cmd/compile: enable late expansion for interface calls

Includes a few tweaks to Value.copyOf(a) (make it a no-op for
a self-copy) and new pattern hack "___" (3 underscores) is
like ellipsis, except the replacement doesn't need to have
matching ellipsis/underscores.

Moved the arg-length check in generated pattern-matching code
BEFORE the args are probed, because not all instances of
variable length OpFoo will have all the args mentioned in
some rule for OpFoo, and when that happens, the compiler
panics without the early check.

Change-Id: I66de40672b3794a6427890ff96c805a488d783f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/247537
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -2556,7 +2556,7 @@ func (s *state) expr(n *Node) *ssa.Value {
 		return s.addr(n.Left)
 
 	case ORESULT:
-		if s.prevCall == nil || s.prevCall.Op != ssa.OpStaticLECall {
+		if s.prevCall == nil || s.prevCall.Op != ssa.OpStaticLECall && s.prevCall.Op != ssa.OpInterLECall && s.prevCall.Op != ssa.OpClosureLECall {
 			// Do the old thing
 			addr := s.constOffPtrSP(types.NewPtr(n.Type), n.Xoffset)
 			return s.rawLoad(n.Type, addr)
@@ -4409,6 +4409,9 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 		iclosure, rcvr = s.getClosureAndRcvr(fn)
 		if k == callNormal {
 			codeptr = s.load(types.Types[TUINTPTR], iclosure)
+			if ssa.LateCallExpansionEnabledWithin(s.f) {
+				testLateExpansion = true
+			}
 		} else {
 			closure = iclosure
 		}
@@ -4555,16 +4558,17 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 			codeptr = s.rawLoad(types.Types[TUINTPTR], closure)
 			call = s.newValue3A(ssa.OpClosureCall, types.TypeMem, ssa.ClosureAuxCall(ACArgs, ACResults), codeptr, closure, s.mem())
 		case codeptr != nil:
+			if testLateExpansion {
+				aux := ssa.InterfaceAuxCall(ACArgs, ACResults)
+				call = s.newValue1A(ssa.OpInterLECall, aux.LateExpansionResultType(), aux, codeptr)
+				call.AddArgs(callArgs...)
+			} else {
 				call = s.newValue2A(ssa.OpInterCall, types.TypeMem, ssa.InterfaceAuxCall(ACArgs, ACResults), codeptr, s.mem())
+			}
 		case sym != nil:
 			if testLateExpansion {
-				var tys []*types.Type
 				aux := ssa.StaticAuxCall(sym.Linksym(), ACArgs, ACResults)
-				for i := int64(0); i < aux.NResults(); i++ {
-					tys = append(tys, aux.TypeOfResult(i))
-				}
-				tys = append(tys, types.TypeMem)
-				call = s.newValue0A(ssa.OpStaticLECall, types.NewResults(tys), aux)
+				call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 				call.AddArgs(callArgs...)
 			} else {
 				call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, ssa.StaticAuxCall(sym.Linksym(), ACArgs, ACResults), s.mem())
@@ -4713,7 +4717,7 @@ func (s *state) addr(n *Node) *ssa.Value {
 		}
 	case ORESULT:
 		// load return from callee
-		if s.prevCall == nil || s.prevCall.Op != ssa.OpStaticLECall {
+		if s.prevCall == nil || s.prevCall.Op != ssa.OpStaticLECall && s.prevCall.Op != ssa.OpInterLECall && s.prevCall.Op != ssa.OpClosureLECall {
 			return s.constOffPtrSP(t, n.Xoffset)
 		}
 		which := s.prevCall.Aux.(*ssa.AuxCall).ResultForOffset(n.Xoffset)

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

@@ -38,6 +38,7 @@ func expandCalls(f *Func) {
 	} else {
 		hiOffset = 4
 	}
+
 	pairTypes := func(et types.EType) (tHi, tLo *types.Type) {
 		tHi = tUint32
 		if et == types.TINT64 {
@@ -231,46 +232,64 @@ func expandCalls(f *Func) {
 		return x
 	}
 
