1 files changed, 62 insertions, 0 deletions
diff --git a/src/runtime/trace2region.go b/src/runtime/trace2region.go
new file mode 100644
index 0000000..b514d12
--- /dev/null
+++ b/src/runtime/trace2region.go
@@ -0,0 +1,62 @@
+// Copyright 2023 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.
+
+//go:build goexperiment.exectracer2
+
+// Simple not-in-heap bump-pointer traceRegion allocator.
+
+package runtime
+
+import (
+	"internal/goarch"
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+// traceRegionAlloc is a non-thread-safe region allocator.
+// It holds a linked list of traceRegionAllocBlock.
+type traceRegionAlloc struct {
+	head *traceRegionAllocBlock
+	off  uintptr
+}
+
+// traceRegionAllocBlock is a block in traceRegionAlloc.
+//
+// traceRegionAllocBlock is allocated from non-GC'd memory, so it must not
+// contain heap pointers. Writes to pointers to traceRegionAllocBlocks do
+// not need write barriers.
+type traceRegionAllocBlock struct {
+	_    sys.NotInHeap
+	next *traceRegionAllocBlock
+	data [64<<10 - goarch.PtrSize]byte
+}
+
+// alloc allocates n-byte block.
+func (a *traceRegionAlloc) alloc(n uintptr) *notInHeap {
+	n = alignUp(n, goarch.PtrSize)
+	if a.head == nil || a.off+n > uintptr(len(a.head.data)) {
+		if n > uintptr(len(a.head.data)) {
+			throw("traceRegion: alloc too large")
+		}
+		block := (*traceRegionAllocBlock)(sysAlloc(unsafe.Sizeof(traceRegionAllocBlock{}), &memstats.other_sys))
+		if block == nil {
+			throw("traceRegion: out of memory")
+		}
+		block.next = a.head
+		a.head = block
+		a.off = 0
+	}
+	p := &a.head.data[a.off]
+	a.off += n
+	return (*notInHeap)(unsafe.Pointer(p))
+}
+
+// drop frees all previously allocated memory and resets the allocator.
+func (a *traceRegionAlloc) drop() {
+	for a.head != nil {
+		block := a.head
+		a.head = block.next
+		sysFree(unsafe.Pointer(block), unsafe.Sizeof(traceRegionAllocBlock{}), &memstats.other_sys)
+	}
+}