一个完整的编译器前端(Java 实现)
李欣
4月 17, 2018
LiXinCompiler
Referenced from the dragon-book, just a little implementation of the dragon-book language.
参考自龙书上的语言，自己实现了一个编译器的前端。
GitHub链接
博客文章链接
源语言
这个语言由一个程序和一个块组成，该块中包含可选的声名和语句。语法符号basic表示基本类型。
program -> block
block -> { declause statemets }
declause -> decaluse debracket | ϵ
debrcket -> type identity ;
type -> type [ num ] | basic
statements -> statements statement | ϵ
为了简化翻译工作，我们把赋值当成了一个语句.
statement -> location = bool ;
| if ( bool ) statement
| if ( bool ) stetement else statement
| while ( bool ) statement
| do statement while ( bool ) ;
| break ;
| block
location -> location [ bool ] | identity
表达式的产生式处理了运算符的结合性和优先级。它们对每个优先级都使用了一个非终结符号，而非终结符号factor用来表示括号中的表达式、标识符、数组引用和常量.
bool -> bool || join | join
join -> join && equality | equality
equality -> equality == relation | equality != relation | relation
relation -> expression < expression | expressoion <= expression |
expressoion >= expression | expressoion > expression | expression
expression -> expression + term | expression - term | term
term -> term * unary | term / unary | unary
factor -> ( bool ) | location | numeric | real | true | false
测试样例
block:
输入
lxc>
{
int a; int b; a = 0; b = 0;
{
int b; b = 1;
{
int a; a = 2;
}
{
int b; b = 3;
}
a = a + 1; b = b + 1;
}
a = a + 1; b = b + 1;
}
输出
L1: a = 0
L3: b = 0
L4: b = 1
L6: a = 2
L7: b = 3
L8: a = a + 1
L9: b = b + 1
L5: a = a + 1
L10: b = b + 1
L2:
expression:
输入
lxc>
{
int i; float x; bool b;
i = 0;
i = 365;
x = 0.0;
x = 3.14159;
b = true;
b = false;
i = x;
x = i;
}
输出
L1: i = 0
L3: i = 365
L4: x = 0.0
L5: x = 3.1415896
L6: b = true
L7: b = false
L8: i = x
L9: x = i
L2:
identity:
输入
lxc>
{
int i; int j; float[10][10] a;
i = 0;
while ( i < 10 ) {
j = 0;
while ( j < 10 ) {
a[i][j] = 0.0;
j = j + 1;
}
i = i + 1;
}
i = 0;
while ( i < 10 ) {
a[i][i] = 1.0;
i = i + 1;
}
}
输出
L1: i = 0
L3: if not i < 10 goto L4
L5: j = 0
L6: if not j < 10 goto L7
L8: t1 = i * 80
t2 = j * 8
t3 = t1 + t2
a [ t3 ] = 0.0
L9: j = j + 1
goto L6
L7: i = i + 1
goto L3
L4: i = 0
L10: if not i < 10 goto L2
L11: t4 = i * 80
t5 = i * 8
t6 = t4 + t5
a [ t6 ] = 1.0
L12: i = i + 1
goto L10
L2:
jump:
输入
lxc>
{
int x; int y; int a; int b;
if( true ) a = 0;
if( false ) x = 0;
if ( a < b ) a = b;
if ( x <= y ) x = y;
if ( a == b ) a = b;
if ( x != y ) x = y;
if ( a >= b ) b = a;
if ( x > y ) y = x;
if ( a == b );
if( x < 100 || x > 200 ) x = 0;
if( a < 100 && a > 200 ) b = 0;
if( x < 100 || (x > 200 && x != y) ) x = 0;
if( a < 100 || (a > 200 && a != 150) || a != 0 ) a = 0;
if( x > 200 && x != b || x < 100 ) x = 0;
if( a < 100 || a > 200 && a != b ) a = 0;
}
输出
L1:L4: a = 0
L3: goto L5
L6: x = 0
L5: if not a < b goto L7
L8: a = b
L7: if not x <= y goto L9
L10: x = y
L9: if not a == b goto L11
L12: a = b
L11: if not x != y goto L13
L14: x = y
L13: if not a >= b goto L15
L16: b = a
L15: if not x > y goto L17
L18: y = x
L17: if not a == b goto L19
L20:L19: if x < 100 goto L23
if not x > 200 goto L21
L23:L22: x = 0
L21: if not a < 100 goto L24
if not a > 200 goto L24
L25: b = 0
L24: if x < 100 goto L28
if not x > 200 goto L26
if not x != y goto L26
L28:L27: x = 0
L26: if a < 100 goto L31
if a != 150 goto L31
L32: if not a != 0 goto L29
L31:L30: a = 0
L29: if x != b goto L35
L36: if not x < 100 goto L33
L35:L34: x = 0
L33: if a < 100 goto L38
if not a > 200 goto L2
if not a != b goto L2
L38:L37: a = 0
L2:
program:
输入
lxc>
{
int i; int j; float v; float x; float[100] a;
while( true ) {
do i = i+1; while( a[i] < v);
do j = j-1; while( a[j] > v);
if( i >= j ) break;
x = a[i]; a[i] = a[j]; a[j] = x;
}
}
输出
L1:L3: i = i + 1
L5: t1 = i * 8
t2 = a [ t1 ]
if t2 < v goto L3
L4: j = j - 1
L7: t3 = j * 8
t4 = a [ t3 ]
if t4 > v goto L4
L6: if not i >= j goto L8
L9: goto L2
L8: t5 = i * 8
x = a [ t5 ]
L10: t6 = i * 8
t7 = j * 8
t8 = a [ t7 ]
a [ t6 ] = t8
L11: t9 = j * 8
a [ t9 ] = x
goto L1
L2:
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本文链接：http://Great-Li-Xin.github.io/2018/04/17/LiXinCompiler/