6c, 8c: make floating point code NaN-safe

R=ken2
CC=golang-dev
https://golang.org/cl/5569071

Author: rsc

src/cmd/6c/cgen.c

@@ -1237,11 +1237,12 @@ void
 boolgen(Node *n, int true, Node *nn)
 {
 	int o;
-	Prog *p1, *p2;
+	Prog *p1, *p2, *p3;
 	Node *l, *r, nod, nod1;
 	int32 curs;
 
 	if(debug['g']) {
+		print("boolgen %d\n", true);
 		prtree(nn, "boolgen lhs");
 		prtree(n, "boolgen");
 	}
@@ -1353,6 +1354,15 @@ boolgen(Node *n, int true, Node *nn)
 	case OLO:
 	case OLS:
 		o = n->op;
+		if(true && typefd[l->type->etype] && (o == OEQ || o == ONE)) {
+			// Cannot rewrite !(l == r) into l != r with float64; it breaks NaNs.
+			// Jump around instead.
+			boolgen(n, 0, Z);
+			p1 = p;
+			gbranch(OGOTO);
+			patch(p1, pc);
+			goto com;
+		}
 		if(true)
 			o = comrel[relindex(o)];
 		if(l->complex >= FNX && r->complex >= FNX) {
@@ -1367,6 +1377,10 @@ boolgen(Node *n, int true, Node *nn)
 			break;
 		}
 		if(immconst(l)) {
+			// NOTE: Reversing the comparison here is wrong
+			// for floating point ordering comparisons involving NaN,
+			// but we don't have any of those yet so we don't
+			// bother worrying about it.
 			o = invrel[relindex(o)];
 			/* bad, 13 is address of external that becomes constant */
 			if(r->addable < INDEXED || r->addable == 13) {
@@ -1388,10 +1402,11 @@ boolgen(Node *n, int true, Node *nn)
 				cgen(r, &nod1);
 				gopcode(o, l->type, &nod, &nod1);
 				regfree(&nod1);
-			} else
+			} else {
 				gopcode(o, l->type, &nod, r);
+			}
 			regfree(&nod);
-			goto com;
+			goto fixfloat;
 		}
 		regalloc(&nod, r, nn);
 		cgen(r, &nod);
@@ -1406,6 +1421,33 @@ boolgen(Node *n, int true, Node *nn)
 		} else
 			gopcode(o, l->type, l, &nod);
 		regfree(&nod);
+	fixfloat:
+		if(typefd[l->type->etype]) {
+			switch(o) {
+			case OEQ:
+				// Already emitted AJEQ; want AJEQ and AJPC.
+				p1 = p;
+				gbranch(OGOTO);
+				p2 = p;
+				patch(p1, pc);
+				gins(AJPC, Z, Z);
+				patch(p2, pc);
+				break;
+
+			case ONE:
+				// Already emitted AJNE; want AJNE or AJPS.
+				p1 = p;
+				gins(AJPS, Z, Z);
+				p2 = p;
+				gbranch(OGOTO);
+				p3 = p;
+				patch(p1, pc);
+				patch(p2, pc);
+				gbranch(OGOTO);
+				patch(p3, pc);
+				break;
+			}
+		}
 
 	com:
 		if(nn != Z) {

src/cmd/8c/cgen.c

@@ -1221,7 +1221,7 @@ void
 boolgen(Node *n, int true, Node *nn)
 {
 	int o;
-	Prog *p1, *p2;
+	Prog *p1, *p2, *p3;
 	Node *l, *r, nod, nod1;
 	int32 curs;
 
@@ -1346,6 +1346,15 @@ boolgen(Node *n, int true, Node *nn)
 			cgen64(n, Z);
 			goto com;
 		}
+		if(true && typefd[l->type->etype] && (o == OEQ || o == ONE)) {
+			// Cannot rewrite !(l == r) into l != r with float64; it breaks NaNs.
+			// Jump around instead.
+			boolgen(n, 0, Z);
+			p1 = p;
+			gbranch(OGOTO);
+			patch(p1, pc);
+			goto com;
+		}
 		if(true)
 			o = comrel[relindex(o)];
 		if(l->complex >= FNX && r->complex >= FNX) {
@@ -1378,6 +1387,30 @@ boolgen(Node *n, int true, Node *nn)
 				} else
 					fgopcode(o, l, &fregnode0, 0, 1);
 			}
+			switch(o) {
+			case OEQ:
+				// Already emitted AJEQ; want AJEQ and AJPC.
+				p1 = p;
+				gbranch(OGOTO);
+				p2 = p;
+				patch(p1, pc);
+				gins(AJPC, Z, Z);
+				patch(p2, pc);
+				break;
+
+			case ONE:
+				// Already emitted AJNE; want AJNE or AJPS.
+				p1 = p;
+				gins(AJPS, Z, Z);
+				p2 = p;
+				gbranch(OGOTO);
+				p3 = p;
+				patch(p1, pc);
+				patch(p2, pc);
+				gbranch(OGOTO);
+				patch(p3, pc);
+				break;
+			}
 			goto com;
 		}
 		if(l->op == OCONST) {