diff options
Diffstat (limited to 'src/cmd/compile/internal/ssa/expand_calls.go')
| -rw-r--r-- | src/cmd/compile/internal/ssa/expand_calls.go | 786 |
1 files changed, 732 insertions, 54 deletions
diff --git a/src/cmd/compile/internal/ssa/expand_calls.go b/src/cmd/compile/internal/ssa/expand_calls.go index 34cff51c00..3e3573ff39 100644 --- a/src/cmd/compile/internal/ssa/expand_calls.go +++ b/src/cmd/compile/internal/ssa/expand_calls.go @@ -4,14 +4,140 @@ package ssa -import "cmd/compile/internal/types" +import ( + "cmd/compile/internal/types" + "cmd/internal/src" + "fmt" + "sort" +) + +type selKey struct { + from *Value + offset int64 + size int64 + typ types.EType +} + +type offsetKey struct { + from *Value + offset int64 + pt *types.Type +} // expandCalls converts LE (Late Expansion) calls that act like they receive value args into a lower-level form -// that is more oriented to a platform's ABI. The SelectN operations that extract results are also rewritten into -// more appropriate forms. +// that is more oriented to a platform's ABI. The SelectN operations that extract results are rewritten into +// more appropriate forms, and any StructMake or ArrayMake inputs are decomposed until non-struct values are +// reached. func expandCalls(f *Func) { + // Calls that need lowering have some number of inputs, including a memory input, + // and produce a tuple of (value1, value2, ..., mem) where valueK may or may not be SSA-able. + + // With the current ABI those inputs need to be converted into stores to memory, + // rethreading the call's memory input to the first, and the new call now receiving the last. + + // With the current ABI, the outputs need to be converted to loads, which will all use the call's + // memory output as their input. + if !LateCallExpansionEnabledWithin(f) { + return + } + debug := f.pass.debug > 0 + canSSAType := f.fe.CanSSA + regSize := f.Config.RegSize sp, _ := f.spSb() + typ := &f.Config.Types + ptrSize := f.Config.PtrSize + + // For 32-bit, need to deal with decomposition of 64-bit integers, which depends on endianness. + var hiOffset, lowOffset int64 + if f.Config.BigEndian { + lowOffset = 4 + } else { + hiOffset = 4 + } + + namedSelects := make(map[*Value][]namedVal) + + // intPairTypes returns the pair of 32-bit int types needed to encode a 64-bit integer type on a target + // that has no 64-bit integer registers. + intPairTypes := func(et types.EType) (tHi, tLo *types.Type) { + tHi = typ.UInt32 + if et == types.TINT64 { + tHi = typ.Int32 + } + tLo = typ.UInt32 + return + } + + // isAlreadyExpandedAggregateType returns whether a type is an SSA-able "aggregate" (multiple register) type + // that was expanded in an earlier phase (currently, expand_calls is intended to run after decomposeBuiltin, + // so this is all aggregate types -- small struct and array, complex, interface, string, slice, and 64-bit + // integer on 32-bit). + isAlreadyExpandedAggregateType := func(t *types.Type) bool { + if !canSSAType(t) { + return false + } + return t.IsStruct() || t.IsArray() || t.IsComplex() || t.IsInterface() || t.IsString() || t.IsSlice() || + t.Size() > regSize && t.IsInteger() + } + + offsets := make(map[offsetKey]*Value) + + // offsetFrom creates an offset from a pointer, simplifying chained offsets and offsets from SP + // TODO should also optimize offsets from SB? + offsetFrom := func(from *Value, offset int64, pt *types.Type) *Value { + if offset == 0 && from.Type == pt { // this is not actually likely + return from + } + // Simplify, canonicalize + for from.Op == OpOffPtr { + offset += from.AuxInt + from = from.Args[0] + } + if from == sp { + return f.ConstOffPtrSP(pt, offset, sp) + } + key := offsetKey{from, offset, pt} + v := offsets[key] + if v != nil { + return v + } + v = from.Block.NewValue1I(from.Pos.WithNotStmt(), OpOffPtr, pt, offset, from) + offsets[key] = v + return v + } + + splitSlots := func(ls []LocalSlot, sfx string, offset int64, ty *types.Type) []LocalSlot { + var locs []LocalSlot + for i := range ls { + locs = append(locs, f.fe.SplitSlot(&ls[i], sfx, offset, ty)) + } + return locs + } + + // removeTrivialWrapperTypes unwraps layers of + // struct { singleField SomeType } and [1]SomeType + // until a non-wrapper type is reached. This is useful + // for working with assignments to/from interface data + // fields (either second operand to OpIMake or OpIData) + // where the wrapping or type conversion can be elided + // because of type conversions/assertions in source code + // that do not appear in SSA. + removeTrivialWrapperTypes := func(t *types.Type) *types.Type { + for { + if t.IsStruct() && t.NumFields() == 1 { + t = t.Field(0).Type + continue + } + if t.IsArray() && t.NumElem() == 1 { + t = t.Elem() + continue + } + break + } + return t + } + // Calls that need lowering have some number of inputs, including a memory input, // and produce a tuple of (value1, value2, ..., mem) where valueK may or may not be SSA-able. @@ -21,79 +147,631 @@ func expandCalls(f *Func) { // With the current ABI, the outputs need to be converted to loads, which will all use the call's // memory output as their input. - // Step 1: find all references to calls as values and rewrite those. + // rewriteSelect recursively walks leaf selector to a root (OpSelectN) through + // a chain of Struct/Array Select operations. If the chain of selectors does not + // end in OpSelectN, it does nothing (this can happen depending on compiler phase ordering). + // It emits the code necessary to implement the leaf select operation that leads to the call. + // TODO when registers really arrive, must also decompose anything split across two registers or registers and memory. + var rewriteSelect func(leaf *Value, selector *Value, offset int64) []LocalSlot + rewriteSelect = func(leaf *Value, selector *Value, offset int64) []LocalSlot { + var locs []LocalSlot + leafType := leaf.Type + switch selector.Op { + case OpSelectN: + // TODO these may be duplicated. Should memoize. Intermediate selectors will go dead, no worries there. + for _, s := range namedSelects[selector] { + locs = append(locs, f.Names[s.locIndex]) + } + call := selector.Args[0] + aux := call.Aux.(*AuxCall) + which := selector.AuxInt + if which == aux.NResults() { // mem is after the results. + // rewrite v as a Copy of call -- the replacement call will produce a mem. + leaf.copyOf(call) + } else { + leafType := removeTrivialWrapperTypes(leaf.Type) + if canSSAType(leafType) { + for leafType.Etype == types.TSTRUCT && leafType.NumFields() == 1 { + // This may not be adequately general -- consider [1]etc but this is caused by immediate IDATA + leafType = leafType.Field(0).Type + } + pt := types.NewPtr(leafType) + off := offsetFrom(sp, offset+aux.OffsetOfResult(which), pt) + // Any selection right out of the arg area/registers has to be same Block as call, use call as mem input. + if leaf.Block == call.Block { + leaf.reset(OpLoad) + leaf.SetArgs2(off, call) + leaf.Type = leafType + } else { + w := call.Block.NewValue2(leaf.Pos, OpLoad, leafType, off, call) + leaf.copyOf(w) + } + } else { + f.Fatalf("Should not have non-SSA-able OpSelectN, selector=%s", selector.LongString()) + } + } + case OpStructSelect: + w := selector.Args[0] + var ls []LocalSlot + if w.Type.Etype != types.TSTRUCT { + f.Fatalf("Bad type for w: v=%v; sel=%v; w=%v; ,f=%s\n", leaf.LongString(), selector.LongString(), w.LongString(), f.Name) + // Artifact of immediate interface idata + ls = rewriteSelect(leaf, w, offset) + } else { + ls = rewriteSelect(leaf, w, offset+w.Type.FieldOff(int(selector.AuxInt))) + for _, l := range ls { + locs = append(locs, f.fe.SplitStruct(l, int(selector.AuxInt))) + } + } + + case OpArraySelect: + w := selector.Args[0] + rewriteSelect(leaf, w, offset+selector.Type.Size()*selector.AuxInt) + + case OpInt64Hi: + w := selector.Args[0] + ls := rewriteSelect(leaf, w, offset+hiOffset) + locs = splitSlots(ls, ".hi", hiOffset, leafType) + + case OpInt64Lo: + w := selector.Args[0] + ls := rewriteSelect(leaf, w, offset+lowOffset) + locs = splitSlots(ls, ".lo", lowOffset, leafType) + + case OpStringPtr: + ls := rewriteSelect(leaf, selector.Args[0], offset) + locs = splitSlots(ls, ".ptr", 0, typ.BytePtr) + //for i := range ls { + // locs = append(locs, f.fe.SplitSlot(&ls[i], ".ptr", 0, typ.BytePtr)) + //} + case OpSlicePtr: + w := selector.Args[0] + ls := rewriteSelect(leaf, w, offset) + locs = splitSlots(ls, ".ptr", 0, types.NewPtr(w.Type.Elem())) + + case OpITab: + w := selector.Args[0] + ls := rewriteSelect(leaf, w, offset) + sfx := ".itab" + if w.Type.IsEmptyInterface() { + sfx = ".type" + } + locs = splitSlots(ls, sfx, 0, typ.Uintptr) + + case OpComplexReal: + ls := rewriteSelect(leaf, selector.Args[0], offset) + locs = splitSlots(ls, ".real", 0, leafType) + + case OpComplexImag: + ls := rewriteSelect(leaf, selector.Args[0], offset+leafType.Width) // result is FloatNN, width of result is offset of imaginary part. + locs = splitSlots(ls, ".imag", leafType.Width, leafType) + + case OpStringLen, OpSliceLen: + ls := rewriteSelect(leaf, selector.Args[0], offset+ptrSize) + locs = splitSlots(ls, ".len", ptrSize, leafType) + + case OpIData: + ls := rewriteSelect(leaf, selector.Args[0], offset+ptrSize) + locs = splitSlots(ls, ".data", ptrSize, leafType) + + case OpSliceCap: + ls := rewriteSelect(leaf, selector.Args[0], offset+2*ptrSize) + locs = splitSlots(ls, ".cap", 2*ptrSize, leafType) + + case OpCopy: // If it's an intermediate result, recurse + locs = rewriteSelect(leaf, selector.Args[0], offset) + for _, s := range namedSelects[selector] { + // this copy may have had its own name, preserve that, too. + locs = append(locs, f.Names[s.locIndex]) + } + + default: + // Ignore dead ends. These can occur if this phase is run before decompose builtin (which is not intended, but allowed). + } + + return locs + } + + // storeArg converts stores of SSA-able aggregate arguments (passed to a call) into a series of stores of + // smaller types into individual parameter slots. + var storeArg func(pos src.XPos, b *Block, a *Value, t *types.Type, offset int64, mem *Value) *Value + storeArg = func(pos src.XPos, b *Block, a *Value, t *types.Type, offset int64, mem *Value) *Value { + if debug { + fmt.Printf("\tstoreArg(%s; %s; %v; %d; %s)\n", b, a.LongString(), t, offset, mem.String()) + } + + switch a.Op { + case OpArrayMake0, OpStructMake0: + return mem + + case OpStructMake1, OpStructMake2, OpStructMake3, OpStructMake4: + for i := 0; i < t.NumFields(); i++ { + fld := t.Field(i) + mem = storeArg(pos, b, a.Args[i], fld.Type, offset+fld.Offset, mem) + } + return mem + + case OpArrayMake1: + return storeArg(pos, b, a.Args[0], t.Elem(), offset, mem) + + case OpInt64Make: + tHi, tLo := intPairTypes(t.Etype) + mem = storeArg(pos, b, a.Args[0], tHi, offset+hiOffset, mem) + return storeArg(pos, b, a.Args[1], tLo, offset+lowOffset, mem) + + case OpComplexMake: + tPart := typ.Float32 + wPart := t.Width / 2 + if wPart == 8 { + tPart = typ.Float64 + } + mem = storeArg(pos, b, a.Args[0], tPart, offset, mem) + return storeArg(pos, b, a.Args[1], tPart, offset+wPart, mem) + + case OpIMake: + mem = storeArg(pos, b, a.Args[0], typ.Uintptr, offset, mem) + return storeArg(pos, b, a.Args[1], typ.BytePtr, offset+ptrSize, mem) + + case OpStringMake: + mem = storeArg(pos, b, a.Args[0], typ.BytePtr, offset, mem) + return storeArg(pos, b, a.Args[1], typ.Int, offset+ptrSize, mem) + + case OpSliceMake: + mem = storeArg(pos, b, a.Args[0], typ.BytePtr, offset, mem) + mem = storeArg(pos, b, a.Args[1], typ.Int, offset+ptrSize, mem) + return