YJIT: Use general definedivar at the end of chains

[k0kubun]

Running #7755 locally with a bare SFR stats hash, I confirmed definedivar exit reasons consist of:

definedivar exit reasons:
    megamorphic: 27,640,363 (100.0%)

which makes up 4.3% overall.

Similar to what we do for getivar and setivar, I think we should use a general case at the last chain to avoid side exits.

[k0kubun]

definedivar exits are gone from SFR.

before

***YJIT: Printing YJIT statistics on exit***
method call exit reasons: 
                           kw_splat: 138,512,397 (24.8%)
                    iseq_has_kwrest: 87,926,421 (15.7%)
                iseq_ruby2_keywords: 86,721,978 (15.5%)
                  klass_megamorphic: 47,312,117 ( 8.5%)
                     iseq_has_no_kw: 37,672,650 ( 6.7%)
                    args_splat_ivar: 31,393,187 ( 5.6%)
          args_splat_cfunc_var_args: 26,013,784 ( 4.7%)
                      zsuper_method: 16,043,009 ( 2.9%)
                          block_arg: 15,188,953 ( 2.7%)
                        not_fixnums: 15,086,768 ( 2.7%)
                   iseq_arity_error: 14,897,090 ( 2.7%)
                args_splat_opt_call:  9,592,944 ( 1.7%)
                           keywords:  9,068,512 ( 1.6%)
                        send_getter:  7,017,789 ( 1.3%)
                        iseq_zsuper:  4,145,652 ( 0.7%)
                         send_chain:  3,833,858 ( 0.7%)
                       mid_mismatch:  2,424,494 ( 0.4%)
                    ivar_set_method:  1,785,988 ( 0.3%)
           iseq_missing_optional_kw:    615,573 ( 0.1%)
    args_splat_cfunc_ruby2_keywords:    488,318 ( 0.1%)
         instance_of_class_mismatch:    420,809 ( 0.1%)
              send_chain_not_string:    407,641 ( 0.1%)
                 iseq_splat_with_kw:    364,148 ( 0.1%)
            iseq_materialized_block:    228,930 ( 0.0%)
              cfunc_ruby_array_varg:    208,540 ( 0.0%)
                is_a_class_mismatch:    204,008 ( 0.0%)
        iseq_has_rest_opt_and_block:    196,447 ( 0.0%)
             iseq_has_rest_and_send:    160,641 ( 0.0%)
        optimized_method_block_call:    146,535 ( 0.0%)
             args_splat_cfunc_zuper:    116,185 ( 0.0%)
                        interrupted:    111,641 ( 0.0%)
                     refined_method:     59,025 ( 0.0%)
                         call_kwarg:      1,580 ( 0.0%)
                 cfunc_toomany_args:        239 ( 0.0%)
        splatarray_length_not_equal:         33 ( 0.0%)
             iseq_splat_arity_error:         12 ( 0.0%)
invokeblock exit reasons: 
                  proc:  2,962,922 (57.8%)
    iseq_block_changed:  1,544,216 (30.2%)
                symbol:    614,624 (12.0%)
invokesuper exit reasons: 
         block:  3,836,620 (54.8%)
    me_changed:  3,166,781 (45.2%)
leave exit reasons: 
    interp_return: 3,519,061,934 (100.0%)
     se_interrupt:     91,507 ( 0.0%)
getblockparamproxy exit reasons: 
    block_param_modified:    149,526 (100.0%)
getinstancevariable exit reasons:
    megamorphic:      2,217 (100.0%)
setinstancevariable exit reasons:
    (all relevant counters are zero)