+	rewriteArgs := func(v *Value, firstArg int) *Value {
+		// Thread the stores on the memory arg
+		aux := v.Aux.(*AuxCall)
+		pos := v.Pos.WithNotStmt()
+		m0 := v.Args[len(v.Args)-1]
+		mem := m0
+		for i, a := range v.Args {
+			if i < firstArg {
+				continue
+			}
+			if a == m0 { // mem is last.
+				break
+			}
+			auxI := int64(i - firstArg)
+			if a.Op == OpDereference {
+				if a.MemoryArg() != m0 {
+					f.Fatalf("Op...LECall and OpDereference have mismatched mem, %s and %s", v.LongString(), a.LongString())
+				}
+				// "Dereference" of addressed (probably not-SSA-eligible) value becomes Move
+				// TODO this will be more complicated with registers in the picture.
+				src := a.Args[0]
+				dst := f.ConstOffPtrSP(src.Type, aux.OffsetOfArg(auxI), sp)
+				if a.Uses == 1 {
+					a.reset(OpMove)
+					a.Pos = pos
+					a.Type = types.TypeMem
+					a.Aux = aux.TypeOfArg(auxI)
+					a.AuxInt = aux.SizeOfArg(auxI)
+					a.SetArgs3(dst, src, mem)
+					mem = a
+				} else {
+					mem = a.Block.NewValue3A(pos, OpMove, types.TypeMem, aux.TypeOfArg(auxI), dst, src, mem)
+					mem.AuxInt = aux.SizeOfArg(auxI)
+				}
+			} else {
+				mem = storeArg(pos, v.Block, a, aux.TypeOfArg(auxI), aux.OffsetOfArg(auxI), mem)
+			}
+		}
+		v.resetArgs()
+		return mem
+	}
+
 	// Step 0: rewrite the calls to convert incoming args to stores.
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			switch v.Op {
 			case OpStaticLECall:
-				// Thread the stores on the memory arg
-				m0 := v.MemoryArg()
-				mem := m0
-				pos := v.Pos.WithNotStmt()
-				aux := v.Aux.(*AuxCall)
-				for i, a := range v.Args {
-					if a == m0 { // mem is last.
-						break
-					}
-					if a.Op == OpDereference {
-						// "Dereference" of addressed (probably not-SSA-eligible) value becomes Move
-						// TODO this will be more complicated with registers in the picture.
-						if a.MemoryArg() != m0 {
-							f.Fatalf("Op...LECall and OpDereference have mismatched mem, %s and %s", v.LongString(), a.LongString())
-						}
-						src := a.Args[0]
-						dst := f.ConstOffPtrSP(src.Type, aux.OffsetOfArg(int64(i)), sp)
-						if a.Uses == 1 {
-							a.reset(OpMove)
-							a.Pos = pos
-							a.Type = types.TypeMem
-							a.Aux = aux.TypeOfArg(int64(i))
-							a.AuxInt = aux.SizeOfArg(int64(i))
-							a.SetArgs3(dst, src, mem)
-							mem = a
-						} else {
-							mem = a.Block.NewValue3A(pos, OpMove, types.TypeMem, aux.TypeOfArg(int64(i)), dst, src, mem)
-							mem.AuxInt = aux.SizeOfArg(int64(i))
-						}
-					} else {
-						mem = storeArg(pos, b, a, aux.TypeOfArg(int64(i)), aux.OffsetOfArg(int64(i)), mem)
-					}
-				}
-				v.resetArgs()
+				mem := rewriteArgs(v, 0)
 				v.SetArgs1(mem)
+			case OpClosureLECall:
+				code := v.Args[0]
+				context := v.Args[1]
+				mem := rewriteArgs(v, 2)
+				v.SetArgs3(code, context, mem)
+			case OpInterLECall:
+				code := v.Args[0]
+				mem := rewriteArgs(v, 1)
+				v.SetArgs2(code, mem)
 			}
 		}
 	}
@@ -370,6 +389,12 @@ func expandCalls(f *Func) {
 			case OpStaticLECall:
 				v.Op = OpStaticCall
 				v.Type = types.TypeMem
+			case OpClosureLECall:
+				v.Op = OpClosureCall
+				v.Type = types.TypeMem
+			case OpInterLECall:
+				v.Op = OpInterCall
+				v.Type = types.TypeMem
 			}
 		}
 	}

