Optimize File.join common use case

`File.join` is a hotspot for common libraries such as Zeitwerk
and Bootsnap. It has a fairly flexible signature, but 99% of
the time it's called with just two (or a small number of) UTF-8 strings.

If we optimistically optimize for that use case we can cut down a large
number of type and encoding checks, significantly speeding up the method.

The one remaining expensive check we could try to optimize is `str_null_check`.
Given it's common to use the same base string for joining, we could memoize it.
Also we could precompute it for literal strings.

```
compare-ruby: ruby 4.1.0dev (2026-01-17T14:40:03Z master 00a3b71) +PRISM [arm64-darwin25]
built-ruby: ruby 4.1.0dev (2026-01-18T12:10:38Z spedup-file-join 069bab5) +PRISM [arm64-darwin25]
warming up....

|              |compare-ruby|built-ruby|
|:-------------|-----------:|---------:|
|two_strings   |      2.475M|    9.444M|
|              |           -|     3.82x|
|many_strings  |    551.975k|    2.346M|
|              |           -|     4.25x|
|array         |    514.946k|  522.034k|
|              |           -|     1.01x|
|mixed         |    621.236k|  633.189k|
|              |           -|     1.02x|
```

Author: byroot

benchmark/file_join.yml

@@ -0,0 +1,7 @@
+prelude: |
+  # frozen_string_literal: true
+benchmark:
+  two_strings: File.join(__FILE__, "path")
+  many_strings: File.join(__FILE__, "path", "a", "b", "c", "d")
+  array: File.join([__FILE__, "path", "a", "b", "c", "d"])
+  mixed: File.join(__FILE__, "path", "a", "b", ["c", "d"])