opt_aref exit reasons: 
    not_hash:    270,298 (100.0%)
expandarray exit reasons: 
    rhs_too_small:  8,025,061 (97.9%)
            splat:    131,383 ( 1.6%)
        not_array:     43,762 ( 0.5%)
opt_getinlinecache exit reasons: 
    miss:        101 (100.0%)
invalidation reasons: 
          method_lookup:      1,762 (47.3%)
    constant_state_bump:      1,037 (27.8%)
       constant_ic_fill:        929 (24.9%)
num_send:              28,495,181,529
num_send_known_class:  2,022,941,852 ( 7.1%)
num_send_polymorphic:  7,444,498,730 (26.1%)
num_send_x86_rel32:          173,603
num_send_x86_reg:              1,221
iseq_stack_too_large:              0
iseq_too_long:                     0
temp_reg_opnd:               962,911
temp_mem_opnd:               705,647
temp_spill:                  616,158
bindings_allocations:         28,025
bindings_set:                  8,210
compiled_iseq_count:          12,176
compiled_blockid_count:      117,805
compiled_block_count:        193,239
versions_per_block:            1.640
compiled_branch_count:       372,116
block_next_count:            179,550
defer_count:                  54,051
defer_empty_count:            14,584
branch_insn_count:            15,035
branch_known_count:            3,460 (23.0%)
freed_iseq_count:                  2
invalidation_count:            3,728
constant_state_bumps:              0
get_ivar_max_depth:      282,052,080
inline_code_size:         20,471,779
outlined_code_size:       18,199,192
code_region_size:         39,731,200
freed_code_size:                   0
yjit_alloc_size:          82,951,025
live_context_size:         9,459,046
live_context_count:          326,174
live_page_count:               2,425
freed_page_count:                  0
code_gc_count:                     0
num_gc_obj_refs:             167,652
object_shape_count:           12,808
side_exit_count:         620,909,705
total_exit_count:      4,139,971,639
total_insns_count:     162,001,101,279
vm_insns_count:        10,891,620,583
yjit_insns_count:      151,730,390,401
ratio_in_yjit:                 93.3%
avg_len_in_yjit:                36.5
Top-20 most frequent exit ops (100.0% of exits):
    opt_send_without_block: 349,422,703 (56.3%)
                      send: 149,153,481 (24.0%)
               invokesuper: 39,778,122 ( 6.4%)
               definedivar: 24,080,770 ( 3.9%)
               invokeblock: 20,018,852 ( 3.2%)
                    opt_eq: 14,506,897 ( 2.3%)
               expandarray:  8,200,206 ( 1.3%)
       setinstancevariable:  7,152,400 ( 1.2%)
                checkmatch:  2,683,982 ( 0.4%)
             setlocal_WC_0:  1,501,025 ( 0.2%)
        getblockparamproxy:  1,407,182 ( 0.2%)
      opt_getconstant_path:  1,216,310 ( 0.2%)
                  opt_aref:    595,269 ( 0.1%)
             opt_aref_with:    423,661 ( 0.1%)
                   opt_not:    157,774 ( 0.0%)
                      once:    141,807 ( 0.0%)
             opt_aset_with:    138,409 ( 0.0%)
             setblockparam:     91,751 ( 0.0%)
                     leave:     91,507 ( 0.0%)
           newarraykwsplat:     52,364 ( 0.0%)

