From ea0b7192fa85c42d688d50a2f48f04ae94ef78b2 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 6 Mar 2024 08:04:20 +0100
Subject: [PATCH] Revert "LibJS/Bytecode: Don't fuse unrelated compare and jump
 in peephole pass"

This reverts commit c1dbde72e963a3ed6e930b8e8e6a45c848dbb193.
---
 .../LibJS/Bytecode/Pass/Peephole.cpp          | 39 ++++++++++---------
 .../Libraries/LibJS/Tests/optimizer-bugs.js   | 10 -----
 2 files changed, 21 insertions(+), 28 deletions(-)
 delete mode 100644 Userland/Libraries/LibJS/Tests/optimizer-bugs.js

diff --git a/Userland/Libraries/LibJS/Bytecode/Pass/Peephole.cpp b/Userland/Libraries/LibJS/Bytecode/Pass/Peephole.cpp
index cddae5da840..2c5b53693c6 100644
--- a/Userland/Libraries/LibJS/Bytecode/Pass/Peephole.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Pass/Peephole.cpp
@@ -40,29 +40,32 @@ void Peephole::perform(PassPipelineExecutable& executable)
 
                     if (instruction.type() == Instruction::Type::Not) {
                         auto const& not_ = static_cast<Op::Not const&>(instruction);
-                        if (jump.condition() != not_.dst()) {
-                            auto slot_offset = new_block->size();
-                            new_block->grow(not_.length());
-                            memcpy(new_block->data() + slot_offset, &not_, not_.length());
-                            continue;
-                        }
+                        VERIFY(jump.condition() == not_.dst());
+                        new_block->append<Op::JumpIfNot>(
+                            not_.source_record().source_start_offset,
+                            not_.source_record().source_end_offset,
+                            not_.src(),
+                            *jump.true_target(),
+                            *jump.false_target());
+                        ++it;
+                        VERIFY(it.at_end());
+                        continue;
                     }
 
 #define DO_FUSE_JUMP(PreOp, ...)                                          \
     if (instruction.type() == Instruction::Type::PreOp) {                 \
         auto const& compare = static_cast<Op::PreOp const&>(instruction); \
-        if (jump.condition() == compare.dst()) {                          \
-            new_block->append<Op::Jump##PreOp>(                           \
-                compare.source_record().source_start_offset,              \
-                compare.source_record().source_end_offset,                \
-                compare.lhs(),                                            \
-                compare.rhs(),                                            \
-                *jump.true_target(),                                      \
-                *jump.false_target());                                    \
-            ++it;                                                         \
-            VERIFY(it.at_end());                                          \
-            continue;                                                     \
-        }                                                                 \
+        VERIFY(jump.condition() == compare.dst());                        \
+        new_block->append<Op::Jump##PreOp>(                               \
+            compare.source_record().source_start_offset,                  \
+            compare.source_record().source_end_offset,                    \
+            compare.lhs(),                                                \
+            compare.rhs(),                                                \
+            *jump.true_target(),                                          \
+            *jump.false_target());                                        \
+        ++it;                                                             \
+        VERIFY(it.at_end());                                              \
+        continue;                                                         \
     }
                     JS_ENUMERATE_FUSABLE_BINARY_OPS(DO_FUSE_JUMP)
                 }
diff --git a/Userland/Libraries/LibJS/Tests/optimizer-bugs.js b/Userland/Libraries/LibJS/Tests/optimizer-bugs.js
deleted file mode 100644
index c8c2d48d20f..00000000000
--- a/Userland/Libraries/LibJS/Tests/optimizer-bugs.js
+++ /dev/null
@@ -1,10 +0,0 @@
-test("Don't fuse unrelated jump and compare", () => {
-    function go(a) {
-        a < 3;
-        a &&= 1;
-
-        a < 3;
-        a ||= 1;
-    }
-    go();
-});