storeArg(pos, b, a.Args[2], typ.Int, offset+2*ptrSize, mem) + } + + dst := offsetFrom(sp, offset, types.NewPtr(t)) + x := b.NewValue3A(pos, OpStore, types.TypeMem, t, dst, a, mem) + if debug { + fmt.Printf("\t\tstoreArg returns %s\n", x.LongString()) + } + return x + } + + // splitStore converts a store of an SSA-able aggregate into a series of smaller stores, emitting + // appropriate Struct/Array Select operations (which will soon go dead) to obtain the parts. + // This has to handle aggregate types that have already been lowered by an earlier phase. + var splitStore func(dest, source, mem, v *Value, t *types.Type, offset int64, firstStorePos src.XPos) *Value + splitStore = func(dest, source, mem, v *Value, t *types.Type, offset int64, firstStorePos src.XPos) *Value { + if debug { + fmt.Printf("\tsplitStore(%s; %s; %s; %s; %v; %d; %v)\n", dest.LongString(), source.LongString(), mem.String(), v.LongString(), t, offset, firstStorePos) + } + pos := v.Pos.WithNotStmt() + switch t.Etype { + case types.TARRAY: + elt := t.Elem() + if t.NumElem() == 1 && t.Width == regSize && elt.Width == regSize { + t = removeTrivialWrapperTypes(t) + if t.Etype == types.TSTRUCT || t.Etype == types.TARRAY { + f.Fatalf("Did not expect to find IDATA-immediate with non-trivial struct/array in it") + } + break // handle the leaf type. + } + for i := int64(0); i < t.NumElem(); i++ { + sel := source.Block.NewValue1I(pos, OpArraySelect, elt, i, source) + mem = splitStore(dest, sel, mem, v, elt, offset+i*elt.Width, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + } + return mem + + case types.TSTRUCT: + if t.NumFields() == 1 && t.Field(0).Type.Width == t.Width && t.Width == regSize { + // This peculiar test deals with accesses to immediate interface data. + // It works okay because everything is the same size. + // Example code that triggers this can be found in go/constant/value.go, function ToComplex + // v119 (+881) = IData <intVal> v6 + // v121 (+882) = StaticLECall <floatVal,mem> {AuxCall{"".itof([intVal,0])[floatVal,8]}} [16] v119 v1 + // This corresponds to the generic rewrite rule "(StructSelect [0] (IData x)) => (IData x)" + // Guard against "struct{struct{*foo}}" + // Other rewriting phases create minor glitches when they transform IData, for instance the + // interface-typed Arg "x" of ToFloat in go/constant/value.go + // v6 (858) = Arg <Value> {x} (x[Value], x[Value]) + // is rewritten by decomposeArgs into + // v141 (858) = Arg <uintptr> {x} + // v139 (858) = Arg <*uint8> {x} [8] + // because of a type case clause on line 862 of go/constant/value.go + // case intVal: + // return itof(x) + // v139 is later stored as an intVal == struct{val *big.Int} which naively requires the fields of + // of a *uint8, which does not succeed. + t = removeTrivialWrapperTypes(t) + + // it could be a leaf type, but the "leaf" could be complex64 (for example) + return splitStore(dest, source, mem, v, t, offset, firstStorePos) + } + + for i := 0; i < t.NumFields(); i++ { + fld := t.Field(i) + sel := source.Block.NewValue1I(pos, OpStructSelect, fld.Type, int64(i), source) + mem = splitStore(dest, sel, mem, v, fld.Type, offset+fld.Offset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + } + return mem + + case types.TINT64, types.TUINT64: + if t.Width == regSize { + break + } + tHi, tLo := intPairTypes(t.Etype) + sel := source.Block.NewValue1(pos, OpInt64Hi, tHi, source) + mem = splitStore(dest, sel, mem, v, tHi, offset+hiOffset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + sel = source.Block.NewValue1(pos, OpInt64Lo, tLo, source) + return splitStore(dest, sel, mem, v, tLo, offset+lowOffset, firstStorePos) + + case types.TINTER: + sel := source.Block.NewValue1(pos, OpITab, typ.BytePtr, source) + mem = splitStore(dest, sel, mem, v, typ.BytePtr, offset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + sel = source.Block.NewValue1(pos, OpIData, typ.BytePtr, source) + return splitStore(dest, sel, mem, v, typ.BytePtr, offset+ptrSize, firstStorePos) + + case types.TSTRING: + sel := source.Block.NewValue1(pos, OpStringPtr, typ.BytePtr, source) + mem = splitStore(dest, sel, mem, v, typ.BytePtr, offset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + sel = source.Block.NewValue1(pos, OpStringLen, typ.Int, source) + return splitStore(dest, sel, mem, v, typ.Int, offset+ptrSize, firstStorePos) + + case types.TSLICE: + et := types.NewPtr(t.Elem()) + sel := source.Block.NewValue1(pos, OpSlicePtr, et, source) + mem = splitStore(dest, sel, mem, v, et, offset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + sel = source.Block.NewValue1(pos, OpSliceLen, typ.Int, source) + mem = splitStore(dest, sel, mem, v, typ.Int, offset+ptrSize, firstStorePos) + sel = source.Block.NewValue1(pos, OpSliceCap, typ.Int, source) + return splitStore(dest, sel, mem, v, typ.Int, offset+2*ptrSize, firstStorePos) + + case types.TCOMPLEX64: + sel := source.Block.NewValue1(pos, OpComplexReal, typ.Float32, source) + mem = splitStore(dest, sel, mem, v, typ.Float32, offset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + sel = source.Block.NewValue1(pos, OpComplexImag, typ.Float32, source) + return splitStore(dest, sel, mem, v, typ.Float32, offset+4, firstStorePos) + + case types.TCOMPLEX128: + sel := source.Block.NewValue1(pos, OpComplexReal, typ.Float64, source) + mem = splitStore(dest, sel, mem, v, typ.Float64, offset, firstStorePos) + firstStorePos = firstStorePos.WithNotStmt() + sel = source.Block.NewValue1(pos, OpComplexImag, typ.Float64, source) + return splitStore(dest, sel, mem, v, typ.Float64, offset+8, firstStorePos) + } + // Default, including for aggregates whose single element exactly fills their container + // TODO this will be a problem for cast interfaces containing floats when we move to registers. + x := v.Block.NewValue3A(firstStorePos, OpStore, types.TypeMem, t, offsetFrom(dest, offset, types.NewPtr(t)), source, mem) + if debug { + fmt.Printf("\t\tsplitStore returns %s\n", x.LongString()) + } + + return x + } + + // rewriteArgs removes all the Args from a call and converts the call args into appropriate + // stores (or later, register movement). Extra args for interface and closure calls are ignored, + // but removed. + 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. + source := a.Args[0] + dst := f.ConstOffPtrSP(source.Type, aux.OffsetOfArg(auxI), sp) + if a.Uses == 1 && a.Block == v.Block { + a.reset(OpMove) + a.Pos = pos + a.Type = types.TypeMem + a.Aux = aux.TypeOfArg(auxI) + a.AuxInt = aux.SizeOfArg(auxI) + a.SetArgs3(dst, source, mem) + mem = a + } else { + mem = v.Block.NewValue3A(pos, OpMove, types.TypeMem, aux.TypeOfArg(auxI), dst, source, mem) + mem.AuxInt = aux.SizeOfArg(auxI) + } + } else { + if debug { + fmt.Printf("storeArg %s, %v, %d\n", a.LongString(), aux.TypeOfArg(auxI), aux.OffsetOfArg(auxI)) + } + mem = storeArg(pos, v.Block, a, aux.TypeOfArg(auxI), aux.OffsetOfArg(auxI), mem) + } + } + v.resetArgs() + return mem + } + + // TODO if too slow, whole program iteration can be replaced w/ slices of appropriate values, accumulated in first loop here. + + // 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: + 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) + } + } + } + + for i, name := range f.Names { + t := name.Type + if isAlreadyExpandedAggregateType(t) { + for j, v := range f.NamedValues[name] { + if v.Op == OpSelectN { + ns := namedSelects[v] + namedSelects[v] = append(ns, namedVal{locIndex: i, valIndex: j}) + } + } + } + } + + // Step 1: any stores of aggregates remaining are believed to be sourced from call results. + // Decompose those stores into a series of smaller stores, adding selection ops as necessary. + for _, b := range f.Blocks { + for _, v := range b.Values { + if v.Op == OpStore { + t := v.Aux.