cmd/gc, cmd/6g: fix error on large stacks.

Fixes #4666.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://golang.org/cl/7141047

src/cmd/6g/cgen.c

@@ -1329,7 +1329,7 @@ void
 sgen(Node *n, Node *ns, int64 w)
 {
 	Node nodl, nodr, nodsi, noddi, cx, oldcx, tmp;
-	int32 c, q, odst, osrc;
+	vlong c, q, odst, osrc;
 
 	if(debug['g']) {
 		print("\nsgen w=%lld\n", w);

src/cmd/gc/go.h

@@ -320,7 +320,7 @@ struct	Node
 	int32	lineno;
 	int32	endlineno;
 	vlong	xoffset;
-	int32	stkdelta;	// offset added by stack frame compaction phase.
+	vlong	stkdelta;	// offset added by stack frame compaction phase.
 	int32	ostk;
 	int32	iota;
 	uint32	walkgen;
@@ -912,8 +912,8 @@ EXTERN	int	loophack;
 EXTERN	int32	iota;
 EXTERN	NodeList*	lastconst;
 EXTERN	Node*	lasttype;
-EXTERN	int32	maxarg;
-EXTERN	int32	stksize;		// stack size for current frame
+EXTERN	vlong	maxarg;
+EXTERN	vlong	stksize;		// stack size for current frame
 EXTERN	int32	blockgen;		// max block number
 EXTERN	int32	block;			// current block number
 EXTERN	int	hasdefer;		// flag that curfn has defer statetment

test/fixedbugs/bug385_64.go

@@ -8,11 +8,17 @@
 // license that can be found in the LICENSE file.
 
 // Issue 2444
+// Issue 4666: issue with arrays of exactly 4GB.
 
 package main
+
 func main() { // ERROR "stack frame too large"
 	var arr [1000200030]int32
 	arr_bkup := arr
 	_ = arr_bkup
 }
 
+func F() { // ERROR "stack frame too large"
+	var arr [1 << 30]int32
+	_ = arr[42]
+}

test/fixedbugs/issue4348.go

-// compile
+// skip
+
+// NOTE: this test is now skipped because the relevant code
+// is rejected after fixing issue 4666.
 
 // Copyright 2012 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style