[wasm] [asm.js] Ignore unused function tables in AsmWasmBuilder.

src/asmjs/asm-wasm-builder.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/v8.h"
 
 // Required to get M_E etc. in MSVC.
 #if defined(_WIN32)
 #define _USE_MATH_DEFINES
 #endif
@@ skipping 764 matching lines @@
     ZoneHashMap::Entry* entry =
         function_tables_.Lookup(v, ComputePointerHash(v));
     if (entry == nullptr) {
       return nullptr;
     }
     return reinterpret_cast<FunctionTableIndices*>(entry->value);
   }
 
   void PopulateFunctionTable(VariableProxy* table, ArrayLiteral* funcs) {
     FunctionTableIndices* indices = LookupFunctionTable(table->var());
-    DCHECK_NOT_NULL(indices);
+    // Ignore unused function tables.
+    if (indices == nullptr) {
+      return;
+    }
     for (int i = 0; i < funcs->values()->length(); ++i) {
       VariableProxy* func = funcs->values()->at(i)->AsVariableProxy();
       DCHECK_NOT_NULL(func);
       builder_->SetIndirectFunction(
           indices->start_index + i,
           LookupOrInsertFunction(func->var())->func_index());
     }
   }
 
   class ImportedFunctionTable {
@@ skipping 1163 matching lines @@
   impl.builder_->WriteAsmJsOffsetTable(*asm_offsets_buffer);
   return {module_buffer, asm_offsets_buffer, success};
 }
 
 const char* AsmWasmBuilder::foreign_init_name = "__foreign_init__";
 const char* AsmWasmBuilder::single_function_name = "__single_function__";
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8