diff --git a/src/cmd/5g/cgen.c b/src/cmd/5g/cgen.c
index 90cc88d5a7..354e0cbfd6 100644
--- a/src/cmd/5g/cgen.c
+++ b/src/cmd/5g/cgen.c
@@ -1148,27 +1148,20 @@ bgen(Node *n, int true, int likely, Prog *to)
 		goto ret;
 
 	case OANDAND:
-		if(!true)
-			goto caseor;
-
-	caseand:
-		p1 = gbranch(AB, T, 0);
-		p2 = gbranch(AB, T, 0);
-		patch(p1, pc);
-		bgen(n->left, !true, -likely, p2);
-		bgen(n->right, !true, -likely, p2);
-		p1 = gbranch(AB, T, 0);
-		patch(p1, to);
-		patch(p2, pc);
-		goto ret;
-
 	case OOROR:
-		if(!true)
-			goto caseand;
-
-	caseor:
-		bgen(n->left, true, likely, to);
-		bgen(n->right, true, likely, to);
+		if((n->op == OANDAND) == true) {
+			p1 = gbranch(AJMP, T, 0);
+			p2 = gbranch(AJMP, T, 0);
+			patch(p1, pc);
+			bgen(n->left, !true, -likely, p2);
+			bgen(n->right, !true, -likely, p2);
+			p1 = gbranch(AJMP, T, 0);
+			patch(p1, to);
+			patch(p2, pc);
+		} else {
+			bgen(n->left, true, likely, to);
+			bgen(n->right, true, likely, to);
+		}
 		goto ret;
 
 	case OEQ:
diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index b7a177d4ea..bdb70270a8 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -69,7 +69,7 @@ gclean(void)
 			yyerror("reg %R left allocated\n", i);
 }
 
-int32
+int
 anyregalloc(void)
 {
 	int i, j;
@@ -239,22 +239,25 @@ split64(Node *n, Node *lo, Node *hi)
 	nsclean++;
 	switch(n->op) {
 	default:
-		if(!dotaddable(n, &n1)) {
-			igen(n, &n1, N);
-			sclean[nsclean-1] = n1;
-		}
-		n = &n1;
-		goto common;
-	case ONAME:
-		if(n->class == PPARAMREF) {
-			cgen(n->heapaddr, &n1);
-			sclean[nsclean-1] = n1;
-			// fall through.
+		switch(n->op) {
+		default:
+			if(!dotaddable(n, &n1)) {
+				igen(n, &n1, N);
+				sclean[nsclean-1] = n1;
+			}
 			n = &n1;
+			break;
+		case ONAME:
+			if(n->class == PPARAMREF) {
+				cgen(n->heapaddr, &n1);
+				sclean[nsclean-1] = n1;
+				n = &n1;
+			}
+			break;
+		case OINDREG:
+			// nothing
+			break;
 		}
-		goto common;
-	case OINDREG:
-	common:
 		*lo = *n;
 		*hi = *n;
 		lo->type = types[TUINT32];
diff --git a/src/cmd/5g/peep.c b/src/cmd/5g/peep.c
index fe0969be4b..7fe3e1071f 100644
--- a/src/cmd/5g/peep.c
+++ b/src/cmd/5g/peep.c
@@ -122,15 +122,14 @@ loop1:
 			}
 			break;
 
-#ifdef NOTDEF
-XXX
+			/*
 			if(p->scond == C_SCOND_NONE)
 			if(regtyp(&p->to))
 			if(isdconst(&p->from)) {
 				constprop(&p->from, &p->to, r->s1);
 			}
 			break;
-#endif
+			*/
 		}
 	}
 	if(t)
@@ -562,8 +561,6 @@ gotit:
  * AXXX (x<<y),a,b
  * ..
  */
-#define FAIL(msg) { if(debug['P']) print("\t%s; FAILURE\n", msg); return 0; }
-/*c2go void FAIL(char*); */
 
 int
 shiftprop(Flow *r)
@@ -574,8 +571,11 @@ shiftprop(Flow *r)
 	Adr a;
 
 	p = r->prog;
-	if(p->to.type != TYPE_REG)
-		FAIL("BOTCH: result not reg");
+	if(p->to.type != TYPE_REG) {
+		if(debug['P'])
+			print("\tBOTCH: result not reg; FAILURE\n");
+		return 0;
+	}
 	n = p->to.reg;
 	a = zprog.from;
 	if(p->reg != 0 && p->reg != p->to.reg) {
@@ -588,28 +588,43 @@ shiftprop(Flow *r)
 	for(;;) {
 		/* find first use of shift result; abort if shift operands or result are changed */
 		r1 = uniqs(r1);
-		if(r1 == nil)
-			FAIL("branch");
-		if(uniqp(r1) == nil)
-			FAIL("merge");
+		if(r1 == nil) {
+			if(debug['P'])
+				print("\tbranch; FAILURE\n");
+			return 0;
+		}
+		if(uniqp(r1) == nil) {
+			if(debug['P'])
+				print("\tmerge; FAILURE\n");
+			return 0;
+		}
 		p1 = r1->prog;
 		if(debug['P'])
 			print("\n%P", p1);
 		switch(copyu(p1, &p->to, nil)) {
 		case 0:	/* not used or set */
 			if((p->from.type == TYPE_REG && copyu(p1, &p->from, nil) > 1) ||
-			   (a.type == TYPE_REG && copyu(p1, &a, nil) > 1))
-				FAIL("args modified");
+			   (a.type == TYPE_REG && copyu(p1, &a, nil) > 1)) {
+				if(debug['P'])
+					print("\targs modified; FAILURE\n");
+				return 0;
+			}
 			continue;
-		case 3:	/* set, not used */
-			FAIL("BOTCH: noref");
+		case 3:	/* set, not used */ {
+			if(debug['P'])
+				print("\tBOTCH: noref; FAILURE\n");
+			return 0;
+		}
 		}
 		break;
 	}
 	/* check whether substitution can be done */
 	switch(p1->as) {
 	default:
-		FAIL("non-dpi");
+		if(debug['P'])
+			print("\tnon-dpi; FAILURE\n");
+		return 0;
+
 	case AAND:
 	case AEOR:
 	case AADD:
@@ -620,8 +635,11 @@ shiftprop(Flow *r)
 	case ARSB:
 	case ARSC:
 		if(p1->reg == n || (p1->reg == 0 && p1->to.type == TYPE_REG && p1->to.reg == n)) {
-			if(p1->from.type != TYPE_REG)
-				FAIL("can't swap");
+			if(p1->from.type != TYPE_REG) {
+				if(debug['P'])
+					print("\tcan't swap; FAILURE\n");
+				return 0;
+			}
 			p1->reg = p1->from.reg;
 			p1->from.reg = n;
 			switch(p1->as) {
@@ -645,15 +663,27 @@ shiftprop(Flow *r)
 	case ATST:
 	case ACMP:
 	case ACMN:
-		if(p1->reg == n)
-			FAIL("can't swap");
-		if(p1->reg == 0 && p1->to.reg == n)
-			FAIL("shift result used twice");
+		if(p1->reg == n) {
+			if(debug['P'])
+				print("\tcan't swap; FAILURE\n");
+			return 0;
+		}
+		if(p1->reg == 0 && p1->to.reg == n) {
+			if(debug['P'])
+				print("\tshift result used twice; FAILURE\n");
+			return 0;
+		}
 //	case AMVN:
-		if(p1->from.type == TYPE_SHIFT)
-			FAIL("shift result used in shift");
-		if(p1->from.type != TYPE_REG || p1->from.reg != n)
-			FAIL("BOTCH: where is it used?");
+		if(p1->from.type == TYPE_SHIFT) {
+			if(debug['P'])
+				print("\tshift result used in shift; FAILURE\n");
+			return 0;
+		}
+		if(p1->from.type != TYPE_REG || p1->from.reg != n) {
+			if(debug['P'])
+				print("\tBOTCH: where is it used?; FAILURE\n");
+			return 0;
+		}
 		break;
 	}
 	/* check whether shift result is used subsequently */
@@ -661,8 +691,11 @@ shiftprop(Flow *r)
 	if(p1->to.reg != n)
 	for (;;) {
 		r1 = uniqs(r1);
-		if(r1 == nil)
-			FAIL("inconclusive");
+		if(r1 == nil) {
+			if(debug['P'])
+				print("\tinconclusive; FAILURE\n");
+			return 0;
+		}
 		p1 = r1->prog;
 		if(debug['P'])
 			print("\n%P", p1);
@@ -672,7 +705,9 @@ shiftprop(Flow *r)
 		case 3: /* set, not used */
 			break;
 		default:/* used */
-			FAIL("reused");
+			if(debug['P'])
+				print("\treused; FAILURE\n");
+			return 0;
 		}
 		break;
 	}
diff --git a/src/cmd/6g/cgen.c b/src/cmd/6g/cgen.c
index 2a25724361..77ab2d2167 100644
--- a/src/cmd/6g/cgen.c
+++ b/src/cmd/6g/cgen.c
@@ -790,7 +790,7 @@ agenr(Node *n, Node *a, Node *res)
 void
 agen(Node *n, Node *res)
 {
-	Node *nl, *nr;
+	Node *nl;
 	Node n1, n2;
 