depend

@@ -799,6 +799,7 @@ box.$(OBJEXT): {$(VPATH)}constant.h
 box.$(OBJEXT): {$(VPATH)}darray.h
 box.$(OBJEXT): {$(VPATH)}debug_counter.h
 box.$(OBJEXT): {$(VPATH)}defines.h
+box.$(OBJEXT): {$(VPATH)}encindex.h
 box.$(OBJEXT): {$(VPATH)}encoding.h
 box.$(OBJEXT): {$(VPATH)}eval_intern.h
 box.$(OBJEXT): {$(VPATH)}id.h
@@ -1250,6 +1251,7 @@ class.$(OBJEXT): {$(VPATH)}config.h
 class.$(OBJEXT): {$(VPATH)}constant.h
 class.$(OBJEXT): {$(VPATH)}debug_counter.h
 class.$(OBJEXT): {$(VPATH)}defines.h
+class.$(OBJEXT): {$(VPATH)}encindex.h
 class.$(OBJEXT): {$(VPATH)}encoding.h
 class.$(OBJEXT): {$(VPATH)}id.h
 class.$(OBJEXT): {$(VPATH)}id_table.h
@@ -1449,6 +1451,7 @@ compar.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 compar.$(OBJEXT): {$(VPATH)}compar.c
 compar.$(OBJEXT): {$(VPATH)}config.h
 compar.$(OBJEXT): {$(VPATH)}defines.h
+compar.$(OBJEXT): {$(VPATH)}encindex.h
 compar.$(OBJEXT): {$(VPATH)}encoding.h
 compar.$(OBJEXT): {$(VPATH)}id.h
 compar.$(OBJEXT): {$(VPATH)}intern.h
@@ -1921,6 +1924,7 @@ complex.$(OBJEXT): {$(VPATH)}config.h
 complex.$(OBJEXT): {$(VPATH)}constant.h
 complex.$(OBJEXT): {$(VPATH)}debug_counter.h
 complex.$(OBJEXT): {$(VPATH)}defines.h
+complex.$(OBJEXT): {$(VPATH)}encindex.h
 complex.$(OBJEXT): {$(VPATH)}encoding.h
 complex.$(OBJEXT): {$(VPATH)}id.h
 complex.$(OBJEXT): {$(VPATH)}id_table.h
@@ -2126,6 +2130,7 @@ concurrent_set.$(OBJEXT): {$(VPATH)}concurrent_set.c
 concurrent_set.$(OBJEXT): {$(VPATH)}config.h
 concurrent_set.$(OBJEXT): {$(VPATH)}debug_counter.h
 concurrent_set.$(OBJEXT): {$(VPATH)}defines.h
+concurrent_set.$(OBJEXT): {$(VPATH)}encindex.h
 concurrent_set.$(OBJEXT): {$(VPATH)}encoding.h
 concurrent_set.$(OBJEXT): {$(VPATH)}id.h
 concurrent_set.$(OBJEXT): {$(VPATH)}id_table.h
@@ -2364,6 +2369,7 @@ cont.$(OBJEXT): {$(VPATH)}constant.h
 cont.$(OBJEXT): {$(VPATH)}cont.c
 cont.$(OBJEXT): {$(VPATH)}debug_counter.h
 cont.$(OBJEXT): {$(VPATH)}defines.h
+cont.$(OBJEXT): {$(VPATH)}encindex.h
 cont.$(OBJEXT): {$(VPATH)}encoding.h
 cont.$(OBJEXT): {$(VPATH)}eval_intern.h
 cont.$(OBJEXT): {$(VPATH)}fiber/scheduler.h
@@ -4906,6 +4912,7 @@ enumerator.$(OBJEXT): {$(VPATH)}config.h
 enumerator.$(OBJEXT): {$(VPATH)}constant.h
 enumerator.$(OBJEXT): {$(VPATH)}debug_counter.h
 enumerator.$(OBJEXT): {$(VPATH)}defines.h
+enumerator.$(OBJEXT): {$(VPATH)}encindex.h
 enumerator.$(OBJEXT): {$(VPATH)}encoding.h
 enumerator.$(OBJEXT): {$(VPATH)}enumerator.c
 enumerator.$(OBJEXT): {$(VPATH)}id.h
@@ -5126,6 +5133,7 @@ error.$(OBJEXT): {$(VPATH)}config.h
 error.$(OBJEXT): {$(VPATH)}constant.h
 error.$(OBJEXT): {$(VPATH)}debug_counter.h
 error.$(OBJEXT): {$(VPATH)}defines.h
+error.$(OBJEXT): {$(VPATH)}encindex.h
 error.$(OBJEXT): {$(VPATH)}encoding.h
 error.$(OBJEXT): {$(VPATH)}error.c
 error.$(OBJEXT): {$(VPATH)}id.h
@@ -5373,6 +5381,7 @@ eval.$(OBJEXT): {$(VPATH)}config.h
