Chapter 7- Stack Arithmetic Flashcards
The vim language has what kind of data type?
It has one 16 bit data type that can be used as integer, Boolean or pointer.
What are the formats of vm command?
There are 3 formats
- Command (add)
- Command ARG (goto loop)
- Command arg1 arg2 ( push local 3)
How many arithmetic commands are there?
Add, sub, neg, eq, gt, lt, and, or, not
What are all the memory segments?
Argument, local, static, constant, this, that, pointer, temp
What are the memory access commands?
Push segment index //push the value of segment[index] into stack
Pop segment index // pop the topmost element into segment[index]
If I have a foo.vm file with 3 functions, what is the memory distribution?
Local, argument, this, that, pointer for each function. Static is shared between all the functions. Temp and constant are program wised
From jack program of two classes foo.jack and Bar.jack with methods m,n,p and m,n- what are he products of the vim to assembly to hack?
2 files Foo.vm and Bar.vm with Foo.m, Foo.n Foo.p and Bar.m and Bar.n functions. After one prog.asm file
And then prog.hack binary code
What is the memory distribution of the hack?
O-15 are 16 virtual registers // notice that everything is on the RAM! 16-255 are static variables 256-2047 is the stack 2048-16384 is the heap 16384-24575 is memory mapped I/O
What are the 16 virtual registers?
SP RAM[0], LCL RAM[1], ARG RAM[2], THIS RAM [3], THAT RAM[4].
RAM[5-12] is temp, RAM[13-15] are general purpose
How to do memory segment mapping from vm to asm?
We have the 4 virtual registers that are mapped to the RAM.
AnY entry to one of those segments should be translated as
: if to the i’th entry of LCL for example
(base + i).
How does access to pointer memory should be decoded?
Pointer i should be treated as access RAM[3 +i]
How does access to temp should be decoded?
temp i should be RAM[5 + i]
How to write arithmetic command?
Pop = @sp, AM = M-1// A = memory[0] -1..takes the sp down D=M//put the data in D If binary... @sp AM=M-1, A=M Let's say add command D=D+A Now we should push D @sp, A=M, M=D, @sp, M=M+1
When implementing a call xxx operation, what is the return address?
The address of the next command in the caller’s code.
What are the 3 program flow commands in the vm?
Label label
Goto label
If-goto label
What is the label label command?
His command labels the current location in the function’s code. Only label locations can be jumped to from other parts of the program? The scope is the function where it is defined
What is goto label command?
Effects an unconditional goto operation, causing execution to continue from the location marked by the label. The jump destination must be located at the same function
What is if-goto label command?
The stack topmost element is popped. If the value is not zero, execution continues from the location marked by the label
Method bar in class foo in jack language will be compiled to?
To a vm function named foo.bar
What are the 3 function related commands?
Function f n
Call f m
Return
What is the function
Function f n?
Here starts the code of a function named f that has n local variables.
Implemantation:
Repeat n times:
PUSH 0
What is the function
Call f m?
Call function f, stating that m arguments have already been pushed onto the stack by the caller Implementation: Push return-address Push LCL Push ARG push THIS push THAT ARG = sp - m -5 //in order to reposition ARG TO THE called func LCL = sp Goto f (return address)
What is the function
Return?
FIX THIS PAGE 164
Return to the calling function Implementation: FRAME =LCL // frame is temporary RET = *(FRAME - 5) *ARG = pop() Sp = ARG + 1 THAT = *(FRAME - 1)
What is the protocol of the calling function?
- The caller has to push as many arguments as needed
- The caller invokes the function using the call command
- After the called function has returned, the arguments that the caller pushed are no longer in the stack and the topmost element is the return parameter
- After the called function returns, the caller’s memory segments argument, local, static,this,that,pointer are the same as they were and the temp segment is undefined!
What is the called function protocol?
When it starts, it’s argument segment is already initialized with actual values and it’s local variables segment has been allocated and init to zeros.
- The static segments the static segment of the vm file and the working stack is empty
- The segments this, that, pointer and temp are undefined
- Before return the called function must push an element into the stack
What is a must to start a vm program?
Each vm program has to have Sys.init function.