 	if(debug['g']) {
@@ -827,8 +827,6 @@ agen(Node *n, Node *res)
 	}
 
 	nl = n->left;
-	nr = n->right;
-	USED(nr);
 
 	switch(n->op) {
 	default:
@@ -1065,17 +1063,7 @@ bgen(Node *n, int true, int likely, Prog *to)
 
 	switch(n->op) {
 	default:
-	def:
-		regalloc(&n1, n->type, N);
-		cgen(n, &n1);
-		nodconst(&n2, n->type, 0);
-		gins(optoas(OCMP, n->type), &n1, &n2);
-		a = AJNE;
-		if(!true)
-			a = AJEQ;
-		patch(gbranch(a, n->type, likely), to);
-		regfree(&n1);
-		goto ret;
+		goto def;
 
 	case OLITERAL:
 		// need to ask if it is bool?
@@ -1095,27 +1083,20 @@ bgen(Node *n, int true, int likely, Prog *to)
 		goto ret;
 
 	case OANDAND:
-		if(!true)
-			goto caseor;
-
-	caseand:
-		p1 = gbranch(AJMP, T, 0);
-		p2 = gbranch(AJMP, T, 0);
-		patch(p1, pc);
-		bgen(n->left, !true, -likely, p2);
-		bgen(n->right, !true, -likely, p2);
-		p1 = gbranch(AJMP, T, 0);
-		patch(p1, to);
-		patch(p2, pc);
-		goto ret;
-
 	case OOROR:
-		if(!true)
-			goto caseand;
-
-	caseor:
-		bgen(n->left, true, likely, to);
-		bgen(n->right, true, likely, to);
+		if((n->op == OANDAND) == true) {
+			p1 = gbranch(AJMP, T, 0);
+			p2 = gbranch(AJMP, T, 0);
+			patch(p1, pc);
+			bgen(n->left, !true, -likely, p2);
+			bgen(n->right, !true, -likely, p2);
+			p1 = gbranch(AJMP, T, 0);
+			patch(p1, to);
+			patch(p2, pc);
+		} else {
+			bgen(n->left, true, likely, to);
+			bgen(n->right, true, likely, to);
+		}
 		goto ret;
 
 	case OEQ:
@@ -1273,6 +1254,18 @@ bgen(Node *n, int true, int likely, Prog *to)
 	}
 	goto ret;
 
+def:
+	regalloc(&n1, n->type, N);
+	cgen(n, &n1);
+	nodconst(&n2, n->type, 0);
+	gins(optoas(OCMP, n->type), &n1, &n2);
+	a = AJNE;
+	if(!true)
+		a = AJEQ;
+	patch(gbranch(a, n->type, likely), to);
+	regfree(&n1);
+	goto ret;
+
 ret:
 	;
 }
diff --git a/src/cmd/6g/gsubr.c b/src/cmd/6g/gsubr.c
index 725ed8f819..55d3425081 100644
--- a/src/cmd/6g/gsubr.c
+++ b/src/cmd/6g/gsubr.c
@@ -95,7 +95,7 @@ gclean(void)
 			yyerror("reg %R left allocated\n", i);
 }
 
-int32
+int
 anyregalloc(void)
 {
 	int i, j;
diff --git a/src/cmd/6g/peep.c b/src/cmd/6g/peep.c
index 1140a3d4bb..261cb6e0a1 100644
--- a/src/cmd/6g/peep.c
+++ b/src/cmd/6g/peep.c
@@ -767,7 +767,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 	case ACALL:
 		if(REGEXT && v->type == TYPE_REG && v->reg <= REGEXT && v->reg > exregoffset)
 			return 2;
-		if(REGARG >= 0 && v->type == TYPE_REG && v->reg == (uchar)REGARG)
+		if(REGARG >= 0 && v->type == TYPE_REG && v->reg == REGARG)
 			return 2;
 		if(v->type == p->from.type && v->reg == p->from.reg)
 			return 2;
@@ -782,7 +782,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 		return 3;
 
 	case ATEXT:
-		if(REGARG >= 0 && v->type == TYPE_REG && v->reg == (uchar)REGARG)
+		if(REGARG >= 0 && v->type == TYPE_REG && v->reg == REGARG)
 			return 3;
 		return 0;
 	}
diff --git a/src/cmd/8g/cgen.c b/src/cmd/8g/cgen.c
index c38aa0bcc1..f06927c905 100644
--- a/src/cmd/8g/cgen.c
+++ b/src/cmd/8g/cgen.c
@@ -956,17 +956,7 @@ bgen(Node *n, int true, int likely, Prog *to)
 
 	switch(n->op) {
 	default:
-	def:
-		regalloc(&n1, n->type, N);
-		cgen(n, &n1);
-		nodconst(&n2, n->type, 0);
-		gins(optoas(OCMP, n->type), &n1, &n2);
-		a = AJNE;
-		if(!true)
-			a = AJEQ;
-		patch(gbranch(a, n->type, likely), to);
-		regfree(&n1);
-		return;
+		goto def;
 
 	case OLITERAL:
 		// need to ask if it is bool?
@@ -986,27 +976,20 @@ bgen(Node *n, int true, int likely, Prog *to)
 		return;
 
 	case OANDAND:
-		if(!true)
-			goto caseor;
-
-	caseand:
-		p1 = gbranch(AJMP, T, 0);
-		p2 = gbranch(AJMP, T, 0);
-		patch(p1, pc);
-		bgen(n->left, !true, -likely, p2);
-		bgen(n->right, !true, -likely, p2);
-		p1 = gbranch(AJMP, T, 0);
-		patch(p1, to);
-		patch(p2, pc);
-		return;
-
 	case OOROR:
-		if(!true)
-			goto caseand;
-
-	caseor:
-		bgen(n->left, true, likely, to);
-		bgen(n->right, true, likely, to);
+		if((n->op == OANDAND) == true) {
+			p1 = gbranch(AJMP, T, 0);
+			p2 = gbranch(AJMP, T, 0);
+			patch(p1, pc);
+			bgen(n->left, !true, -likely, p2);
+			bgen(n->right, !true, -likely, p2);
+			p1 = gbranch(AJMP, T, 0);
+			patch(p1, to);
+			patch(p2, pc);
+		} else {
+			bgen(n->left, true, likely, to);
+			bgen(n->right, true, likely, to);
+		}
 		return;
 
 	case OEQ:
@@ -1150,6 +1133,19 @@ cmp:
 		regfree(nr);
 		break;
 	}
+	return;
+
+def:
+	regalloc(&n1, n->type, N);
+	cgen(n, &n1);
+	nodconst(&n2, n->type, 0);
+	gins(optoas(OCMP, n->type), &n1, &n2);
+	a = AJNE;
+	if(!true)
+		a = AJEQ;
+	patch(gbranch(a, n->type, likely), to);
+	regfree(&n1);
+	return;
 }
 
 /*
diff --git a/src/cmd/8g/gsubr.c b/src/cmd/8g/gsubr.c
index 959ef20592..b82f7622ef 100644
--- a/src/cmd/8g/gsubr.c
+++ b/src/cmd/8g/gsubr.c
@@ -667,7 +667,7 @@ gclean(void)
 			yyerror("reg %R left allocated\n", i);
 }
 
-int32
+int
 anyregalloc(void)
 {
 	int i, j;
@@ -724,9 +724,9 @@ regalloc(Node *n, Type *t, Node *o)
 			if(reg[i] == 0)
 				goto out;
 
-		fprint(2, "registers allocated at\n");
+		print("registers allocated at\n");
 		for(i=REG_AX; i<=REG_DI; i++)
-			fprint(2, "\t%R\t%#lux\n", i, regpc[i]);
+			print("\t%R\t%#lux\n", i, regpc[i]);
 		fatal("out of fixed registers");
 		goto err;
 
@@ -744,9 +744,9 @@ regalloc(Node *n, Type *t, Node *o)
 		for(i=REG_X0; i<=REG_X7; i++)
 			if(reg[i] == 0)
 				goto out;
-		fprint(2, "registers allocated at\n");
+		print("registers allocated at\n");
 		for(i=REG_X0; i<=REG_X7; i++)
-			fprint(2, "\t%R\t%#lux\n", i, regpc[i]);
+			print("\t%R\t%#lux\n", i, regpc[i]);
 		fatal("out of floating registers");
 	}
 	yyerror("regalloc: unknown type %T", t);
@@ -853,22 +853,25 @@ split64(Node *n, Node *lo, Node *hi)
 	nsclean++;
 	switch(n->op) {
 	default:
-		if(!dotaddable(n, &n1)) {
-			igen(n, &n1, N);
-			sclean[nsclean-1] = n1;
-		}
-		n = &n1;
-		goto common;
-	case ONAME:
-		if(n->class == PPARAMREF) {
-			cgen(n->heapaddr, &n1);
-			sclean[nsclean-1] = n1;
-			// fall through.
+		switch(n->op) {
+		default:
+			if(!dotaddable(n, &n1)) {
+				igen(n, &n1, N);
+				sclean[nsclean-1] = n1;
+			}
 			n = &n1;
+			break;
+		case ONAME:
+			if(n->class == PPARAMREF) {
+				cgen(n->heapaddr, &n1);
+				sclean[nsclean-1] = n1;
+				n = &n1;
+			}
+			break;
+		case OINDREG:
+			// nothing
+			break;
 		}
-		goto common;
-	case OINDREG:
-	common:
 		*lo = *n;
 		*hi = *n;
 		lo->type = types[TUINT32];
@@ -1466,7 +1469,7 @@ floatmove_387(Node *f, Node *t)
 		gmove(f, &t1);
 		switch(tt) {
 		default:
-			fatal("gmove %T", t);
+			fatal("gmove %N", t);
 		case TINT8:
 			gins(ACMPL, &t1, ncon(-0x80));
 			p1 = gbranch(optoas(OLT, types[TINT32]), T, -1);
diff --git a/src/cmd/9g/cgen.c b/src/cmd/9g/cgen.c
index b73f207fb3..009ea1ed7a 100644
--- a/src/cmd/9g/cgen.c
+++ b/src/cmd/9g/cgen.c
@@ -805,7 +805,7 @@ ginsadd(int as, vlong off, Node *dst)
 void
 agen(Node *n, Node *res)
 {
-	Node *nl, *nr;
+	Node *nl;
 	Node n1, n2, n3;
 
 	if(debug['g']) {
@@ -848,8 +848,6 @@ agen(Node *n, Node *res)
 	}
 
 	nl = n->left;
-	nr = n->right;
-	USED(nr);
 
 	switch(n->op) {
 	default:
@@ -1109,27 +1107,20 @@ bgen(Node *n, int true, int likely, Prog *to)
 		goto ret;
 
 	case OANDAND:
-		if(!true)
-			goto caseor;
-
-	caseand:
-		p1 = gbranch(ABR, T, 0);
-		p2 = gbranch(ABR, T, 0);
-		patch(p1, pc);
-		bgen(n->left, !true, -likely, p2);
-		bgen(n->right, !true, -likely, p2);
-		p1 = gbranch(ABR, T, 0);
-		patch(p1, to);
-		patch(p2, pc);
-		goto ret;
-
 	case OOROR:
-		if(!true)
-			goto caseand;
-
-	caseor:
-		bgen(n->left, true, likely, to);
-		bgen(n->right, true, likely, to);
+		if((n->op == OANDAND) == true) {
+			p1 = gbranch(AJMP, T, 0);
+			p2 = gbranch(AJMP, T, 0);
+			patch(p1, pc);
+			bgen(n->left, !true, -likely, p2);
+			bgen(n->right, !true, -likely, p2);
+			p1 = gbranch(AJMP, T, 0);
+			patch(p1, to);
+			patch(p2, pc);
+		} else {
+			bgen(n->left, true, likely, to);
+			bgen(n->right, true, likely, to);
+		}
 		goto ret;
 
 	case OEQ:
diff --git a/src/cmd/9g/gg.h b/src/cmd/9g/gg.h
index cc44f3586c..938675937e 100644
--- a/src/cmd/9g/gg.h
+++ b/src/cmd/9g/gg.h
@@ -9,9 +9,6 @@
 #include "../gc/go.h"
 #include "../9l/9.out.h"
 
-// TODO(minux): Remove when no longer used.
-#define noimpl sysfatal("%s not implemented (%s:%d).", __func__, __FILE__, __LINE__)
-
 EXTERN	uchar	reg[NREG+NFREG];
 EXTERN	Node*	panicdiv;
 extern	vlong	unmappedzero;
diff --git a/src/cmd/9g/gsubr.c b/src/cmd/9g/gsubr.c
index e01b587031..1fb1511361 100644
--- a/src/cmd/9g/gsubr.c
+++ b/src/cmd/9g/gsubr.c
@@ -87,7 +87,7 @@ gclean(void)
 			yyerror("reg %R left allocated, %p\n", i+REG_R0, regpc[i]);
 }
 
