go/ssa: add Node interface: common parts of Value+Instruction, plus Operands/Referrers.
Also:
- extend Parent() to all Values and add to interface:
(Builtin/Const/Global => nil; Function => Enclosing)
- hide Function.Enclosing since it's now redundant wrt Parent()
- make (*Function).String robust for synthetics without pkg object
LGTM=gri
R=gri
CC=golang-codereviews, khr
https://golang.org/cl/87580044
diff --git a/go/ssa/ssa.go b/go/ssa/ssa.go
index 9151c97..b940255 100644
--- a/go/ssa/ssa.go
+++ b/go/ssa/ssa.go
@@ -123,6 +123,10 @@
// types of their operands.
Type() types.Type
+ // Parent returns the function to which this Value belongs.
+ // It returns nil for named Functions, Builtin, Const and Global.
+ Parent() *Function
+
// Referrers returns the list of instructions that have this
// value as one of their operands; it may contain duplicates
// if an instruction has a repeated operand.
@@ -130,9 +134,9 @@
// Referrers actually returns a pointer through which the
// caller may perform mutations to the object's state.
//
- // Referrers is currently only defined for the function-local
- // values Capture, Parameter, Functions (iff anonymous) and
- // all value-defining instructions.
+ // Referrers is currently only defined if Parent()!=nil,
+ // i.e. for the function-local values Capture, Parameter,
+ // Functions (iff anonymous) and all value-defining instructions.
// It returns nil for named Functions, Builtin, Const and Global.
//
// Instruction.Operands contains the inverse of this relation.
@@ -199,9 +203,10 @@
// user-provided slice, and returns the resulting slice,
// permitting avoidance of memory allocation.
//
- // The operands are appended in undefined order; the addresses
- // are always non-nil but may point to a nil Value. Clients
- // may store through the pointers, e.g. to effect a value
+ // The operands are appended in undefined order, but the order
+ // is consistent for a given Instruction; the addresses are
+ // always non-nil but may point to a nil Value. Clients may
+ // store through the pointers, e.g. to effect a value
// renaming.
//
// Value.Referrers is a subset of the inverse of this
@@ -229,6 +234,28 @@
Pos() token.Pos
}
+// A Node is a node in the SSA value graph. Every concrete type that
+// implements Node is also either a Value, an Instruction, or both.
+//
+// Node contains the methods common to Value and Instruction, plus the
+// Operands and Referrers methods generalized to return nil for
+// non-Instructions and non-Values, respectively.
+//
+// Node is provided to simplify SSA graph algorithms. Clients should
+// use the more specific and informative Value or Instruction
+// interfaces where appropriate.
+//
+type Node interface {
+ // Common methods:
+ String() string
+ Pos() token.Pos
+ Parent() *Function
+
+ // Partial methods:
+ Operands(rands []*Value) []*Value // nil for non-Instructions
+ Referrers() *[]Instruction // nil for non-Values
+}
+
// Function represents the parameters, results and code of a function
// or method.
//
@@ -250,11 +277,11 @@
// of the function's named return parameters followed by a return of
// the loaded values.
//
-// A nested function that refers to one or more lexically enclosing
-// local variables ("free variables") has Capture parameters. Such
-// functions cannot be called directly but require a value created by
-// MakeClosure which, via its Bindings, supplies values for these
-// parameters.
+// A nested function (Parent()!=nil) that refers to one or more
+// lexically enclosing local variables ("free variables") has Capture
+// parameters. Such functions cannot be called directly but require a
+// value created by MakeClosure which, via its Bindings, supplies
+// values for these parameters.
//
// If the function is a method (Signature.Recv() != nil) then the first
// element of Params is the receiver parameter.
@@ -275,7 +302,7 @@
Synthetic string // provenance of synthetic function; "" for true source functions
syntax ast.Node // *ast.Func{Decl,Lit}; replaced with simple ast.Node after build, unless debug mode
- Enclosing *Function // enclosing function if anon; nil if global
+ parent *Function // enclosing function if anon; nil if global
Pkg *Package // enclosing package; nil for shared funcs (wrappers and error.Error)
Prog *Program // enclosing program
Params []*Parameter // function parameters; for methods, includes receiver
@@ -284,7 +311,7 @@
Blocks []*BasicBlock // basic blocks of the function; nil => external
Recover *BasicBlock // optional; control transfers here after recovered panic
AnonFuncs []*Function // anonymous functions directly beneath this one
- referrers []Instruction // referring instructions (iff Enclosing != nil)
+ referrers []Instruction // referring instructions (iff Parent() != nil)
// The following fields are set transiently during building,
// then cleared.
@@ -1359,6 +1386,7 @@
func (*Builtin) Referrers() *[]Instruction { return nil }
func (v *Builtin) Pos() token.Pos { return token.NoPos }
func (v *Builtin) Object() types.Object { return v.object }
+func (v *Builtin) Parent() *Function { return nil }
func (v *Capture) Type() types.Type { return v.typ }
func (v *Capture) Name() string { return v.name }
@@ -1368,6 +1396,7 @@
func (v *Global) Type() types.Type { return v.typ }
func (v *Global) Name() string { return v.name }
+func (v *Global) Parent() *Function { return nil }
func (v *Global) Pos() token.Pos { return v.pos }
func (v *Global) Referrers() *[]Instruction { return nil }
func (v *Global) Token() token.Token { return token.VAR }
@@ -1383,8 +1412,9 @@
func (v *Function) Object() types.Object { return v.object }
func (v *Function) String() string { return v.RelString(nil) }
func (v *Function) Package() *Package { return v.Pkg }
+func (v *Function) Parent() *Function { return v.parent }
func (v *Function) Referrers() *[]Instruction {
- if v.Enclosing != nil {
+ if v.parent != nil {
return &v.referrers
}
return nil
@@ -1412,6 +1442,7 @@
func (v *anInstruction) Parent() *Function { return v.block.parent }
func (v *anInstruction) Block() *BasicBlock { return v.block }
func (v *anInstruction) setBlock(block *BasicBlock) { v.block = block }
+func (v *anInstruction) Referrers() *[]Instruction { return nil }
func (t *Type) Name() string { return t.object.Name() }
func (t *Type) Pos() token.Pos { return t.object.Pos() }
@@ -1638,3 +1669,11 @@
func (v *UnOp) Operands(rands []*Value) []*Value {
return append(rands, &v.X)
}
+
+// Non-Instruction Values:
+func (v *Builtin) Operands(rands []*Value) []*Value { return rands }
+func (v *Capture) Operands(rands []*Value) []*Value { return rands }
+func (v *Const) Operands(rands []*Value) []*Value { return rands }
+func (v *Function) Operands(rands []*Value) []*Value { return rands }
+func (v *Global) Operands(rands []*Value) []*Value { return rands }
+func (v *Parameter) Operands(rands []*Value) []*Value { return rands }
