1 // Copyright 2015 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
8 "cmd/compile/internal/logopt"
9 "cmd/compile/internal/types"
11 "cmd/internal/obj/s390x"
23 type deadValueChoice bool
26 leaveDeadValues deadValueChoice = false
27 removeDeadValues = true
30 // deadcode indicates whether rewrite should try to remove any values that become dead.
31 func applyRewrite(f *Func, rb blockRewriter, rv valueRewriter, deadcode deadValueChoice) {
32 // repeat rewrites until we find no more rewrites
33 pendingLines := f.cachedLineStarts // Holds statement boundaries that need to be moved to a new value/block
37 fmt.Printf("%s: rewriting for %s\n", f.pass.name, f.Name)
41 for _, b := range f.Blocks {
46 b0.Succs = append([]Edge{}, b.Succs...) // make a new copy, not aliasing
48 for i, c := range b.ControlValues() {
51 b.ReplaceControl(i, c)
57 fmt.Printf("rewriting %s -> %s\n", b0.LongString(), b.LongString())
60 for j, v := range b.Values {
65 v0.Args = append([]*Value{}, v.Args...) // make a new copy, not aliasing
67 if v.Uses == 0 && v.removeable() {
68 if v.Op != OpInvalid && deadcode == removeDeadValues {
69 // Reset any values that are now unused, so that we decrement
70 // the use count of all of its arguments.
71 // Not quite a deadcode pass, because it does not handle cycles.
72 // But it should help Uses==1 rules to fire.
76 // No point rewriting values which aren't used.
80 vchange := phielimValue(v)
81 if vchange && debug > 1 {
82 fmt.Printf("rewriting %s -> %s\n", v0.LongString(), v.LongString())
85 // Eliminate copy inputs.
86 // If any copy input becomes unused, mark it
87 // as invalid and discard its argument. Repeat
88 // recursively on the discarded argument.
89 // This phase helps remove phantom "dead copy" uses
90 // of a value so that a x.Uses==1 rule condition
92 for i, a := range v.Args {
98 // If a, a copy, has a line boundary indicator, attempt to find a new value
99 // to hold it. The first candidate is the value that will replace a (aa),
100 // if it shares the same block and line and is eligible.
101 // The second option is v, which has a as an input. Because aa is earlier in
102 // the data flow, it is the better choice.
103 if a.Pos.IsStmt() == src.PosIsStmt {
104 if aa.Block == a.Block && aa.Pos.Line() == a.Pos.Line() && aa.Pos.IsStmt() != src.PosNotStmt {
105 aa.Pos = aa.Pos.WithIsStmt()
106 } else if v.Block == a.Block && v.Pos.Line() == a.Pos.Line() && v.Pos.IsStmt() != src.PosNotStmt {
107 v.Pos = v.Pos.WithIsStmt()
109 // Record the lost line and look for a new home after all rewrites are complete.
110 // TODO: it's possible (in FOR loops, in particular) for statement boundaries for the same
111 // line to appear in more than one block, but only one block is stored, so if both end
112 // up here, then one will be lost.
113 pendingLines.set(a.Pos, int32(a.Block.ID))
115 a.Pos = a.Pos.WithNotStmt()
124 if vchange && debug > 1 {
125 fmt.Printf("rewriting %s -> %s\n", v0.LongString(), v.LongString())
128 // apply rewrite function
131 // If value changed to a poor choice for a statement boundary, move the boundary
132 if v.Pos.IsStmt() == src.PosIsStmt {
133 if k := nextGoodStatementIndex(v, j, b); k != j {
134 v.Pos = v.Pos.WithNotStmt()
135 b.Values[k].Pos = b.Values[k].Pos.WithIsStmt()
140 change = change || vchange
141 if vchange && debug > 1 {
142 fmt.Printf("rewriting %s -> %s\n", v0.LongString(), v.LongString())
150 // remove clobbered values
151 for _, b := range f.Blocks {
153 for i, v := range b.Values {
155 if v.Op == OpInvalid {
156 if v.Pos.IsStmt() == src.PosIsStmt {
157 pendingLines.set(vl, int32(b.ID))
162 if v.Pos.IsStmt() != src.PosNotStmt && !notStmtBoundary(v.Op) && pendingLines.get(vl) == int32(b.ID) {
163 pendingLines.remove(vl)
164 v.Pos = v.Pos.WithIsStmt()
171 if pendingLines.get(b.Pos) == int32(b.ID) {
172 b.Pos = b.Pos.WithIsStmt()
173 pendingLines.remove(b.Pos)
179 // Common functions called from rewriting rules
181 func is64BitFloat(t *types.Type) bool {
182 return t.Size() == 8 && t.IsFloat()
185 func is32BitFloat(t *types.Type) bool {
186 return t.Size() == 4 && t.IsFloat()
189 func is64BitInt(t *types.Type) bool {
190 return t.Size() == 8 && t.IsInteger()
193 func is32BitInt(t *types.Type) bool {
194 return t.Size() == 4 && t.IsInteger()
197 func is16BitInt(t *types.Type) bool {
198 return t.Size() == 2 && t.IsInteger()
201 func is8BitInt(t *types.Type) bool {
202 return t.Size() == 1 && t.IsInteger()
205 func isPtr(t *types.Type) bool {
206 return t.IsPtrShaped()
209 func isSigned(t *types.Type) bool {
213 // mergeSym merges two symbolic offsets. There is no real merging of
214 // offsets, we just pick the non-nil one.
