8 files changed, 45 insertions, 1 deletions
diff --git a/src/cmd/gc/builtin.c.boot b/src/cmd/gc/builtin.c.boot
index fc8a6d1f6..8b794efdb 100644
--- a/src/cmd/gc/builtin.c.boot
+++ b/src/cmd/gc/builtin.c.boot
@@ -25,6 +25,7 @@ char *runtimeimport =
 	"func runtime.sliceinttostring (? []int) (? string)\n"
 	"func runtime.stringiter (? string, ? int) (? int)\n"
 	"func runtime.stringiter2 (? string, ? int) (retk int, retv int)\n"
+	"func runtime.slicecopy (to any, fr any, wid uint32) (? int)\n"
 	"func runtime.ifaceI2E (iface any) (ret any)\n"
 	"func runtime.ifaceE2I (typ *uint8, iface any) (ret any)\n"
 	"func runtime.ifaceT2E (typ *uint8, elem any) (ret any)\n"
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index f5b88ff59..7702efbf7 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -346,6 +346,7 @@ enum
 	OCMPIFACE, OCMPSTR,
 	OCOMPLIT, OMAPLIT, OSTRUCTLIT, OARRAYLIT,
 	OCONV, OCONVNOP, OCONVIFACE, OCONVSLICE,
+	OCOPY,
 	ODCL, ODCLFUNC, ODCLFIELD, ODCLCONST, ODCLTYPE,
 	ODOT, ODOTPTR, ODOTMETH, ODOTINTER, OXDOT,
 	ODOTTYPE,
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 14500dc75..f858aa95e 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -1245,6 +1245,7 @@ static	struct
 	"cap",		LNAME,		Txxx,		OCAP,
 	"close",	LNAME,		Txxx,		OCLOSE,
 	"closed",	LNAME,		Txxx,		OCLOSED,
+	"copy",		LNAME,		Txxx,		OCOPY,
 	"len",		LNAME,		Txxx,		OLEN,
 	"make",		LNAME,		Txxx,		OMAKE,
 	"new",		LNAME,		Txxx,		ONEW,
diff --git a/src/cmd/gc/print.c b/src/cmd/gc/print.c
index ce4f721ae..bbb7b0fbd 100644
--- a/src/cmd/gc/print.c
+++ b/src/cmd/gc/print.c
@@ -44,6 +44,7 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OCAP:
 	case OCLOSE:
 	case OCLOSED:
+	case OCOPY:
 	case OLEN:
 	case OMAKE:
 	case ONEW:
@@ -305,6 +306,7 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OCLOSE:
 	case OCLOSED:
 	case OLEN:
+	case OCOPY:
 	case OMAKE:
 	case ONEW:
 	case OPANIC:
diff --git a/src/cmd/gc/runtime.go b/src/cmd/gc/runtime.go
index 5e3632920..1f078f2da 100644
--- a/src/cmd/gc/runtime.go
+++ b/src/cmd/gc/runtime.go
@@ -33,6 +33,7 @@ func slicebytetostring([]byte) string
 func sliceinttostring([]int) string
 func stringiter(string, int) int
 func stringiter2(string, int) (retk int, retv int)
+func slicecopy(to any, fr any, wid uint32) int
 
 func ifaceI2E(iface any) (ret any)
 func ifaceE2I(typ *byte, iface any) (ret any)
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 75ece477d..22e59c5c8 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -746,6 +746,7 @@ goopnames[] =
 	[OCLOSE]	= "close",
 	[OCOM]		= "^",
 	[OCONTINUE]	= "continue",
+	[OCOPY]		= "copy",
 	[ODEC]		= "--",
 	[ODEFER]	= "defer",
 	[ODIV]		= "/",
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 108a2d3e9..86633b86d 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -761,6 +761,32 @@ reswitch:
 			ok |= Etop;
 		goto ret;
 
+	case OCOPY:
+		ok |= Erv;
+		args = n->list;
+		if(args == nil || args->next == nil) {
+			yyerror("missing arguments to copy");
+			goto error;
+		}
+		if(args->next->next != nil) {
+			yyerror("too many arguments to copy");
+			goto error;
+		}
+		typecheck(&args->n, Erv);
+		typecheck(&args->next->n, Erv);
+		if(!isslice(args->n->type) || !isslice(args->next->n->type)) {
+			yyerror("arguments to copy must be slices");
+			goto error;
+		}
+		if(!eqtype(args->n->type, args->next->n->type)) {
+			yyerror("arguments to copy must be slices of the same type");
+			goto error;
+		}
+		n->left = args->n;
+		n->right = args->next->n;
+		n->type = types[TINT];
+		goto ret;
+
 	case OCONV:
 	doconv:
 		ok |= Erv;
diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c
index 6aa23783f..bb100b971 100644
--- a/src/cmd/gc/walk.c
+++ b/src/cmd/gc/walk.c
@@ -307,6 +307,7 @@ walkstmt(Node **np)
 	case OAS2MAPR:
 	case OCLOSE:
 	case OCLOSED:
+	case OCOPY:
 	case OCALLMETH:
 	case OCALLINTER:
 	case OCALL:
@@ -904,6 +905,15 @@ walkexpr(Node **np, NodeList **init)
 			conv(n->right, types[TINT]));
 		goto ret;
 
+	case OCOPY:
+		fn = syslook("slicecopy", 1);
+		argtype(fn, n->left->type);
+		argtype(fn, n->right->type);
+		n = mkcall1(fn, n->type, init,
+			n->left, n->right,
+			nodintconst(n->left->type->width));
+		goto ret;
+
 	case OCLOSE:
 		// cannot use chanfn - closechan takes any, not chan any
 		fn = syslook("closechan", 1);
@@ -950,7 +960,8 @@ walkexpr(Node **np, NodeList **init)
 
 	case ORUNESTR:
 		// sys_intstring(v)
-		n = mkcall("intstring", n->type, init, conv(n->left, types[TINT64]));	// TODO(rsc): int64?!
+		n = mkcall("intstring", n->type, init,
+			conv(n->left, types[TINT64]));	// TODO(rsc): int64?!
 		goto ret;
 
 	case OARRAYBYTESTR: