Dragon Compiler,
which took a whole semester,
it breathes fire at last.
PASCAL files can be compiled using the command ./compiler <file_name.p>. The command gcc <file_name.s> will then convert the generated assembly file to an executable, which can be run with ./a.out.
At this point, I think my compiler has successfully implemented all of the required components of a compiler for this class. For more details regarding the specified requirements, please see checklist.txt. All test cases are located in the subdirectory testing/.
My compiler has an incredibly unique strategy to resolve potential if then if then else conflicts. Rather than specifying that each else belongs to the nearest if, I instead modified the keywords so that the two control flow statements are if then and if than else. This will reduce programmer confusion and make it immediately apparent to which if clause the else begins.
I also included a few additional control flow statements, such as repeat ... until and do ... while.
- Register Usage:
rax = return value, division
rbx = for loops
rcx = nonlocal variable access
rsp = stack pointer
rbp = base pointer
rip = instruction pointer
rdi = reserved for io use, temp regs
rsi = reserved for io use, temp regs
rdx = reserved for io use, division
r8 = temp var (top of stack)
r9 = temp var
r10 = temp var
r11 = temp var
r12 = temp var
r13 = temp var
r14 = temp var
r15 = temp var (bottom of stack)
- Stack Frame Contents:
low memory addresses
.
.
.
-------------------
| temp_reg3 | <--- rsp
-------------------
| temp_reg2 |
-------------------
| temp_reg1 |
-------------------
| local3 |
-------------------
| local2 |
-------------------
| local1 |
-------------------
| parent | rbp - 16
-------------------
| return_val | rbp - 8
-------------------
| old_rbp | <--- rbp
-------------------
| old_rip | (automatically added/removed by call/ret)
-------------------
| param3 |
-------------------
| param2 |
-------------------
| param1 |
-------------------
.
.
.
high memory addresses
- Register Stack
------------------- the value of each register is its initial index
| r8 | 7 positive-index values are stored in reg array
------------------- register name is given by static name list
| r9 | 6
-------------------
| r10 | 5
-------------------
| r11 | 4
-------------------
| r12 | 3
-------------------
| r13 | 2
-------------------
| r14 | 1
-------------------
| r15 | 0
------------------------- negative-index values stored in temp array
| temp1 | -1 index 0 of temp array is never used
------------------- names are calculated based on offset from rbp
| temp2 | -2 temp array can grow to arbitrary size
-------------------
| temp3 | -3
-------------------
.
.
.
Some potential extensions of my existing compiler are:
- adding support for strings or pointers
- generating code for arrays and floating point numbers