215 func mergeSym(x, y Sym) Sym {
222 panic(fmt.Sprintf("mergeSym with two non-nil syms %v %v", x, y))
225 func canMergeSym(x, y Sym) bool {
226 return x == nil || y == nil
229 // canMergeLoadClobber reports whether the load can be merged into target without
230 // invalidating the schedule.
231 // It also checks that the other non-load argument x is something we
232 // are ok with clobbering.
233 func canMergeLoadClobber(target, load, x *Value) bool {
234 // The register containing x is going to get clobbered.
235 // Don't merge if we still need the value of x.
236 // We don't have liveness information here, but we can
237 // approximate x dying with:
238 // 1) target is x's only use.
239 // 2) target is not in a deeper loop than x.
243 loopnest := x.Block.Func.loopnest()
244 loopnest.calculateDepths()
245 if loopnest.depth(target.Block.ID) > loopnest.depth(x.Block.ID) {
248 return canMergeLoad(target, load)
251 // canMergeLoad reports whether the load can be merged into target without
252 // invalidating the schedule.
253 func canMergeLoad(target, load *Value) bool {
254 if target.Block.ID != load.Block.ID {
255 // If the load is in a different block do not merge it.
259 // We can't merge the load into the target if the load
260 // has more than one use.
265 mem := load.MemoryArg()
267 // We need the load's memory arg to still be alive at target. That
268 // can't be the case if one of target's args depends on a memory
269 // state that is a successor of load's memory arg.
271 // For example, it would be invalid to merge load into target in
272 // the following situation because newmem has killed oldmem
273 // before target is reached:
274 // load = read ... oldmem
275 // newmem = write ... oldmem
276 // arg0 = read ... newmem
277 // target = add arg0 load
279 // If the argument comes from a different block then we can exclude
280 // it immediately because it must dominate load (which is in the
281 // same block as target).
283 for _, a := range target.Args {
284 if a != load && a.Block.ID == target.Block.ID {
285 args = append(args, a)
289 // memPreds contains memory states known to be predecessors of load's
290 // memory state. It is lazily initialized.
291 var memPreds map[*Value]bool
292 for i := 0; len(args) > 0; i++ {
295 // Give up if we have done a lot of iterations.
298 v := args[len(args)-1]
299 args = args[:len(args)-1]
300 if target.Block.ID != v.Block.ID {
301 // Since target and load are in the same block
302 // we can stop searching when we leave the block.
306 // A Phi implies we have reached the top of the block.
307 // The memory phi, if it exists, is always
308 // the first logical store in the block.
311 if v.Type.IsTuple() && v.Type.FieldType(1).IsMemory() {
312 // We could handle this situation however it is likely
316 if v.Op.SymEffect()&SymAddr != 0 {
317 // This case prevents an operation that calculates the
318 // address of a local variable from being forced to schedule
319 // before its corresponding VarDef.
325 // We don't want to combine the CMPQ with the load, because
326 // that would force the CMPQ to schedule before the VARDEF, which
327 // in turn requires the LEAQ to schedule before the VARDEF.
330 if v.Type.IsMemory() {
332 // Initialise a map containing memory states
333 // known to be predecessors of load's memory
335 memPreds = make(map[*Value]bool)
338 for i := 0; i < limit; i++ {
340 // The memory phi, if it exists, is always
341 // the first logical store in the block.
