offlineasm is generating the wrong load/store for the "orh" instruction.

[Mark Lam]

For example, on ARM64E, it was generating the following:

    "\tldr w17, [x1, #0]\n"                                  // JavaScriptCore/llint/LowLevelInterpreter64.asm:919
    "\torr w17, w17, #64\n"                                  // JavaScriptCore/llint/LowLevelInterpreter64.asm:919
    "\tstr w17, [x1, #0]\n"                                  // JavaScriptCore/llint/LowLevelInterpreter64.asm:919

i.e. a 32-bit load, followed by a 32-bit OR, followed by a 32-bit store.

Instead, it should be generating the following:

    "\tldrh w17, [x1, #0]\n"                                 // JavaScriptCore/llint/LowLevelInterpreter64.asm:919
    "\torr w17, w17, #64\n"                                  // JavaScriptCore/llint/LowLevelInterpreter64.asm:919
    "\tstrh w17, [x1, #0]\n"                                 // JavaScriptCore/llint/LowLevelInterpreter64.asm:919

i.e. a 16-bit load, followed by a 32-bit OR, followed by a 16-bit store.

This bug also affects ARM64, ARMv7, and MIPS (basically any backend that uses riscLowerMisplacedAddresses() from rise.rb).
It does not affect x86, x86_64, and C_LOOP (which was written based on x86).

<rdar://problem/21501876>

[Mark Lam]

Created attachment 396743 [details]
proposed patch.

[Robin Morisset]

Comment on attachment 396743 [details]
proposed patch.

r=me

[Mark Lam]

Thanks for the review.  Landed in r260246: <http://trac.webkit.org/r260246>.