 eval.$(OBJEXT): {$(VPATH)}constant.h
 eval.$(OBJEXT): {$(VPATH)}debug_counter.h
 eval.$(OBJEXT): {$(VPATH)}defines.h
+eval.$(OBJEXT): {$(VPATH)}encindex.h
 eval.$(OBJEXT): {$(VPATH)}encoding.h
 eval.$(OBJEXT): {$(VPATH)}eval.c
 eval.$(OBJEXT): {$(VPATH)}eval_error.c
@@ -5584,6 +5593,7 @@ file.$(OBJEXT): $(top_srcdir)/internal/array.h
 file.$(OBJEXT): $(top_srcdir)/internal/class.h
 file.$(OBJEXT): $(top_srcdir)/internal/compilers.h
 file.$(OBJEXT): $(top_srcdir)/internal/dir.h
+file.$(OBJEXT): $(top_srcdir)/internal/encoding.h
 file.$(OBJEXT): $(top_srcdir)/internal/error.h
 file.$(OBJEXT): $(top_srcdir)/internal/file.h
 file.$(OBJEXT): $(top_srcdir)/internal/gc.h
@@ -5865,6 +5875,7 @@ gc.$(OBJEXT): {$(VPATH)}darray.h
 gc.$(OBJEXT): {$(VPATH)}debug.h
 gc.$(OBJEXT): {$(VPATH)}debug_counter.h
 gc.$(OBJEXT): {$(VPATH)}defines.h
+gc.$(OBJEXT): {$(VPATH)}encindex.h
 gc.$(OBJEXT): {$(VPATH)}encoding.h
 gc.$(OBJEXT): {$(VPATH)}eval_intern.h
 gc.$(OBJEXT): {$(VPATH)}gc.c
@@ -6373,6 +6384,7 @@ hash.$(OBJEXT): {$(VPATH)}config.h
 hash.$(OBJEXT): {$(VPATH)}constant.h
 hash.$(OBJEXT): {$(VPATH)}debug_counter.h
 hash.$(OBJEXT): {$(VPATH)}defines.h
+hash.$(OBJEXT): {$(VPATH)}encindex.h
 hash.$(OBJEXT): {$(VPATH)}encoding.h
 hash.$(OBJEXT): {$(VPATH)}hash.c
 hash.$(OBJEXT): {$(VPATH)}hash.rbinc
@@ -7203,6 +7215,7 @@ io_buffer.$(OBJEXT): {$(VPATH)}backward/2/stdalign.h
 io_buffer.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 io_buffer.$(OBJEXT): {$(VPATH)}config.h
 io_buffer.$(OBJEXT): {$(VPATH)}defines.h
+io_buffer.$(OBJEXT): {$(VPATH)}encindex.h
 io_buffer.$(OBJEXT): {$(VPATH)}encoding.h
 io_buffer.$(OBJEXT): {$(VPATH)}fiber/scheduler.h
 io_buffer.$(OBJEXT): {$(VPATH)}id.h
@@ -7454,6 +7467,7 @@ iseq.$(OBJEXT): {$(VPATH)}config.h
 iseq.$(OBJEXT): {$(VPATH)}constant.h
 iseq.$(OBJEXT): {$(VPATH)}debug_counter.h
 iseq.$(OBJEXT): {$(VPATH)}defines.h
+iseq.$(OBJEXT): {$(VPATH)}encindex.h
 iseq.$(OBJEXT): {$(VPATH)}encoding.h
 iseq.$(OBJEXT): {$(VPATH)}eval_intern.h
 iseq.$(OBJEXT): {$(VPATH)}id.h
@@ -7702,6 +7716,7 @@ jit.$(OBJEXT): {$(VPATH)}config.h
 jit.$(OBJEXT): {$(VPATH)}constant.h
 jit.$(OBJEXT): {$(VPATH)}debug_counter.h
 jit.$(OBJEXT): {$(VPATH)}defines.h
+jit.$(OBJEXT): {$(VPATH)}encindex.h
 jit.$(OBJEXT): {$(VPATH)}encoding.h
 jit.$(OBJEXT): {$(VPATH)}id.h
 jit.$(OBJEXT): {$(VPATH)}id_table.h
@@ -7956,6 +7971,7 @@ load.$(OBJEXT): {$(VPATH)}constant.h
 load.$(OBJEXT): {$(VPATH)}darray.h
 load.$(OBJEXT): {$(VPATH)}defines.h
 load.$(OBJEXT): {$(VPATH)}dln.h
+load.$(OBJEXT): {$(VPATH)}encindex.h
 load.$(OBJEXT): {$(VPATH)}encoding.h
 load.$(OBJEXT): {$(VPATH)}eval_intern.h
 load.$(OBJEXT): {$(VPATH)}id.h
@@ -9979,6 +9995,7 @@ numeric.$(OBJEXT): {$(VPATH)}builtin.h
 numeric.$(OBJEXT): {$(VPATH)}config.h
 numeric.$(OBJEXT): {$(VPATH)}constant.h
 numeric.$(OBJEXT): {$(VPATH)}defines.h
