Import WAMR Fast JIT (#1343)

Import WAMR Fast JIT which is a lightweight JIT with quick startup, small footprint,
relatively good performance (~40% to ~50% of LLVM JIT) and good portability.

Platforms supported: Linux, MacOS and Linux SGX.
Arch supported: x86-64.

doc/build_wamr.md

@@ -29,19 +29,20 @@ The script `runtime_lib.cmake` defines a number of variables for configuring the
 cmake -DWAMR_BUILD_PLATFORM=linux -DWAMR_BUILD_TARGET=ARM
 ```
 
-#### **Configure interpreter**
+#### **Configure interpreters**
 
 - **WAMR_BUILD_INTERP**=1/0: enable or disable WASM interpreter
 
 - **WAMR_BUILD_FAST_INTERP**=1/0: build fast (default) or classic WASM interpreter.
 
-  NOTE: the fast interpreter runs ~2X faster than classic interpreter, but consumes about 2X memory to hold the WASM bytecode code.
+  NOTE: the fast interpreter runs ~2X faster than classic interpreter, but consumes about 2X memory to hold the pre-compiled code.
 
-#### **Configure AOT and JIT**
+#### **Configure AOT and JITs**
 
-- **WAMR_BUILD_AOT**=1/0, default to enable if not set
-- **WAMR_BUILD_JIT**=1/0, default to disable if not set
+- **WAMR_BUILD_AOT**=1/0, enable AOT or not, default to enable if not set
+- **WAMR_BUILD_JIT**=1/0, enable LLVM JIT or not, default to disable if not set
 - **WAMR_BUILD_LAZY_JIT**=1/0, whether to use Lazy JIT mode or not when *WAMR_BUILD_JIT* is set, default to enable if not set
+- **WAMR_BUILD_FAST_JIT**=1/0, enable Fast JIT or not, default to disable if not set
 
 #### **Configure LIBC**
 
@@ -206,8 +207,7 @@ sudo dnf install glibc-devel.i686
 After installing dependencies, build the source code:
 ``` Bash
 cd product-mini/platforms/linux/
-mkdir build
-cd build
+mkdir build && cd build
 cmake ..
 make
 # iwasm is generated under current directory
@@ -216,30 +216,49 @@ make
 By default in Linux, the `fast interpreter`, `AOT` and `Libc WASI` are enabled, and JIT is disabled.
 And the build target is set to X86_64 or X86_32 depending on the platform's bitwidth.
 
-To run a wasm file with interpreter mode:
+There are total 6 running modes supported: fast interpreter, classi interpreter, AOT, LLVM Lazy JIT, LLVM MC JIT and Fast JIT.
+
+(1) To run a wasm file with `fast interpreter` mode - build iwasm with default build and then:
 ```Bash
 iwasm <wasm file>
 ```
-To run an AOT file, firstly please refer to [Build wamrc AOT compiler](../README.md#build-wamrc-aot-compiler) to build wamrc, and then:
+Or
+```Bash
+mkdir build && cd build
+cmake .. -DWAMR_BUILD_INTERP=1
+make
+```
+
+(2) To disable `fast interpreter` and enable `classic interpreter` instead:
+``` Bash
+mkdir build && cd build
+cmake .. -DWAMR_BUILD_FAST_INTERP=0
+make
+```
+
+(3) To run an AOT file, firstly please refer to [Build wamrc AOT compiler](../README.md#build-wamrc-aot-compiler) to build wamrc, and then:
 ```Bash
 wamrc -o <AOT file> <WASM file>
 iwasm <AOT file>
 ```
 
-To enable the `JIT` mode, firstly we should build LLVM:
-
+(4) To enable the `LLVM Lazy JIT` mode, firstly we should build LLVM library:
 ``` Bash
 cd product-mini/platforms/linux/
 ./build_llvm.sh     (The llvm source code is cloned under <wamr_root_dir>/core/deps/llvm and auto built)
 ```
 
-Then pass argument `-DWAMR_BUILD_JIT=1` to cmake to enable WASM JIT:
-
+Then pass argument `-DWAMR_BUILD_JIT=1` to cmake to enable LLVM Lazy JIT:
 ``` Bash
-mkdir build
-cd build
+mkdir build && cd build
 cmake .. -DWAMR_BUILD_JIT=1
-# or "cmake .. -DWAMR_BUILD_JIT=1 -DWAMR_BUILD_LAZY_JIT=0" to disable LLVM Lazy JIT and enable LLVM MC JIT
+make
+```
+
+(5) Or disable `LLVM Lazy JIT` and enable `LLVM MC JIT` instead:
+```Bash
+mkdir build && cd build
+cmake .. -DWAMR_BUILD_JIT=1 -DWAMR_BUILD_LAZY_JIT=0
 make
 ```
 
@@ -248,13 +267,13 @@ by creating threads to compile the WASM functions parallely, and for the main th
 module will not be compiled until they are firstly called and haven't been compiled by the compilation threads.
 To disable it and enable LLVM MC JIT instead, please pass argument `-DWAMR_BUILD_LAZY_JIT=0` to cmake.
 
-To disable `fast interpreter` and enable `classic interpreter` instead:
+(6) To enable the `Fast JIT` mode:
 ``` Bash
-mkdir build
-cd build
-cmake .. -DWAMR_BUILD_FAST_INTERP=0
+mkdir build && cd build
+cmake .. -DWAMR_BUILD_FAST_JIT=1
 make
 ```
+The Fast JIT is a lightweight JIT engine with quick startup, small footprint and good portability, and gains ~50% performance of AOT.
 
 Linux SGX (Intel Software Guard Extension)
 -------------------------

doc/linux_sgx.md

@@ -11,12 +11,18 @@ After installing the dependencies, build the source code:
 ``` Bash
 source <SGX_SDK dir>/environment
 cd product-mini/platforms/linux-sgx/
-mkdir build
-cd build
+mkdir build && cd build
 cmake ..
 make
 ```
 
+By default the `fast interpreter` and `AOT` is enabled. If to enable `Fast JIT`, run:
+```Bash
+mkdir build && cd build
+cmake .. -DWAMR_BUILD_FAST_JIT=1
+make
+```
+
 This builds two libraries required by SGX application:
  - libvmlib.a for Enclave part
  - libvmlib_untrusted.a for App part