(*types.Type) + iAEATt := isAlreadyExpandedAggregateType(t) + if !iAEATt { + // guarding against store immediate struct into interface data field -- store type is *uint8 + // TODO can this happen recursively? + tSrc := v.Args[1].Type + iAEATt = isAlreadyExpandedAggregateType(tSrc) + if iAEATt { + t = tSrc + } + } + if iAEATt { + if debug { + fmt.Printf("Splitting store %s\n", v.LongString()) + } + dst, source, mem := v.Args[0], v.Args[1], v.Args[2] + mem = splitStore(dst, source, mem, v, t, 0, v.Pos) + v.copyOf(mem) + } + } + } + } + + val2Preds := make(map[*Value]int32) // Used to accumulate dependency graph of selection operations for topological ordering. + + // Step 2: transform or accumulate selection operations for rewrite in topological order. + // + // Aggregate types that have already (in earlier phases) been transformed must be lowered comprehensively to finish + // the transformation (user-defined structs and arrays, slices, strings, interfaces, complex, 64-bit on 32-bit architectures), + // + // Any select-for-addressing applied to call results can be transformed directly. for _, b := range f.Blocks { for _, v := range b.Values { + // Accumulate chains of selectors for processing in topological order switch v.Op { + case OpStructSelect, OpArraySelect, + OpIData, OpITab, + OpStringPtr, OpStringLen, + OpSlicePtr, OpSliceLen, OpSliceCap, + OpComplexReal, OpComplexImag, + OpInt64Hi, OpInt64Lo: + w := v.Args[0] + switch w.Op { + case OpStructSelect, OpArraySelect, OpSelectN: + val2Preds[w] += 1 + if debug { + fmt.Printf("v2p[%s] = %d\n", w.LongString(), val2Preds[w]) + } + } + fallthrough + case OpSelectN: - call := v.Args[0] - aux := call.Aux.(*AuxCall) - which := v.AuxInt - t := v.Type - if which == aux.NResults() { // mem is after the results. - // rewrite v as a Copy of call -- the replacement call will produce a mem. - v.copyOf(call) - } else { - pt := types.NewPtr(t) - if canSSAType(t) { - off := f.ConstOffPtrSP(pt, aux.OffsetOfResult(which), sp) - v.reset(OpLoad) - v.SetArgs2(off, call) - } else { - panic("Should not have non-SSA-able OpSelectN") + if _, ok := val2Preds[v]; !ok { + val2Preds[v] = 0 + if debug { + fmt.Printf("v2p[%s] = %d\n", v.LongString(), val2Preds[v]) } } - v.Type = t // not right for the mem operand yet, but will be when call is rewritten. case OpSelectNAddr: + // Do these directly, there are no chains of selectors. call := v.Args[0] which := v.AuxInt aux := call.Aux.(*AuxCall) pt := v.Type - off := f.ConstOffPtrSP(pt, aux.OffsetOfResult(which), sp) + off := offsetFrom(sp, aux.OffsetOfResult(which), pt) v.copyOf(off) } } } - // Step 2: rewrite the calls + // Step 3: Compute topological order of selectors, + // then process it in reverse to eliminate duplicates, + // then forwards to rewrite selectors. + // + // All chains of selectors end up in same block as the call. + sdom := f.Sdom() + + // Compilation must be deterministic, so sort after extracting first zeroes from map. + // Sorting allows dominators-last order within each batch, + // so that the backwards scan for duplicates will most often find copies from dominating blocks (it is best-effort). + var toProcess []*Value + less := func(i, j int) bool { + vi, vj := toProcess[i], toProcess[j] + bi, bj := vi.Block, vj.Block + if bi == bj { + return vi.ID < vj.ID + } + return sdom.domorder(bi) > sdom.domorder(bj) // reverse the order to put dominators last. + } + + // Accumulate order in allOrdered + var allOrdered []*Value + for v, n := range val2Preds { + if n == 0 { + allOrdered = append(allOrdered, v) + } + } + last := 0 // allOrdered[0:last] has been top-sorted and processed + for len(val2Preds) > 0 { + toProcess = allOrdered[last:] + last = len(allOrdered) + sort.SliceStable(toProcess, less) + for _, v := range toProcess { + w := v.Args[0] + delete(val2Preds, v) + n, ok := val2Preds[w] + if !ok { + continue + } + if n == 1 { + allOrdered = append(allOrdered, w) + delete(val2Preds, w) + continue + } + val2Preds[w] = n - 1 + } + } + + common := make(map[selKey]*Value) + // Rewrite duplicate selectors as copies where possible. + for i := len(allOrdered) - 1; i >= 0; i-- { + v := allOrdered[i] + w := v.Args[0] + for w.Op == OpCopy { + w = w.Args[0] + } + typ := v.Type + if typ.IsMemory() { + continue // handled elsewhere, not an indexable result + } + size := typ.Width + offset := int64(0) + switch v.Op { + case OpStructSelect: + if w.Type.Etype == types.TSTRUCT { + offset = w.Type.FieldOff(int(v.AuxInt)) + } else { // Immediate interface data artifact, offset is zero. + f.Fatalf("Expand calls interface data problem, func %s, v=%s, w=%s\n", f.Name, v.LongString(), w.LongString()) + } + case OpArraySelect: + offset = size * v.AuxInt + case OpSelectN: + offset = w.Aux.(*AuxCall).OffsetOfResult(v.AuxInt) + case OpInt64Hi: + offset = hiOffset + case OpInt64Lo: + offset = lowOffset + case OpStringLen, OpSliceLen, OpIData: + offset = ptrSize + case OpSliceCap: + offset = 2 * ptrSize + case OpComplexImag: + offset = size + } + sk := selKey{from: w, size: size, offset: offset, typ: typ.Etype} + dupe := common[sk] + if dupe == nil { + common[sk] = v + } else if sdom.IsAncestorEq(dupe.Block, v.Block) { + v.copyOf(dupe) + } else { + // Because values are processed in dominator order, the old common[s] will never dominate after a miss is seen. + // Installing the new value might match some future values. + common[sk] = v + } + } + + // Indices of entries in f.Names that need to be deleted. + var toDelete []namedVal + + // Rewrite selectors. + for i, v := range allOrdered { + if debug { + b := v.Block + fmt.Printf("allOrdered[%d] = b%d, %s, uses=%d\n", i, b.ID, v.LongString(), v.Uses) + } + if v.Uses == 0 { + v.reset(OpInvalid) + continue + } + if v.Op == OpCopy { + continue + } + locs := rewriteSelect(v, v, 0) + // Install new names. + if v.Type.IsMemory() { + continue + } + // Leaf types may have debug locations + if !isAlreadyExpandedAggregateType(v.Type) { + for _, l := range locs { + f.NamedValues[l] = append(f.NamedValues[l], v) + } + f.Names = append(f.Names, locs...) + continue + } + // Not-leaf types that had debug locations need to lose them. + if ns, ok := namedSelects[v]; ok { + toDelete = append(toDelete, ns...) + } + } + + deleteNamedVals(f, toDelete) + + // Step 4: rewrite the calls themselves, correcting the type for _, b := range f.Blocks { for _, v := range b.Values { switch v.Op { case OpStaticLECall: - // Thread the stores on the memory arg - m0 := v.Args[len(v.Args)-1] - mem := m0 - pos := v.Pos.WithNotStmt() - aux := v.Aux.(*AuxCall) - auxInt := v.AuxInt - for i, a := range v.Args { - if a == m0 { - break - } - if a.Op == OpDereference { - // "Dereference" of addressed (probably not-SSA-eligible) value becomes Move - src := a.Args[0] - dst := f.ConstOffPtrSP(src.Type, aux.OffsetOfArg(int64(i)), sp) - 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 { - // Add a new store. - t := aux.TypeOfArg(int64(i)) - dst := f.ConstOffPtrSP(types.NewPtr(t), aux.OffsetOfArg(int64(i)), sp) - mem = b.NewValue3A(pos, OpStore, types.TypeMem, t, dst, a, mem) - } - } - v.reset(OpStaticCall) + v.Op = OpStaticCall v.Type = types.TypeMem - v.Aux = aux - v.AuxInt = auxInt - v.SetArgs1(mem) + case OpClosureLECall: + v.Op = OpClosureCall + v.Type = types.TypeMem + case OpInterLECall: + v.Op = OpInterCall + v.Type = types.TypeMem + } + } + } + + // Step 5: elide any copies introduced. + for _, b := range f.Blocks { + for _, v := range b.Values { + for i, a := range v.Args { + if a.Op != OpCopy { + continue + } + aa := copySource(a) + v.SetArg(i, aa) + for a.Uses == 0 { + b := a.Args[0] + a.reset(OpInvalid) + a = b + } } } } |