+numeric.$(OBJEXT): {$(VPATH)}encindex.h
 numeric.$(OBJEXT): {$(VPATH)}encoding.h
 numeric.$(OBJEXT): {$(VPATH)}id.h
 numeric.$(OBJEXT): {$(VPATH)}id_table.h
@@ -10200,6 +10217,7 @@ object.$(OBJEXT): {$(VPATH)}config.h
 object.$(OBJEXT): {$(VPATH)}constant.h
 object.$(OBJEXT): {$(VPATH)}debug_counter.h
 object.$(OBJEXT): {$(VPATH)}defines.h
+object.$(OBJEXT): {$(VPATH)}encindex.h
 object.$(OBJEXT): {$(VPATH)}encoding.h
 object.$(OBJEXT): {$(VPATH)}id.h
 object.$(OBJEXT): {$(VPATH)}id_table.h
@@ -10418,6 +10436,7 @@ pack.$(OBJEXT): {$(VPATH)}builtin.h
 pack.$(OBJEXT): {$(VPATH)}config.h
 pack.$(OBJEXT): {$(VPATH)}constant.h
 pack.$(OBJEXT): {$(VPATH)}defines.h
+pack.$(OBJEXT): {$(VPATH)}encindex.h
 pack.$(OBJEXT): {$(VPATH)}encoding.h
 pack.$(OBJEXT): {$(VPATH)}id.h
 pack.$(OBJEXT): {$(VPATH)}id_table.h
@@ -10644,6 +10663,7 @@ parse.$(OBJEXT): {$(VPATH)}config.h
 parse.$(OBJEXT): {$(VPATH)}constant.h
 parse.$(OBJEXT): {$(VPATH)}defines.h
 parse.$(OBJEXT): {$(VPATH)}defs/keywords
+parse.$(OBJEXT): {$(VPATH)}encindex.h
 parse.$(OBJEXT): {$(VPATH)}encoding.h
 parse.$(OBJEXT): {$(VPATH)}id.h
 parse.$(OBJEXT): {$(VPATH)}id_table.h
@@ -12125,6 +12145,7 @@ proc.$(OBJEXT): {$(VPATH)}config.h
 proc.$(OBJEXT): {$(VPATH)}constant.h
 proc.$(OBJEXT): {$(VPATH)}debug_counter.h
 proc.$(OBJEXT): {$(VPATH)}defines.h
+proc.$(OBJEXT): {$(VPATH)}encindex.h
 proc.$(OBJEXT): {$(VPATH)}encoding.h
 proc.$(OBJEXT): {$(VPATH)}eval_intern.h
 proc.$(OBJEXT): {$(VPATH)}id.h
@@ -12356,6 +12377,7 @@ process.$(OBJEXT): {$(VPATH)}constant.h
 process.$(OBJEXT): {$(VPATH)}debug_counter.h
 process.$(OBJEXT): {$(VPATH)}defines.h
 process.$(OBJEXT): {$(VPATH)}dln.h
+process.$(OBJEXT): {$(VPATH)}encindex.h
 process.$(OBJEXT): {$(VPATH)}encoding.h
 process.$(OBJEXT): {$(VPATH)}fiber/scheduler.h
 process.$(OBJEXT): {$(VPATH)}hrtime.h
@@ -12585,6 +12607,7 @@ ractor.$(OBJEXT): {$(VPATH)}config.h
 ractor.$(OBJEXT): {$(VPATH)}constant.h
 ractor.$(OBJEXT): {$(VPATH)}debug_counter.h
 ractor.$(OBJEXT): {$(VPATH)}defines.h
+ractor.$(OBJEXT): {$(VPATH)}encindex.h
 ractor.$(OBJEXT): {$(VPATH)}encoding.h
 ractor.$(OBJEXT): {$(VPATH)}eval_intern.h
 ractor.$(OBJEXT): {$(VPATH)}id.h
@@ -13018,6 +13041,7 @@ range.$(OBJEXT): {$(VPATH)}backward/2/stdalign.h
 range.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 range.$(OBJEXT): {$(VPATH)}config.h
 range.$(OBJEXT): {$(VPATH)}defines.h
+range.$(OBJEXT): {$(VPATH)}encindex.h
 range.$(OBJEXT): {$(VPATH)}encoding.h
 range.$(OBJEXT): {$(VPATH)}id.h
 range.$(OBJEXT): {$(VPATH)}id_table.h
@@ -14688,6 +14712,7 @@ ruby.$(OBJEXT): {$(VPATH)}constant.h
 ruby.$(OBJEXT): {$(VPATH)}debug_counter.h
 ruby.$(OBJEXT): {$(VPATH)}defines.h
 ruby.$(OBJEXT): {$(VPATH)}dln.h
+ruby.$(OBJEXT): {$(VPATH)}encindex.h
 ruby.$(OBJEXT): {$(VPATH)}encoding.h
 ruby.$(OBJEXT): {$(VPATH)}eval_intern.h
 ruby.$(OBJEXT): {$(VPATH)}id.h