344 if m.Block.ID != target.Block.ID {
347 if !m.Type.IsMemory() {
351 if len(m.Args) == 0 {
358 // We can merge if v is a predecessor of mem.
360 // For example, we can merge load into target in the
361 // following scenario:
364 // load = read ... mem
365 // target = add x load
371 if len(v.Args) > 0 && v.Args[len(v.Args)-1] == mem {
372 // If v takes mem as an input then we know mem
373 // is valid at this point.
376 for _, a := range v.Args {
377 if target.Block.ID == a.Block.ID {
378 args = append(args, a)
386 // isSameCall reports whether sym is the same as the given named symbol
387 func isSameCall(sym interface{}, name string) bool {
388 fn := sym.(*AuxCall).Fn
389 return fn != nil && fn.String() == name
392 // nlz returns the number of leading zeros.
393 func nlz64(x int64) int { return bits.LeadingZeros64(uint64(x)) }
394 func nlz32(x int32) int { return bits.LeadingZeros32(uint32(x)) }
395 func nlz16(x int16) int { return bits.LeadingZeros16(uint16(x)) }
396 func nlz8(x int8) int { return bits.LeadingZeros8(uint8(x)) }
398 // ntzX returns the number of trailing zeros.
399 func ntz64(x int64) int { return bits.TrailingZeros64(uint64(x)) }
400 func ntz32(x int32) int { return bits.TrailingZeros32(uint32(x)) }
401 func ntz16(x int16) int { return bits.TrailingZeros16(uint16(x)) }
402 func ntz8(x int8) int { return bits.TrailingZeros8(uint8(x)) }
404 func oneBit(x int64) bool { return x&(x-1) == 0 && x != 0 }
405 func oneBit8(x int8) bool { return x&(x-1) == 0 && x != 0 }
406 func oneBit16(x int16) bool { return x&(x-1) == 0 && x != 0 }
407 func oneBit32(x int32) bool { return x&(x-1) == 0 && x != 0 }
408 func oneBit64(x int64) bool { return x&(x-1) == 0 && x != 0 }
410 // nto returns the number of trailing ones.
411 func nto(x int64) int64 {
412 return int64(ntz64(^x))
415 // logX returns logarithm of n base 2.
416 // n must be a positive power of 2 (isPowerOfTwoX returns true).
417 func log8(n int8) int64 {
418 return int64(bits.Len8(uint8(n))) - 1
420 func log16(n int16) int64 {
421 return int64(bits.Len16(uint16(n))) - 1
423 func log32(n int32) int64 {
424 return int64(bits.Len32(uint32(n))) - 1
426 func log64(n int64) int64 {
427 return int64(bits.Len64(uint64(n))) - 1
430 // log2uint32 returns logarithm in base 2 of uint32(n), with log2(0) = -1.
432 func log2uint32(n int64) int64 {
433 return int64(bits.Len32(uint32(n))) - 1
436 // isPowerOfTwo functions report whether n is a power of 2.
437 func isPowerOfTwo8(n int8) bool {
438 return n > 0 && n&(n-1) == 0
440 func isPowerOfTwo16(n int16) bool {
441 return n > 0 && n&(n-1) == 0
443 func isPowerOfTwo32(n int32) bool {
444 return n > 0 && n&(n-1) == 0
446 func isPowerOfTwo64(n int64) bool {
447 return n > 0 && n&(n-1) == 0
450 // isUint64PowerOfTwo reports whether uint64(n) is a power of 2.
451 func isUint64PowerOfTwo(in int64) bool {
453 return n > 0 && n&(n-1) == 0
456 // isUint32PowerOfTwo reports whether uint32(n) is a power of 2.
457 func isUint32PowerOfTwo(in int64) bool {
458 n := uint64(uint32(in))
459 return n > 0 && n&(n-1) == 0
462 // is32Bit reports whether n can be represented as a signed 32 bit integer.
463 func is32Bit(n int64) bool {
464 return n == int64(int32(n))
467 // is16Bit reports whether n can be represented as a signed 16 bit integer.
468 func is16Bit(n int64) bool {
469 return n == int64(int16(n))
472 // is8Bit reports whether n can be represented as a signed 8 bit integer.
473 func is8Bit(n int64) bool {
474 return n == int64(int8(n))
477 // isU8Bit reports whether n can be represented as an unsigned 8 bit integer.
