vfp emulation is not necessary for these machines.  this is done
for consistency.

Reference: /n/atom/patch/applied2013/vfpemu
Date: Sat Jun 15 04:22:23 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/9/teg2/fpiarm.c	Sat Jun 15 04:22:00 2013
+++ /sys/src/9/teg2/fpiarm.c	Sat Jun 15 04:22:00 2013
@@ -15,18 +15,13 @@
 #include	"arm.h"
 #include	"../port/fpi.h"
 
-#define ARM7500			/* emulate old pre-VFP opcodes */
-
 /* undef this if correct kernel r13 isn't in Ureg;
  * check calculation in fpiarm below
  */
 
+
 #define	REG(ur, x) (*(long*)(((char*)(ur))+roff[(x)]))
-#ifdef ARM7500
 #define	FR(ufp, x) (*(Internal*)(ufp)->regs[(x)&7])
-#else
-#define	FR(ufp, x) (*(Internal*)(ufp)->regs[(x)&(Nfpregs - 1)])
-#endif
 
 typedef struct FP2 FP2;
 typedef struct FP1 FP1;
@@ -63,7 +58,7 @@
 	OFR(r12), OFR(r13), OFR(r14), OFR(pc),
 };
 
-static Internal fpconst[8] = {		/* indexed by op&7 (ARM 7500 FPA) */
+static Internal fpconst[8] = {	/* indexed by op&7 */
 	/* s, e, l, h */
 	{0, 0x1, 0x00000000, 0x00000000}, /* 0.0 */
 	{0, 0x3FF, 0x00000000, 0x08000000},	/* 1.0 */
@@ -163,10 +158,6 @@
 	}
 }
 
-/*
- * ARM 7500 FPA opcodes
- */
-
 static	FP1	optab1[16] = {	/* Fd := OP Fm */
 [0]	{"MOVF",	fmov},
 [1]	{"NEGF",	fmovn},
@@ -458,15 +449,102 @@
 	}
 }
 
+void
+casemu(ulong pc, ulong op, Ureg *ur)
+{
+	ulong *rp, ro, rn, *rd;
+
+	USED(pc);
+
+	rp = (ulong*)ur;
+	ro = rp[op>>16 & 0x7];
+	rn = rp[op>>0 & 0x7];
+	rd = rp + (op>>12 & 0x7);
+	rp = (ulong*)*rd;
+	validaddr((ulong)rp, 4, 1);
+	splhi();
+	if(*rd = (*rp == ro))
+		*rp = rn;
+	spllo();
+}
+
+int ldrexvalid;
+
+void
+ldrex(ulong pc, ulong op, Ureg *ur)
+{
+	ulong *rp, *rd, *addr;
+
+	USED(pc);
+
+	rp = (ulong*)ur;
+	rd = rp + (op>>16 & 0x7);
+	addr = (ulong*)*rd;
+	validaddr((ulong)addr, 4, 0);
+	ldrexvalid = 1;
+	rp[op>>12 & 0x7] = *addr;
+	if(fpemudebug)
+		print("ldrex, r%ld = [r%ld]@0x%8.8p = 0x%8.8lux",
+			op>>12 & 0x7, op>>16 & 0x7, addr, rp[op>>12 & 0x7]);
+}
+
+void
+clrex(ulong, ulong, Ureg *)
+{
+	ldrexvalid = 0;
+	if(fpemudebug)
+		print("clrex");
+}
+
+void
+strex(ulong pc, ulong op, Ureg *ur)
+{
+	ulong *rp, rn, *rd, *addr;
+
+	USED(pc);
+
+	rp = (ulong*)ur;
+	rd = rp + (op>>16 & 0x7);
+	rn = rp[op>>0 & 0x7];
+	addr = (ulong*)*rd;
+	validaddr((ulong)addr, 4, 1);
+	splhi();
+	if(ldrexvalid){
+		if(fpemudebug)
+			print("strex valid, [r%ld]@0x%8.8p = r%ld = 0x%8.8lux",
+				op>>16 & 0x7, addr, op>>0 & 0x7, rn);
+		*addr = rn;
+		ldrexvalid = 0;
+		rp[op>>12 & 0x7] = 0;
+	}else{
+		if(fpemudebug)
+			print("strex invalid, r%ld = 1", op>>16 & 0x7);
+		rp[op>>12 & 0x7] = 1;
+	}
+	spllo();
+}
+
+struct {
+	ulong	opc;
+	ulong	mask;
+	void	(*f)(ulong, ulong, Ureg*);
+} specialopc[] = {
+	{ 0x01900f9f, 0x0ff00fff, ldrex },
+	{ 0x01800f90, 0x0ff00ff0, strex },
+	{ 0xf57ff01f, 0xffffffff, clrex },
+	{ 0x0ed00100, 0x0ef08100, casemu },
+	{ 0x00000000, 0x00000000, nil }
+};
+
 /*
  * returns the number of FP instructions emulated
  */
 int
 fpiarm(Ureg *ur)
 {
-	ulong op, o, cp;
+	ulong op, o;
 	FPsave *ufp;
-	int n;
+	int i, n;
 