@@ -14896,6 +14921,7 @@ ruby_parser.$(OBJEXT): {$(VPATH)}backward/2/stdalign.h
 ruby_parser.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 ruby_parser.$(OBJEXT): {$(VPATH)}config.h
 ruby_parser.$(OBJEXT): {$(VPATH)}defines.h
+ruby_parser.$(OBJEXT): {$(VPATH)}encindex.h
 ruby_parser.$(OBJEXT): {$(VPATH)}encoding.h
 ruby_parser.$(OBJEXT): {$(VPATH)}intern.h
 ruby_parser.$(OBJEXT): {$(VPATH)}internal.h
@@ -15306,6 +15332,7 @@ set.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 set.$(OBJEXT): {$(VPATH)}config.h
 set.$(OBJEXT): {$(VPATH)}constant.h
 set.$(OBJEXT): {$(VPATH)}defines.h
+set.$(OBJEXT): {$(VPATH)}encindex.h
 set.$(OBJEXT): {$(VPATH)}encoding.h
 set.$(OBJEXT): {$(VPATH)}id.h
 set.$(OBJEXT): {$(VPATH)}id_table.h
@@ -15678,6 +15705,7 @@ shape.$(OBJEXT): {$(VPATH)}config.h
 shape.$(OBJEXT): {$(VPATH)}constant.h
 shape.$(OBJEXT): {$(VPATH)}debug_counter.h
 shape.$(OBJEXT): {$(VPATH)}defines.h
+shape.$(OBJEXT): {$(VPATH)}encindex.h
 shape.$(OBJEXT): {$(VPATH)}encoding.h
 shape.$(OBJEXT): {$(VPATH)}id.h
 shape.$(OBJEXT): {$(VPATH)}id_table.h
@@ -15892,6 +15920,7 @@ signal.$(OBJEXT): {$(VPATH)}config.h
 signal.$(OBJEXT): {$(VPATH)}constant.h
 signal.$(OBJEXT): {$(VPATH)}debug_counter.h
 signal.$(OBJEXT): {$(VPATH)}defines.h
+signal.$(OBJEXT): {$(VPATH)}encindex.h
 signal.$(OBJEXT): {$(VPATH)}encoding.h
 signal.$(OBJEXT): {$(VPATH)}eval_intern.h
 signal.$(OBJEXT): {$(VPATH)}id.h
@@ -16101,6 +16130,7 @@ sprintf.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 sprintf.$(OBJEXT): {$(VPATH)}config.h
 sprintf.$(OBJEXT): {$(VPATH)}constant.h
 sprintf.$(OBJEXT): {$(VPATH)}defines.h
+sprintf.$(OBJEXT): {$(VPATH)}encindex.h
 sprintf.$(OBJEXT): {$(VPATH)}encoding.h
 sprintf.$(OBJEXT): {$(VPATH)}id.h
 sprintf.$(OBJEXT): {$(VPATH)}id_table.h
@@ -16457,6 +16487,7 @@ strftime.$(OBJEXT): {$(VPATH)}backward/2/stdalign.h
 strftime.$(OBJEXT): {$(VPATH)}backward/2/stdarg.h
 strftime.$(OBJEXT): {$(VPATH)}config.h
 strftime.$(OBJEXT): {$(VPATH)}defines.h
+strftime.$(OBJEXT): {$(VPATH)}encindex.h
 strftime.$(OBJEXT): {$(VPATH)}encoding.h
 strftime.$(OBJEXT): {$(VPATH)}intern.h
 strftime.$(OBJEXT): {$(VPATH)}internal.h
@@ -16925,6 +16956,7 @@ struct.$(OBJEXT): {$(VPATH)}config.h
 struct.$(OBJEXT): {$(VPATH)}constant.h
 struct.$(OBJEXT): {$(VPATH)}debug_counter.h
 struct.$(OBJEXT): {$(VPATH)}defines.h
+struct.$(OBJEXT): {$(VPATH)}encindex.h
 struct.$(OBJEXT): {$(VPATH)}encoding.h
 struct.$(OBJEXT): {$(VPATH)}id.h
 struct.$(OBJEXT): {$(VPATH)}id_table.h
@@ -17141,6 +17173,7 @@ symbol.$(OBJEXT): {$(VPATH)}constant.h
 symbol.$(OBJEXT): {$(VPATH)}darray.h
 symbol.$(OBJEXT): {$(VPATH)}debug_counter.h
 symbol.$(OBJEXT): {$(VPATH)}defines.h
+symbol.$(OBJEXT): {$(VPATH)}encindex.h
 symbol.$(OBJEXT): {$(VPATH)}encoding.h
 symbol.$(OBJEXT): {$(VPATH)}id.c
 symbol.$(OBJEXT): {$(VPATH)}id.h