478 func isU8Bit(n int64) bool {
479 return n == int64(uint8(n))
482 // isU12Bit reports whether n can be represented as an unsigned 12 bit integer.
483 func isU12Bit(n int64) bool {
484 return 0 <= n && n < (1<<12)
487 // isU16Bit reports whether n can be represented as an unsigned 16 bit integer.
488 func isU16Bit(n int64) bool {
489 return n == int64(uint16(n))
492 // isU32Bit reports whether n can be represented as an unsigned 32 bit integer.
493 func isU32Bit(n int64) bool {
494 return n == int64(uint32(n))
497 // is20Bit reports whether n can be represented as a signed 20 bit integer.
498 func is20Bit(n int64) bool {
499 return -(1<<19) <= n && n < (1<<19)
502 // b2i translates a boolean value to 0 or 1 for assigning to auxInt.
503 func b2i(b bool) int64 {
510 // b2i32 translates a boolean value to 0 or 1.
511 func b2i32(b bool) int32 {
518 // shiftIsBounded reports whether (left/right) shift Value v is known to be bounded.
519 // A shift is bounded if it is shifting by less than the width of the shifted value.
520 func shiftIsBounded(v *Value) bool {
524 // canonLessThan returns whether x is "ordered" less than y, for purposes of normalizing
525 // generated code as much as possible.
526 func canonLessThan(x, y *Value) bool {
530 if !x.Pos.SameFileAndLine(y.Pos) {
531 return x.Pos.Before(y.Pos)
536 // truncate64Fto32F converts a float64 value to a float32 preserving the bit pattern
537 // of the mantissa. It will panic if the truncation results in lost information.
538 func truncate64Fto32F(f float64) float32 {
539 if !isExactFloat32(f) {
540 panic("truncate64Fto32F: truncation is not exact")
545 // NaN bit patterns aren't necessarily preserved across conversion
546 // instructions so we need to do the conversion manually.
547 b := math.Float64bits(f)
548 m := b & ((1 << 52) - 1) // mantissa (a.k.a. significand)
549 // | sign | exponent | mantissa |
550 r := uint32(((b >> 32) & (1 << 31)) | 0x7f800000 | (m >> (52 - 23)))
551 return math.Float32frombits(r)
554 // extend32Fto64F converts a float32 value to a float64 value preserving the bit
555 // pattern of the mantissa.
556 func extend32Fto64F(f float32) float64 {
557 if !math.IsNaN(float64(f)) {
560 // NaN bit patterns aren't necessarily preserved across conversion
561 // instructions so we need to do the conversion manually.
562 b := uint64(math.Float32bits(f))
563 // | sign | exponent | mantissa |
564 r := ((b << 32) & (1 << 63)) | (0x7ff << 52) | ((b & 0x7fffff) << (52 - 23))
565 return math.Float64frombits(r)
568 // DivisionNeedsFixUp reports whether the division needs fix-up code.
569 func DivisionNeedsFixUp(v *Value) bool {
573 // auxFrom64F encodes a float64 value so it can be stored in an AuxInt.
574 func auxFrom64F(f float64) int64 {
576 panic("can't encode a NaN in AuxInt field")
578 return int64(math.Float64bits(f))
581 // auxFrom32F encodes a float32 value so it can be stored in an AuxInt.
582 func auxFrom32F(f float32) int64 {
584 panic("can't encode a NaN in AuxInt field")
586 return int64(math.Float64bits(extend32Fto64F(f)))
589 // auxTo32F decodes a float32 from the AuxInt value provided.
590 func auxTo32F(i int64) float32 {
591 return truncate64Fto32F(math.Float64frombits(uint64(i)))
594 // auxTo64F decodes a float64 from the AuxInt value provided.
