Using WASM function size as the cap for choosing a register allocator causes performance regressions.
https://bugs.webkit.org/show_bug.cgi?id=217290
Reviewed by Michael Saboff.
Previously in https://bugs.webkit.org/show_bug.cgi?id=212105 we
limited the size of WASM functions we compile with OMG because
sufficiently large functions caused us to OOM while register
allocating. The memory growth we saw is because the memory usage
of graph coloring is O((number of tmps)2). However, some large
WASM functions may not have that many tmps by the time we get to
register allocation. This patch changes our heuristic to instead
use the total number of tmps right before register allocation
instead of the WASM function size. The number of tmps is more
likely to represent the worst case memory usage of register
allocation. This fixes a performance regression in Safari 14 when running
https://dos.zone/en/play/https%3A%2F%2Fp.rizon.top%3A443%2Fhttps%2Fdoszone-uploads.s3.dualstack.eu-central-1.amazonaws.com%2Foriginal%2F2X%2Fb%2Fb4b5275904d86a4ab8a20917b2b7e34f0df47bf7.jsdos
(JSC::B3::Air::prepareForGeneration):
- runtime/OptionsList.h:
- wasm/WasmAirIRGenerator.cpp:
(JSC::Wasm::AirIRGenerator::AirIRGenerator):
- wasm/WasmB3IRGenerator.cpp:
(JSC::Wasm::B3IRGenerator::B3IRGenerator):
(JSC::Wasm::parseAndCompile):
- wasm/WasmCompilationMode.cpp:
(JSC::Wasm::wasmFunctionSizeCanBeOMGCompiled): Deleted.
- wasm/WasmCompilationMode.h:
- wasm/WasmOperations.cpp:
(JSC::Wasm::JSC_DEFINE_JIT_OPERATION):
