[wasm] Support undefined indirect table entries, behind a flag.

src/compiler/wasm-compiler.cc

Index: src/compiler/wasm-compiler.cc
diff --git a/src/compiler/wasm-compiler.cc b/src/compiler/wasm-compiler.cc
index 09290af06aa7023f3da35cb95f735427f4b24834..93392ad66545551aac0d1f6ca4ba9a69ba7b3b49 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -1931,10 +1931,22 @@ Node* WasmGraphBuilder::CallIndirect(uint32_t index, Node** args,
   // Bounds check the index.
   int table_size = static_cast<int>(module_->FunctionTableSize());
   if (table_size > 0) {
-    // Bounds check against the table size.
-    Node* size = Int32Constant(static_cast<int>(table_size));
-    Node* in_bounds = graph()->NewNode(machine->Uint32LessThan(), key, size);
-    trap_->AddTrapIfFalse(wasm::kTrapFuncInvalid, in_bounds, position);
+    if (FLAG_wasm_jit_prototype) {
+      int indirect_table_size =

[bradn, 2016/06/16 08:00:20]

Can we move the computation of the size to FunctionTableSize so this is the same
in both cases?

+          static_cast<int>(module_->instance->function_table->length());
+
+      Node* lower_bound = Int32Constant(indirect_table_size / 2 -
+                                        module_->instance->padded_entries);
+      Node* more_than_lower_bound =
+          graph()->NewNode(machine->Uint32LessThanOrEqual(), lower_bound, key);
+      trap_->AddTrapIfTrue(wasm::kTrapFuncInvalid, more_than_lower_bound,
+                           position);
+    } else {
+      // Bounds check against the table size.
+      Node* size = Int32Constant(static_cast<int>(table_size));
+      Node* in_bounds = graph()->NewNode(machine->Uint32LessThan(), key, size);
+      trap_->AddTrapIfFalse(wasm::kTrapFuncInvalid, in_bounds, position);
+    }
   } else {
     // No function table. Generate a trap and return a constant.
     trap_->AddTrapIfFalse(wasm::kTrapFuncInvalid, Int32Constant(0), position);