@@ -17398,6 +17431,7 @@ thread.$(OBJEXT): {$(VPATH)}constant.h
 thread.$(OBJEXT): {$(VPATH)}debug.h
 thread.$(OBJEXT): {$(VPATH)}debug_counter.h
 thread.$(OBJEXT): {$(VPATH)}defines.h
+thread.$(OBJEXT): {$(VPATH)}encindex.h
 thread.$(OBJEXT): {$(VPATH)}encoding.h
 thread.$(OBJEXT): {$(VPATH)}eval_intern.h
 thread.$(OBJEXT): {$(VPATH)}fiber/scheduler.h
@@ -17628,6 +17662,7 @@ time.$(OBJEXT): {$(VPATH)}builtin.h
 time.$(OBJEXT): {$(VPATH)}config.h
 time.$(OBJEXT): {$(VPATH)}constant.h
 time.$(OBJEXT): {$(VPATH)}defines.h
+time.$(OBJEXT): {$(VPATH)}encindex.h
 time.$(OBJEXT): {$(VPATH)}encoding.h
 time.$(OBJEXT): {$(VPATH)}id.h
 time.$(OBJEXT): {$(VPATH)}id_table.h
@@ -17830,6 +17865,7 @@ transcode.$(OBJEXT): {$(VPATH)}config.h
 transcode.$(OBJEXT): {$(VPATH)}constant.h
 transcode.$(OBJEXT): {$(VPATH)}debug_counter.h
 transcode.$(OBJEXT): {$(VPATH)}defines.h
+transcode.$(OBJEXT): {$(VPATH)}encindex.h
 transcode.$(OBJEXT): {$(VPATH)}encoding.h
 transcode.$(OBJEXT): {$(VPATH)}id.h
 transcode.$(OBJEXT): {$(VPATH)}id_table.h
@@ -18211,6 +18247,7 @@ variable.$(OBJEXT): {$(VPATH)}config.h
 variable.$(OBJEXT): {$(VPATH)}constant.h
 variable.$(OBJEXT): {$(VPATH)}debug_counter.h
 variable.$(OBJEXT): {$(VPATH)}defines.h
+variable.$(OBJEXT): {$(VPATH)}encindex.h
 variable.$(OBJEXT): {$(VPATH)}encoding.h
 variable.$(OBJEXT): {$(VPATH)}id.h
 variable.$(OBJEXT): {$(VPATH)}id_table.h
@@ -18687,6 +18724,7 @@ vm.$(OBJEXT): {$(VPATH)}constant.h
 vm.$(OBJEXT): {$(VPATH)}debug_counter.h
 vm.$(OBJEXT): {$(VPATH)}defines.h
 vm.$(OBJEXT): {$(VPATH)}defs/opt_operand.def
+vm.$(OBJEXT): {$(VPATH)}encindex.h
 vm.$(OBJEXT): {$(VPATH)}encoding.h
 vm.$(OBJEXT): {$(VPATH)}eval_intern.h
 vm.$(OBJEXT): {$(VPATH)}id.h
@@ -18951,6 +18989,7 @@ vm_backtrace.$(OBJEXT): {$(VPATH)}constant.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}debug.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}debug_counter.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}defines.h
+vm_backtrace.$(OBJEXT): {$(VPATH)}encindex.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}encoding.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}eval_intern.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}id.h
@@ -20087,6 +20126,7 @@ yjit.$(OBJEXT): {$(VPATH)}constant.h
 yjit.$(OBJEXT): {$(VPATH)}debug.h
 yjit.$(OBJEXT): {$(VPATH)}debug_counter.h
 yjit.$(OBJEXT): {$(VPATH)}defines.h
+yjit.$(OBJEXT): {$(VPATH)}encindex.h
 yjit.$(OBJEXT): {$(VPATH)}encoding.h
 yjit.$(OBJEXT): {$(VPATH)}id.h
 yjit.$(OBJEXT): {$(VPATH)}id_table.h
@@ -20342,6 +20382,7 @@ zjit.$(OBJEXT): {$(VPATH)}constant.h
 zjit.$(OBJEXT): {$(VPATH)}debug.h
 zjit.$(OBJEXT): {$(VPATH)}debug_counter.h
 zjit.$(OBJEXT): {$(VPATH)}defines.h
+zjit.$(OBJEXT): {$(VPATH)}encindex.h
 zjit.$(OBJEXT): {$(VPATH)}encoding.h
 zjit.$(OBJEXT): {$(VPATH)}id.h
 zjit.$(OBJEXT): {$(VPATH)}id_table.h

