On Thu, Sep 6, 2012 at 11:02 PM, Mark Lam <mark....@apple.com> wrote: > As part of an effort to simplify future development, the JSC team is > deprecating the classic C++ interpreter (and will delete it shortly on Sept > 24). In its place, we will use the LLINT (low level interpreter) with the > C++ back-end (see https://bugs.webkit.org/show_bug.cgi?id=91052) to generate > a llint C++ interpreter for new ports that do not support the JITs yet. > > In order to deprecate the classic C++ interpreter, we will need your help to > convert your ports to use the llint (if you are using JSC for your port). I > will lay out some details below on how this conversion works: > > > Why deprecate the classic C++ interpreter? > ================================= > The llint is where active development will take place as we add new JIT and > runtime enhancements. Having the classic C++ interpreter around only slows > down the development effort. The classic C++ interpreter is also prone to > experience bit-rot, and hence will easily get buggy over time. > > > How will you bring up a new platform without the classic C++ interpreter? > ======================================================== > You will have to add the llint offline ASM build phase to generate the llint > C++ interpreter (see below for details on the llint offline build phase). > Alternatively, you can generate the llint C++ interpreter on a port that > already supports it, and use the generated LLIntAssembly.h from there to > bootstrap your port. It is preferred that every port supports the llint > natively because this will enable you to get the latest bug fixes and > performance enhancements. > > > What is the performance of the llint C++ interpreter? > ======================================== > The performance of the new llint C++ interpreter is currently slower than > the classic C++ interpreter, but within approximately 10% on average. The > goal of the llint C++ interpreter is not to achieve the highest performance, > but to provide a functional C++ interpreter to help bootstrap new ports. As > such, we don't plan to spend a lot of time on optimizing it. > > sunspider results: > classic C++ interpreter llint C++ interpreter > <arithmetic> * 18.3123+-0.1593 ! 18.6551+-0.1095 ! > definitely 1.0187x slower > > > v8-real results: > classic C++ interpreter llint C++ interpreter > <geometric> * 15.31772+-0.22338 ! 16.92580+-0.09735 ! > definitely 1.1050x slower > > > How is the llint built? > ================ > Here's a summary of the steps: > > Step 1: Generate LLIntDesiredOffsets.h > > mkdir -p "${BUILT_PRODUCTS_DIR}/LLIntOffsets/" > > /usr/bin/env ruby "${SRCROOT}/offlineasm/generate_offset_extractor.rb" > "${SRCROOT}/llint/LowLevelInterpreter.asm" > "${BUILT_PRODUCTS_DIR}/LLIntOffsets/LLIntDesiredOffsets.h" > > Step 2: Build LLIntOffsetsExtractor from LLIntDesiredOffsets.h (from step 1) > and Source/JavaScriptCore/llint/LLIntOffsetsExtrator.cpp using the > cross-compiler for your target. > > LLIntOffsetsExtractor is supposed to be an executable binary for your target > port. However, we will only be using it to extract offsets that we need for > the next step, and won't be running it. > > Step 3: Generate LLIntAssembly.h > > /usr/bin/env ruby JavaScriptCore/offlineasm/asm.rb > JavaScriptCore/llint/LowLevelInterpreter.asm > ${BUILT_PRODUCTS_DIR}/JSCLLIntOffsetsExtractor LLIntAssembly.h || exit 1 > > LLIntAssembly.h provides the body of the interpreter, and will be #included > in Source/JavaScriptCore/llint/LowLevelInterpreter.cpp to be built into JSC. > > > How to get JSC to build with the llint C++ interpreter? > ======================================== > > In Platform.h (or equivalent), set the following settings: > > #define ENABLE_JIT 0 > #define ENABLE_LLINT 1 > #define ENABLE_CLASSIC_INTERPRETER 0 > > This combination of settings will ENABLE(LLINT_C_LOOP) which builds the > llint C++ interpreter. Eventually, ENABLE_CLASSIC_INTERPRETER won't be > needed when the classic C++ interpreter gets deprecated and deleted. > > > What do you need to do for your port? > ============================= > The Mac port already works with the llint. I'm planning to fix the Windows > port to also work with the llint. On Sept 24, we plan to delete the classic > C++ interpreter. This means your port will cease to build if you are still > relying on the classic C++ interpreter then. > > Please look into migrating your port to use the llint C++ interpreter (if > not the Assembly one) within the next few weeks. If you encounter issues > and need some help getting the llint to work for your port, please feel free > to contact me. I will do my best to help you out.
The work for CMake-based port is being done here: https://bugs.webkit.org/show_bug.cgi?id=92682 Cheers, _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo/webkit-dev
