luajit: fix string.find recording

Fix provided within 587532e leads to invalid end index of the string
being matched while recording

Test related to this bug is also provided within this changeset

Relates to: LuaJIT LuaJITgh-505
Fix: tarantool gh-4476

Author: igormunkin

src/lj_ffrecord.c

@@ -950,8 +950,8 @@ static void LJ_FASTCALL recff_string_find(jit_State *J, RecordFFData *rd)
       TRef pos;
       emitir(IRTG(IR_NE, IRT_PGC), tr, trp0);
       /* Caveat: can't use STRREF trstr 0 here because that might be pointing into a wrong string due to folding. */
-      pos = emitir(IRTI(IR_SUB), tr, trsptr);
-      J->base[0] = emitir(IRTI(IR_ADD), pos, emitir(IRTI(IR_ADD), trstart, lj_ir_kint(J, 1)));
+      pos = emitir(IRTI(IR_ADD), trstart, emitir(IRTI(IR_SUB), tr, trsptr));
+      J->base[0] = emitir(IRTI(IR_ADD), pos, lj_ir_kint(J, 1));
       J->base[1] = emitir(IRTI(IR_ADD), pos, trplen);
       rd->nres = 2;
     } else {

test/fix_string_find_recording.test.lua

@@ -0,0 +1,79 @@
+#!/usr/bin/env tarantool
+
+tap = require('tap')
+
+test = tap.test("fix-string-find-recording")
+test:plan(1)
+
+local err = [[module 'kit.1.10.3-136' not found:
+	no field package.preload['kit.1.10.3-136']
+	no file './kit/1/10/3-136.lua'
+	no file './kit/1/10/3-136/init.lua'
+	no file './kit/1/10/3-136.so'
+	no file '/bug/.rocks/share/tarantool/kit/1/10/3-136.lua'
+	no file '/bug/.rocks/share/tarantool/kit/1/10/3-136/init.lua'
+	no file '/.rocks/share/tarantool/kit/1/10/3-136.lua'
+	no file '/.rocks/share/tarantool/kit/1/10/3-136/init.lua'
+	no file '/bug/.rocks/lib/tarantool/kit/1/10/3-136.so'
+	no file '/.rocks/lib/tarantool/kit/1/10/3-136.so'
+	no file '/bug/app/kit/1/10/3-136.lua'
+	no file '/bug/app/kit/1/10/3-136/init.lua'
+	no file '/bug/libs/share/lua/5.1/kit/1/10/3-136.lua'
+	no file '/bug/libs/share/lua/5.1/kit/1/10/3-136/init.lua'
+	no file '/root/.luarocks/share/lua/5.1/kit/1/10/3-136.lua'
+	no file '/root/.luarocks/share/lua/5.1/kit/1/10/3-136/init.lua'
+	no file '/root/.luarocks/share/lua/kit/1/10/3-136.lua'
+	no file '/root/.luarocks/share/lua/kit/1/10/3-136/init.lua'
+	no file '/usr/local/share/tarantool/kit/1/10/3-136.lua'
+	no file '/usr/local/share/tarantool/kit/1/10/3-136/init.lua'
+	no file '/usr/share/tarantool/kit/1/10/3-136.lua'
+	no file '/usr/share/tarantool/kit/1/10/3-136/init.lua'
+	no file '/usr/local/share/lua/5.1/kit/1/10/3-136.lua'
+	no file '/usr/local/share/lua/5.1/kit/1/10/3-136/init.lua'
+	no file '/usr/share/lua/5.1/kit/1/10/3-136.lua'
+	no file '/usr/share/lua/5.1/kit/1/10/3-136/init.lua'
+	no file '/bug/libs/lib/lua/5.1/kit/1/10/3-136.so'
+	no file '/bug/libs/lib/lua/kit/1/10/3-136.so'
+	no file '/bug/libs/lib64/lua/5.1/kit/1/10/3-136.so'
+	no file '/root/.luarocks/lib/lua/5.1/kit/1/10/3-136.so'
+	no file '/root/.luarocks/lib/lua/kit/1/10/3-136.so'
+	no file '/usr/local/lib64/tarantool/kit/1/10/3-136.so'
+	no file '/usr/lib64/tarantool/kit/1/10/3-136.so'
+	no file '/usr/local/lib64/lua/5.1/kit/1/10/3-136.so'
+	no file '/usr/lib64/lua/5.1/kit/1/10/3-136.so'
+	no file '/bug/libs/lib/lua/5.1/kit.so'
+	no file '/bug/libs/lib/lua/kit.so'
+	no file '/bug/libs/lib64/lua/5.1/kit.so'
+	no file '/root/.luarocks/lib/lua/5.1/kit.so'
+	no file '/root/.luarocks/lib/lua/kit.so'
+	no file '/usr/local/lib64/tarantool/kit.so'
+	no file '/usr/lib64/tarantool/kit.so'
+	no file '/usr/local/lib64/lua/5.1/kit.so'
+	no file '/usr/lib64/lua/5.1/kit.so']]
+
+local at, s, e
+local count_vm = 0
+
+jit.off()
+
+repeat
+  s, e = err:find("\n\t", at, true)
+  at = e
+  count_vm = count_vm + 1
+until not e
+
+local count_jit = 0
+
+jit.on()
+jit.opt.start(0, 'hotloop=1')
+
+repeat
+  s, e = err:find("\n\t", at, true)
+  at = e
+  count_jit = count_jit + 1
+  assert(count_jit <= count_vm, "Trace goes in cycles")
+until not e
+
+test:is(count_vm, count_jit)
+
+test:check()