5c: implement uint32 -> float

There are other missing conversion cases
still but they do not show up in my tests.
This one is needed for vlrt.c's _v2d (int64, uint64 -> float).

Thankfully, VFP has a single instruction to do this.

R=ken2
CC=golang-dev
https://golang.org/cl/2726041

src/cmd/5c/txt.c

@@ -580,7 +580,8 @@ void
 gmove(Node *f, Node *t)
 {
 	int ft, tt, a;
-	Node nod;
+	Node nod, nod1;
+	Prog *p1;
 
 	ft = f->type->etype;
 	tt = t->type->etype;
@@ -709,21 +710,53 @@ gmove(Node *f, Node *t)
 		}
 		break;
 	case TUINT:
-	case TINT:
 	case TULONG:
+		if(tt == TFLOAT || tt == TDOUBLE) {
+			// ugly and probably longer than necessary,
+			// but vfp has a single instruction for this,
+			// so hopefully it won't last long.
+			//
+			//	tmp = f
+			//	tmp1 = tmp & 0x80000000
+			//	tmp ^= tmp1
+			//	t = float(int32(tmp))
+			//	if(tmp1)
+			//		t += 2147483648.
+			//
+			regalloc(&nod, f, Z);
+			regalloc(&nod1, f, Z);
+			gins(AMOVW, f, &nod);
+			gins(AMOVW, &nod, &nod1);
+			gins(AAND, nodconst(0x80000000), &nod1);
+			gins(AEOR, &nod1, &nod);
+			if(tt == TFLOAT)
+				gins(AMOVWF, &nod, t);
+			else
+				gins(AMOVWD, &nod, t);
+			gins(ACMP, nodconst(0), Z);
+			raddr(&nod1, p);
+			gins(ABEQ, Z, Z);
+			regfree(&nod);
+			regfree(&nod1);
+			p1 = p;
+			regalloc(&nod, t, Z);
+			gins(AMOVF, nodfconst(2147483648.), &nod);
+			gins(AADDF, &nod, t);
+			regfree(&nod);
+			patch(p1, pc);
+			return;
+		}
+		// fall through
+	
+	case TINT:
 	case TLONG:
 	case TIND:
 		switch(tt) {
 		case TDOUBLE:
-		case TVLONG:
 			gins(AMOVWD, f, t);
-			if(ft == TULONG) {
-			}
 			return;
 		case TFLOAT:
 			gins(AMOVWF, f, t);
-			if(ft == TULONG) {
-			}
 			return;
 		case TINT:
 		case TUINT:
@@ -741,7 +774,6 @@ gmove(Node *f, Node *t)
 	case TSHORT:
 		switch(tt) {
 		case TDOUBLE:
-		case TVLONG:
 			regalloc(&nod, f, Z);
 			gins(AMOVH, f, &nod);
 			gins(AMOVWD, &nod, t);
@@ -771,7 +803,6 @@ gmove(Node *f, Node *t)
 	case TUSHORT:
 		switch(tt) {
 		case TDOUBLE:
-		case TVLONG:
 			regalloc(&nod, f, Z);
 			gins(AMOVHU, f, &nod);
 			gins(AMOVWD, &nod, t);
@@ -801,7 +832,6 @@ gmove(Node *f, Node *t)
 	case TCHAR:
 		switch(tt) {
 		case TDOUBLE:
-		case TVLONG:
 			regalloc(&nod, f, Z);
 			gins(AMOVB, f, &nod);
 			gins(AMOVWD, &nod, t);
@@ -831,7 +861,6 @@ gmove(Node *f, Node *t)
 	case TUCHAR:
 		switch(tt) {
 		case TDOUBLE:
-		case TVLONG:
 			regalloc(&nod, f, Z);
 			gins(AMOVBU, f, &nod);
 			gins(AMOVWD, &nod, t);