From: takashikkbn@... Date: 2020-06-11T05:13:59+00:00 Subject: [ruby-core:98730] [Ruby master Bug#16941] MJIT doesn't identify Struct kind of instruction Issue #16941 has been updated by k0kubun (Takashi Kokubun). Status changed from Open to Feedback > Are structs not recognised by JIT compiler? To be precise, `opt_call_c_function` insn is not supported by JIT compiler, and Struct is one of a few things which may generate `opt_call_c_function` insn. It's something to be fixed for sure, but as of now priority of fixing it is low. > We have this call in our programs many number of times (~ 106), it attempts every time and fails. Can this be a cause of programs to get slower with --jit enabled ? Well, if it attempts of JIT compilation every time, it'd be compiled every time even if JIT supported `opt_call_c_function`. The fundamental problem in the script you provided is that it's defining a brand-new class by `Struct.new` every time `my_method` is called. Note that it's not good for VM's performance either. You should define a Struct class outside `my_method` and `my_method` should just refer to it. If it's not possible in your use case, there's nothing we can do. One thing to note is that `--jit-min-calls` is 5 in Ruby 2.6's default, and it's 10000 in Ruby 2.7's default. Therefore the problem may not happen in the `my_method` with Ruby 2.7 or later. ---------------------------------------- Bug #16941: MJIT doesn't identify Struct kind of instruction https://bugs.ruby-lang.org/issues/16941#change-86086 * Author: abhsha (Abhishek Sharma) * Status: Feedback * Priority: Normal * Assignee: k0kubun (Takashi Kokubun) * ruby -v: 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux] * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN ---------------------------------------- MJIT does not identify Struct instructions and gives a warning while compiling to C. Example: def my_method 1.times do a_struct = Struct.new(:a).new a_struct.a = "a" end end my_method $: ruby --jit-save-temps --jit-min-calls=1 --disable-gems --jit --jit-verbose=2 --jit-wait test.rb output: start compilation: a=@test.rb:3 -> /tmp/_ruby_mjit_p30696u2.c MJIT warning: Skipped to compile unsupported instruction: opt_call_c_function JIT failure (0.0ms): a=@test.rb:3 -> /tmp/_ruby_mjit_p30696u2.c Are structs not recognised by JIT compiler? We have this call in our programs many number of times (~ 10^6), it attempts every time and fails. Can this be a cause of programs to get slower with --jit enabled ? -- https://bugs.ruby-lang.org/ Unsubscribe: