[08] Fixes frame restoration, so return works properly now

README.md

@@ -120,6 +120,6 @@ wc -l file.hack
 
 ## Function Calling Commands
 
-- [ ] `SimpleFunction.vm`
+- [x] `SimpleFunction.vm` (128)
 - [ ] `FibonacciElement.vm`
 - [ ] `StaticsTest.vm`

projects/08/FunctionCalls/SimpleFunction/SimpleFunction.asm

@@ -78,21 +78,52 @@ A=A-1
 M=M-D
 @SP
 M=M-1 // end sub (L8)
+@SP
+A=M-1
+D=M
+@ARG
+A=M
+M=D
 @ARG
 D=M+1
 @SP
 M=D // @SP = ARG+1
 @LCL
-D=M // D=@LCL
+D=M
-@THAT
+@R13
-MD=D-1 // THAT = LCL-1
+M=D // Save LCL to R13
-@THIS
+A=D-1 // A=*LCL-1
-MD=D-1 // THIS = LCL-2
+D=M // D=*(*LCL-1)
-@ARG
+@THAT // A=THAT
-MD=D-1 // ARG  = LCL-3
+M=D   // *that = *(*lcl-1)
-@LCL
+@R13
-MD=D-1 // LCL = LCL-4
+A=M-1
-A=D-1 // A = LCL-5
+A=A-1 // A=*LCL-2
+D=M // D=*(*LCL-2)
+@THIS // A=THIS
+M=D   // *THIS = *(*lcl-2)
+@R13
+A=M-1
+A=A-1
+A=A-1 // A=*LCL-3
+D=M // D=*(*LCL-3)
+@ARG // A=ARG
+M=D   // *ARG = *(*lcl-3)
+@R13
+A=M-1
+A=A-1
+A=A-1
+A=A-1 // A=*LCL-4
+D=M // D=*(*LCL-4)
+@LCL // A=LCL
+M=D   // *LCL = *(*lcl-4)
+@R13
+A=M-1
+A=A-1
+A=A-1
+A=A-1
+A=A-1 // A=*LCL-5
+A=M  // A=*(*LCL-5)
 0;JMP // Jump to *(LCL-5)
-@97
+@128
 0;JMP

projects/08/FunctionCalls/SimpleFunction/SimpleFunction.out

@@ -1 +1,2 @@
 | RAM[0] | RAM[1] | RAM[2] | RAM[3] | RAM[4] |RAM[310]|
+|    311 |    305 |    300 |   3010 |   4010 |   1196 |

vm/CodeWriter.php

@@ -14,26 +14,64 @@ class CodeWriter {
 
   public function writeReturn() {
     $this->write([
+      "@SP",
+      "A=M-1",
+      "D=M",// Popped value to D
+      // And then write it to *ARG = pop()
+      "@ARG",
+      "A=M",
+      "M=D",
+
       // SP=ARG+1
       "@ARG",
       "D=M+1",
       "@SP",
       "M=D // @SP = ARG+1",
-      // THAT = LCL-1
       "@LCL",
-      "D=M // D=@LCL",
+      "D=M",
-      "@THAT",
+      "@R13",
-      "MD=D-1 // THAT = LCL-1",
+      "M=D // Save LCL to R13",
-      // THIS = LCL-2
+
-      "@THIS",
+      // now we go restoring THAT, THIS, ARG, LCL
-      "MD=D-1 // THIS = LCL-2",
+      "A=D-1 // A=*LCL-1",
-      // ARG = LCL-3
+      "D=M // D=*(*LCL-1)",
-      "@ARG",
+      "@THAT // A=THAT",
-      "MD=D-1 // ARG  = LCL-3",
+      "M=D   // *that = *(*lcl-1)",
-      // LCL = LCL-4
+      // now we restore THIS
-      "@LCL",
+      "@R13",
-      "MD=D-1 // LCL = LCL-4",
+      "A=M-1",
-      "A=D-1 // A = LCL-5",
+      "A=A-1 // A=*LCL-2",
+      "D=M // D=*(*LCL-2)",
+      "@THIS // A=THIS",
+      "M=D   // *THIS = *(*lcl-2)",
+
+      // now we restore ARG
+      "@R13",
+      "A=M-1",
+      "A=A-1",
+      "A=A-1 // A=*LCL-3",
+      "D=M // D=*(*LCL-3)",
+      "@ARG // A=ARG",
+      "M=D   // *ARG = *(*lcl-3)",
+
+      // now we restore LCL
+      "@R13",
+      "A=M-1",
+      "A=A-1",
+      "A=A-1",
+      "A=A-1 // A=*LCL-4",
+      "D=M // D=*(*LCL-4)",
+      "@LCL // A=LCL",
+      "M=D   // *LCL = *(*lcl-4)",
+
+      // Now we hyperjump
+      "@R13",
+      "A=M-1",
+      "A=A-1",
+      "A=A-1",
+      "A=A-1",
+      "A=A-1 // A=*LCL-5",
+      "A=M  // A=*(*LCL-5)",
       "0;JMP // Jump to *(LCL-5)",
     ]);
   }