 	if(up == nil)
 		panic("fpiarm not in a process");
@@ -475,15 +553,11 @@
 	 * because all the emulated fp state is in the proc structure,
 	 * it need not be saved/restored
 	 */
-	switch(up->fpstate){
-	case FPactive:
-	case FPinactive:
-		error("illegal instruction: emulated fpu opcode in VFP mode");
-	case FPinit:
-		assert(sizeof(Internal) <= sizeof(ufp->regs[0]));
-		up->fpstate = FPemu;
+	if(up->fpstate != FPactive){
+//		assert(sizeof(Internal) == sizeof(ufp->regs[0]));
+		up->fpstate = FPactive;
 		ufp->control = 0;
-		ufp->status = (0x01<<28)|(1<<12); /* sw emulation, alt. C flag */
+		ufp->status = (0x01<<28)|(1<<12);	/* software emulation, alternative C flag */
 		for(n = 0; n < 8; n++)
 			FR(ufp, n) = fpconst[0];
 	}
@@ -493,14 +567,20 @@
 		if(fpemudebug)
 			print("%#lux: %#8.8lux ", ur->pc, op);
 		o = (op>>24) & 0xF;
-		cp = (op>>8) & 0xF;
-		if(!ISFPAOP(cp, o))
+		if(condok(ur->psr, op>>28)){
+			for(i = 0; specialopc[i].f; i++)
+				if((op & specialopc[i].mask) == specialopc[i].opc)
+					break;
+			if(specialopc[i].f)
+				specialopc[i].f(ur->pc, op, ur);
+			else if((op & 0xF00) != 0x100 || o != 0xE && (o&~1) != 0xC)
+				break;
+			else
+				fpemu(ur->pc, op, ur, ufp);
+		}else if((op & 0xF00) != 0x100 || o != 0xE && (o&~1) != 0xC)
 			break;
-		if(condok(ur->psr, op>>28))
-			fpemu(ur->pc, op, ur, ufp);
-		ur->pc += 4;		/* pretend cpu executed the instr */
+		ur->pc += 4;
 	}
-	if(fpemudebug)
-		print("\n");
+	if(fpemudebug) print("\n");
 	return n;
 }
--- /sys/src/9/omap/fpiarm.c	Sat Jun 15 04:22:00 2013
+++ /sys/src/9/omap/fpiarm.c	Sat Jun 15 04:22:00 2013
@@ -549,7 +549,8 @@
 	if(up == nil)
 		panic("fpiarm not in a process");
 	ufp = &up->fpsave;
-	/* because all the state is in the proc structure,
+	/*
+	 * because all the emulated fp state is in the proc structure,
 	 * it need not be saved/restored
 	 */
 	if(up->fpstate != FPactive){