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5c: dont emit conditional integer division instructions

the integer division instructions are emulated with _div()
function patched in by 5l which does not handle conditional
execution. so do not optimize away the branch in that case.

--- a/sys/src/cmd/5c/peep.c

+++ b/sys/src/cmd/5c/peep.c

@@ -1354,6 +1354,15 @@

 			j->end = r->s2;

 			return Branch;

 		}

+		switch(r->prog->as){

+		case ADIV:

+		case ADIVU:

+		case AMOD:

+		case AMODU:

+			/* emulated by 5l, doesnt handle conditionals */

+			j->end = r->s1;

+			return Toolong;

+		}

 		if (modifiescpsr(r->prog)) {

 			j->end = r->s1;

 			return Setcond;

-- 

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