Fix unaligned accesses in back_edge tables.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 722901889301955d4cdd515044fa076507e65439..d0ce7dca460aa0daf3c287477e56d0ca68a8c60d 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -8538,13 +8538,13 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_CompileForOnStackReplacement) {
     Address table_cursor = start + unoptimized->back_edge_table_offset();
     uint32_t table_length = Memory::uint32_at(table_cursor);
     table_cursor += kIntSize;
-    uint8_t loop_depth = 0;
+    uint32_t loop_depth = 0;
     for (unsigned i = 0; i < table_length; ++i) {
       // Table entries are (AST id, pc offset) pairs.
       uint32_t pc_offset = Memory::uint32_at(table_cursor + kIntSize);
       if (pc_offset == target_pc_offset) {
         ast_id = BailoutId(static_cast<int>(Memory::uint32_at(table_cursor)));
-        loop_depth = Memory::uint8_at(table_cursor + 2 * kIntSize);
+        loop_depth = Memory::uint32_at(table_cursor + 2 * kIntSize);
         break;
       }
       table_cursor += FullCodeGenerator::kBackEdgeEntrySize;