CSE443 Compilers Dr. Carl Alphonce alphonce@buffalo.edu 343 Davis - PowerPoint PPT Presentation

CSE443 Compilers Dr. Carl Alphonce alphonce@buffalo.edu 343 Davis Hall http:/ /www.cse.buffalo.edu/faculty/alphonce/SP17 /CSE443/index.php https:/ /piazza.com/class/iybn4ndqa1s3ei

Phases of a compiler Intermediate Representation (IR): specification and generation Figure 1.6, page 5 of text

6.6.4 Control-flow translation of Boolean Expressions B1.false = newlabel() B1.true = B.true B2.true = B.true B -> B1 || B2 B2.false = B.false B.code = B1.code || label(B1.false) || B2.code B1.true B2.true B.true newlabel() B1 B2 B2.false B1.false B.false

6.6.4 Control-flow translation of Boolean Expressions backpatch(B1.falselist, M.instr) B.truelist = merge(B1.truelist, B2.truelist) B -> B1 || M B2 B.falselist = B2.falselist B1.truelist B2.truelist B.truelist M B1 B2 B.falselist B2.falselist B1.falselist

6.6.4 Control-flow translation of Boolean Expressions B1.true = newlabel() B1.false = B.false B2.false = B.false B -> B1 && B2 B2.true = B.true B.code = B1.code || label(B1.true) || B2.code B1.false B2.false B.false newlabel() B1 B2 B2.true B1.true B.true

6.6.4 Control-flow translation of Boolean Expressions backpatch(B1.truelist, M.instr) B.falselist = merge(B1.falselist, B2.falselist) B -> B1 && M B2 B.truelist = B2.truelist B1.falselist B2.falselist B.falselist M B1 B2 B.truelist B2.truelist B1.truelist

6.7.3 Backpatching Flow-of-Control statements B.true = newlabel() B.false = newlabel() S -> if (B) S1 S1.next = S2.next = S.next else S2 S.code = B.code || label(B.true) || S1.code || gen('goto',S.next) || label(B.false) || S2.code backpatch(B.truelist, M1.instr) S -> if (B) M1 S1 backpatch(B.falselist, M2.instr) N else M2 S2 temp = merge(S1.nextlist, N.nextlist) S.nextlist = merge(temp, S2.nextlist)

6.6.4 Control-flow translation of Boolean Expressions B.true = newlabel() B.false = newlabel() S -> if (B) S1 S1.next = S2.next = S.next else S2 S.code = B.code || label(B.true) || S1.code || gen('goto',S.next) || label(B.false) || S2.code newlabel() B1.true S1 B newlabel() S2 B1.false

6.6.4 Control-flow translation of Boolean Expressions backpatch(B.truelist, M1.instr) S -> if (B) M1 S1 backpatch(B.falselist, M2.instr) N else M2 S2 temp = merge(S1.nextlist, N.nextlist) S.nextlist = merge(temp, S2.nextlist) M1 B1.truelist S1 N B M2 S2 B1.falselist

WW example Show the intermediate code that should result from processing the following statement: while ( x < 25 ) { x := x + 1; }

WW example Show the intermediate code that should result from processing the following statement: x = … while ( x < 25 ) { x := x + 1; }

WW example Show the intermediate code that should result from processing the following statement: x = … 100: x1 = … 101: goto 106 while ( x < 25 ) { 102: if x2 < 25 goto 004 x := x + 1; 103: goto 008 } 104: t1 = x2 + 1 105: x3 = t2 105: goto 001 106: x2 = 𝜚 (x1,x3) 107: goto 102 108: "rest of program"