595 func auxTo64F(i int64) float64 {
596 return math.Float64frombits(uint64(i))
599 func auxIntToBool(i int64) bool {
605 func auxIntToInt8(i int64) int8 {
608 func auxIntToInt16(i int64) int16 {
611 func auxIntToInt32(i int64) int32 {
614 func auxIntToInt64(i int64) int64 {
617 func auxIntToUint8(i int64) uint8 {
620 func auxIntToFloat32(i int64) float32 {
621 return float32(math.Float64frombits(uint64(i)))
623 func auxIntToFloat64(i int64) float64 {
624 return math.Float64frombits(uint64(i))
626 func auxIntToValAndOff(i int64) ValAndOff {
629 func auxIntToArm64BitField(i int64) arm64BitField {
630 return arm64BitField(i)
632 func auxIntToInt128(x int64) int128 {
634 panic("nonzero int128 not allowed")
638 func auxIntToFlagConstant(x int64) flagConstant {
639 return flagConstant(x)
642 func auxIntToOp(cc int64) Op {
646 func boolToAuxInt(b bool) int64 {
652 func int8ToAuxInt(i int8) int64 {
655 func int16ToAuxInt(i int16) int64 {
658 func int32ToAuxInt(i int32) int64 {
661 func int64ToAuxInt(i int64) int64 {
664 func uint8ToAuxInt(i uint8) int64 {
665 return int64(int8(i))
667 func float32ToAuxInt(f float32) int64 {
668 return int64(math.Float64bits(float64(f)))
670 func float64ToAuxInt(f float64) int64 {
671 return int64(math.Float64bits(f))
673 func valAndOffToAuxInt(v ValAndOff) int64 {
676 func arm64BitFieldToAuxInt(v arm64BitField) int64 {
679 func int128ToAuxInt(x int128) int64 {
681 panic("nonzero int128 not allowed")
685 func flagConstantToAuxInt(x flagConstant) int64 {
689 func opToAuxInt(o Op) int64 {
693 // Aux is an interface to hold miscellaneous data in Blocks and Values.
698 // stringAux wraps string values for use in Aux.
699 type stringAux string
701 func (stringAux) CanBeAnSSAAux() {}
703 func auxToString(i Aux) string {
704 return string(i.(stringAux))
706 func auxToSym(i Aux) Sym {
707 // TODO: kind of a hack - allows nil interface through
711 func auxToType(i Aux) *types.Type {
712 return i.(*types.Type)
714 func auxToCall(i Aux) *AuxCall {
717 func auxToS390xCCMask(i Aux) s390x.CCMask {
718 return i.(s390x.CCMask)
720 func auxToS390xRotateParams(i Aux) s390x.RotateParams {
721 return i.(s390x.RotateParams)
724 func StringToAux(s string) Aux {
727 func symToAux(s Sym) Aux {
730 func callToAux(s *AuxCall) Aux {
733 func typeToAux(t *types.Type) Aux {
736 func s390xCCMaskToAux(c s390x.CCMask) Aux {
739 func s390xRotateParamsToAux(r s390x.RotateParams) Aux {
743 // uaddOvf reports whether unsigned a+b would overflow.
744 func uaddOvf(a, b int64) bool {
745 return uint64(a)+uint64(b) < uint64(a)
748 // loadLSymOffset simulates reading a word at an offset into a
749 // read-only symbol's runtime memory. If it would read a pointer to
750 // another symbol, that symbol is returned. Otherwise, it returns nil.
751 func loadLSymOffset(lsym *obj.LSym, offset int64) *obj.LSym {
752 if lsym.Type != objabi.SRODATA {
756 for _, r := range lsym.R {
757 if int64(r.Off) == offset && r.Type&^objabi.R_WEAK == objabi.R_ADDR && r.Add == 0 {
765 // de-virtualize an InterLECall
766 // 'sym' is the symbol for the itab
767 func devirtLESym(v *Value, aux Aux, sym Sym, offset int64) *obj.LSym {
768 n, ok := sym.(*obj.LSym)
773 lsym := loadLSymOffset(n, offset)
774 if f := v.Block.Func; f.pass.debug > 0 {
776 f.Warnl(v.Pos, "de-virtualizing call")
778 f.Warnl(v.Pos, "couldn't de-virtualize call")
784 func devirtLECall(v *Value, sym *obj.LSym) *Value {
785 v.Op = OpStaticLECall
786 auxcall := v.Aux.(*AuxCall)
792 // isSamePtr reports whether p1 and p2 point to the same address.
793 func isSamePtr(p1, p2 *Value) bool {
802 return p1.AuxInt == p2.AuxInt && isSamePtr(p1.Args[0], p2.Args[0])
803 case OpAddr, OpLocalAddr:
804 // OpAddr's 0th arg is either OpSP or OpSB, which means that it is uniquely identified by its Op.
805 // Checking for value equality only works after [z]cse has run.
806 return p1.Aux == p2.Aux && p1.Args[0].Op == p2.Args[0].Op
808 return p1.Args[1] == p2.Args[1] && isSamePtr(p1.Args[0], p2.Args[0])
813 func isStackPtr(v *Value) bool {
814 for v.Op == OpOffPtr || v.Op == OpAddPtr {
817 return v.Op == OpSP || v.Op == OpLocalAddr
820 // disjoint reports whether the memory region specified by [p1:p1+n1)
821 // does not overlap with [p2:p2+n2).