-int32
+int
 anyregalloc(void)
 {
 	int i, j;
@@ -732,8 +732,7 @@ fixlargeoffset(Node *n)
 	if(n->xoffset != (int32)n->xoffset) {
 		// TODO(minux): offset too large, move into R31 and add to R31 instead.
 		// this is used only in test/fixedbugs/issue6036.go.
-		print("offset too large: %N\n", n);
-		noimpl;
+		fatal("offset too large: %N", n);
 		a = *n;
 		a.op = OREGISTER;
 		a.type = types[tptr];
diff --git a/src/cmd/9g/peep.c b/src/cmd/9g/peep.c
index 0980039c9d..cf96d5dcda 100644
--- a/src/cmd/9g/peep.c
+++ b/src/cmd/9g/peep.c
@@ -575,7 +575,7 @@ copyu(Prog *p, Addr *v, Addr *s)
 {
 	if(p->from3.type != TYPE_NONE)
 		// 9g never generates a from3
-		print("copyu: from3 (%D) not implemented\n", p->from3);
+		print("copyu: from3 (%D) not implemented\n", &p->from3);
 
 	switch(p->as) {
 
diff --git a/src/cmd/gc/builtin.c b/src/cmd/gc/builtin.c
index d381566d1f..1178f622e5 100644
--- a/src/cmd/gc/builtin.c
+++ b/src/cmd/gc/builtin.c
@@ -1,4 +1,7 @@
 // AUTO-GENERATED by mkbuiltin; DO NOT EDIT
+#include <u.h>
+#include <libc.h>
+#include "go.h"
 char *runtimeimport =
 	"package runtime\n"
 	"import runtime \"runtime\"\n"
diff --git a/src/cmd/gc/closure.c b/src/cmd/gc/closure.c
index eb72ea14ce..0391ece379 100644
--- a/src/cmd/gc/closure.c
+++ b/src/cmd/gc/closure.c
@@ -208,10 +208,19 @@ capturevars(Node *xfunc)
 			v->closure->addrtaken = 1;
 			outer = nod(OADDR, outer, N);
 		}
-		if(debug['m'] > 1)
+		if(debug['m'] > 1) {
+			Sym *name;
+			char *how;
+			name = nil;
+			if(v->curfn && v->curfn->nname)
+				name = v->curfn->nname->sym;
+			how = "ref";
+			if(v->byval)
+				how = "value";
 			warnl(v->lineno, "%S capturing by %s: %S (addr=%d assign=%d width=%d)",
-				(v->curfn && v->curfn->nname) ? v->curfn->nname->sym : S, v->byval ? "value" : "ref",
+				name, how,
 				v->sym, v->closure->addrtaken, v->closure->assigned, (int32)v->type->width);
+		}
 		typecheck(&outer, Erv);
 		func->enter = list(func->enter, outer);
 	}
diff --git a/src/cmd/gc/const.c b/src/cmd/gc/const.c
index e418b9c561..50accb93a3 100644
--- a/src/cmd/gc/const.c
+++ b/src/cmd/gc/const.c
@@ -696,14 +696,7 @@ evconst(Node *n)
 	// run op
 	switch(TUP(n->op, v.ctype)) {
 	default:
-	illegal:
-		if(!n->diag) {
-			yyerror("illegal constant expression: %T %O %T",
-				nl->type, n->op, nr->type);
-			n->diag = 1;
-		}
-		return;
-
+		goto illegal;
 	case TUP(OADD, CTINT):
 	case TUP(OADD, CTRUNE):
 		mpaddfixfix(v.u.xval, rv.u.xval, 0);
@@ -1036,6 +1029,14 @@ setfalse:
 	*n = *nodbool(0);
 	n->orig = norig;
 	return;
+
+illegal:
+	if(!n->diag) {
+		yyerror("illegal constant expression: %T %O %T",
+			nl->type, n->op, nr->type);
+		n->diag = 1;
+	}
+	return;
 }
 
 Node*
@@ -1214,28 +1215,31 @@ defaultlit(Node **np, Type *t)
 	case CTCPLX:
 		t1 = types[TCOMPLEX128];
 		goto num;
-	num:
-		if(t != T) {
-			if(isint[t->etype]) {
-				t1 = t;
-				n->val = toint(n->val);
-			}
-			else
-			if(isfloat[t->etype]) {
-				t1 = t;
-				n->val = toflt(n->val);
-			}
-			else
-			if(iscomplex[t->etype]) {
-				t1 = t;
-				n->val = tocplx(n->val);
-			}
-		}
-		overflow(n->val, t1);
-		convlit(np, t1);
-		break;
 	}
 	lineno = lno;
+	return;
+
+num:
+	if(t != T) {
+		if(isint[t->etype]) {
+			t1 = t;
+			n->val = toint(n->val);
+		}
+		else
+		if(isfloat[t->etype]) {
+			t1 = t;
+			n->val = toflt(n->val);
+		}
+		else
+		if(iscomplex[t->etype]) {
+			t1 = t;
+			n->val = tocplx(n->val);
+		}
+	}
+	overflow(n->val, t1);
+	convlit(np, t1);
+	lineno = lno;
+	return;
 }
 
 /*
diff --git a/src/cmd/gc/fmt.c b/src/cmd/gc/fmt.c
index f9eb0ba2b3..bd0a29f6e1 100644
--- a/src/cmd/gc/fmt.c
+++ b/src/cmd/gc/fmt.c
@@ -171,7 +171,7 @@ goopnames[] =
 };
 
 // Fmt "%O":  Node opcodes
-static int
+int
 Oconv(Fmt *fp)
 {
 	int o;
@@ -1558,7 +1558,7 @@ Sconv(Fmt *fp)
 // Flags: 'l' print definition, not name
 //	  'h' omit 'func' and receiver from function types, short type names
 //	  'u' package name, not prefix (FTypeId mode, sticky)
-static int
+int
 Tconv(Fmt *fp)
 {
 	Type *t;
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index d99a7d431f..c5ef74586d 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -743,6 +743,7 @@ struct	Var
 	Node*	node;
 	Var*	nextinnode;
 	int	width;
+	int	id;
 	char	name;
 	char	etype;
 	char	addr;
@@ -1732,6 +1733,13 @@ void datagostring(Strlit *sval, Addr *a);
 int ismem(Node*);
 int samereg(Node*, Node*);
 void	regopt(Prog*);
+int	Tconv(Fmt*);
+int	Oconv(Fmt*);
+Prog*	gbranch(int as, Type *t, int likely);
+void	nodindreg(Node *n, Type *t, int r);
+void	nodreg(Node *n, Type *t, int r);
+Prog*	prog(int as);
+void	datastring(char*, int, Addr*);
 
 EXTERN int32	pcloc;
 
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index b915e9fed2..a4b832aa0b 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -660,7 +660,7 @@ importfile(Val *f, int line)
 	Biobuf *imp;
 	char *file, *p, *q, *tag;
 	int32 c;
-	int len;
+	int n;
 	Strlit *path;
 	char *cleanbuf, *prefix;
 
@@ -758,8 +758,8 @@ importfile(Val *f, int line)
 	}
 	file = strdup(namebuf);
 
-	len = strlen(namebuf);
-	if(len > 2 && namebuf[len-2] == '.' && namebuf[len-1] == 'a') {
+	n = strlen(namebuf);
+	if(n > 2 && namebuf[n-2] == '.' && namebuf[n-1] == 'a') {
 		if(!skiptopkgdef(imp)) {
 			yyerror("import %s: not a package file", file);
 			errorexit();
@@ -783,7 +783,7 @@ importfile(Val *f, int line)
 
