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Test Yourself #2
Test Yourself #3
• Initial code: a := x ** 2 b := 3 c := x d := c * c e := b * 2 f := a + d g := e * f
An Example
• Algebraic optimization: a := x ** 2 b := 3 c := x d := c * c e := b * 2 f := a + d g := e * f
An Example
• Algebraic optimization: a := x * x b := 3 c := x d := c * c e := b << 1 f := a + d g := e * f
An Example
• Copy propagation: a := x * x b := 3 c := x d := c * c e := b << 1 f := a + d g := e * f
An Example
• Copy propagation: a := x * x b := 3 c := x d := x * x e := 3 << 1 f := a + d g := e * f
An Example
• Constant folding: a := x * x b := 3 c := x d := x * x e := 3 << 1 f := a + d g := e * f
An Example
• Constant folding: a := x * x b := 3 c := x d := x * x e := 6 f := a + d g := e * f
An Example
• Common subexpression elimination: a := x * x b := 3 c := x d := x * x e := 6 f := a + d g := e * f
An Example
• Common subexpression elimination: a := x * x b := 3 c := x d := a e := 6 f := a + d g := e * f
An Example
• Copy propagation: a := x * x b := 3 c := x d := a e := 6 f := a + d g := e * f
An Example
• Copy propagation: a := x * x b := 3 c := x d := a e := 6 f := a + a g := 6 * f
An Example
• Dead code elimination: a := x * x b := 3 c := x d := a e := 6 f := a + a g := 6 * f
An Example
• Dead code elimination: a := x * x
f := a + a g := 6 * f
• This is the final form
Test Yourself #4
. תכנוה נורשת
Int id1,id2
D
T L
INT L
ID1
ID2,
L.in
T.type
L.in
DL
LL1,id {L.in = L1.in;
addtype(id.entery,L1.in);}
LT id {L.in = T.type;
addtype(id.entery,T.type);}
Tint | {T.type= integer;}
real {T.type= real;}
פתרון:
DInt id1,id2
L
L1 , id1
T id2
9תרגיל
פתרון
E.true:
S1.next=E.false
S2.next=E.true
E.place++If(E.place=3)
Goto S.nextS1.code
E.place++If(E.place=3)
Goto S.nextS2.code
Goto E.true
E.false:
S.next:
E.trueE.place=0
E.code E.false
S if E then start with S1 else start with S2
{S.code=Gen(E.place’=0’) ||
E.code ||
gen(E.true ‘:’ E.place ‘++ if(’ E.place ‘=3) goto’ S.next ) ||
S1.code ||
gen(E.false ‘:’ E.place ‘++ if(’ E.place ‘=3) goto’ S.next ) ||
S2.code ||
gen(‘goto’ E.true) }
Backpatchingפתרון עם
S if R E then start with M1 T1 S1 else start with M2 T2 S2
{S.next_list= merge(T1.next_list,T2.next_list)
backpatch (E.true_list, M1.quad)
backpatch (E.false_list, M2.quad)
backpatch (S1.next_list,M2.quad)
backpatch (S2.next_list,M1_quad)
Emit(‘goto’ M1.quad) }
R ε {Emit(E.place=0(}
T ε {Emit(E.place ‘++(
T.next_list=makelist(nextquad);
Emit(if(’ E.place ‘=3) goto’ _______) )}
דוגמא:• S if a<b then start with a:=1 else start
with if true then b:=2100: E.place =0 /* Produced by R ε*/
101: if a < b goto______ /*Produced by Ea <b*/
102: goto_______ /* Produced by Ea <b */
103: E.place++; /*Produced by T1ε*/
104: if E.place ==3 goto________ /*Produced by T1ε*/
105: a:=1 /*Produces by S1a:=1*/
106: E.place++; /*Produced by T2ε*/107: if E.place ==3 goto________ /*Produced by T2ε*/
108: goto___ /*Produced by ETRUE*/
109: b:=2 /*Produced by b:=2*/
110: goto 103 /*Produces by S if E then start with ….*/
דוגמא:• S if a<b then start with a:=1 else start
with if true then b:=2100: E.place =0 /* */
101: if a < b goto__103 (M1.quad) /* Backpatched by S if E then start with…*/
102: goto__106 (M2.quad) /* Backpatched by S if E then start with…*/
103: E.place++; /**/
104: if E.place ==3 goto________ /**/
105: a:=1 /**/
106: E.place++; /**/107: if E.place ==3 goto________ /**/
108: goto___ /**/
109: b:=2 /**/
110: goto 103 /**/
דוגמא:• S if a<b then start with a:=1 else start
with if true then b:=2100: E.place =0 /* */
101: if a < b goto__103 (M1.quad) /* Backpatched by S if E then start with…*/
102: goto__106 (M2.quad) /* Backpatched by S if E then start with…*/
103: E.place++; /**/
104: if E.place ==3 goto________ /**/
105: a:=1 /**/
106: E.place++; /**/107: if E.place ==3 goto________ /**/
108: goto__109 /*Backpatched by S if E then S1*/
109: b:=2 /**/
110: goto 103 /**/
דוגמא:• S if a<b then start with a:=1 else start
with if true then b:=2100: E.place =0 /* */
101: if a < b goto__103 (M1.quad) /* Backpatched by S if E then start with…*/
102: goto__106 (M2.quad) /* Backpatched by S if E then start with…*/
103: E.place++; /**/
104: if E.place ==3 goto________ /* Can’t BAckpatched but S.next_list 104*/
105: a:=1 /**/
106: E.place++; /**/107: if E.place ==3 goto________ /*Can’t BAckpatched but S.next_list 107*/
108: goto__109 /*Backpatched by S if E then S1*/
109: b:=2 /**/
110: goto 103 /**/
Test yourself #5