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -2024,6 +2024,13 @@
 (InterCall [argsize] {auxCall} (Load (OffPtr [off] (ITab (IMake (Addr {itab} (SB)) _))) _) mem) && devirt(v, auxCall, itab, off) != nil =>
 	(StaticCall [int32(argsize)] {devirt(v, auxCall, itab, off)} mem)
 
+// De-virtualize late-expanded interface calls into late-expanded static calls.
+// Note that (ITab (IMake)) doesn't get rewritten until after the first opt pass,
+// so this rule should trigger reliably.
+// devirtLECall removes the first argument, adds the devirtualized symbol to the AuxCall, and changes the opcode
+(InterLECall [argsize] {auxCall} (Load (OffPtr [off] (ITab (IMake (Addr {itab} (SB)) _))) _) ___) && devirtLESym(v, auxCall, itab, off) !=
+    nil => devirtLECall(v, devirtLESym(v, auxCall, itab, off))
+
 // Move and Zero optimizations.
 // Move source and destination may overlap.
 

src/cmd/compile/internal/ssa/gen/genericOps.go

@@ -392,7 +392,9 @@ var genericOps = []opData{
 	{name: "ClosureCall", argLength: 3, aux: "CallOff", call: true},    // arg0=code pointer, arg1=context ptr, arg2=memory.  auxint=arg size.  Returns memory.
 	{name: "StaticCall", argLength: 1, aux: "CallOff", call: true},     // call function aux.(*obj.LSym), arg0=memory.  auxint=arg size.  Returns memory.
 	{name: "InterCall", argLength: 2, aux: "CallOff", call: true},      // interface call.  arg0=code pointer, arg1=memory, auxint=arg size.  Returns memory.
+	{name: "ClosureLECall", argLength: -1, aux: "CallOff", call: true}, // late-expanded closure call. arg0=code pointer, arg1=context ptr,  arg2..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
 	{name: "StaticLECall", argLength: -1, aux: "CallOff", call: true},  // late-expanded static call function aux.(*ssa.AuxCall.Fn). arg0..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
+	{name: "InterLECall", argLength: -1, aux: "CallOff", call: true},   // late-expanded interface call. arg0=code pointer, arg1..argN-1 are inputs, argN is mem. auxint = arg size. Result is tuple of result(s), plus mem.
 
 	// Conversions: signed extensions, zero (unsigned) extensions, truncations
 	{name: "SignExt8to16", argLength: 1, typ: "Int16"},

src/cmd/compile/internal/ssa/gen/rulegen.go

@@ -50,8 +50,12 @@ import (
 // variable ::= some token
 // opcode   ::= one of the opcodes from the *Ops.go files
 
+// special rules: trailing ellipsis "..." (in the outermost sexpr?) must match on both sides of a rule.
+//                trailing three underscore "___" in the outermost match sexpr indicate the presence of
+//                   extra ignored args that need not appear in the replacement
+
 // extra conditions is just a chunk of Go that evaluates to a boolean. It may use
-// variables declared in the matching sexpr. The variable "v" is predefined to be
+// variables declared in the matching tsexpr. The variable "v" is predefined to be
 // the value matched by the entire rule.
 
 // If multiple rules match, the first one in file order is selected.
@@ -1019,6 +1023,19 @@ func genMatch0(rr *RuleRewrite, arch arch, match, v string, cnt map[string]int,
 		pos = v + ".Pos"
 	}
 
+	// If the last argument is ___, it means "don't care about trailing arguments, really"
+	// The likely/intended use is for rewrites that are too tricky to express in the existing pattern language
+	// Do a length check early because long patterns fed short (ultimately not-matching) inputs will
+	// do an indexing error in pattern-matching.
+	if op.argLength == -1 {
+		l := len(args)
+		if l == 0 || args[l-1] != "___" {
+			rr.add(breakf("len(%s.Args) != %d", v, l))
+		} else if l > 1 && args[l-1] == "___" {
+			rr.add(breakf("len(%s.Args) < %d", v, l-1))
+		}
+	}
+
 	for _, e := range []struct {
 		name, field, dclType string
 	}{
@@ -1159,9 +1176,6 @@ func genMatch0(rr *RuleRewrite, arch arch, match, v string, cnt map[string]int,
 		}
 	}
 