822 // A return value of false does not imply the regions overlap.
823 func disjoint(p1 *Value, n1 int64, p2 *Value, n2 int64) bool {
824 if n1 == 0 || n2 == 0 {
830 baseAndOffset := func(ptr *Value) (base *Value, offset int64) {
831 base, offset = ptr, 0
832 for base.Op == OpOffPtr {
833 offset += base.AuxInt
838 p1, off1 := baseAndOffset(p1)
839 p2, off2 := baseAndOffset(p2)
840 if isSamePtr(p1, p2) {
841 return !overlap(off1, n1, off2, n2)
843 // p1 and p2 are not the same, so if they are both OpAddrs then
844 // they point to different variables.
845 // If one pointer is on the stack and the other is an argument
846 // then they can't overlap.
848 case OpAddr, OpLocalAddr:
849 if p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpSP {
852 return (p2.Op == OpArg || p2.Op == OpArgIntReg) && p1.Args[0].Op == OpSP
853 case OpArg, OpArgIntReg:
854 if p2.Op == OpSP || p2.Op == OpLocalAddr {
858 return p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpArg || p2.Op == OpArgIntReg || p2.Op == OpSP
863 // moveSize returns the number of bytes an aligned MOV instruction moves
864 func moveSize(align int64, c *Config) int64 {
866 case align%8 == 0 && c.PtrSize == 8:
876 // mergePoint finds a block among a's blocks which dominates b and is itself
877 // dominated by all of a's blocks. Returns nil if it can't find one.
878 // Might return nil even if one does exist.
879 func mergePoint(b *Block, a ...*Value) *Block {
880 // Walk backward from b looking for one of the a's blocks.
886 for _, x := range a {
891 if len(b.Preds) > 1 {
892 // Don't know which way to go back. Abort.
898 return nil // too far away
900 // At this point, r is the first value in a that we find by walking backwards.
901 // if we return anything, r will be it.
904 // Keep going, counting the other a's that we find. They must all dominate r.
907 for _, x := range a {
913 // Found all of a in a backwards walk. We can return r.
916 if len(b.Preds) > 1 {
923 return nil // too far away
926 // clobber invalidates values. Returns true.
927 // clobber is used by rewrite rules to:
928 // A) make sure the values are really dead and never used again.
929 // B) decrement use counts of the values' args.
930 func clobber(vv ...*Value) bool {
931 for _, v := range vv {
933 // Note: leave v.Block intact. The Block field is used after clobber.
938 // clobberIfDead resets v when use count is 1. Returns true.
939 // clobberIfDead is used by rewrite rules to decrement
940 // use counts of v's args when v is dead and never used.
941 func clobberIfDead(v *Value) bool {
945 // Note: leave v.Block intact. The Block field is used after clobberIfDead.
949 // noteRule is an easy way to track if a rule is matched when writing
950 // new ones. Make the rule of interest also conditional on
951 // noteRule("note to self: rule of interest matched")
952 // and that message will print when the rule matches.
953 func noteRule(s string) bool {
958 // countRule increments Func.ruleMatches[key].
959 // If Func.ruleMatches is non-nil at the end
960 // of compilation, it will be printed to stdout.
961 // This is intended to make it easier to find which functions
962 // which contain lots of rules matches when developing new rules.
963 func countRule(v *Value, key string) bool {
965 if f.ruleMatches == nil {
966 f.ruleMatches = make(map[string]int)
972 // warnRule generates compiler debug output with string s when
973 // v is not in autogenerated code, cond is true and the rule has fired.
974 func warnRule(cond bool, v *Value, s string) bool {
975 if pos := v.Pos; pos.Line() > 1 && cond {
976 v.Block.Func.Warnl(pos, s)
981 // for a pseudo-op like (LessThan x), extract x
982 func flagArg(v *Value) *Value {
983 if len(v.Args) != 1 || !v.Args[0].Type.IsFlags() {
989 // arm64Negate finds the complement to an ARM64 condition code,
990 // for example !Equal -> NotEqual or !LessThan -> GreaterEqual
992 // For floating point, it's more subtle because NaN is unordered. We do
993 // !LessThanF -> NotLessThanF, the latter takes care of NaNs.
