Wasm shared heap

[WenLY1]

Implementation tasks:

• add WAMR_BUILD_SHARED_HEAP and WASM_ENABLE_SHARED_HEAP

• add wamrc --enable-shared-heap

• consider the behavior of import memory in multi-module feature

• adapt address conversion/validation
  aot code boundary check
  wasm_runtime_invoke_native
  wasm_runtime_invoke_native_raw
  wasm_runtime_validate_app_addr
  wasm_runtime_addr_app_to_native
  wasm_runtime_addr_native_to_app
  wasm_runtime_validate_native_addr

• interpreter/fast-jit do boundary check
  classic interp mode
  fast interp mode
  jit

• Support setting shared heap’s size and shared heap’s alloc options in RuntimeInitArgs for wasm_runtime_full_init

• Add check in load module, default memory’s max_memory_size should be no larger than 4G-shared_heap_size, if not, reduce it to 4G-shared_heap_size

• Add API wasm_runtime_shared_malloc/wasm_runtime_shared_free

• App allocates memory from shared heap with API shared_malloc/shared_free
  example

            #include <stdio.h>  
            #include <stdlib.h>  
            extern void *shared_malloc(int size);  
            extern void shared_free(void *ptr);  
            int main()  
            {  
	            int *pa = (int *)malloc(4);  
	            *pa = 4;  
	            printf("pa value is %d\n", *pa);  
	            free(pa);  
	            int *ps = (int *)shared_malloc(4);  
	            *ps = 5;  
	            printf("ps value is %d\n", *ps);  
	            shared_free(ps);  
            } 

#3543

[WenLY1]

If wasm shared heap is enable, should the boundary check keep enabled ? In the following code, if bounds checks is disabled, should we return the offset directly or judge whether the addr is in shared heap?
In function wasm_runtime_addr_native_to_app

    if (bounds_checks) {
        if (memory_inst->memory_data <= addr && addr < memory_inst->memory_data_end) {
            ret = (uint64)(addr - memory_inst->memory_data);
            SHARED_MEMORY_UNLOCK(memory_inst);
            return ret;
        }
    }
    /* If bounds checks is disabled, return the offset directly */
    else if (addr != NULL) {
        ret = (uint64)(addr - memory_inst->memory_data);
        SHARED_MEMORY_UNLOCK(memory_inst);
        return ret;
    }

[lum1n0us]

Would u mind giving us, the community, a quick introduction about:

• What's shared heap?
• What kind of questions does shared heap try to answer?
• Is there any other options? And why we choose shared heap?

[wenyongh]

@WenLY1 Many people may not know the background and the design details of the shared heap, I submitted issue #3546 to try to illustrate that, suggest you to post tasks in that issue to track and discuss instead.