cmd/compile,runtime: pass elem type to {make,grow}slice

No point in passing the slice type to these functions.
All they need is the element type.  One less indirection,
maybe a few less []T type descriptors in the binary.

Change-Id: Ib0b83b5f14ca21d995ecc199ce8ac00c4eb375e6
Reviewed-on: https://go-review.googlesource.com/22275Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/compile/internal/gc/cgen.go

@@ -2876,7 +2876,7 @@ func cgen_append(n, res *Node) {
 	arg.Addable = true
 	arg.Xoffset = Ctxt.FixedFrameSize()
 	arg.Type = Ptrto(Types[TUINT8])
-	Cgen(typename(res.Type), &arg)
+	Cgen(typename(res.Type.Elem()), &arg)
 	arg.Xoffset += int64(Widthptr)
 
 	arg.Type = Types[Tptr]

src/cmd/compile/internal/gc/ssa.go

@@ -2185,7 +2185,7 @@ func (s *state) append(n *Node, inplace bool) *ssa.Value {
 
 	// Call growslice
 	s.startBlock(grow)
-	taddr := s.newValue1A(ssa.OpAddr, Types[TUINTPTR], &ssa.ExternSymbol{Types[TUINTPTR], typenamesym(n.Type)}, s.sb)
+	taddr := s.newValue1A(ssa.OpAddr, Types[TUINTPTR], &ssa.ExternSymbol{Types[TUINTPTR], typenamesym(n.Type.Elem())}, s.sb)
 
 	r := s.rtcall(growslice, true, []*Type{pt, Types[TINT], Types[TINT]}, taddr, p, l, c, nl)
 

src/cmd/compile/internal/gc/walk.go

@@ -1420,11 +1420,11 @@ opswitch:
 			r = walkexpr(r, init)
 			n = r
 		} else {
-			// makeslice(t *Type, nel int64, max int64) (ary []any)
+			// makeslice(et *Type, nel int64, max int64) (ary []any)
 			fn := syslook("makeslice")
 
 			fn = substArgTypes(fn, t.Elem()) // any-1
-			n = mkcall1(fn, n.Type, init, typename(n.Type), conv(l, Types[TINT64]), conv(r, Types[TINT64]))
+			n = mkcall1(fn, n.Type, init, typename(t.Elem()), conv(l, Types[TINT64]), conv(r, Types[TINT64]))
 		}
 
 	case ORUNESTR:
@@ -2799,7 +2799,7 @@ func appendslice(n *Node, init *Nodes) *Node {
 	fn = substArgTypes(fn, s.Type.Elem(), s.Type.Elem())
 
 	// s = growslice(T, s, n)
-	nif.Nbody.Set1(Nod(OAS, s, mkcall1(fn, s.Type, &nif.Ninit, typename(s.Type), s, nn)))
+	nif.Nbody.Set1(Nod(OAS, s, mkcall1(fn, s.Type, &nif.Ninit, typename(s.Type.Elem()), s, nn)))
 	l = append(l, nif)
 
 	// s = s[:n]
@@ -2929,7 +2929,7 @@ func walkappend(n *Node, init *Nodes, dst *Node) *Node {
 	fn = substArgTypes(fn, ns.Type.Elem(), ns.Type.Elem())
 
 	nx.Nbody.Set1(Nod(OAS, ns,
-		mkcall1(fn, ns.Type, &nx.Ninit, typename(ns.Type), ns,
+		mkcall1(fn, ns.Type, &nx.Ninit, typename(ns.Type.Elem()), ns,
 			Nod(OADD, Nod(OLEN, ns, nil), na))))
 
 	l = append(l, nx)

src/runtime/slice.go

@@ -37,14 +37,14 @@ func maxSliceCap(elemsize uintptr) uintptr {
 }
 
 // TODO: take uintptrs instead of int64s?
-func makeslice(t *slicetype, len64, cap64 int64) slice {
+func makeslice(et *_type, len64, cap64 int64) slice {
 	// NOTE: The len > maxElements check here is not strictly necessary,
 	// but it produces a 'len out of range' error instead of a 'cap out of range' error
 	// when someone does make([]T, bignumber). 'cap out of range' is true too,
 	// but since the cap is only being supplied implicitly, saying len is clearer.
 	// See issue 4085.
 
-	maxElements := maxSliceCap(t.elem.size)
+	maxElements := maxSliceCap(et.size)
 	len := int(len64)
 	if len64 < 0 || int64(len) != len64 || uintptr(len) > maxElements {
 		panic(errorString("makeslice: len out of range"))
@@ -55,7 +55,6 @@ func makeslice(t *slicetype, len64, cap64 int64) slice {
 		panic(errorString("makeslice: cap out of range"))
 	}
 
-	et := t.elem
 	var flags uint32
 	if et.kind&kindNoPointers != 0 {
 		flags = flagNoScan
@@ -65,7 +64,7 @@ func makeslice(t *slicetype, len64, cap64 int64) slice {
 }
 
 // growslice handles slice growth during append.
-// It is passed the slice type, the old slice, and the desired new minimum capacity,
+// It is passed the slice element type, the old slice, and the desired new minimum capacity,
 // and it returns a new slice with at least that capacity, with the old data
 // copied into it.
 // The new slice's length is set to the old slice's length,
@@ -74,16 +73,15 @@ func makeslice(t *slicetype, len64, cap64 int64) slice {
 // to calculate where to write new values during an append.
 // TODO: When the old backend is gone, reconsider this decision.
 // The SSA backend might prefer the new length or to return only ptr/cap and save stack space.
-func growslice(t *slicetype, old slice, cap int) slice {
+func growslice(et *_type, old slice, cap int) slice {
 	if raceenabled {
-		callerpc := getcallerpc(unsafe.Pointer(&t))
-		racereadrangepc(old.array, uintptr(old.len*int(t.elem.size)), callerpc, funcPC(growslice))
+		callerpc := getcallerpc(unsafe.Pointer(&et))
+		racereadrangepc(old.array, uintptr(old.len*int(et.size)), callerpc, funcPC(growslice))
 	}
 	if msanenabled {
-		msanread(old.array, uintptr(old.len*int(t.elem.size)))
+		msanread(old.array, uintptr(old.len*int(et.size)))
 	}
 
-	et := t.elem
 	if et.size == 0 {
 		if cap < old.cap {
 			panic(errorString("growslice: cap out of range"))