 	// assume files move (get installed)
 	// so don't record the full path.
-	linehist(file + len - path->len - 2, -1, 1);	// acts as #pragma lib
+	linehist(file + n - path->len - 2, -1, 1);	// acts as #pragma lib
 
 	/*
 	 * position the input right
@@ -987,17 +987,7 @@ l0:
 			rune = c;
 			clen += runetochar(cp+clen, &rune);
 		}
-
-	strlit:
-		*(int32*)cp = clen-sizeof(int32);	// length
-		do {
-			cp[clen++] = 0;
-		} while(clen & MAXALIGN);
-		yylval.val.u.sval = (Strlit*)cp;
-		yylval.val.ctype = CTSTR;
-		DBG("lex: string literal\n");
-		strcpy(litbuf, "string literal");
-		return LLITERAL;
+		goto strlit;
 
 	case '\'':
 		/* '.' */
@@ -1292,7 +1282,7 @@ talph:
 		if(c >= Runeself) {
 			ungetc(c);
 			rune = getr();
-			// 0xb7 · is used for internal names
+			// 0xb7 · is used for internal names
 			if(!isalpharune(rune) && !isdigitrune(rune) && (importpkg == nil || rune != 0xb7))
 				yyerror("invalid identifier character U+%04x", rune);
 			cp += runetochar(cp, &rune);
@@ -1480,6 +1470,17 @@ caseout:
 	strcpy(litbuf, "literal ");
 	strcat(litbuf, lexbuf);
 	return LLITERAL;
+
+strlit:
+	*(int32*)cp = clen-sizeof(int32);	// length
+	do {
+		cp[clen++] = 0;
+	} while(clen & MAXALIGN);
+	yylval.val.u.sval = (Strlit*)cp;
+	yylval.val.ctype = CTSTR;
+	DBG("lex: string literal\n");
+	strcpy(litbuf, "string literal");
+	return LLITERAL;
 }
 
 static void pragcgo(char*);
diff --git a/src/cmd/gc/mkbuiltin b/src/cmd/gc/mkbuiltin
index 1dab1c9a05..696aa82424 100755
--- a/src/cmd/gc/mkbuiltin
+++ b/src/cmd/gc/mkbuiltin
@@ -20,6 +20,10 @@ GC=${GOCHAR}g
 gcc -o mkbuiltin1 mkbuiltin1.c
 rm -f _builtin.c
 echo "// AUTO-GENERATED by mkbuiltin; DO NOT EDIT" >>_builtin.c
+echo "#include <u.h>" >>_builtin.c
+echo "#include <libc.h>" >>_builtin.c
+echo '#include "go.h"' >>_builtin.c
+
 for i in runtime unsafe
 do
 	go tool $GC -A $i.go
diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index 371db2895f..3df78e7f9a 100644
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -161,6 +161,7 @@ compile(Node *fn)
 	Iter save;
 	vlong oldstksize;
 	NodeList *l;
+	Node *nam;
 	Sym *gcargs;
 	Sym *gclocals;
 
@@ -229,7 +230,10 @@ compile(Node *fn)
 	setlineno(curfn);
 
 	nodconst(&nod1, types[TINT32], 0);
-	ptxt = thearch.gins(ATEXT, isblank(curfn->nname) ? N : curfn->nname, &nod1);
+	nam = curfn->nname;
+	if(isblank(nam))
+		nam = N;
+	ptxt = thearch.gins(ATEXT, nam, &nod1);
 	if(fn->dupok)
 		ptxt->from3.offset |= DUPOK;
 	if(fn->wrapper)
diff --git a/src/cmd/gc/plive.c b/src/cmd/gc/plive.c
index 283c5125e3..c0d1e57932 100644
--- a/src/cmd/gc/plive.c
+++ b/src/cmd/gc/plive.c
@@ -1909,15 +1909,15 @@ static void
 twobitwritesymbol(Array *arr, Sym *sym)
 {
 	Bvec *bv;
-	int off, i, j, len;
+	int off, i, j, n;
 	uint32 word;
 
-	len = arraylength(arr);
+	n = arraylength(arr);
 	off = 0;
 	off += 4; // number of bitmaps, to fill in later
 	bv = *(Bvec**)arrayget(arr, 0);
 	off = duint32(sym, off, bv->n); // number of bits in each bitmap
-	for(i = 0; i < len; i++) {
+	for(i = 0; i < n; i++) {
 		// bitmap words
 		bv = *(Bvec**)arrayget(arr, i);
 		if(bv == nil)
diff --git a/src/cmd/gc/popt.c b/src/cmd/gc/popt.c
index af7e5b1ff3..b02d58e663 100644
--- a/src/cmd/gc/popt.c
+++ b/src/cmd/gc/popt.c
@@ -782,10 +782,9 @@ mergetemp(Prog *firstp)
 	}
 
 	// Clear aux structures.
-	for(i = 0; i < nvar; i++) {
-		v = &var[i];
-		v->node->opt = nil;
-	}
+	for(i = 0; i < nvar; i++)
+		var[i].node->opt = nil;
+
 	free(var);
 	free(bystart);
 	free(inuse);
diff --git a/src/cmd/gc/popt.h b/src/cmd/gc/popt.h
index 2bae0d770d..0a30e81f55 100644
--- a/src/cmd/gc/popt.h
+++ b/src/cmd/gc/popt.h
@@ -31,33 +31,24 @@
 #define	Z	N
 #define	Adr	Addr
 
-#define	D_HI	TYPE_NONE
-#define	D_LO	TYPE_NONE
-
 #define	BLOAD(r)	band(bnot(r->refbehind), r->refahead)
 #define	BSTORE(r)	band(bnot(r->calbehind), r->calahead)
 #define	LOAD(r)		(~r->refbehind.b[z] & r->refahead.b[z])
 #define	STORE(r)	(~r->calbehind.b[z] & r->calahead.b[z])
 
-#define	CLOAD	5
-#define	CREF	5
-#define	CINF	1000
-#define	LOOP	3
+enum
+{
+	CLOAD = 5,
+	CREF = 5,
+	CINF = 1000,
+	LOOP = 3,
+};
 
 typedef	struct	Reg	Reg;
 typedef	struct	Rgn	Rgn;
 
 /*c2go
 extern Node *Z;
-enum
-{
-	D_HI = TYPE_NONE,
-	D_LO = TYPE_NONE,
-	CLOAD = 5,
-	CREF = 5,
-	CINF = 1000,
-	LOOP = 3,
-};
 
 uint32 BLOAD(Reg*);
 uint32 BSTORE(Reg*);
diff --git a/src/cmd/gc/range.c b/src/cmd/gc/range.c
index ff05820b58..ff9de6c349 100644
--- a/src/cmd/gc/range.c
+++ b/src/cmd/gc/range.c
@@ -13,6 +13,7 @@
 void
 typecheckrange(Node *n)
 {
+	int toomany;
 	char *why;
 	Type *t, *t1, *t2;
 	Node *v1, *v2;
@@ -41,6 +42,7 @@ typecheckrange(Node *n)
 		t = t->type;
 	n->type = t;
 
