From 911506af9f2c487298e1419f24b1b907364ea770 Mon Sep 17 00:00:00 2001
From: Hendiadyoin1 <leon.a@serenityos.org>
Date: Fri, 9 Sep 2022 16:47:42 +0200
Subject: [PATCH] LibJS: Align Instructions as void* and roundup variably sized
 ones sizes

Both is indeed needed,
the standard alignment would have been 4, but some Instructions, like
Jumps need an alignment of 8

Fixes #12127.
---
 Userland/Libraries/LibJS/Bytecode/Generator.h   | 7 +++++--
 Userland/Libraries/LibJS/Bytecode/Instruction.h | 2 +-
 Userland/Libraries/LibJS/Bytecode/Op.h          | 5 +++--
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.h b/Userland/Libraries/LibJS/Bytecode/Generator.h
index 5473e11ca8..85ee15a3b4 100644
--- a/Userland/Libraries/LibJS/Bytecode/Generator.h
+++ b/Userland/Libraries/LibJS/Bytecode/Generator.h
@@ -65,12 +65,15 @@ public:
     OpType& emit_with_extra_register_slots(size_t extra_register_slots, Args&&... args)
     {
         VERIFY(!is_current_block_terminated());
+
+        size_t size_to_allocate = round_up_to_power_of_two(sizeof(OpType) + extra_register_slots * sizeof(Register), alignof(void*));
+
         // If the block doesn't have enough space, switch to another block
         if constexpr (!OpType::IsTerminator)
-            ensure_enough_space(sizeof(OpType) + extra_register_slots * sizeof(Register));
+            ensure_enough_space(size_to_allocate);
 
         void* slot = next_slot();
-        grow(sizeof(OpType) + extra_register_slots * sizeof(Register));
+        grow(size_to_allocate);
         new (slot) OpType(forward<Args>(args)...);
         if constexpr (OpType::IsTerminator)
             m_current_basic_block->terminate({});
diff --git a/Userland/Libraries/LibJS/Bytecode/Instruction.h b/Userland/Libraries/LibJS/Bytecode/Instruction.h
index 18fd91de85..ca64c8bfc7 100644
--- a/Userland/Libraries/LibJS/Bytecode/Instruction.h
+++ b/Userland/Libraries/LibJS/Bytecode/Instruction.h
@@ -92,7 +92,7 @@
 
 namespace JS::Bytecode {
 
-class Instruction {
+class alignas(void*) Instruction {
 public:
     constexpr static bool IsTerminator = false;
 
diff --git a/Userland/Libraries/LibJS/Bytecode/Op.h b/Userland/Libraries/LibJS/Bytecode/Op.h
index a8c4fbf855..db951a337e 100644
--- a/Userland/Libraries/LibJS/Bytecode/Op.h
+++ b/Userland/Libraries/LibJS/Bytecode/Op.h
@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <AK/StdLibExtras.h>
 #include <LibCrypto/BigInt/SignedBigInteger.h>
 #include <LibJS/Bytecode/IdentifierTable.h>
 #include <LibJS/Bytecode/Instruction.h>
@@ -990,9 +991,9 @@ ALWAYS_INLINE void Instruction::replace_references(BasicBlock const& from, Basic
 ALWAYS_INLINE size_t Instruction::length() const
 {
     if (type() == Type::NewArray)
-        return static_cast<Op::NewArray const&>(*this).length_impl();
+        return round_up_to_power_of_two(static_cast<Op::NewArray const&>(*this).length_impl(), alignof(void*));
     if (type() == Type::CopyObjectExcludingProperties)
-        return static_cast<Op::CopyObjectExcludingProperties const&>(*this).length_impl();
+        return round_up_to_power_of_two(static_cast<Op::CopyObjectExcludingProperties const&>(*this).length_impl(), alignof(void*));
 
 #define __BYTECODE_OP(op) \
     case Type::op:        \