994 func arm64Negate(op Op) Op {
996 case OpARM64LessThan:
997 return OpARM64GreaterEqual
998 case OpARM64LessThanU:
999 return OpARM64GreaterEqualU
1000 case OpARM64GreaterThan:
1001 return OpARM64LessEqual
1002 case OpARM64GreaterThanU:
1003 return OpARM64LessEqualU
1004 case OpARM64LessEqual:
1005 return OpARM64GreaterThan
1006 case OpARM64LessEqualU:
1007 return OpARM64GreaterThanU
1008 case OpARM64GreaterEqual:
1009 return OpARM64LessThan
1010 case OpARM64GreaterEqualU:
1011 return OpARM64LessThanU
1013 return OpARM64NotEqual
1014 case OpARM64NotEqual:
1016 case OpARM64LessThanF:
1017 return OpARM64NotLessThanF
1018 case OpARM64NotLessThanF:
1019 return OpARM64LessThanF
1020 case OpARM64LessEqualF:
1021 return OpARM64NotLessEqualF
1022 case OpARM64NotLessEqualF:
1023 return OpARM64LessEqualF
1024 case OpARM64GreaterThanF:
1025 return OpARM64NotGreaterThanF
1026 case OpARM64NotGreaterThanF:
1027 return OpARM64GreaterThanF
1028 case OpARM64GreaterEqualF:
1029 return OpARM64NotGreaterEqualF
1030 case OpARM64NotGreaterEqualF:
1031 return OpARM64GreaterEqualF
1033 panic("unreachable")
1037 // arm64Invert evaluates (InvertFlags op), which
1038 // is the same as altering the condition codes such
1039 // that the same result would be produced if the arguments
1040 // to the flag-generating instruction were reversed, e.g.
1041 // (InvertFlags (CMP x y)) -> (CMP y x)
1042 func arm64Invert(op Op) Op {
1044 case OpARM64LessThan:
1045 return OpARM64GreaterThan
1046 case OpARM64LessThanU:
1047 return OpARM64GreaterThanU
1048 case OpARM64GreaterThan:
1049 return OpARM64LessThan
1050 case OpARM64GreaterThanU:
1051 return OpARM64LessThanU
1052 case OpARM64LessEqual:
1053 return OpARM64GreaterEqual
1054 case OpARM64LessEqualU:
1055 return OpARM64GreaterEqualU
1056 case OpARM64GreaterEqual:
1057 return OpARM64LessEqual
1058 case OpARM64GreaterEqualU:
1059 return OpARM64LessEqualU
1060 case OpARM64Equal, OpARM64NotEqual:
1062 case OpARM64LessThanF:
1063 return OpARM64GreaterThanF
1064 case OpARM64GreaterThanF:
1065 return OpARM64LessThanF
1066 case OpARM64LessEqualF:
1067 return OpARM64GreaterEqualF
1068 case OpARM64GreaterEqualF:
1069 return OpARM64LessEqualF
1070 case OpARM64NotLessThanF:
1071 return OpARM64NotGreaterThanF
1072 case OpARM64NotGreaterThanF:
1073 return OpARM64NotLessThanF
1074 case OpARM64NotLessEqualF:
1075 return OpARM64NotGreaterEqualF
1076 case OpARM64NotGreaterEqualF:
1077 return OpARM64NotLessEqualF
1079 panic("unreachable")
1083 // evaluate an ARM64 op against a flags value
1084 // that is potentially constant; return 1 for true,
1085 // -1 for false, and 0 for not constant.
1086 func ccARM64Eval(op Op, flags *Value) int {
1088 if fop == OpARM64InvertFlags {
1089 return -ccARM64Eval(op, flags.Args[0])
1091 if fop != OpARM64FlagConstant {
1094 fc := flagConstant(flags.AuxInt)
1095 b2i := func(b bool) int {
1104 case OpARM64NotEqual:
1106 case OpARM64LessThan:
1108 case OpARM64LessThanU:
1109 return b2i(fc.ult())
1110 case OpARM64GreaterThan:
1112 case OpARM64GreaterThanU:
1113 return b2i(fc.ugt())
1114 case OpARM64LessEqual:
1116 case OpARM64LessEqualU:
1117 return b2i(fc.ule())
1118 case OpARM64GreaterEqual:
1120 case OpARM64GreaterEqualU:
1121 return b2i(fc.uge())
1126 // logRule logs the use of the rule s. This will only be enabled if
1127 // rewrite rules were generated with the -log option, see gen/rulegen.go.
