Code generation
source
code
front
end
opt.
back
end
target
code
IR IR
Code generation steps
1. Source co de
!
intermediate representation
generate intermediate representation during
parse based on syntax, sy mbol tables
2. Intermediate representation
!
target co de
instruction selection
choose inst ructi ons based on target instr set
memory management
decide storage for variables; allo cate registers
linkage code
determine prolog/epi l og code
instruction scheduling
choose inst ructi on execution order
CMSC 430
Lecture 12, Page 1
Abstract syntax trees
Abstract syntax tree (AST)
stores syntactic structure of program
+
<
x
>
*
<
2
> <
y
>
Building the AST
construct no de for LHS of production
ll i n elds using RHS of production
Example
E
0
::= E
1
'+' E
2
f
E
0
.val = node('+', E
1
.val, E
2
.val);
g
j
E
1
'*' E
2
f
E
0
.val = no de('*', E
1
.val, E
2
.val);
g
j
id
f
E
0
.val = no de(
id
.val);
g
j
num
f
E
0
.val = no de(
num
.val);
g
CMSC 430
Lecture 12, Page 2
