[C extension parser] Disable function outlining on Clang

[samyron]

Starting with commit cc010c46889c8516a9a357336b262ce35779985f some of the generated instructions in the C extension parser started getting outlined into function calls when compiling with Clang on ARM64. This is most noticeable in json_eat_whitespace_resume_at:

Example of one of the outlined functions. They're all small.

Comparing the commit cc010c46889c8516a9a357336b262ce35779985f with cc010c46889c8516a9a357336b262ce35779985f:

== Parsing twitter.json (567916 bytes)
ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
               after   103.000 i/100ms
Calculating -------------------------------------
               after      1.080k (± 0.6%) i/s  (926.34 μs/i) -      5.459k in   5.056880s

Comparison:
before:     1182.5 i/s
 after:     1079.5 i/s - 1.10x  slower


== Parsing citm_catalog.json (1727030 bytes)
ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
               after    45.000 i/100ms
Calculating -------------------------------------
               after    454.163 (± 1.1%) i/s    (2.20 ms/i) -      2.295k in   5.053253s

Comparison:
before:      552.4 i/s
 after:      454.2 i/s - 1.22x  slower

Compiling with -Rpass=machine-outliner shows the result of the outlining pass:

remark: Saved 56 bytes by outlining 4 instructions from 6 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:866:17,
      ../../../../../../ext/json/ext/parser/parser.c:866:17, ../../../../../../ext/json/ext/parser/parser.c:866:17,
      ../../../../../../ext/json/ext/parser/parser.c:866:17, ../../../../../../ext/json/ext/parser/parser.c:866:17,
      ../../../../../../ext/json/ext/parser/parser.c:866:17) [-Rpass=machine-outliner]
remark: Saved 56 bytes by outlining 5 instructions from 5 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:851:74,
      ../../../../../../ext/json/ext/parser/parser.c:851:74, ../../../../../../ext/json/ext/parser/parser.c:851:74,
      ../../../../../../ext/json/ext/parser/parser.c:851:74, ../../../../../../ext/json/ext/parser/parser.c:851:74) [-Rpass=machine-outliner]
remark: Saved 52 bytes by outlining 4 instructions from 6 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:0:0,
      ../../../../../../ext/json/ext/parser/parser.c:0:0, ../../../../../../ext/json/ext/parser/parser.c:0:0,
      ../../../../../../ext/json/ext/parser/parser.c:0:0, ../../../../../../ext/json/ext/parser/parser.c:0:0,
      ../../../../../../ext/json/ext/parser/parser.c:0:0) [-Rpass=machine-outliner]
remark: Saved 40 bytes by outlining 4 instructions from 5 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:839:30,
      ../../../../../../ext/json/ext/parser/parser.c:839:30, ../../../../../../ext/json/ext/parser/parser.c:839:30,
      ../../../../../../ext/json/ext/parser/parser.c:839:30, ../../../../../../ext/json/ext/parser/parser.c:839:30) [-Rpass=machine-outliner]
remark: Saved 20 bytes by outlining 7 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1751:30,
      ../../../../../../ext/json/ext/parser/parser.c:1722:30) [-Rpass=machine-outliner]
remark: Saved 20 bytes by outlining 8 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/../simd/simd.h:116:54,
      ../../../../../../ext/json/ext/parser/../simd/simd.h:116:54) [-Rpass=machine-outliner]
remark: Saved 16 bytes by outlining 7 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1878:41,
      ../../../../../../ext/json/ext/parser/parser.c:1925:41) [-Rpass=machine-outliner]
remark: Saved 12 bytes by outlining 2 instructions from 6 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1674:25,
      ../../../../../../ext/json/ext/parser/parser.c:1877:44, ../../../../../../ext/json/ext/parser/parser.c:1651:25,
      ../../../../../../ext/json/ext/parser/parser.c:1384:18, ../../../../../../ext/json/ext/parser/parser.c:1921:28,
      ../../../../../../ext/json/ext/parser/parser.c:0:0) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 4 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:866:17,
      ../../../../../../ext/json/ext/parser/parser.c:866:17) [-Rpass=machine-outliner]
remark: Saved 12 bytes by outlining 2 instructions from 6 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1741:34,
      ../../../../../../ext/json/ext/parser/parser.c:1712:34, ../../../../../../ext/json/ext/parser/parser.c:1381:22,
      ../../../../../../ext/json/ext/parser/parser.c:1872:26, ../../../../../../ext/json/ext/parser/parser.c:0:0,
