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To perform a regular method call, the VM needs two structs, `rb_call_info` and `rb_call_cache`. At the moment, we allocate these two structures in separate buffers. In the worst case, the CPU needs to read 4 cache lines to complete a method call. Putting the two structures together reduces the maximum number of cache line reads to 2. Combining the structures also saves 8 bytes per call site as the current layout uses separate two pointers for the call info and the call cache. This saves about 2 MiB on Discourse. This change improves the Optcarrot benchmark at least 3%. For more details, see attached bugs.ruby-lang.org ticket. Complications: - A new instruction attribute `comptime_sp_inc` is introduced to calculate SP increase at compile time without using call caches. At compile time, a `TS_CALLDATA` operand points to a call info struct, but at runtime, the same operand points to a call data struct. Instruction that explicitly define `sp_inc` also need to define `comptime_sp_inc`. - MJIT code for copying call cache becomes slightly more complicated. - This changes the bytecode format, which might break existing tools. [Misc #16258] |
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attribute.rb | ||
bare_instructions.rb | ||
c_expr.rb | ||
instructions.rb | ||
instructions_unifications.rb | ||
operands_unifications.rb | ||
trace_instructions.rb | ||
typemap.rb |