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.

core/iwasm/interpreter/wasm_interp.h

@@ -26,6 +26,10 @@ typedef struct WASMInterpFrame {
     /* Instruction pointer of the bytecode array.  */
     uint8 *ip;
 
+#if WASM_ENABLE_FAST_JIT != 0
+    uint8 *jitted_return_addr;
+#endif
+
 #if WASM_ENABLE_PERF_PROFILING != 0
     uint64 time_started;
 #endif
@@ -47,12 +51,13 @@ typedef struct WASMInterpFrame {
     WASMBranchBlock *csp_boundary;
     WASMBranchBlock *csp;
 
-    /* Frame data, the layout is:
-       lp: param_cell_count + local_cell_count
-       sp_bottom to sp_boundary: stack of data
-       csp_bottom to csp_boundary: stack of block
-       ref to frame end: data types of local vairables and stack data
-       */
+    /**
+     * Frame data, the layout is:
+     *  lp: parameters and local variables
+     *  sp_bottom to sp_boundary: wasm operand stack
+     *  csp_bottom to csp_boundary: wasm label stack
+     *  jit spill cache: only available for fast jit
+     */
     uint32 lp[1];
 #endif
 } WASMInterpFrame;