diff --git a/src/cmd/compile/internal/ssa/dom.go b/src/cmd/compile/internal/ssa/dom.go
index db991f6b7e..ee2748e6df 100644
--- a/src/cmd/compile/internal/ssa/dom.go
+++ b/src/cmd/compile/internal/ssa/dom.go
@@ -37,7 +37,9 @@ func postorderWithNumbering(f *Func, ponums []int32) []*Block {
 	var order []*Block
 
 	// stack of blocks and next child to visit
-	var s []blockAndIndex
+	// A constant bound allows this to be stack-allocated. 32 is
+	// enough to cover almost every postorderWithNumbering call.
+	s := make([]blockAndIndex, 0, 32)
 	s = append(s, blockAndIndex{b: f.Entry})
 	mark[f.Entry.ID] = explored
 	for len(s) > 0 {
diff --git a/src/cmd/compile/internal/ssa/schedule.go b/src/cmd/compile/internal/ssa/schedule.go
index ff8bac8409..78c72f8146 100644
--- a/src/cmd/compile/internal/ssa/schedule.go
+++ b/src/cmd/compile/internal/ssa/schedule.go
@@ -74,7 +74,9 @@ func schedule(f *Func) {
 	score := make([]int8, f.NumValues())
 
 	// scheduling order. We queue values in this list in reverse order.
-	var order []*Value
+	// A constant bound allows this to be stack-allocated. 64 is
+	// enough to cover almost every schedule call.
+	order := make([]*Value, 0, 64)
 
 	// maps mem values to the next live memory value
 	nextMem := make([]*Value, f.NumValues())