-	if op.argLength == -1 {
-		rr.add(breakf("len(%s.Args) != %d", v, len(args)))
-	}
 	return pos, checkOp
 }
 

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

@@ -127,6 +127,17 @@ func (a *AuxCall) NResults() int64 {
 	return int64(len(a.results))
 }
 
+// LateExpansionResultType returns the result type (including trailing mem)
+// for a call that will be expanded later in the SSA phase.
+func (a *AuxCall) LateExpansionResultType() *types.Type {
+	var tys []*types.Type
+	for i := int64(0); i < a.NResults(); i++ {
+		tys = append(tys, a.TypeOfResult(i))
+	}
+	tys = append(tys, types.TypeMem)
+	return types.NewResults(tys)
+}
+
 // NArgs returns the number of arguments
 func (a *AuxCall) NArgs() int64 {
 	return int64(len(a.args))

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

@@ -2732,7 +2732,9 @@ const (
 	OpClosureCall
 	OpStaticCall
 	OpInterCall
+	OpClosureLECall
 	OpStaticLECall
+	OpInterLECall
 	OpSignExt8to16
 	OpSignExt8to32
 	OpSignExt8to64
@@ -34851,6 +34853,13 @@ var opcodeTable = [...]opInfo{
 		call:    true,
 		generic: true,
 	},
+	{
+		name:    "ClosureLECall",
+		auxType: auxCallOff,
+		argLen:  -1,
+		call:    true,
+		generic: true,
+	},
 	{
 		name:    "StaticLECall",
 		auxType: auxCallOff,
@@ -34858,6 +34867,13 @@ var opcodeTable = [...]opInfo{
 		call:    true,
 		generic: true,
 	},
+	{
+		name:    "InterLECall",
+		auxType: auxCallOff,
+		argLen:  -1,
+		call:    true,
+		generic: true,
+	},
 	{
 		name:    "SignExt8to16",
 		argLen:  1,

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

@@ -764,6 +764,36 @@ func devirt(v *Value, aux interface{}, sym Sym, offset int64) *AuxCall {
 	return StaticAuxCall(lsym, va.args, va.results)
 }
 
+// de-virtualize an InterLECall
+// 'sym' is the symbol for the itab
+func devirtLESym(v *Value, aux interface{}, sym Sym, offset int64) *obj.LSym {
+	n, ok := sym.(*obj.LSym)
+	if !ok {
+		return nil
+	}
+
+	f := v.Block.Func
+	lsym := f.fe.DerefItab(n, offset)
+	if f.pass.debug > 0 {
+		if lsym != nil {
+			f.Warnl(v.Pos, "de-virtualizing call")
+		} else {
+			f.Warnl(v.Pos, "couldn't de-virtualize call")
+		}
+	}
+	if lsym == nil {
+		return nil
+	}
+	return lsym
+}
+
+func devirtLECall(v *Value, sym *obj.LSym) *Value {
+	v.Op = OpStaticLECall
+	v.Aux.(*AuxCall).Fn = sym
+	v.RemoveArg(0)
+	return v
+}
+
 // isSamePtr reports whether p1 and p2 point to the same address.
 func isSamePtr(p1, p2 *Value) bool {
 	if p1 == p2 {

