              dynamic_definedivar_count:   1,294,854 ( 0.7%)
              iseq_optimized_send_count:  54,154,353 (29.7%)
      inline_cfunc_optimized_send_count:  74,812,159 (41.0%)
       inline_iseq_optimized_send_count:   6,346,705 ( 3.5%)
non_variadic_cfunc_optimized_send_count:  13,789,249 ( 7.6%)
    variadic_cfunc_optimized_send_count:  10,980,087 ( 6.0%)
compiled_iseq_count:                                  6,166
compiled_side_exit_count:                            80,485
failed_iseq_count:                                        3
compile_time:                                       2,462ms
compile_side_exit_time:                               113ms
compile_side_exit_time_ratio:                          4.6%
compile_hir_time:                                     798ms
compile_hir_build_time:                               238ms
compile_hir_strength_reduce_time:                     322ms
compile_hir_canonicalize_time:                         49ms
compile_hir_fold_constants_time:                       37ms
compile_hir_clean_cfg_time:                            26ms
compile_hir_eliminate_dead_code_time:                  30ms
compile_lir_time:                                   1,525ms
profile_time:                                          39ms
gc_time:                                               33ms
invalidation_time:                                     14ms
vm_write_jit_frame_count:                       137,433,269
vm_write_sp_count:                              137,433,269
vm_write_locals_count:                          131,272,119
vm_write_stack_count:                           131,272,119
vm_write_to_parent_iseq_local_count:                688,492
guard_type_count:                               145,711,992
guard_type_exit_ratio:                                 5.3%
guard_shape_count:                               36,890,099
guard_shape_exit_ratio:                                0.0%
load_field_count:                               210,155,590
store_field_count:                               15,758,742
side_exit_size:                                  13,563,708
code_region_bytes:                               33,505,280
side_exit_size_ratio:                                 40.5%
zjit_alloc_bytes:                                22,783,024
total_mem_bytes:                                 56,288,304
side_exit_count:                                  8,637,525
total_insn_count:                               995,180,861
vm_insn_count:                                  115,515,525
zjit_insn_count:                                879,665,336
ratio_in_zjit:                                        88.4%
```

</details>

<details>

<summary>after patch</summary>

```
Top-2 not optimized method types for send (100.0% of total 65,119):
       null: 44,877 (68.9%)
  optimized: 20,242 (31.1%)
Top-3 not optimized method types for send_without_block (100.0% of total 716,636):
        optimized_send: 711,869 (99.3%)
  optimized_block_call:   4,293 ( 0.6%)
                zsuper:     474 ( 0.1%)
Top-1 not optimized method types for super (100.0% of total 3,676):
  attrset: 3,676 (100.0%)
Top-1 instructions with uncategorized fallback reason (100.0% of total 65,866):
  opt_send_without_block: 65,866 (100.0%)
Top-20 send fallback reasons (99.5% of total 22,409,237):
                             invokeblock_not_specialized: 5,946,405 (26.5%)
                            one_or_more_complex_arg_pass: 4,376,457 (19.5%)
                          send_without_block_polymorphic: 3,775,975 (16.9%)
                          send_without_block_no_profiles: 2,830,029 (12.6%)
                          send_without_block_megamorphic: 1,104,527 ( 4.9%)
                             sendforward_not_specialized:   971,924 ( 4.3%)
                                        send_polymorphic:   806,852 ( 3.6%)
  send_without_block_not_optimized_method_type_optimized:   716,162 ( 3.2%)
                                       super_polymorphic:   337,178 ( 1.5%)
                                   too_many_args_for_lir:   333,625 ( 1.5%)
                      send_not_optimized_need_permission:   238,842 ( 1.1%)
        send_without_block_not_optimized_need_permission:   180,949 ( 0.8%)
                                        send_no_profiles:   176,799 ( 0.8%)
                                     argc_param_mismatch:   124,064 ( 0.6%)
                                 super_complex_args_pass:    89,280 ( 0.4%)
                      invokesuperforward_not_specialized:    80,723 ( 0.4%)
                                           uncategorized:    65,866 ( 0.3%)
                          send_not_optimized_method_type:    65,119 ( 0.3%)
                                        super_from_block:    43,182 ( 0.2%)
                                obj_to_string_not_string:    42,725 ( 0.2%)
Top-4 setivar fallback reasons (100.0% of total 4,182,216):
            not_monomorphic: 3,969,159 (94.9%)
               not_t_object:   119,484 ( 2.9%)
                    complex:    93,131 ( 2.2%)
  new_shape_needs_extension:       442 ( 0.0%)
Top-2 getivar fallback reasons (100.0% of total 11,716,471):
  not_monomorphic: 11,537,150 (98.5%)
          complex:    179,321 ( 1.5%)
Top-3 definedivar fallback reasons (100.0% of total 503,058):
  not_monomorphic: 498,173 (99.0%)
          complex:   4,576 ( 0.9%)
     not_t_object:     309 ( 0.1%)
Top-5 invokeblock handler (100.0% of total 6,968,099):
  monomorphic_ifunc: 4,143,324 (59.5%)
  monomorphic_other: 1,444,457 (20.7%)
   monomorphic_iseq:   865,705 (12.4%)
