cmd/compile: port liveness analysis to SSA

Passes toolstash-check -all.

Change-Id: I92c3c25d6c053f971f346f4fa3bbc76419b58183
Reviewed-on: https://go-review.googlesource.com/38087
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/fmt_test.go

@@ -593,7 +593,6 @@ var knownFormats = map[string]string{
 	"*cmd/compile/internal/ssa.sparseTreeMapEntry %v": "",
 	"*cmd/internal/obj.Addr %v":                       "",
 	"*cmd/internal/obj.LSym %v":                       "",
-	"*cmd/internal/obj.Prog %p":                       "",
 	"*cmd/internal/obj.Prog %s":                       "",
 	"*cmd/internal/obj.Prog %v":                       "",
 	"*math/big.Int %#x":                               "",

src/cmd/compile/internal/gc/gsubr.go

@@ -282,7 +282,7 @@ func Patch(p *obj.Prog, to *obj.Prog) {
 // Gins inserts instruction as. f is from, t is to.
 func Gins(as obj.As, f, t *Node) *obj.Prog {
 	switch as {
-	case obj.AVARKILL, obj.AVARLIVE, obj.AVARDEF, obj.ATEXT, obj.AFUNCDATA:
+	case obj.ATEXT, obj.AFUNCDATA:
 	default:
 		Fatalf("unhandled gins op %v", as)
 	}

src/cmd/compile/internal/gc/pgen.go

@@ -22,14 +22,17 @@ var makefuncdatasym_nsym int
 func makefuncdatasym(nameprefix string, funcdatakind int64) *Sym {
 	sym := lookupN(nameprefix, makefuncdatasym_nsym)
 	makefuncdatasym_nsym++
-	pnod := newname(sym)
-	pnod.Class = PEXTERN
-	p := Gins(obj.AFUNCDATA, nil, pnod)
+	p := Prog(obj.AFUNCDATA)
 	Addrconst(&p.From, funcdatakind)
+	p.To.Type = obj.TYPE_MEM
+	p.To.Name = obj.NAME_EXTERN
+	p.To.Sym = Linksym(sym)
 	return sym
 }
 
-// gvardef inserts a VARDEF for n into the instruction stream.
+// TODO(mdempsky): Update to reference OpVar{Def,Kill,Live} instead
+// and move to plive.go.
+
 // VARDEF is an annotation for the liveness analysis, marking a place
 // where a complete initialization (definition) of a variable begins.
 // Since the liveness analysis can see initialization of single-word
@@ -85,55 +88,6 @@ func makefuncdatasym(nameprefix string, funcdatakind int64) *Sym {
 // that its argument is certainly dead, for use when the liveness analysis
 // would not otherwise be able to deduce that fact.
 
-func gvardefx(n *Node, as obj.As) {
-	if n == nil {
-		Fatalf("gvardef nil")
-	}
-	if n.Op != ONAME {
-		Fatalf("gvardef %#v; %v", n.Op, n)
-		return
-	}
-
-	switch n.Class {
-	case PAUTO, PPARAM, PPARAMOUT:
-		if !n.Used() {
-			Prog(obj.ANOP)
-			return
-		}
-
-		if as == obj.AVARLIVE {
-			Gins(as, n, nil)
-		} else {
-			Gins(as, nil, n)
-		}
-	}
-}
-
-func Gvardef(n *Node) {
-	gvardefx(n, obj.AVARDEF)
-}
-
-func Gvarkill(n *Node) {
-	gvardefx(n, obj.AVARKILL)
-}
-
-func Gvarlive(n *Node) {
-	gvardefx(n, obj.AVARLIVE)
-}
-
-func removevardef(firstp *obj.Prog) {
-	for p := firstp; p != nil; p = p.Link {
-		for p.Link != nil && (p.Link.As == obj.AVARDEF || p.Link.As == obj.AVARKILL || p.Link.As == obj.AVARLIVE) {
-			p.Link = p.Link.Link
-		}
-		if p.To.Type == obj.TYPE_BRANCH {
-			for p.To.Val.(*obj.Prog) != nil && (p.To.Val.(*obj.Prog).As == obj.AVARDEF || p.To.Val.(*obj.Prog).As == obj.AVARKILL || p.To.Val.(*obj.Prog).As == obj.AVARLIVE) {
-				p.To.Val = p.To.Val.(*obj.Prog).Link
-			}
-		}
-	}
-}
-
 func emitptrargsmap() {
 	if Curfn.Func.Nname.Sym.Name == "_" {
 		return
@@ -407,10 +361,7 @@ func compile(fn *Node) {
 		}
 	}
 
-	gcargs := makefuncdatasym("gcargs·", obj.FUNCDATA_ArgsPointerMaps)
-	gclocals := makefuncdatasym("gclocals·", obj.FUNCDATA_LocalsPointerMaps)
-
-	genssa(ssafn, ptxt, gcargs, gclocals)
+	genssa(ssafn, ptxt)
 
 	obj.Flushplist(Ctxt, plist) // convert from Prog list to machine code
 	ptxt = nil                  // nil to prevent misuse; Prog may have been freed by Flushplist

src/cmd/compile/internal/gc/ssa.go

@@ -4231,6 +4231,10 @@ type SSAGenState struct {
 	ScratchFpMem *Node
 
 	maxarg int64 // largest frame size for arguments to calls made by the function
+
+	// Map from GC safe points to stack map index, generated by
+	// liveness analysis.
+	stackMapIndex map[*ssa.Value]int
 }
 
