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HHVM calling convention, hhvmcc, is used by HHVM JIT for functions in translated cache. We currently support LLVM back end to generate code for X86-64 and may support other architectures in the future. In HHVM calling convention any GP register could be used to pass and return values, with the exception of R12 which is reserved for thread-local area and is callee-saved. Other than R12, we always pass RBX and RBP as args, which are our virtual machine's stack pointer and frame pointer respectively. When we enter translation cache via hhvmcc function, we expect the stack to be aligned at 16 bytes, i.e. skewed by 8 bytes as opposed to standard ABI alignment. This affects stack object alignment and stack adjustments for function calls. One extra calling convention, hhvm_ccc, is used to call C++ helpers from HHVM's translation cache. It is almost identical to standard C calling convention with an exception of first argument which is passed in RBP (before we use RDI, RSI, etc.) Differential Revision: http://reviews.llvm.org/D12681 llvm-svn: 248832
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you're writing a package for LLVM, see docs/Packaging.rst for our suggestions.