        polymorphic:   508,659 ( 7.3%)
        megamorphic:     5,954 ( 0.1%)
Top-6 getblockparamproxy handler (100.0% of total 3,321,803):
  polymorphic: 2,370,425 (71.4%)
          nil:   492,172 (14.8%)
         iseq:   242,810 ( 7.3%)
  no_profiles:   168,625 ( 5.1%)
         proc:    40,239 ( 1.2%)
  megamorphic:     7,532 ( 0.2%)
Top-7 popular complex argument-parameter features not optimized (100.0% of total 4,678,011):
    caller_blockarg: 3,092,480 (66.1%)
  param_forwardable:   697,011 (14.9%)
         param_rest:   409,285 ( 8.7%)
       caller_kwarg:   193,450 ( 4.1%)
       param_kwrest:   143,179 ( 3.1%)
    caller_kw_splat:    85,971 ( 1.8%)
       caller_splat:    56,635 ( 1.2%)
Top-3 compile error reasons (100.0% of total 196,386):
                  exception_handler: 191,989 (97.8%)
             native_stack_too_large:   4,342 ( 2.2%)
  validation_mismatched_block_arity:      55 ( 0.0%)
Top-2 unhandled HIR insns (100.0% of total 229,876):
          throw: 194,101 (84.4%)
  invokebuiltin:  35,775 (15.6%)
Top-19 side exit reasons (100.0% of total 8,638,646):
                   guard_type_failure: 7,693,566 (89.1%)
                   unhandled_hir_insn:   229,876 ( 2.7%)
                        compile_error:   196,386 ( 2.3%)
          patchpoint_method_redefined:   118,676 ( 1.4%)
      block_param_proxy_fallback_miss:   112,548 ( 1.3%)
                      no_profile_send:    93,330 ( 1.1%)
            block_param_proxy_not_nil:    75,195 ( 0.9%)
     patchpoint_stable_constant_names:    55,792 ( 0.6%)
        patchpoint_no_singleton_class:    19,326 ( 0.2%)
                  unhandled_block_arg:    14,540 ( 0.2%)
  block_param_proxy_not_iseq_or_ifunc:    13,401 ( 0.2%)
               fixnum_lshift_overflow:    10,165 ( 0.1%)
                   guard_less_failure:     3,119 ( 0.0%)
                  guard_shape_failure:     1,302 ( 0.0%)
             guard_greater_eq_failure:       941 ( 0.0%)
             guard_super_method_entry:       407 ( 0.0%)
                            interrupt:        45 ( 0.0%)
               obj_to_string_fallback:        30 ( 0.0%)
             guard_not_shared_failure:         1 ( 0.0%)
                             send_count: 182,477,537
                     dynamic_send_count:  22,409,237 (12.3%)
                   optimized_send_count: 160,068,300 (87.7%)
                  dynamic_setivar_count:   4,182,216 ( 2.3%)
                  dynamic_getivar_count:  11,716,471 ( 6.4%)
              dynamic_definedivar_count:     503,058 ( 0.3%)
              iseq_optimized_send_count:  54,138,292 (29.7%)
      inline_cfunc_optimized_send_count:  74,815,196 (41.0%)
       inline_iseq_optimized_send_count:   6,346,484 ( 3.5%)
non_variadic_cfunc_optimized_send_count:  13,788,597 ( 7.6%)
    variadic_cfunc_optimized_send_count:  10,979,731 ( 6.0%)
compiled_iseq_count:                                  6,167
compiled_side_exit_count:                            80,471
failed_iseq_count:                                        3
compile_time:                                       2,711ms
compile_side_exit_time:                               125ms
compile_side_exit_time_ratio:                          4.6%
compile_hir_time:                                     870ms
compile_hir_build_time:                               266ms
compile_hir_strength_reduce_time:                     347ms
compile_hir_canonicalize_time:                         52ms
compile_hir_fold_constants_time:                       40ms
compile_hir_clean_cfg_time:                            27ms
compile_hir_eliminate_dead_code_time:                  32ms
compile_lir_time:                                   1,680ms
profile_time:                                          48ms
gc_time:                                               32ms
invalidation_time:                                     15ms
vm_write_jit_frame_count:                       137,425,789
vm_write_sp_count:                              137,425,789
vm_write_locals_count:                          131,264,963
vm_write_stack_count:                           131,264,963
vm_write_to_parent_iseq_local_count:                688,457
guard_type_count:                               146,412,455
guard_type_exit_ratio:                                 5.3%
guard_shape_count:                               36,937,934
guard_shape_exit_ratio:                                0.0%
load_field_count:                               211,394,883
store_field_count:                               15,778,119
side_exit_size:                                  13,563,624
code_region_bytes:                               33,505,280
side_exit_size_ratio:                                 40.5%
zjit_alloc_bytes:                                22,870,223
total_mem_bytes:                                 56,375,503
side_exit_count:                                  8,638,646
total_insn_count:                               995,144,390
vm_insn_count:                                  115,472,694
zjit_insn_count:                                879,671,696
ratio_in_zjit:                                        88.4%
```

</details>

* ZJIT: Add TODO for deduplicating DefinedIvar specialization

* ZJIT: Add more DefinedIvar HIR tests

Cover unsupported receiver profiles and a mixed polymorphic profile with a generic DefinedIvar fallback.

* ZJIT: Add more DefinedIvar polymorphic HIR test

Cover polymorphic definedivar profiles with:
- complex path
- non-T_OBJECT path

0 files changed, 0 insertions, 0 deletions