compile/internal/walk: add walkGrowslice

Move growslice generation to a separate func so that specialization
logic can be shared.

Updates #49480

Change-Id: I9ea5bb898753622d2d767546a46b4db6410dc725
Reviewed-on: https://go-review.googlesource.com/c/go/+/495877
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>

2 files changed, 13 insertions, 16 deletions

diff --git a/src/cmd/compile/internal/walk/assign.go b/src/cmd/compile/internal/walk/assign.go
index bf7592967e..b8dcba5968 100644
--- a/src/cmd/compile/internal/walk/assign.go
+++ b/src/cmd/compile/internal/walk/assign.go
@@ -513,11 +513,8 @@ func appendSlice(n *ir.CallExpr, init *ir.Nodes) ir.Node {
 	slice.SetBounded(true)
 	nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, s, slice)}
 
-	// func growslice(oldPtr unsafe.Pointer, newLen, oldCap, num int, et *_type) []T
-	fn := typecheck.LookupRuntime("growslice", elemtype, elemtype)
-
 	// else { s = growslice(oldPtr, newLen, oldCap, num, T) }
-	call := mkcall1(fn, s.Type(), nif.PtrInit(), oldPtr, newLen, oldCap, num, reflectdata.TypePtrAt(base.Pos, elemtype))
+	call := walkGrowslice(s, nif.PtrInit(), oldPtr, newLen, oldCap, num)
 	nif.Else = []ir.Node{ir.NewAssignStmt(base.Pos, s, call)}
 
 	nodes.Append(nif)
@@ -691,17 +688,13 @@ func extendSlice(n *ir.CallExpr, init *ir.Nodes) ir.Node {
 	nt.SetBounded(true)
 	nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, s, nt)}
 
-	// instantiate growslice(oldPtr *any, newLen, oldCap, num int, typ *type) []any
-	fn := typecheck.LookupRuntime("growslice", elemtype, elemtype)
-
 	// else { s = growslice(s.ptr, n, s.cap, l2, T) }
 	nif.Else = []ir.Node{
-		ir.NewAssignStmt(base.Pos, s, mkcall1(fn, s.Type(), nif.PtrInit(),
+		ir.NewAssignStmt(base.Pos, s, walkGrowslice(s, nif.PtrInit(),
 			ir.NewUnaryExpr(base.Pos, ir.OSPTR, s),
 			nn,
 			ir.NewUnaryExpr(base.Pos, ir.OCAP, s),
-			l2,
-			reflectdata.TypePtrAt(base.Pos, elemtype))),
+			l2)),
 	}
 
 	nodes = append(nodes, nif)
diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go
index c3a641eac9..56dad14f21 100644
--- a/src/cmd/compile/internal/walk/builtin.go
+++ b/src/cmd/compile/internal/walk/builtin.go
@@ -101,17 +101,13 @@ func walkAppend(n *ir.CallExpr, init *ir.Nodes, dst ir.Node) ir.Node {
 		ir.NewAssignStmt(base.Pos, s, slice),
 	}
 
-	//   growslice(ptr *T, newLen, oldCap, num int, <type>) (ret []T)
-	fn := typecheck.LookupRuntime("growslice", s.Type().Elem(), s.Type().Elem())
-
 	// else { s = growslice(s.ptr, n, s.cap, a, T) }
 	nif.Else = []ir.Node{
-		ir.NewAssignStmt(base.Pos, s, mkcall1(fn, s.Type(), nif.PtrInit(),
+		ir.NewAssignStmt(base.Pos, s, walkGrowslice(s, nif.PtrInit(),
 			ir.NewUnaryExpr(base.Pos, ir.OSPTR, s),
 			newLen,
 			ir.NewUnaryExpr(base.Pos, ir.OCAP, s),
-			num,
-			reflectdata.TypePtrAt(base.Pos, s.Type().Elem()))),
+			num)),
 	}
 
 	l = append(l, nif)
@@ -130,6 +126,14 @@ func walkAppend(n *ir.CallExpr, init *ir.Nodes, dst ir.Node) ir.Node {
 	return s
 }
 
+// growslice(ptr *T, newLen, oldCap, num int, <type>) (ret []T)
+func walkGrowslice(slice *ir.Name, init *ir.Nodes, oldPtr, newLen, oldCap, num ir.Node) *ir.CallExpr {
+	elemtype := slice.Type().Elem()
+	fn := typecheck.LookupRuntime("growslice", elemtype, elemtype)
+	elemtypeptr := reflectdata.TypePtrAt(base.Pos, elemtype)
+	return mkcall1(fn, slice.Type(), init, oldPtr, newLen, oldCap, num, elemtypeptr)
+}
+
 // walkClear walks an OCLEAR node.
 func walkClear(n *ir.UnaryExpr) ir.Node {
 	typ := n.X.Type()