+	toomany = 0;
 	switch(t->etype) {
 	default:
 		yyerror("cannot range over %lN", n->right);
@@ -64,7 +66,7 @@ typecheckrange(Node *n)
 		t1 = t->type;
 		t2 = nil;
 		if(count(n->list) == 2)
-			goto toomany;
+			toomany = 1;
 		break;
 
 	case TSTRING:
@@ -73,10 +75,8 @@ typecheckrange(Node *n)
 		break;
 	}
 
-	if(count(n->list) > 2) {
-	toomany:
+	if(count(n->list) > 2 || toomany)
 		yyerror("too many variables in range");
-	}
 
 	v1 = N;
 	if(n->list)
diff --git a/src/cmd/gc/reflect.c b/src/cmd/gc/reflect.c
index 7f81e676f9..14a1f13e33 100644
--- a/src/cmd/gc/reflect.c
+++ b/src/cmd/gc/reflect.c
@@ -1349,7 +1349,7 @@ usegcprog(Type *t)
 
 // Generates sparse GC bitmask (4 bits per word).
 static void
-gengcmask(Type *t, uint8 gcmask[16])
+gengcmask(Type *t, uint8 *gcmask)
 {
 	Bvec *vec;
 	vlong xoffset, nptr, i, j;
diff --git a/src/cmd/gc/select.c b/src/cmd/gc/select.c
index 5d3b71164a..537d0ca928 100644
--- a/src/cmd/gc/select.c
+++ b/src/cmd/gc/select.c
@@ -133,18 +133,16 @@ walkselect(Node *sel)
 				break;
 
 			case OSELRECV:
-				ch = n->right->left;
-			Selrecv1:
-				if(n->left == N)
-					n = n->right;
-				else
-					n->op = OAS;
-				break;
-			
 			case OSELRECV2:
 				ch = n->right->left;
-				if(n->ntest == N)
-					goto Selrecv1;
+				if(n->op == OSELRECV || n->ntest == N) {
+					if(n->left == N)
+						n = n->right;
+					else
+						n->op = OAS;
+					break;
+				}
+			
 				if(n->left == N) {
 					typecheck(&nblank, Erv | Easgn);
 					n->left = nblank;
diff --git a/src/cmd/gc/swt.c b/src/cmd/gc/swt.c
index e75971d477..0dc0065ed9 100644
--- a/src/cmd/gc/swt.c
+++ b/src/cmd/gc/swt.c
@@ -454,31 +454,22 @@ exprbsw(Case *c0, int ncase, int arg)
 			n = c0->node;
 			lno = setlineno(n);
 
-			if(assignop(n->left->type, exprname->type, nil) == OCONVIFACE ||
-			   assignop(exprname->type, n->left->type, nil) == OCONVIFACE)
-				goto snorm;
-
-			switch(arg) {
-			case Strue:
-				a = nod(OIF, N, N);
-				a->ntest = n->left;			// if val
-				a->nbody = list1(n->right);			// then goto l
-				break;
-
-			case Sfalse:
-				a = nod(OIF, N, N);
-				a->ntest = nod(ONOT, n->left, N);	// if !val
-				typecheck(&a->ntest, Erv);
-				a->nbody = list1(n->right);			// then goto l
-				break;
-
-			default:
-			snorm:
+			if((arg != Strue && arg != Sfalse) ||
+			   assignop(n->left->type, exprname->type, nil) == OCONVIFACE ||
+			   assignop(exprname->type, n->left->type, nil) == OCONVIFACE) {
 				a = nod(OIF, N, N);
 				a->ntest = nod(OEQ, exprname, n->left);	// if name == val
 				typecheck(&a->ntest, Erv);
 				a->nbody = list1(n->right);			// then goto l
-				break;
+			} else if(arg == Strue) {
+				a = nod(OIF, N, N);
+				a->ntest = n->left;			// if val
+				a->nbody = list1(n->right);			// then goto l
+			} else { // arg == Sfalse
+				a = nod(OIF, N, N);
+				a->ntest = nod(ONOT, n->left, N);	// if !val
+				typecheck(&a->ntest, Erv);
+				a->nbody = list1(n->right);			// then goto l
 			}
 
 			cas = list(cas, a);
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index c73c34804f..649f1c5120 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -555,178 +555,7 @@ reswitch:
 		if(l->type == T || r->type == T)
 			goto error;
 		op = n->op;
-	arith:
-		if(op == OLSH || op == ORSH)
-			goto shift;
-		// ideal mixed with non-ideal
-		defaultlit2(&l, &r, 0);
-		n->left = l;
-		n->right = r;
-		if(l->type == T || r->type == T)
-			goto error;
-		t = l->type;
-		if(t->etype == TIDEAL)
-			t = r->type;
-		et = t->etype;
-		if(et == TIDEAL)
-			et = TINT;
-		aop = 0;
-		if(iscmp[n->op] && t->etype != TIDEAL && !eqtype(l->type, r->type)) {
-			// comparison is okay as long as one side is
-			// assignable to the other.  convert so they have
-			// the same type.
-			//
-			// the only conversion that isn't a no-op is concrete == interface.
-			// in that case, check comparability of the concrete type.
-			// The conversion allocates, so only do it if the concrete type is huge.
-			if(r->type->etype != TBLANK && (aop = assignop(l->type, r->type, nil)) != 0) {
-				if(isinter(r->type) && !isinter(l->type) && algtype1(l->type, nil) == ANOEQ) {
-					yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(l->type));
-					goto error;
-				}
-				dowidth(l->type);
-				if(isinter(r->type) == isinter(l->type) || l->type->width >= 1<<16) {
-					l = nod(aop, l, N);
-					l->type = r->type;
-					l->typecheck = 1;
-					n->left = l;
-				}
-				t = r->type;
-				goto converted;
-			}
-			if(l->type->etype != TBLANK && (aop = assignop(r->type, l->type, nil)) != 0) {
-				if(isinter(l->type) && !isinter(r->type) && algtype1(r->type, nil) == ANOEQ) {
-					yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(r->type));
-					goto error;
-				}
-				dowidth(r->type);
-				if(isinter(r->type) == isinter(l->type) || r->type->width >= 1<<16) {
-					r = nod(aop, r, N);
-					r->type = l->type;
-					r->typecheck = 1;
-					n->right = r;
-				}
-				t = l->type;
-			}
-		converted:
-			et = t->etype;
-		}
-		if(t->etype != TIDEAL && !eqtype(l->type, r->type)) {
-			defaultlit2(&l, &r, 1);
-			if(n->op == OASOP && n->implicit) {
-				yyerror("invalid operation: %N (non-numeric type %T)", n, l->type);
-				goto error;
-			}
-			if(isinter(r->type) == isinter(l->type) || aop == 0) {
-				yyerror("invalid operation: %N (mismatched types %T and %T)", n, l->type, r->type);
-				goto error;
-			}
-		}
-		if(!okfor[op][et]) {
-			yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(t));
-			goto error;
-		}
-		// okfor allows any array == array, map == map, func == func.
-		// restrict to slice/map/func == nil and nil == slice/map/func.
-		if(isfixedarray(l->type) && algtype1(l->type, nil) == ANOEQ) {
-			yyerror("invalid operation: %N (%T cannot be compared)", n, l->type);
-			goto error;
-		}
-		if(isslice(l->type) && !isnil(l) && !isnil(r)) {
-			yyerror("invalid operation: %N (slice can only be compared to nil)", n);
-			goto error;
-		}
-		if(l->type->etype == TMAP && !isnil(l) && !isnil(r)) {
-			yyerror("invalid operation: %N (map can only be compared to nil)", n);
-			goto error;
-		}
-		if(l->type->etype == TFUNC && !isnil(l) && !isnil(r)) {
-			yyerror("invalid operation: %N (func can only be compared to nil)", n);
-			goto error;
-		}
-		if(l->type->etype == TSTRUCT && algtype1(l->type, &badtype) == ANOEQ) {
-			yyerror("invalid operation: %N (struct containing %T cannot be compared)", n, badtype);
-			goto error;
-		}
-		
-		t = l->type;
-		if(iscmp[n->op]) {
-			evconst(n);
-			t = idealbool;
-			if(n->op != OLITERAL) {
-				defaultlit2(&l, &r, 1);
-				n->left = l;
-				n->right = r;
-			}
-		} else if(n->op == OANDAND || n->op == OOROR) {
-			if(l->type == r->type)
-				t = l->type;
-			else if(l->type == idealbool)
-				t = r->type;
-			else if(r->type == idealbool)
-				t = l->type;
-		// non-comparison operators on ideal bools should make them lose their ideal-ness
-		} else if(t == idealbool)
-			t = types[TBOOL];
-
-		if(et == TSTRING) {
-			if(iscmp[n->op]) {
-				n->etype = n->op;
-				n->op = OCMPSTR;
-			} else if(n->op == OADD) {
-				// create OADDSTR node with list of strings in x + y + z + (w + v) + ...
-				n->op = OADDSTR;
-				if(l->op == OADDSTR)
-					n->list = l->list;
-				else
-					n->list = list1(l);
-				if(r->op == OADDSTR)
-					n->list = concat(n->list, r->list);
-				else
-					n->list = list(n->list, r);
-				n->left = N;
-				n->right = N;
-			}
-		}
-		if(et == TINTER) {
-			if(l->op == OLITERAL && l->val.ctype == CTNIL) {
-				// swap for back end
-				n->left = r;
-				n->right = l;
-			} else if(r->op == OLITERAL && r->val.ctype == CTNIL) {
-				// leave alone for back end
-			} else if(isinter(r->type) == isinter(l->type)) {
-				n->etype = n->op;
-				n->op = OCMPIFACE;
-			}
-		}
-
-		if((op == ODIV || op == OMOD) && isconst(r, CTINT))
-		if(mpcmpfixc(r->val.u.xval, 0) == 0) {
-			yyerror("division by zero");
-			goto error;
-		} 
-
-		n->type = t;
-		goto ret;
-
-	shift:
-		defaultlit(&r, types[TUINT]);
-		n->right = r;
-		t = r->type;
-		if(!isint[t->etype] || issigned[t->etype]) {
-			yyerror("invalid operation: %N (shift count type %T, must be unsigned integer)", n, r->type);
-			goto error;
-		}
-		t = l->type;
-		if(t != T && t->etype != TIDEAL && !isint[t->etype]) {
-			yyerror("invalid operation: %N (shift of type %T)", n, t);
-			goto error;
-		}
-		// no defaultlit for left
-		// the outer context gives the type
-		n->type = l->type;
-		goto ret;
+		goto arith;
 