ext/-test-/stack/depend

@@ -172,6 +172,7 @@ stack.o: $(hdrdir)/ruby/oniguruma.h
 stack.o: $(hdrdir)/ruby/ruby.h
 stack.o: $(hdrdir)/ruby/st.h
 stack.o: $(hdrdir)/ruby/subst.h
+stack.o: $(top_srcdir)/encindex.h
 stack.o: $(top_srcdir)/internal/compilers.h
 stack.o: $(top_srcdir)/internal/string.h
 stack.o: stack.c

ext/-test-/string/depend

@@ -172,6 +172,7 @@ capacity.o: $(hdrdir)/ruby/oniguruma.h
 capacity.o: $(hdrdir)/ruby/ruby.h
 capacity.o: $(hdrdir)/ruby/st.h
 capacity.o: $(hdrdir)/ruby/subst.h
+capacity.o: $(top_srcdir)/encindex.h
 capacity.o: $(top_srcdir)/internal/compilers.h
 capacity.o: $(top_srcdir)/internal/string.h
 capacity.o: capacity.c
@@ -679,6 +680,7 @@ cstr.o: $(hdrdir)/ruby/oniguruma.h
 cstr.o: $(hdrdir)/ruby/ruby.h
 cstr.o: $(hdrdir)/ruby/st.h
 cstr.o: $(hdrdir)/ruby/subst.h
+cstr.o: $(top_srcdir)/encindex.h
 cstr.o: $(top_srcdir)/internal.h
 cstr.o: $(top_srcdir)/internal/compilers.h
 cstr.o: $(top_srcdir)/internal/string.h
@@ -1535,6 +1537,7 @@ fstring.o: $(hdrdir)/ruby/oniguruma.h
 fstring.o: $(hdrdir)/ruby/ruby.h
 fstring.o: $(hdrdir)/ruby/st.h
 fstring.o: $(hdrdir)/ruby/subst.h
+fstring.o: $(top_srcdir)/encindex.h
 fstring.o: $(top_srcdir)/internal/compilers.h
 fstring.o: $(top_srcdir)/internal/string.h
 fstring.o: fstring.c

ext/objspace/depend

@@ -602,6 +602,7 @@ objspace_dump.o: $(top_srcdir)/ccan/list/list.h
 objspace_dump.o: $(top_srcdir)/ccan/str/str.h
 objspace_dump.o: $(top_srcdir)/constant.h
 objspace_dump.o: $(top_srcdir)/debug_counter.h
+objspace_dump.o: $(top_srcdir)/encindex.h
 objspace_dump.o: $(top_srcdir)/id_table.h
 objspace_dump.o: $(top_srcdir)/internal.h
 objspace_dump.o: $(top_srcdir)/internal/array.h

ext/ripper/depend

@@ -578,6 +578,7 @@ ripper.o: $(top_srcdir)/ccan/container_of/container_of.h
 ripper.o: $(top_srcdir)/ccan/list/list.h
 ripper.o: $(top_srcdir)/ccan/str/str.h
 ripper.o: $(top_srcdir)/constant.h
+ripper.o: $(top_srcdir)/encindex.h
 ripper.o: $(top_srcdir)/id_table.h
 ripper.o: $(top_srcdir)/internal.h
 ripper.o: $(top_srcdir)/internal/array.h