Add test cases for return slot allocation.

test/libyul/evmCodeTransform/stackReuse/function_argument_reuse.yul

@@ -0,0 +1,28 @@
+{
+    function f(a, b, c) -> x { pop(address()) sstore(a, c) pop(callvalue()) x := b }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x17
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// DUP4
+// DUP3
+// SSTORE
+// CALLVALUE
+// POP
+// DUP3
+// SWAP1
+// POP
+// JUMPDEST
+// SWAP4
+// SWAP3
+// POP
+// POP
+// POP
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_many_arguments.yul

@@ -0,0 +1,27 @@
+{
+/*    function f(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20) -> x {
+        mstore(0x0100, a1)
+        mstore(0x0120, a2)
+        mstore(0x0140, a3)
+        mstore(0x0160, a4)
+        mstore(0x0180, a5)
+        mstore(0x01A0, a6)
+        mstore(0x01C0, a7)
+        mstore(0x01E0, a8)
+        mstore(0x0200, a9)
+        mstore(0x0220, a10)
+        mstore(0x0240, a11)
+        mstore(0x0260, a12)
+        mstore(0x0280, a13)
+        mstore(0x02A0, a14)
+        mstore(0x02C0, a15)
+        mstore(0x02E0, a16)
+        mstore(0x0300, a17)
+        mstore(0x0320, a18)
+        mstore(0x0340, a19)
+        x := a20
+    }*/
+}
+// ====
+// stackOptimization: true
+// ----

test/libyul/evmCodeTransform/stackReuse/function_retparam_block.yul

@@ -0,0 +1,18 @@
+{
+    function f() -> x { pop(address()) { pop(callvalue()) } }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0xD
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// CALLVALUE
+// POP
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_declaration.yul

@@ -0,0 +1,18 @@
+{
+    function f() -> x { pop(address()) let y := callvalue() }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0xD
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// CALLVALUE
+// POP
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_for.yul

@@ -0,0 +1,27 @@
+{
+    function f() -> x { pop(address()) for { pop(callvalue()) } 0 {} { } }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x19
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// CALLVALUE
+// POP
+// JUMPDEST
+// PUSH1 0x0
+// ISZERO
+// PUSH1 0x15
+// JUMPI
+// JUMPDEST
+// PUSH1 0xA
+// JUMP
+// JUMPDEST
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_if.yul

@@ -0,0 +1,23 @@
+{
+    function f() -> x { pop(address()) if 1 { pop(callvalue()) } }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x14
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// PUSH1 0x1
+// ISZERO
+// PUSH1 0x10
+// JUMPI
+// CALLVALUE
+// POP
+// JUMPDEST
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_leave.yul

@@ -0,0 +1,20 @@
+{
+    function f() -> x { pop(address()) leave pop(callvalue()) }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x10
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// PUSH1 0xD
+// JUMP
+// CALLVALUE
+// POP
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_read.yul

@@ -0,0 +1,21 @@
+{
+    function f() -> x { pop(address()) sstore(0, x) pop(callvalue()) }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x11
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// DUP1
+// PUSH1 0x0
+// SSTORE
+// CALLVALUE
+// POP
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_unassigned.yul

@@ -0,0 +1,16 @@
+{
+    function f() -> x { pop(callvalue()) }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0xB
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// CALLVALUE
+// POP
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST

test/libyul/evmCodeTransform/stackReuse/function_retparam_unassigned_multiple.yul

@@ -0,0 +1,20 @@
+{
+    function f() -> x, y, z { pop(callvalue()) }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x11
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// PUSH1 0x0
+// PUSH1 0x0
+// CALLVALUE
+// POP
+// JUMPDEST
+// SWAP1
+// SWAP2
+// SWAP3
+// JUMP
+// JUMPDEST