 	case OCOM:
 	case OMINUS:
@@ -1454,41 +1283,7 @@ reswitch:
 		goto ret;
 
 	case OCONV:
-	doconv:
-		ok |= Erv;
-		saveorignode(n);
-		typecheck(&n->left, Erv | (top & (Eindir | Eiota)));
-		convlit1(&n->left, n->type, 1);
-		if((t = n->left->type) == T || n->type == T)
-			goto error;
-		if((n->op = convertop(t, n->type, &why)) == 0) {
-			if(!n->diag && !n->type->broke) {
-				yyerror("cannot convert %lN to type %T%s", n->left, n->type, why);
-				n->diag = 1;
-			}
-			n->op = OCONV;
-		}
-		switch(n->op) {
-		case OCONVNOP:
-			if(n->left->op == OLITERAL && n->type != types[TBOOL]) {
-				r = nod(OXXX, N, N);
-				n->op = OCONV;
-				n->orig = r;
-				*r = *n;
-				n->op = OLITERAL;
-				n->val = n->left->val;
-			}
-			break;
-		case OSTRARRAYBYTE:
-			// do not use stringtoarraylit.
-			// generated code and compiler memory footprint is better without it.
-			break;
-		case OSTRARRAYRUNE:
-			if(n->left->op == OLITERAL)
-				stringtoarraylit(&n);
-			break;
-		}
-		goto ret;
+		goto doconv;
 
 	case OMAKE:
 		ok |= Erv;
@@ -1506,13 +1301,14 @@ reswitch:
 
 		switch(t->etype) {
 		default:
-		badmake:
 			yyerror("cannot make type %T", t);
 			goto error;
 
