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go.tools/ssa: clarify that DebugRef relation is a function from ast.Expr to (ssa.Value, IsAddr bool), in docs and printed form.

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R=gri
CC=golang-dev
https://golang.org/cl/18410043
This commit is contained in:
Alan Donovan 2013-10-28 12:05:29 -04:00
parent 7a70c382be
commit e29626539b
2 changed files with 21 additions and 9 deletions
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2
ssa/print.go
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@ -398,7 +398,7 @@ func (s *DebugRef) String() string {
if s.IsAddr {
addr = "address of "
}
return fmt.Sprintf("; %s is %s%s @ %d:%d", s.X.Name(), addr, descr, p.Line, p.Column)
return fmt.Sprintf("; %s%s @ %d:%d is %s", addr, descr, p.Line, p.Column, s.X.Name())
}
func (p *Package) String() string {

28
ssa/ssa.go
View File

@ -1151,8 +1151,9 @@ type MapUpdate struct {
pos token.Pos
}
// A DebugRef instruction provides the position information for a
// specific source-level expression that compiles to the SSA value X.
// A DebugRef instruction maps a source-level expression Expr to the
// SSA value that represents the value (!IsAddr) or address (IsAddr)
// of that expression.
//
// DebugRef is a pseudo-instruction: it has no dynamic effect.
//
@ -1161,22 +1162,33 @@ type MapUpdate struct {
// documented at Value.Pos(). e.g. CallExpr.Pos() does not return the
// position of the ("designated") Lparen token.
//
// Object() returns the source-level (var/const/func) object denoted
// by Expr if it is an *ast.Ident; otherwise it is nil.
// If Expr is an *ast.Ident denoting a var or func, Object() returns
// the object; though this information can be obtained from the type
// checker, including it here greatly facilitates debugging.
// For non-Ident expressions, Object() returns nil.
//
// DebugRefs are generated only for functions built with debugging
// enabled; see Package.SetDebugMode().
//
// DebugRefs are not emitted for ast.Idents referring to constants or
// predeclared identifiers, since they are trivial and numerous.
// Nor are they emitted for ast.ParenExprs.
//
// (By representing these as instructions, rather than out-of-band,
// consistency is maintained during transformation passes by the
// ordinary SSA renaming machinery.)
//
// DebugRefs are generated only for functions built with debugging
// enabled; see Package.SetDebugMode().
// Example printed form:
// ; *ast.CallExpr @ 102:9 is t5
// ; var x float64 @ 109:72 is x
// ; address of *ast.CompositeLit @ 216:10 is t0
//
type DebugRef struct {
anInstruction
X Value // the value whose position we're declaring
Expr ast.Expr // the referring expression (never *ast.ParenExpr)
object types.Object // the identity of the source var/const/func
object types.Object // the identity of the source var/func
IsAddr bool // Expr is addressable and X is the address it denotes
X Value // the value or address of Expr
}
// Embeddable mix-ins and helpers for common parts of other structs. -----------