1 files changed, 88 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/location.go b/src/cmd/compile/internal/ssa/location.go
new file mode 100644
index 0000000..a333982
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/location.go
@@ -0,0 +1,88 @@
+// Copyright 2015 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 ssa
+
+import (
+	"cmd/compile/internal/types"
+	"fmt"
+)
+
+// A place that an ssa variable can reside.
+type Location interface {
+	String() string // name to use in assembly templates: AX, 16(SP), ...
+}
+
+// A Register is a machine register, like AX.
+// They are numbered densely from 0 (for each architecture).
+type Register struct {
+	num    int32 // dense numbering
+	objNum int16 // register number from cmd/internal/obj/$ARCH
+	gcNum  int16 // GC register map number (dense numbering of registers that can contain pointers)
+	name   string
+}
+
+func (r *Register) String() string {
+	return r.name
+}
+
+// ObjNum returns the register number from cmd/internal/obj/$ARCH that
+// corresponds to this register.
+func (r *Register) ObjNum() int16 {
+	return r.objNum
+}
+
+// GCNum returns the runtime GC register index of r, or -1 if this
+// register can't contain pointers.
+func (r *Register) GCNum() int16 {
+	return r.gcNum
+}
+
+// A LocalSlot is a location in the stack frame, which identifies and stores
+// part or all of a PPARAM, PPARAMOUT, or PAUTO ONAME node.
+// It can represent a whole variable, part of a larger stack slot, or part of a
+// variable that has been decomposed into multiple stack slots.
+// As an example, a string could have the following configurations:
+//
+//           stack layout              LocalSlots
+//
+// Optimizations are disabled. s is on the stack and represented in its entirety.
+// [ ------- s string ---- ] { N: s, Type: string, Off: 0 }
+//
+// s was not decomposed, but the SSA operates on its parts individually, so
+// there is a LocalSlot for each of its fields that points into the single stack slot.
+// [ ------- s string ---- ] { N: s, Type: *uint8, Off: 0 }, {N: s, Type: int, Off: 8}
+//
+// s was decomposed. Each of its fields is in its own stack slot and has its own LocalSLot.
+// [ ptr *uint8 ] [ len int] { N: ptr, Type: *uint8, Off: 0, SplitOf: parent, SplitOffset: 0},
+//                           { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8}
+//                           parent = &{N: s, Type: string}
+type LocalSlot struct {
+	N    GCNode      // an ONAME *gc.Node representing a stack location.
+	Type *types.Type // type of slot
+	Off  int64       // offset of slot in N
+
+	SplitOf     *LocalSlot // slot is a decomposition of SplitOf
+	SplitOffset int64      // .. at this offset.
+}
+
+func (s LocalSlot) String() string {
+	if s.Off == 0 {
+		return fmt.Sprintf("%v[%v]", s.N, s.Type)
+	}
+	return fmt.Sprintf("%v+%d[%v]", s.N, s.Off, s.Type)
+}
+
+type LocPair [2]Location
+
+func (t LocPair) String() string {
+	n0, n1 := "nil", "nil"
+	if t[0] != nil {
+		n0 = t[0].String()
+	}
+	if t[1] != nil {
+		n1 = t[1].String()
+	}
+	return fmt.Sprintf("<%s,%s>", n0, n1)
+}