1 files changed, 54 insertions, 0 deletions
diff --git a/src/cmd/link/internal/ld/heap.go b/src/cmd/link/internal/ld/heap.go
new file mode 100644
index 0000000..ea2d772
--- /dev/null
+++ b/src/cmd/link/internal/ld/heap.go
@@ -0,0 +1,54 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ld
+
+import "cmd/link/internal/loader"
+
+// Min-heap implementation, for the deadcode pass.
+// Specialized for loader.Sym elements.
+
+type heap []loader.Sym
+
+func (h *heap) push(s loader.Sym) {
+	*h = append(*h, s)
+	// sift up
+	n := len(*h) - 1
+	for n > 0 {
+		p := (n - 1) / 2 // parent
+		if (*h)[p] <= (*h)[n] {
+			break
+		}
+		(*h)[n], (*h)[p] = (*h)[p], (*h)[n]
+		n = p
+	}
+}
+
+func (h *heap) pop() loader.Sym {
+	r := (*h)[0]
+	n := len(*h) - 1
+	(*h)[0] = (*h)[n]
+	*h = (*h)[:n]
+
+	// sift down
+	i := 0
+	for {
+		c := 2*i + 1 // left child
+		if c >= n {
+			break
+		}
+		if c1 := c + 1; c1 < n && (*h)[c1] < (*h)[c] {
+			c = c1 // right child
+		}
+		if (*h)[i] <= (*h)[c] {
+			break
+		}
+		(*h)[i], (*h)[c] = (*h)[c], (*h)[i]
+		i = c
+	}
+
+	return r
+}
+
+func (h *heap) empty() bool { return len(*h) == 0 }