From bd982eab2cf2d2e17d2fd267a79443a719d81629 Mon Sep 17 00:00:00 2001
From: Evgeny Ukhanov <evgeny@aurora.dev>
Date: Fri, 13 Dec 2024 21:47:43 +0100
Subject: [PATCH] EIP-4750: RETF

---
 gasometer/src/lib.rs         |  3 +++
 runtime/src/eval/eof/call.rs | 17 +++++++++++++++++
 runtime/src/eval/mod.rs      |  2 +-
 runtime/src/eval/system.rs   |  5 -----
 4 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/gasometer/src/lib.rs b/gasometer/src/lib.rs
index 9fd669d9..eaa0844a 100644
--- a/gasometer/src/lib.rs
+++ b/gasometer/src/lib.rs
@@ -893,6 +893,9 @@ pub fn dynamic_opcode_cost<H: Handler>(
 		Opcode::CALLF if config.has_eof => GasCost::Low,
 		Opcode::CALLF => GasCost::Invalid(opcode),
 
+		Opcode::RETF if config.has_eof => GasCost::VeryLow,
+		Opcode::RETF => GasCost::Invalid(opcode),
+
 		_ => GasCost::Invalid(opcode),
 	};
 
diff --git a/runtime/src/eval/eof/call.rs b/runtime/src/eval/eof/call.rs
index f3327f2c..1f8be0e4 100644
--- a/runtime/src/eval/eof/call.rs
+++ b/runtime/src/eval/eof/call.rs
@@ -46,3 +46,20 @@ pub fn callf<H: Handler>(runtime: &mut Runtime, _handler: &mut H) -> Control<H>
 
 	Control::Continue
 }
+
+pub fn retf<H: Handler>(runtime: &mut Runtime, _handler: &mut H) -> Control<H> {
+	let eof = require_eof!(runtime);
+	let Some(function_return_state) = runtime.context.eof_function_stack.pop() else {
+		return Control::Exit(ExitFatal::CallErrorAsFatal(ExitError::EOFUnexpectedCall).into());
+	};
+
+	let Some(code_section) = eof.body.code_section.get(function_return_state.index) else {
+		return Control::Exit(ExitFatal::CallErrorAsFatal(ExitError::EOFUnexpectedCall).into());
+	};
+	// Set machine code to target code section
+	runtime.machine.set_code(code_section);
+	// Set PC to position 0
+	runtime.machine.set_pc(function_return_state.pc);
+
+	Control::Continue
+}
diff --git a/runtime/src/eval/mod.rs b/runtime/src/eval/mod.rs
index a6cfec75..4bfdded8 100644
--- a/runtime/src/eval/mod.rs
+++ b/runtime/src/eval/mod.rs
@@ -78,7 +78,7 @@ pub fn eval<H: Handler>(state: &mut Runtime, opcode: Opcode, handler: &mut H) ->
 		Opcode::RJUMPI => eof::control::rjumpi(state, handler),
 		Opcode::RJUMPV => eof::control::rjumpv(state, handler),
 		Opcode::CALLF => eof::call::callf(state, handler),
-		Opcode::RETF => system::retf(state, handler),
+		Opcode::RETF => eof::call::retf(state, handler),
 		Opcode::JUMPF => system::jumpf(state, handler),
 		Opcode::DUPN => eof::stack::dupn(state),
 		Opcode::SWAPN => eof::stack::swapn(state),
diff --git a/runtime/src/eval/system.rs b/runtime/src/eval/system.rs
index aee7ebbc..281d5292 100644
--- a/runtime/src/eval/system.rs
+++ b/runtime/src/eval/system.rs
@@ -586,11 +586,6 @@ pub fn call<H: Handler>(runtime: &mut Runtime, scheme: CallScheme, handler: &mut
 //===========================
 // EOF related functions
 
-#[allow(dead_code)]
-pub fn retf<H: Handler>(_runtime: &mut Runtime, _handler: &mut H) -> Control<H> {
-	todo!()
-}
-
 #[allow(dead_code)]
 pub fn jumpf<H: Handler>(_runtime: &mut Runtime, _handler: &mut H) -> Control<H> {
 	todo!()