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

@@ -124,6 +124,8 @@ func rewriteValuegeneric(v *Value) bool {
 		return rewriteValuegeneric_OpIMake(v)
 	case OpInterCall:
 		return rewriteValuegeneric_OpInterCall(v)
+	case OpInterLECall:
+		return rewriteValuegeneric_OpInterLECall(v)
 	case OpIsInBounds:
 		return rewriteValuegeneric_OpIsInBounds(v)
 	case OpIsNonNil:
@@ -8522,6 +8524,46 @@ func rewriteValuegeneric_OpInterCall(v *Value) bool {
 	}
 	return false
 }
+func rewriteValuegeneric_OpInterLECall(v *Value) bool {
+	// match: (InterLECall [argsize] {auxCall} (Load (OffPtr [off] (ITab (IMake (Addr {itab} (SB)) _))) _) ___)
+	// cond: devirtLESym(v, auxCall, itab, off) != nil
+	// result: devirtLECall(v, devirtLESym(v, auxCall, itab, off))
+	for {
+		if len(v.Args) < 1 {
+			break
+		}
+		auxCall := auxToCall(v.Aux)
+		v_0 := v.Args[0]
+		if v_0.Op != OpLoad {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpOffPtr {
+			break
+		}
+		off := auxIntToInt64(v_0_0.AuxInt)
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpITab {
+			break
+		}
+		v_0_0_0_0 := v_0_0_0.Args[0]
+		if v_0_0_0_0.Op != OpIMake {
+			break
+		}
+		v_0_0_0_0_0 := v_0_0_0_0.Args[0]
+		if v_0_0_0_0_0.Op != OpAddr {
+			break
+		}
+		itab := auxToSym(v_0_0_0_0_0.Aux)
+		v_0_0_0_0_0_0 := v_0_0_0_0_0.Args[0]
+		if v_0_0_0_0_0_0.Op != OpSB || !(devirtLESym(v, auxCall, itab, off) != nil) {
+			break
+		}
+		v.copyOf(devirtLECall(v, devirtLESym(v, auxCall, itab, off)))
+		return true
+	}
+	return false
+}
 func rewriteValuegeneric_OpIsInBounds(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
@@ -18549,6 +18591,9 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 	// match: (Phi (Const8 [c]) (Const8 [c]))
 	// result: (Const8 [c])
 	for {
+		if len(v.Args) != 2 {
+			break
+		}
 		_ = v.Args[1]
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst8 {
@@ -18556,7 +18601,7 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 		}
 		c := auxIntToInt8(v_0.AuxInt)
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst8 || auxIntToInt8(v_1.AuxInt) != c || len(v.Args) != 2 {
+		if v_1.Op != OpConst8 || auxIntToInt8(v_1.AuxInt) != c {
 			break
 		}
 		v.reset(OpConst8)
@@ -18566,6 +18611,9 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 	// match: (Phi (Const16 [c]) (Const16 [c]))
 	// result: (Const16 [c])
 	for {
+		if len(v.Args) != 2 {
+			break
+		}
 		_ = v.Args[1]
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst16 {
@@ -18573,7 +18621,7 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 		}
 		c := auxIntToInt16(v_0.AuxInt)
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst16 || auxIntToInt16(v_1.AuxInt) != c || len(v.Args) != 2 {
+		if v_1.Op != OpConst16 || auxIntToInt16(v_1.AuxInt) != c {
 			break
 		}
 		v.reset(OpConst16)
@@ -18583,6 +18631,9 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 	// match: (Phi (Const32 [c]) (Const32 [c]))
 	// result: (Const32 [c])
 	for {
+		if len(v.Args) != 2 {
+			break
+		}
 		_ = v.Args[1]
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst32 {
@@ -18590,7 +18641,7 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 		}
 		c := auxIntToInt32(v_0.AuxInt)
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst32 || auxIntToInt32(v_1.AuxInt) != c || len(v.Args) != 2 {
+		if v_1.Op != OpConst32 || auxIntToInt32(v_1.AuxInt) != c {
 			break
 		}
 		v.reset(OpConst32)
@@ -18600,6 +18651,9 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 	// match: (Phi (Const64 [c]) (Const64 [c]))
 	// result: (Const64 [c])
 	for {
+		if len(v.Args) != 2 {
+			break
+		}
 		_ = v.Args[1]
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst64 {
@@ -18607,7 +18661,7 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 		}
 		c := auxIntToInt64(v_0.AuxInt)
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst64 || auxIntToInt64(v_1.AuxInt) != c || len(v.Args) != 2 {
+		if v_1.Op != OpConst64 || auxIntToInt64(v_1.AuxInt) != c {
 			break
 		}
 		v.reset(OpConst64)

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

@@ -348,6 +348,9 @@ func (v *Value) reset(op Op) {
 // It modifies v to be (Copy a).
 //go:noinline
 func (v *Value) copyOf(a *Value) {
+	if v == a {
+		return
+	}
 	if v.InCache {
 		v.Block.Func.unCache(v)
 	}