The document summarizes the key components of a toy compiler, including the front end, back end, and their functions. The front end performs lexical, syntax and semantic analysis to determine the validity and meaning of source statements. It outputs symbol tables and intermediate code. The back end performs memory allocation and code generation using the symbol tables and intermediate code. Code generation determines instruction selection and addressing modes to synthesize assembly code from the intermediate representation.

1. Toy Compiler

2. Toy compiler
Front end :
It performs lexical , syntax and semantic Involved functions…
1.Determining validity of a source statement from the view point
of analysis.
2.Determine the “content” of source statement.
3.Construct a suitable representation of the source statement for
being used by subsequent analysis function (or)the synthesis
phase of the language processor.

3. FrontEnd…
•Lexical analysis=Content in lexical class.
•Syntax analysis=syntactic structure of source
statement.
•Semantic analysis=In meaning of statement
_ For a declaration statement
_ It is set of attributes of a declared variable
Example: Type, length and dimensionality

4. FrontEnd…
Output of Front end:
1.Tables of information.
2.An intermediate code which is the
description of the source program.

5. Analysis phase for the program..
I : integer;
a ,b :=real;
a :=b+I;
Symbol table:
Intermediate code:
1.Convert(Id,#1)to real , giving(Id,#4)
2.Add(Id,#4)to(Id,#3),giving(Id,#5)
3.Store(Id,#5)in(Id,#2)
Symbol type length address
i int
a real
b real
i* real
Temp real

6. Lexical analysis(scanning):
Identifies lexical units in source statement.Its
Classifies units into different lexical classes.
Eg: id’s,constants,reserved id’s etc.
Eg:the statement a := b+i represented as string
of tokens.
Id#2 Op#5 Id#3 OP#3 Id#1 Op#10

7. Syntax Analysis:
Syntax analysis processes the string of tokens
built by lexical analysis to determine the
statement classes.
Eg: assignment statement,if statement ,etc..
real :=
a b a +
b i

8. •Semantic Analysis:
:= := :=
a,real + a,real + a,real temp,real
b,real i,int b,real i*,real

9. Back End:
• Involves Two phases
• Memory Allocation
• Code Generation

10. Memory Allocation
• It is a simple task given the presence of the
symbol table.
• The memory requirement of an identifier is
computed from its type,length,dimensionality
and memory is allocated
• For example
Symbol Type Length Address
1 i int 2000
2 a real 2001
3 a real 2002

11. Code Generation
• It uses knowledge of the target architectue i.e.. Knowledge of
instructions and addressing modes
• Issues
• 1.Detremine the places where the intermediate results to be
kept (either on memory locations or in machine registers)
• 2.Determine which instruction should be used for type
conversion
• 3.determine which addressing mode to be used while
accessing variables.

12. Code Generation
• a:=b+i
• 1.convert I to real, giving i*
• 2.add i* to b giving temp
• 3.store temp in a
• Synthesis phase may decide to hold values of i* and temp in
machine register and may generate assembly code
• CONV_R AREG,I
• ADD_R AREG,B
• MOVEM AREG,A