Adding the IREE_VM_BYTE_BUFFER_ORIGIN_* marker.

This enables us to know the source of a byte buffer without trusting
modules about its lifetime guarantees. A byte buffer that has a lifetime
of the entire module can safely be aliased as by construction it will
outlive any use from the module while allocated or external buffers
may not have the same guarantees.

iree/modules/hal/hal_module.c

@@ -833,6 +833,10 @@ IREE_VM_ABI_EXPORT(iree_hal_module_executable_create, rrrCrD, r) {
   if (iree_status_is_ok(status)) {
     iree_hal_executable_spec_t spec;
     iree_hal_executable_spec_initialize(&spec);
+    spec.caching_mode |=
+        executable_data->origin == IREE_VM_BYTE_BUFFER_ORIGIN_MODULE
+            ? IREE_HAL_EXECUTABLE_CACHING_MODE_ALIAS_PROVIDED_DATA
+            : 0;
     spec.executable_format = executable_format_str;
     spec.executable_data = executable_data->data;
     spec.executable_layout_count = executable_layout_count;

iree/vm/builtin_types.h

@@ -22,11 +22,25 @@
 extern "C" {
 #endif  // __cplusplus
 
+// Describes where a byte buffer originates from and what guarantees can be made
+// about its lifetime and ownership.
+enum iree_vm_byte_buffer_origin_e {
+  // Buffer references memory in the module space (rodata or rwdata) that is
+  // guaranteed to be live for the lifetime of the module.
+  IREE_VM_BYTE_BUFFER_ORIGIN_MODULE = 0,
+  // Buffer references memory created by the guest module code. It has a
+  // lifetime less than that of the module but is always tracked with proper
+  // references (a handle existing to the memory implies it is valid).
+  IREE_VM_BYTE_BUFFER_ORIGIN_GUEST = 1,
+};
+typedef uint32_t iree_vm_byte_buffer_origin_t;
+
 // The built-in constant buffer type.
 // This simply points at a span of memory. The memory could be owned (in which
 // case a destroy function must be provided) or unowned (NULL destroy function).
 typedef struct {
   iree_vm_ref_object_t ref_object;
+  iree_vm_byte_buffer_origin_t origin;
   iree_const_byte_span_t data;
   iree_vm_ref_destroy_t destroy;
 } iree_vm_ro_byte_buffer_t;
@@ -44,6 +58,7 @@ static inline iree_string_view_t iree_vm_ro_byte_buffer_as_string(
 // case a destroy function must be provided) or unowned (NULL destroy function).
 typedef struct {
   iree_vm_ref_object_t ref_object;
+  iree_vm_byte_buffer_origin_t origin;
   iree_byte_span_t data;
   iree_vm_ref_destroy_t destroy;
 } iree_vm_rw_byte_buffer_t;

iree/vm/bytecode_module.c

@@ -577,6 +577,7 @@ static iree_status_t iree_vm_bytecode_module_alloc_state(
         iree_vm_RodataSegmentDef_vec_at(rodata_segments, i);
     iree_vm_ro_byte_buffer_t* ref = &state->rodata_ref_table[i];
     iree_atomic_ref_count_init(&ref->ref_object.counter);
+    ref->origin = IREE_VM_BYTE_BUFFER_ORIGIN_MODULE;
     ref->data.data = iree_vm_RodataSegmentDef_data(segment);
     ref->data.data_length =
         flatbuffers_uint8_vec_len(iree_vm_RodataSegmentDef_data(segment));