Flow of Control .

S if E then S1 else S2	S.else := newlabel
	S.after := newlabel
E.code	S.code = E.code ||
if E.place = 0 goto S.else	gen(if E.place = 0 goto S.else) ||
S1 .code	S 1 .code ||
goto S.after	gen(goto S.after) ||
S.else:	gen(S.else :) ||
S 2 .code	gen(S.after :)
S.after:

In translating the if-then-else statement the Boolean expression E jumps out of it to the first instruction of the code for S1 if E is true, and to first instruction of the code for S2 if E is false, as illustrated in the figure above. As with the if-then statement, an inherited attribute s.next gives the label of the three-address instruction to be executed next after executing the code for S. An explicit goto S.next appears after the code for S1, but not after S2.