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

src/compiler/wasm-compiler.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/wasm-compiler.h"
 
 #include "src/isolate-inl.h"
 
 #include "src/base/platform/elapsed-timer.h"
 #include "src/base/platform/platform.h"
@@ skipping 1913 matching lines @@
   DCHECK(module_ && module_->instance);
 
   MachineOperatorBuilder* machine = jsgraph()->machine();
 
   // Compute the code object by loading it from the function table.
   Node* key = args[0];
 
   // 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);
     return trap_->GetTrapValue(module_->GetSignature(index));
   }
   Node* table = FunctionTable();
 
   // Load signature from the table and check.
   // The table is a FixedArray; signatures are encoded as SMIs.
   // [sig1, sig2, sig3, ...., code1, code2, code3 ...]
@@ skipping 1349 matching lines @@
                             function_->code_start_offset),
            compile_ms);
   }
 
   return code;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8