 		case TARRAY:
-			if(!isslice(t))
-				goto badmake;
+			if(!isslice(t)) {
+				yyerror("cannot make type %T", t);
+				goto error;
+			}
 			if(args == nil) {
 				yyerror("missing len argument to make(%T)", t);
 				goto error;
@@ -1805,6 +1601,216 @@ reswitch:
 			checkwidth(n->left->type);
 		goto ret;
 	}
+	goto ret;
+
+arith:
+	if(op == OLSH || op == ORSH)
+		goto shift;
+	// ideal mixed with non-ideal
+	defaultlit2(&l, &r, 0);
+	n->left = l;
+	n->right = r;
+	if(l->type == T || r->type == T)
+		goto error;
+	t = l->type;
+	if(t->etype == TIDEAL)
+		t = r->type;
+	et = t->etype;
+	if(et == TIDEAL)
+		et = TINT;
+	aop = 0;
+	if(iscmp[n->op] && t->etype != TIDEAL && !eqtype(l->type, r->type)) {
+		// comparison is okay as long as one side is
+		// assignable to the other.  convert so they have
+		// the same type.
+		//
+		// the only conversion that isn't a no-op is concrete == interface.
+		// in that case, check comparability of the concrete type.
+		// The conversion allocates, so only do it if the concrete type is huge.
+		if(r->type->etype != TBLANK && (aop = assignop(l->type, r->type, nil)) != 0) {
+			if(isinter(r->type) && !isinter(l->type) && algtype1(l->type, nil) == ANOEQ) {
+				yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(l->type));
+				goto error;
+			}
+			dowidth(l->type);
+			if(isinter(r->type) == isinter(l->type) || l->type->width >= 1<<16) {
+				l = nod(aop, l, N);
+				l->type = r->type;
+				l->typecheck = 1;
+				n->left = l;
+			}
+			t = r->type;
+			goto converted;
+		}
+		if(l->type->etype != TBLANK && (aop = assignop(r->type, l->type, nil)) != 0) {
+			if(isinter(l->type) && !isinter(r->type) && algtype1(r->type, nil) == ANOEQ) {
+				yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(r->type));
+				goto error;
+			}
+			dowidth(r->type);
+			if(isinter(r->type) == isinter(l->type) || r->type->width >= 1<<16) {
+				r = nod(aop, r, N);
+				r->type = l->type;
+				r->typecheck = 1;
+				n->right = r;
+			}
+			t = l->type;
+		}
+	converted:
+		et = t->etype;
+	}
+	if(t->etype != TIDEAL && !eqtype(l->type, r->type)) {
+		defaultlit2(&l, &r, 1);
+		if(n->op == OASOP && n->implicit) {
+			yyerror("invalid operation: %N (non-numeric type %T)", n, l->type);
+			goto error;
+		}
+		if(isinter(r->type) == isinter(l->type) || aop == 0) {
+			yyerror("invalid operation: %N (mismatched types %T and %T)", n, l->type, r->type);
+			goto error;
+		}
+	}
+	if(!okfor[op][et]) {
+		yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(t));
+		goto error;
+	}
+	// okfor allows any array == array, map == map, func == func.
+	// restrict to slice/map/func == nil and nil == slice/map/func.
+	if(isfixedarray(l->type) && algtype1(l->type, nil) == ANOEQ) {
+		yyerror("invalid operation: %N (%T cannot be compared)", n, l->type);
+		goto error;
+	}
+	if(isslice(l->type) && !isnil(l) && !isnil(r)) {
+		yyerror("invalid operation: %N (slice can only be compared to nil)", n);
+		goto error;
+	}
+	if(l->type->etype == TMAP && !isnil(l) && !isnil(r)) {
+		yyerror("invalid operation: %N (map can only be compared to nil)", n);
+		goto error;
+	}
+	if(l->type->etype == TFUNC && !isnil(l) && !isnil(r)) {
+		yyerror("invalid operation: %N (func can only be compared to nil)", n);
+		goto error;
+	}
+	if(l->type->etype == TSTRUCT && algtype1(l->type, &badtype) == ANOEQ) {
+		yyerror("invalid operation: %N (struct containing %T cannot be compared)", n, badtype);
+		goto error;
+	}
+	
+	t = l->type;
+	if(iscmp[n->op]) {
+		evconst(n);
+		t = idealbool;
+		if(n->op != OLITERAL) {
+			defaultlit2(&l, &r, 1);
+			n->left = l;
+			n->right = r;
+		}
+	} else if(n->op == OANDAND || n->op == OOROR) {
+		if(l->type == r->type)
+			t = l->type;
+		else if(l->type == idealbool)
+			t = r->type;
+		else if(r->type == idealbool)
+			t = l->type;
+	// non-comparison operators on ideal bools should make them lose their ideal-ness
+	} else if(t == idealbool)
+		t = types[TBOOL];
+
+	if(et == TSTRING) {
+		if(iscmp[n->op]) {
+			n->etype = n->op;
+			n->op = OCMPSTR;
+		} else if(n->op == OADD) {
+			// create OADDSTR node with list of strings in x + y + z + (w + v) + ...
+			n->op = OADDSTR;
+			if(l->op == OADDSTR)
+				n->list = l->list;
+			else
+				n->list = list1(l);
+			if(r->op == OADDSTR)
+				n->list = concat(n->list, r->list);
+			else
+				n->list = list(n->list, r);
+			n->left = N;
+			n->right = N;
+		}
+	}
+	if(et == TINTER) {
+		if(l->op == OLITERAL && l->val.ctype == CTNIL) {
+			// swap for back end
+			n->left = r;
+			n->right = l;
+		} else if(r->op == OLITERAL && r->val.ctype == CTNIL) {
+			// leave alone for back end
+		} else if(isinter(r->type) == isinter(l->type)) {
+			n->etype = n->op;
+			n->op = OCMPIFACE;
+		}
+	}
+
+	if((op == ODIV || op == OMOD) && isconst(r, CTINT))
+	if(mpcmpfixc(r->val.u.xval, 0) == 0) {
+		yyerror("division by zero");
+		goto error;
+	} 
+
+	n->type = t;
+	goto ret;
+
+shift:
+	defaultlit(&r, types[TUINT]);
+	n->right = r;
+	t = r->type;
+	if(!isint[t->etype] || issigned[t->etype]) {
+		yyerror("invalid operation: %N (shift count type %T, must be unsigned integer)", n, r->type);
+		goto error;
+	}
+	t = l->type;
+	if(t != T && t->etype != TIDEAL && !isint[t->etype]) {
+		yyerror("invalid operation: %N (shift of type %T)", n, t);
+		goto error;
+	}
+	// no defaultlit for left
+	// the outer context gives the type
+	n->type = l->type;
+	goto ret;
+
+doconv:
+	ok |= Erv;
+	saveorignode(n);
+	typecheck(&n->left, Erv | (top & (Eindir | Eiota)));
+	convlit1(&n->left, n->type, 1);
+	if((t = n->left->type) == T || n->type == T)
+		goto error;
+	if((n->op = convertop(t, n->type, &why)) == 0) {
+		if(!n->diag && !n->type->broke) {
+			yyerror("cannot convert %lN to type %T%s", n->left, n->type, why);
+			n->diag = 1;
+		}
+		n->op = OCONV;
+	}
+	switch(n->op) {
+	case OCONVNOP:
+		if(n->left->op == OLITERAL && n->type != types[TBOOL]) {
+			r = nod(OXXX, N, N);
+			n->op = OCONV;
+			n->orig = r;
+			*r = *n;
+			n->op = OLITERAL;
+			n->val = n->left->val;
+		}
+		break;
+	case OSTRARRAYBYTE:
+		// do not use stringtoarraylit.
+		// generated code and compiler memory footprint is better without it.
+		break;
+	case OSTRARRAYRUNE:
+		if(n->left->op == OLITERAL)
+			stringtoarraylit(&n);
+		break;
+	}
+	goto ret;
 
 ret:
 	t = n->type;
@@ -1925,7 +1931,7 @@ checkdefergo(Node *n)
 	case OPRINTN:
 	case ORECOVER:
 		// ok
-		break;
+		return;
 	case OAPPEND:
 	case OCAP:
 	case OCOMPLEX:
@@ -1939,23 +1945,21 @@ checkdefergo(Node *n)
 	case OREAL:
 	case OLITERAL: // conversion or unsafe.Alignof, Offsetof, Sizeof
 		if(n->left->orig != N && n->left->orig->op == OCONV)
-			goto conv;
-		yyerror("%s discards result of %N", what, n->left);
-		break;
-	default:
-	conv:
-		// type is broken or missing, most likely a method call on a broken type
-		// we will warn about the broken type elsewhere. no need to emit a potentially confusing error
-		if(n->left->type == T || n->left->type->broke)
 			break;
+		yyerror("%s discards result of %N", what, n->left);
+		return;
+	}
 
-		if(!n->diag) {
-			// The syntax made sure it was a call, so this must be
-			// a conversion.
-			n->diag = 1;
-			yyerror("%s requires function call, not conversion", what);
-		}
-		break;
+	// type is broken or missing, most likely a method call on a broken type
+	// we will warn about the broken type elsewhere. no need to emit a potentially confusing error
+	if(n->left->type == T || n->left->type->broke)
+		return;
+
+	if(!n->diag) {
+		// The syntax made sure it was a call, so this must be
+		// a conversion.
+		n->diag = 1;
+		yyerror("%s requires function call, not conversion", what);
 	}
 }
 
@@ -3048,15 +3052,20 @@ typecheckas2(Node *n)
 			goto out;
 		switch(r->op) {
 		case OINDEXMAP:
-			n->op = OAS2MAPR;
-			goto common;
 		case ORECV:
-			n->op = OAS2RECV;
-			goto common;
 		case ODOTTYPE:
-			n->op = OAS2DOTTYPE;
-			r->op = ODOTTYPE2;
-		common:
+			switch(r->op) {
+			case OINDEXMAP:
+				n->op = OAS2MAPR;
+				break;
+			case ORECV:
+				n->op = OAS2RECV;
+				break;
+			case ODOTTYPE:
+				n->op = OAS2DOTTYPE;
+				r->op = ODOTTYPE2;
+				break;
+			}
 			if(l->type != T)
 				checkassignto(r->type, l);
 			if(l->defn == n)