after

***YJIT: Printing YJIT statistics on exit***
method call exit reasons: 
                           kw_splat: 138,538,119 (25.5%)
                    iseq_has_kwrest: 86,612,208 (15.9%)
                iseq_ruby2_keywords: 82,446,689 (15.2%)
                  klass_megamorphic: 40,675,817 ( 7.5%)
                     iseq_has_no_kw: 37,771,333 ( 6.9%)
                    args_splat_ivar: 30,390,897 ( 5.6%)
          args_splat_cfunc_var_args: 25,287,339 ( 4.6%)
                          block_arg: 14,918,890 ( 2.7%)
                      zsuper_method: 14,838,000 ( 2.7%)
                   iseq_arity_error: 14,485,930 ( 2.7%)
                        not_fixnums: 14,467,830 ( 2.7%)
                args_splat_opt_call:  9,294,140 ( 1.7%)
                           keywords:  8,695,549 ( 1.6%)
                         send_chain:  6,718,814 ( 1.2%)
                        send_getter:  5,628,936 ( 1.0%)
                        iseq_zsuper:  3,957,430 ( 0.7%)
                       mid_mismatch:  3,490,123 ( 0.6%)
                    ivar_set_method:  1,681,428 ( 0.3%)
                is_a_class_mismatch:    630,974 ( 0.1%)
           iseq_missing_optional_kw:    588,419 ( 0.1%)
    args_splat_cfunc_ruby2_keywords:    479,239 ( 0.1%)
              send_chain_not_string:    425,260 ( 0.1%)
         instance_of_class_mismatch:    404,002 ( 0.1%)
                 iseq_splat_with_kw:    342,420 ( 0.1%)
              cfunc_ruby_array_varg:    202,462 ( 0.0%)
            iseq_materialized_block:    196,259 ( 0.0%)
        iseq_has_rest_opt_and_block:    194,387 ( 0.0%)
             iseq_has_rest_and_send:    147,423 ( 0.0%)
        optimized_method_block_call:    112,669 ( 0.0%)
                        interrupted:    106,689 ( 0.0%)
             args_splat_cfunc_zuper:    106,666 ( 0.0%)
                     refined_method:     56,767 ( 0.0%)
                         call_kwarg:      1,594 ( 0.0%)
                 cfunc_toomany_args:        236 ( 0.0%)
        splatarray_length_not_equal:         52 ( 0.0%)
invokeblock exit reasons: 
                  proc:  3,539,894 (60.1%)
    iseq_block_changed:  1,715,118 (29.1%)
                symbol:    637,913 (10.8%)
invokesuper exit reasons: 
         block:  3,564,030 (56.0%)
    me_changed:  2,804,991 (44.0%)
leave exit reasons: 
    interp_return: 3,312,802,571 (100.0%)
     se_interrupt:     80,528 ( 0.0%)
getblockparamproxy exit reasons: 
    block_param_modified:    150,158 (100.0%)
getinstancevariable exit reasons:
    megamorphic:      8,561 (100.0%)
setinstancevariable exit reasons:
    (all relevant counters are zero)
definedivar exit reasons:
    (all relevant counters are zero)
opt_aref exit reasons: 
     not_hash:    168,327 (98.9%)
    not_array:      1,812 ( 1.1%)
expandarray exit reasons: 
    rhs_too_small:  7,679,962 (98.1%)
            splat:    107,600 ( 1.4%)
        not_array:     38,513 ( 0.5%)
opt_getinlinecache exit reasons: 
    miss:         99 (100.0%)
invalidation reasons: 
          method_lookup:      1,782 (47.6%)
    constant_state_bump:      1,059 (28.3%)
       constant_ic_fill:        899 (24.0%)
num_send:              27,539,091,296
num_send_known_class:  2,011,466,186 ( 7.3%)
num_send_polymorphic:  7,499,671,938 (27.2%)
num_send_x86_rel32:          174,331
num_send_x86_reg:              1,065
iseq_stack_too_large:              0
iseq_too_long:                     0
temp_reg_opnd:               962,985
temp_mem_opnd:               705,639
temp_spill:                  616,263
bindings_allocations:         26,822
bindings_set:                  6,236
compiled_iseq_count:          12,220
compiled_blockid_count:      117,997
compiled_block_count:        193,349
versions_per_block:            1.639
compiled_branch_count:       372,128
block_next_count:            179,607
defer_count:                  53,866
defer_empty_count:            14,506
branch_insn_count:            15,109
branch_known_count:            3,478 (23.0%)
freed_iseq_count:                  2
invalidation_count:            3,740
constant_state_bumps:              0
get_ivar_max_depth:      202,816,588
inline_code_size:         20,084,594
outlined_code_size:       18,206,022
code_region_size:         39,813,120
freed_code_size:                   0
yjit_alloc_size:          82,911,029
live_context_size:         9,440,080
live_context_count:          325,520
live_page_count:               2,430
freed_page_count:                  0
code_gc_count:                     0
num_gc_obj_refs:             168,689
object_shape_count:           12,661
side_exit_count:         579,706,989
total_exit_count:      3,892,509,560
total_insns_count:     153,027,715,476
vm_insns_count:        10,042,681,460
yjit_insns_count:      143,564,741,005
ratio_in_yjit:                 93.4%
avg_len_in_yjit:                36.7
Top-20 most frequent exit ops (100.0% of exits):
    opt_send_without_block: 343,236,814 (59.2%)
                      send: 142,985,861 (24.7%)
               invokesuper: 37,283,738 ( 6.4%)
               invokeblock: 20,378,855 ( 3.5%)
                    opt_eq: 13,894,669 ( 2.4%)
               expandarray:  7,826,075 ( 1.4%)
       setinstancevariable:  6,351,328 ( 1.1%)
                checkmatch:  2,421,566 ( 0.4%)
        getblockparamproxy:  1,452,102 ( 0.3%)
             setlocal_WC_0:  1,369,166 ( 0.2%)
      opt_getconstant_path:  1,126,081 ( 0.2%)
                  opt_aref:    458,485 ( 0.1%)
             opt_aref_with:    350,915 ( 0.1%)
             opt_aset_with:    117,266 ( 0.0%)
                      once:    109,614 ( 0.0%)
             setblockparam:     88,404 ( 0.0%)
                     leave:     80,528 ( 0.0%)
                 opt_nil_p:     59,510 ( 0.0%)
           newarraykwsplat:     51,163 ( 0.0%)
                   opt_not:     20,493 ( 0.0%)

[maximecb]

Very nice! Well done! :D