from cinap: add idiv instruction.


Reference: /n/atom/patch/applied/realemuidiv
Date: Tue Mar  4 21:49:49 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/aux/realemu/main.c	Tue Mar  4 21:49:35 2014
+++ /sys/src/cmd/aux/realemu/main.c	Tue Mar  4 21:49:36 2014
@@ -288,7 +288,7 @@
 	/* B */ nil,	rrealmem, wrealmem,	/* RAM: VGA framebuffer */
 	/* C */ memory,	rmem, wmem,	/* ROM: VGA BIOS */
 	/* D */ nil,	rbad, wbad,
-	/* E */ memory,	rmem, wbad,	/* ROM: BIOS */
+	/* E */ memory,	rmem, wmem,	/* ROM: BIOS */
 	/* F */ memory,	rmem, wbad,	/* ROM: BIOS */
 };
 
--- /sys/src/cmd/aux/realemu/xec.c	Tue Mar  4 21:49:38 2014
+++ /sys/src/cmd/aux/realemu/xec.c	Tue Mar  4 21:49:40 2014
@@ -769,12 +769,45 @@
 	n = (uvlong)ar(ra)<<s | (uvlong)ar(qa);
 	q = n/d;
 	if(q > m)
-		trap(cpu, EGPF);
+		trap(cpu, EDIV0);
 	r = n%d;
 	aw(ra, r);
 	aw(qa, q);
 }
-	
+
+static void
+opidiv(Cpu *cpu, Inst *i)
+{
+	Iarg *qa, *ra;
+	vlong n, q, min, max;
+	long r, d;
+	int s;
+
+	s = i->a1->len*8;
+	d = ars(i->a1);
+	if(d == 0)
+		trap(cpu, EDIV0);
+	if(s == 8){
+		qa = areg(cpu, 1, RAX);
+		ra = adup(qa);
+		ra->tag |= TH;
+	} else {
+		qa = areg(cpu, i->olen, RAX);
+		ra = areg(cpu, i->olen, RDX);
+	}
+	n = (vlong)ars(ra)<<s | (uvlong)ars(qa);
+	q = n/d;
+	r = n%d;
+
+	max = sign(s)-1;
+	min = ~max;
+
+	if(q > max || q < min)
+		trap(cpu, EDIV0);
+
+	aw(ra, r);
+	aw(qa, q);
+}	
 
 static int
 cctrue(Cpu *cpu, Inst *i)
@@ -1249,6 +1282,7 @@
 	[OMUL] = opmul,
 	[OIMUL] = opimul,
 	[ODIV] = opdiv,
+	[OIDIV] = opidiv,
 
 	[OLEA] = oplea,
 	[OMOV] = opmov,