compiler/runtime: add element layout to sliceAppend

Attach the memory layout of the element type to newly created slices via append when using the precise collector.

src/runtime/slice.go

@@ -3,19 +3,18 @@ package runtime
 // This file implements compiler builtins for slices: append() and copy().
 
 import (
-	"internal/gclayout"
 	"math/bits"
 	"unsafe"
 )
 
 // Builtin append(src, elements...) function: append elements to src and return
 // the modified (possibly expanded) slice.
-func sliceAppend(srcBuf, elemsBuf unsafe.Pointer, srcLen, srcCap, elemsLen, elemSize uintptr) (unsafe.Pointer, uintptr, uintptr) {
+func sliceAppend(srcBuf, elemsBuf unsafe.Pointer, srcLen, srcCap, elemsLen, elemSize uintptr, layout unsafe.Pointer) (unsafe.Pointer, uintptr, uintptr) {
 	newLen := srcLen + elemsLen
 	if elemsLen > 0 {
 		// Allocate a new slice with capacity for elemsLen more elements, if necessary;
 		// otherwise, reuse the passed slice.
-		srcBuf, _, srcCap = sliceGrow(srcBuf, srcLen, srcCap, newLen, elemSize)
+		srcBuf, _, srcCap = sliceGrow(srcBuf, srcLen, srcCap, newLen, elemSize, layout)
 
 		// Append the new elements in-place.
 		memmove(unsafe.Add(srcBuf, srcLen*elemSize), elemsBuf, elemsLen*elemSize)
@@ -36,7 +35,7 @@ func sliceCopy(dst, src unsafe.Pointer, dstLen, srcLen uintptr, elemSize uintptr
 }
 
 // sliceGrow returns a new slice with space for at least newCap elements
-func sliceGrow(oldBuf unsafe.Pointer, oldLen, oldCap, newCap, elemSize uintptr) (unsafe.Pointer, uintptr, uintptr) {
+func sliceGrow(oldBuf unsafe.Pointer, oldLen, oldCap, newCap, elemSize uintptr, layout unsafe.Pointer) (unsafe.Pointer, uintptr, uintptr) {
 	if oldCap >= newCap {
 		// No need to grow, return the input slice.
 		return oldBuf, oldLen, oldCap
@@ -48,12 +47,6 @@ func sliceGrow(oldBuf unsafe.Pointer, oldLen, oldCap, newCap, elemSize uintptr)
 	// memory allocators, this causes some difficult to debug issues.
 	newCap = 1 << bits.Len(uint(newCap))
 
-	var layout unsafe.Pointer
-	// less type info here; can only go off element size
-	if elemSize < unsafe.Sizeof(uintptr(0)) {
-		layout = gclayout.NoPtrs.AsPtr()
-	}
-
 	buf := alloc(newCap*elemSize, layout)
 	if oldLen > 0 {
 		// copy any data to new slice