      ../../../../../../ext/json/ext/parser/parser.c:1381:22) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 4 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1269:17,
      ../../../../../../ext/json/ext/parser/parser.c:1269:17) [-Rpass=machine-outliner]
remark: Saved 12 bytes by outlining 2 instructions from 6 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:845:21,
      ../../../../../../ext/json/ext/parser/parser.c:845:21, ../../../../../../ext/json/ext/parser/parser.c:845:21,
      ../../../../../../ext/json/ext/parser/parser.c:845:21, ../../../../../../ext/json/ext/parser/parser.c:845:21,
      ../../../../../../ext/json/ext/parser/parser.c:845:21) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 3 instructions from 3 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1873:63,
      ../../../../../../ext/json/ext/parser/parser.c:1824:54, ../../../../../../ext/json/ext/parser/parser.c:1847:54) [-Rpass=machine-outliner]
remark: Saved 24 bytes by outlining 5 instructions from 6 locations. (Found at:
      .asdf/installs/ruby/4.0.5/include/ruby-4.0.0/ruby/internal/arithmetic/long_long.h:85:12,
      .asdf/installs/ruby/4.0.5/include/ruby-4.0.0/ruby/internal/arithmetic/long_long.h:98:12, ../../../../../../ext/json/ext/parser/parser.c:1537:1,
      ../../../../../../ext/json/ext/parser/parser.c:1121:12, ../../../../../../ext/json/ext/parser/parser.c:1161:16,
      ../../../../../../ext/json/ext/parser/parser.c:0:0) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 5 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1570:28,
      ../../../../../../ext/json/ext/parser/parser.c:1570:28) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 2 instructions from 5 locations. (Found at: <UNKNOWN LOCATION>, <UNKNOWN LOCATION>, <UNKNOWN LOCATION>,
      <UNKNOWN LOCATION>, <UNKNOWN LOCATION>) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 5 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1454:37,
      ../../../../../../ext/json/ext/parser/parser.c:1454:37) [-Rpass=machine-outliner]
remark: Saved 8 bytes by outlining 2 instructions from 5 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:587:12,
      ../../../../../../ext/json/ext/parser/parser.c:587:12, ../../../../../../ext/json/ext/parser/parser.c:587:12,
      ../../../../../../ext/json/ext/parser/parser.c:587:12, ../../../../../../ext/json/ext/parser/parser.c:587:12) [-Rpass=machine-outliner]
remark: Saved 4 bytes by outlining 3 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1674:25,
      ../../../../../../ext/json/ext/parser/parser.c:1651:25) [-Rpass=machine-outliner]
remark: Saved 4 bytes by outlining 3 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1271:57,
      ../../../../../../ext/json/ext/parser/parser.c:1271:57) [-Rpass=machine-outliner]
remark: Saved 4 bytes by outlining 3 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:464:53,
      ../../../../../../ext/json/ext/parser/parser.c:464:53) [-Rpass=machine-outliner]
remark: Saved 4 bytes by outlining 3 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1877:13,
      ../../../../../../ext/json/ext/parser/parser.c:1924:13) [-Rpass=machine-outliner]
remark: Saved 4 bytes by outlining 4 instructions from 2 locations. (Found at: ../../../../../../ext/json/ext/parser/parser.c:1250:51,
      ../../../../../../ext/json/ext/parser/parser.c:1169:74) [-Rpass=machine-outliner]
remark: Saved 4 bytes by outlining 4 instructions from 2 locations. (Found at:
      .asdf/installs/ruby/4.0.5/include/ruby-4.0.0/ruby/internal/value_type.h:191:30,
      .asdf/installs/ruby/4.0.5/include/ruby-4.0.0/ruby/internal/value_type.h:191:30) [-Rpass=machine-outliner]

Comparing master with this branch:

== Parsing twitter.json (567916 bytes)
ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
               after   109.000 i/100ms
Calculating -------------------------------------
               after      1.185k (± 0.5%) i/s  (843.83 μs/i) -      5.995k in   5.058765s

Comparison:
before:     1095.5 i/s
 after:     1185.1 i/s - 1.08x  faster


== Parsing citm_catalog.json (1727030 bytes)
ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
               after    54.000 i/100ms
Calculating -------------------------------------
               after    539.726 (± 0.9%) i/s    (1.85 ms/i) -      2.700k in   5.002536s

Comparison:
before:      436.2 i/s
 after:      539.7 i/s - 1.24x  faster

Note: It might be worthwhile to consider leaving function outlining enabled if Ruby was compiled with -Os or Oz but I have not attempted to do that.