cmd/5c, cmd/6c, cmd/8c: make failure to optimize fatal

LGTM=bradfitz, dave, r
R=r, bradfitz, dave
CC=golang-codereviews
https://golang.org/cl/152250044

src/cmd/5c/reg.c

@@ -406,7 +406,7 @@ loop2:
 			rgp->cost = change;
 			nregion++;
 			if(nregion >= NRGN) {
-				warn(Z, "too many regions");
+				fatal(Z, "too many regions");
 				goto brk;
 			}
 			rgp++;
@@ -642,11 +642,8 @@ mkvar(Addr *a, int docon)
 	if(s)
 		if(s->name[0] == '.')
 			goto none;
-	if(nvar >= NVAR) {
-		if(debug['w'] > 1 && s)
-			warn(Z, "variable not optimized: %s", s->name);
-		goto none;
-	}
+	if(nvar >= NVAR)
+		fatal(Z, "variable not optimized: %s", s->name);
 	i = nvar;
 	nvar++;
 	v = &var[i];

src/cmd/6c/reg.c

@@ -585,14 +585,11 @@ loop2:
 			}
 			rgp->cost = change;
 			nregion++;
-			if(nregion >= NRGN) {
-				warn(Z, "too many regions");
-				goto brk;
-			}
+			if(nregion >= NRGN)
+				fatal(Z, "too many regions");
 			rgp++;
 		}
 	}
-brk:
 	qsort(region, nregion, sizeof(region[0]), rcmp);
 
 	/*
@@ -808,11 +805,8 @@ mkvar(Reg *r, Addr *a)
 			goto out;
 		v++;
 	}
-	if(nvar >= NVAR) {
-		if(debug['w'] > 1 && s)
-			warn(Z, "variable not optimized: %s", s->name);
-		goto none;
-	}
+	if(nvar >= NVAR)
+		fatal(Z, "variable not optimized: %s", s->name);
 	i = nvar;
 	nvar++;
 	v = &var[i];

src/cmd/8c/reg.c

@@ -518,7 +518,7 @@ loop2:
 			rgp->cost = change;
 			nregion++;
 			if(nregion >= NRGN) {
-				warn(Z, "too many regions");
+				fatal(Z, "too many regions");
 				goto brk;
 			}
 			rgp++;
@@ -746,11 +746,8 @@ mkvar(Reg *r, Addr *a)
 			goto out;
 		v++;
 	}
-	if(nvar >= NVAR) {
-		if(debug['w'] > 1 && s)
-			warn(Z, "variable not optimized: %s", s->name);
-		goto none;
-	}
+	if(nvar >= NVAR)
+		fatal(Z, "variable not optimized: %s", s->name);
 	i = nvar;
 	nvar++;
 	v = &var[i];