Enable multi-thread for tensorflow sample, update wasm-c-api document (#651)

samples/workload/tensorflow/README.md

@@ -17,7 +17,9 @@ Then run
 ./build.sh
 # for linux platform, or
 ./build.sh --sgx
-# for linux-sgx platform
+# for linux-sgx platform or
+./build.sh --threads
+# for multi-thread execution (on linux platform)
 ```
 to build tensorflow and run it with iwasm, which basically contains the following steps:
 - hack emcc to delete some objects in libc.a

samples/workload/tensorflow/build.sh

@@ -1,10 +1,10 @@
+#!/bin/bash
+
 #
 # Copyright (C) 2019 Intel Corporation.  All rights reserved.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 
-#!/bin/bash
-
 ####################################
 #   build tensorflow-lite sample   #
 ####################################
@@ -99,6 +99,8 @@ WAMRC_CMD="$(pwd)/wamrc"
 cd ${OUT_DIR}
 if [[ $1 == '--sgx' ]]; then
     ${WAMRC_CMD} --enable-simd -sgx -o benchmark_model.aot benchmark_model.wasm
+elif [[  $1 == '--threads' ]]; then
+    ${WAMRC_CMD} --enable-simd --enable-multi-thread -o benchmark_model.aot benchmark_model.wasm
 else
     ${WAMRC_CMD} --enable-simd -o benchmark_model.aot benchmark_model.wasm
 fi
@@ -137,7 +139,13 @@ else
     IWASM_CMD="${WAMR_PLATFORM_DIR}/linux/build/iwasm"
 fi
 
-${IWASM_CMD} --heap-size=10475860 \
+if [[  $1 == '--threads' ]]; then
+    ${IWASM_CMD} --heap-size=10475860 \
+             ${OUT_DIR}/benchmark_model.aot --num_threads=4 \
+             --graph=mobilenet_quant_v1_224.tflite --max_secs=300
+else
+    ${IWASM_CMD} --heap-size=10475860 \
              ${OUT_DIR}/benchmark_model.aot \
              --graph=mobilenet_quant_v1_224.tflite --max_secs=300
+fi
 

samples/workload/tensorflow/tf_lite.patch

@@ -19,14 +19,14 @@ index c7ddff58440..ebfebaead35 100644
  endif # ifeq ($(HOST_OS),$(TARGET))
  endif
  
-+CFLAGS+=-msimd128
-+CXXFLAGS+=-msimd128
++CFLAGS+=-msimd128 -mbulk-memory -matomics
++CXXFLAGS+=-msimd128 -mbulk-memory -matomics
 +
-+LIBFLAGS += -s TOTAL_STACK=1048576 \
++LIBFLAGS += -s TOTAL_STACK=1048576 -s MALLOC="none" \
 +            -s INITIAL_MEMORY=16777216 \
 +            -s MAXIMUM_MEMORY=167772160 \
 +            -s ALLOW_MEMORY_GROWTH=1 \
-+            -Wl,--export=__data_end -Wl,--export=__heap_base \
++            -Wl,--export=__data_end -Wl,--export=__heap_base,--shared-memory,--no-check-features \
 +            -s ERROR_ON_UNDEFINED_SYMBOLS=0
 +
  # This library is the main target for this makefile. It will contain a minimal