Download LOL6502 Compiler

LOL6502 Compiler
I CAN HAS LOLCODE?
Things for the Day
Summary of the Project
 The Stack Machine – Expanded
 6502 Assembly Output
 LOLCODE examples… by you
 Demonstration
 Conclusions, Future Goals
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What’s featured?
17-bit integers
 All math operations ensure correct sign
 Conversion bool <> int
 Basic STDOUT (bool, int)
 Support for infinite nested structures
 Variable/function scoping implemented
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What’s missing?
math_mul, math_div
 Floats, Strings, heap operations
 to_int, to bool (partial)
 STDIN, STDOUT (partial)
 Any sort of sane error checking and
testing -.
Overall
Standard Library 70% complete, needs
conversion functions (1.4KB code ;_;)
 Strings/heap are a total mess, needs
clarification
 STDIO – missing a lot of functionality
 Macro Compiler – does not need
changing, save for missing features
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Of Stack Machines
Three basic registers: SP, FP, HP
 One global stack used for all operations
 Machine-specific instructions:
push_var/sp/fp, pop_var/fp, stack_swap,
inc/dec_sp
 Conversion instructions:
to_bool, to_int, to_float, to_string, to_undef
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Of Stack Machines
LOLCODE instructions implemented on a
near 1:1 basis
 Examples (LOL = IR = SM)
SUM OF = ADD = math_add
WON OF = XOR = bool_xor
BOTH SAEM = EQUAL = comp_equal

Of Stack Machines
Almost all operations operate on the stack
 We avoid the headaches of: register
allocation, spilling, any sort of memory
operations
 Variables are stored on stack, and offset
from the FP
 Functions make use of a record for calling
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Of Stack Machines
A push_var, will copy the contents of a
variable onto the stack
 Results of an instruction are saved on the
stack
 Why is this better? No instructions have
side effects on variables save for the
ASSIGN instruction (pop_var)

Of Stack Machines
A function call will push space for a return
value, the current FP value, and args
 Resets SP and pops the SP onto the FP
 Jumps to the correct procedure
 Does stuff, returns, pops the saved FP
back into the FP
 Removes return value if function exited

Of Stack Machines
All conditionals and loops create a
temporary local scope for each case
 Macro compiler ensures these FP offsets
are managed properly (at compile time)
 At the time, unable to limit scope of a
function body (will fix later)

ASM Output
SM compiler spits out tons of ASM code
and STDLIB instructions
 i.e. Conditionals/Loops will print out ASM
code to facilitate structure
 STDLIB is oodles upon oodles of ASM that
manipulate the virtual stack (all
handwritten mind you)

ASM Output
Indirect indexed addressing is the mode
used for almost every major instruction
 In theory, there should be an infinite
amount of nested operations available
 However, most instructions use JSR,
which push machine SP to machine stack
 Machine stack limited to one page (256B)
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LOLCODE Examples
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Demonstrate the compiler and simulator using
examples provided by you
ADD, SUB, MOD, MAX, MIN, AND, OR, XOR,
NOT, EQUAL, IAND, IOR
Supports int/bool, STDOUT of those two types
IF-THEN-ELSE, SWITCH-CASE, FOR LOOP
VAR DEF, FUNC DEF, FUNC CALL
ASSIGN, EXPLICIT/IMPLICIT casting
Conclusions
This was a fun, if long and grueling project
 Developing a compiler from start to finish
provided a lot of knowledge into the
complexities of compiler construction
 Creating a virtual stack machine was
insightful in compiling an otherwise
interpreted language

Conclusions
Wrote a lot of ASM – went crazy with the
STDLIB.
 Rewrote the SM twice – better each time,
but still requires work
 Did not plan accordingly to include
heaps/strings (just ran out of time)
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Future Goals
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Finish up the formalization and implementation
of heaps/strings
Finish implementing the STDIO for more useful
examples
Finish the type conversions at run time, and
allow for error recovery
Create a game in LOLCODE to 6502
Write my own 6502 emulator with advanced
features (bitmapped graphics, etc)