From dfaf6453028684f09de4d0090b214c1e81761fd0 Mon Sep 17 00:00:00 2001
From: Zaggy1024 <zaggy1024@gmail.com>
Date: Sun, 29 Oct 2023 07:36:39 -0500
Subject: [PATCH] LibJS: Add an inline JIT fast path when `ToNumeric` has
 nothing to do

In most cases, this op will do nothing, as it is running on an the
accumulator while it already contains a number. Let's avoid doing that
native call.
---
 Userland/Libraries/LibJS/JIT/Compiler.cpp | 19 +++++++++++++++++++
 Userland/Libraries/LibJS/JIT/Compiler.h   |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/Userland/Libraries/LibJS/JIT/Compiler.cpp b/Userland/Libraries/LibJS/JIT/Compiler.cpp
index a535fd9885..29b0166c86 100644
--- a/Userland/Libraries/LibJS/JIT/Compiler.cpp
+++ b/Userland/Libraries/LibJS/JIT/Compiler.cpp
@@ -237,6 +237,19 @@ void Compiler::compile_jump_undefined(Bytecode::Op::JumpUndefined const& op)
     return BigInt::create(vm, old_value.as_bigint().big_integer().plus(Crypto::SignedBigInteger { 1 }));
 }
 
+void Compiler::jump_if_int32(Assembler::Reg reg, Assembler::Label& label)
+{
+    // GPR0 = reg >> 48;
+    m_assembler.mov(Assembler::Operand::Register(GPR0), Assembler::Operand::Register(reg));
+    m_assembler.shift_right(Assembler::Operand::Register(GPR0), Assembler::Operand::Imm(48));
+
+    m_assembler.jump_if(
+        Assembler::Operand::Register(GPR0),
+        Assembler::Condition::EqualTo,
+        Assembler::Operand::Imm(INT32_TAG),
+        label);
+}
+
 template<typename Codegen>
 void Compiler::branch_if_int32(Assembler::Reg reg, Codegen codegen)
 {
@@ -909,10 +922,16 @@ static Value cxx_to_numeric(VM& vm, Value value)
 
 void Compiler::compile_to_numeric(Bytecode::Op::ToNumeric const&)
 {
+    Assembler::Label fast_case {};
+
     load_vm_register(ARG1, Bytecode::Register::accumulator());
+    jump_if_int32(ARG1, fast_case);
+
     native_call((void*)cxx_to_numeric);
     store_vm_register(Bytecode::Register::accumulator(), RET);
     check_exception();
+
+    fast_case.link(m_assembler);
 }
 
 static Value cxx_resolve_this_binding(VM& vm)
diff --git a/Userland/Libraries/LibJS/JIT/Compiler.h b/Userland/Libraries/LibJS/JIT/Compiler.h
index fb21624ec5..b9bd929316 100644
--- a/Userland/Libraries/LibJS/JIT/Compiler.h
+++ b/Userland/Libraries/LibJS/JIT/Compiler.h
@@ -166,6 +166,8 @@ private:
 
     void native_call(void* function_address, Vector<Assembler::Operand> const& stack_arguments = {});
 
+    void jump_if_int32(Assembler::Reg, Assembler::Label&);
+
     template<typename Codegen>
     void branch_if_int32(Assembler::Reg, Codegen);