1 files changed, 58 insertions, 0 deletions
diff --git a/abi/switch.go b/abi/switch.go
new file mode 100644
index 0000000..a30fdd0
--- /dev/null
+++ b/abi/switch.go
@@ -0,0 +1,58 @@
+// 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.
+
+package abi
+
+import "internal/goarch"
+
+type InterfaceSwitch struct {
+	Cache  *InterfaceSwitchCache
+	NCases int
+
+	// Array of NCases elements.
+	// Each case must be a non-empty interface type.
+	Cases [1]*InterfaceType
+}
+
+type InterfaceSwitchCache struct {
+	Mask    uintptr                      // mask for index. Must be a power of 2 minus 1
+	Entries [1]InterfaceSwitchCacheEntry // Mask+1 entries total
+}
+
+type InterfaceSwitchCacheEntry struct {
+	// type of source value (a *Type)
+	Typ uintptr
+	// case # to dispatch to
+	Case int
+	// itab to use for resulting case variable (a *runtime.itab)
+	Itab uintptr
+}
+
+func UseInterfaceSwitchCache(arch goarch.ArchFamilyType) bool {
+	// We need an atomic load instruction to make the cache multithreaded-safe.
+	// (AtomicLoadPtr needs to be implemented in cmd/compile/internal/ssa/_gen/ARCH.rules.)
+	switch arch {
+	case goarch.AMD64, goarch.ARM64, goarch.LOONG64, goarch.MIPS, goarch.MIPS64, goarch.PPC64, goarch.RISCV64, goarch.S390X:
+		return true
+	default:
+		return false
+	}
+}
+
+type TypeAssert struct {
+	Cache   *TypeAssertCache
+	Inter   *InterfaceType
+	CanFail bool
+}
+type TypeAssertCache struct {
+	Mask    uintptr
+	Entries [1]TypeAssertCacheEntry
+}
+type TypeAssertCacheEntry struct {
+	// type of source value (a *runtime._type)
+	Typ uintptr
+	// itab to use for result (a *runtime.itab)
+	// nil if CanFail is set and conversion would fail.
+	Itab uintptr
+}