 // Pc returns the current Prog.
@@ -4244,12 +4248,16 @@ func (s *SSAGenState) SetPos(pos src.XPos) {
 }
 
 // genssa appends entries to ptxt for each instruction in f.
-// gcargs and gclocals are filled in with pointer maps for the frame.
-func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
+func genssa(f *ssa.Func, ptxt *obj.Prog) {
 	var s SSAGenState
 
 	e := f.Frontend().(*ssafn)
 
+	// Generate GC bitmaps.
+	gcargs := makefuncdatasym("gcargs·", obj.FUNCDATA_ArgsPointerMaps)
+	gclocals := makefuncdatasym("gclocals·", obj.FUNCDATA_LocalsPointerMaps)
+	s.stackMapIndex = liveness(e, f, gcargs, gclocals)
+
 	// Remember where each block starts.
 	s.bstart = make([]*obj.Prog, f.NumBlocks())
 
@@ -4291,14 +4299,8 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
 			case ssa.OpGetG:
 				// nothing to do when there's a g register,
 				// and checkLower complains if there's not
-			case ssa.OpVarDef:
-				Gvardef(v.Aux.(*Node))
-			case ssa.OpVarKill:
-				Gvarkill(v.Aux.(*Node))
-			case ssa.OpVarLive:
-				Gvarlive(v.Aux.(*Node))
-			case ssa.OpKeepAlive:
-				KeepAlive(v)
+			case ssa.OpVarDef, ssa.OpVarKill, ssa.OpVarLive, ssa.OpKeepAlive:
+				// nothing to do; already used by liveness
 			case ssa.OpPhi:
 				CheckLoweredPhi(v)
 
@@ -4378,18 +4380,12 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
 		}
 	}
 
-	// Generate gc bitmaps.
-	liveness(e, ptxt, gcargs, gclocals)
-
 	// Add frame prologue. Zero ambiguously live variables.
 	thearch.Defframe(ptxt, e.curfn, e.stksize+s.maxarg)
 	if Debug['f'] != 0 {
 		frame(0)
 	}
 
-	// Remove leftover instrumentation from the instruction stream.
-	removevardef(ptxt)
-
 	f.HTMLWriter.Close()
 	f.HTMLWriter = nil
 }
@@ -4572,26 +4568,6 @@ func CheckLoweredGetClosurePtr(v *ssa.Value) {
 	}
 }
 
-// KeepAlive marks the variable referenced by OpKeepAlive as live.
-// Called during ssaGenValue.
-func KeepAlive(v *ssa.Value) {
-	if v.Op != ssa.OpKeepAlive {
-		v.Fatalf("KeepAlive called with non-KeepAlive value: %v", v.LongString())
-	}
-	if !v.Args[0].Type.IsPtrShaped() {
-		v.Fatalf("keeping non-pointer alive %v", v.Args[0])
-	}
-	n, _ := AutoVar(v.Args[0])
-	if n == nil {
-		v.Fatalf("KeepAlive with non-spilled value %s %s", v, v.Args[0])
-	}
-	// Note: KeepAlive arg may be a small part of a larger variable n.  We keep the
-	// whole variable n alive at this point. (Typically, this happens when
-	// we are requested to keep the idata portion of an interface{} alive, and
-	// we end up keeping the whole interface{} alive.  That's ok.)
-	Gvarlive(n)
-}
-
 // AutoVar returns a *Node and int64 representing the auto variable and offset within it
 // where v should be spilled.
 func AutoVar(v *ssa.Value) (*Node, int64) {
@@ -4629,6 +4605,14 @@ func (s *SSAGenState) AddrScratch(a *obj.Addr) {
 }
 
 func (s *SSAGenState) Call(v *ssa.Value) *obj.Prog {
+	idx, ok := s.stackMapIndex[v]
+	if !ok {
+		Fatalf("missing stack map index for %v", v.LongString())
+	}
+	p := Prog(obj.APCDATA)
+	Addrconst(&p.From, obj.PCDATA_StackMapIndex)
+	Addrconst(&p.To, int64(idx))
+
 	if sym, _ := v.Aux.(*obj.LSym); sym == Deferreturn {
 		// Deferred calls will appear to be returning to
 		// the CALL deferreturn(SB) that we are about to emit.
@@ -4641,7 +4625,7 @@ func (s *SSAGenState) Call(v *ssa.Value) *obj.Prog {
 		thearch.Ginsnop()
 	}
 
-	p := Prog(obj.ACALL)
+	p = Prog(obj.ACALL)
 	if sym, ok := v.Aux.(*obj.LSym); ok {
 		p.To.Type = obj.TYPE_MEM
 		p.To.Name = obj.NAME_EXTERN

src/cmd/compile/internal/ssa/func.go

@@ -497,6 +497,10 @@ func (f *Func) postorder() []*Block {
 	return f.cachedPostorder
 }
 
+func (f *Func) Postorder() []*Block {
+	return f.postorder()
+}
+
 // Idom returns a map from block ID to the immediate dominator of that block.
 // f.Entry.ID maps to nil. Unreachable blocks map to nil as well.
 func (f *Func) Idom() []*Block {