jacobin-sctcs / subset_compiler

A compiler which produces intermediate code using flex and bison

MINI COMPILER USING FLEX & BISON

This repository has been created as a part of the compiler assignment . The compiler developed is upto the intermediate code generation phase.

Compiling the Code

  flex lexanalyser.l
  bison -d parser.y
  gcc -c lex.yy.c parser.tab.c
  gcc -o com.out lex.yy.o parser.tab.o
  

The 3rd command produces a warning which can be ignored .

Running the Compiler

The above sequence of commands produces an executable com.out which is our compiler . You can feed in the program to be compiled after typing

followed by the input program . Type exit ; to escape from the process The intermediate code will be available in a file named output.txt .

Alternatively you can write a program in a file and put it in the same directory and you canb compile it by using the redirection operator '<' Suppose the filename is program.txt

      ./com.out < program.txt

Dont Forget to put exit; at the end of the program to terminate compilations.

Intermediate Code will be available in output.txt

Sample programs with their outputs

Program	Intermediate Code
print 5; exit;	t1 := 5; print t1;
print ((5+2)*8); exit;	t1 := 5 + 2 t2 := t1 t3 := t2 * 8 t4 := t3 R1 := t4; print R1;
def samplefunction(t,y) { a = 5; } y=4; d=3; samplefunction(y,d); exit;	PROCEDURE samplefunction t,y R1 := 5; a := R1; ENDP R1 := 4; y := R1; R1 := 3; d := R1; samplefunction(y,d)
def samplefunction(t,y) { a=1; if(a<4) { a = a + 1 ; } } samplefunction(y,d); exit;	PROCEDURE samplefunction t,y R1 := 1; a := R1; t1 := a < 4 R1 := t1 IF NZ GO TO 0LABEL: t2 := a + 1 R1 := t2; a := R1; 0LABEL: ENDP samplefunction(y,d)
a=1; while(a<5) { a=a+1; } exit;	R1 := 1; a := R1; 0_LABEL : t1 := a < 5 R1 := t1 IF NZ GOTO 1_LABEL t2 := a + 1 R1 := t2; a := R1; JMP 0_LABEL 1_LABEL:
ans=1; i=5; while(i > 0) { ans = ans * i; i = i - 1; } print ans; exit;	R1 := 1; ans := R1; R1 := 5; i := R1; 0_LABEL : t1 := i > 0 R1 := t1 IF NZ GOTO 1_LABEL t2 := ans * i R1 := t2; ans := R1; t3 := i - 1 R1 := t3; i := R1; JMP 0_LABEL 1_LABEL: R1 := ans; print R1;
ans=1; i=5; do { ans = ans * i; i = i - 1; } while(i > 0); print ans;	R1 := 1; ans := R1; R1 := 5; i := R1; 0_LABEL: t1 := ans * i R1 := t1; ans := R1; t2 := i - 1 R1 := t2; i := R1; t3 := i > 0 R1 := t3 if nz goto 0_LABEL R1 := ans; print R1;

Documentation

The explanation for code portions are present in the comments in code . If you have difficulty raise an issue .

Contribute

If you feel any changes to be made feel free to issue a pull request . The code performs poorly in memory optimisation for generating code

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