1128 func logRule(s string) {
1129 if ruleFile == nil {
1130 // Open a log file to write log to. We open in append
1131 // mode because all.bash runs the compiler lots of times,
1132 // and we want the concatenation of all of those logs.
1133 // This means, of course, that users need to rm the old log
1134 // to get fresh data.
1135 // TODO: all.bash runs compilers in parallel. Need to synchronize logging somehow?
1136 w, err := os.OpenFile(filepath.Join(os.Getenv("GOROOT"), "src", "rulelog"),
1137 os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
1143 _, err := fmt.Fprintln(ruleFile, s)
1149 var ruleFile io.Writer
1151 func min(x, y int64) int64 {
1158 func isConstZero(v *Value) bool {
1162 case OpConst64, OpConst32, OpConst16, OpConst8, OpConstBool, OpConst32F, OpConst64F:
1163 return v.AuxInt == 0
1168 // reciprocalExact64 reports whether 1/c is exactly representable.
1169 func reciprocalExact64(c float64) bool {
1170 b := math.Float64bits(c)
1171 man := b & (1<<52 - 1)
1173 return false // not a power of 2, denormal, or NaN
1175 exp := b >> 52 & (1<<11 - 1)
1176 // exponent bias is 0x3ff. So taking the reciprocal of a number
1177 // changes the exponent to 0x7fe-exp.
1182 return false // ±inf
1184 return false // exponent is not representable
1190 // reciprocalExact32 reports whether 1/c is exactly representable.
1191 func reciprocalExact32(c float32) bool {
1192 b := math.Float32bits(c)
1193 man := b & (1<<23 - 1)
1195 return false // not a power of 2, denormal, or NaN
1197 exp := b >> 23 & (1<<8 - 1)
1198 // exponent bias is 0x7f. So taking the reciprocal of a number
1199 // changes the exponent to 0xfe-exp.
1204 return false // ±inf
1206 return false // exponent is not representable
1212 // check if an immediate can be directly encoded into an ARM's instruction
1213 func isARMImmRot(v uint32) bool {
1214 for i := 0; i < 16; i++ {
1224 // overlap reports whether the ranges given by the given offset and
1225 // size pairs overlap.
1226 func overlap(offset1, size1, offset2, size2 int64) bool {
1227 if offset1 >= offset2 && offset2+size2 > offset1 {
1230 if offset2 >= offset1 && offset1+size1 > offset2 {
1236 func areAdjacentOffsets(off1, off2, size int64) bool {
1237 return off1+size == off2 || off1 == off2+size
1240 // check if value zeroes out upper 32-bit of 64-bit register.
1241 // depth limits recursion depth. In AMD64.rules 3 is used as limit,
1242 // because it catches same amount of cases as 4.
1243 func zeroUpper32Bits(x *Value, depth int) bool {
1245 case OpAMD64MOVLconst, OpAMD64MOVLload, OpAMD64MOVLQZX, OpAMD64MOVLloadidx1,
1246 OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVBload, OpAMD64MOVBloadidx1,
1247 OpAMD64MOVLloadidx4, OpAMD64ADDLload, OpAMD64SUBLload, OpAMD64ANDLload,
1248 OpAMD64ORLload, OpAMD64XORLload, OpAMD64CVTTSD2SL,
1249 OpAMD64ADDL, OpAMD64ADDLconst, OpAMD64SUBL, OpAMD64SUBLconst,
1250 OpAMD64ANDL, OpAMD64ANDLconst, OpAMD64ORL, OpAMD64ORLconst,
1251 OpAMD64XORL, OpAMD64XORLconst, OpAMD64NEGL, OpAMD64NOTL,
1252 OpAMD64SHRL, OpAMD64SHRLconst, OpAMD64SARL, OpAMD64SARLconst,
1253 OpAMD64SHLL, OpAMD64SHLLconst:
1256 return x.Type.Width == 4
1257 case OpPhi, OpSelect0, OpSelect1:
1258 // Phis can use each-other as an arguments, instead of tracking visited values,
1259 // just limit recursion depth.
1263 for i := range x.Args {
1264 if !zeroUpper32Bits(x.Args[i], depth-1) {
1274 // zeroUpper48Bits is similar to zeroUpper32Bits, but for upper 48 bits
1275 func zeroUpper48Bits(x *Value, depth int) bool {
1277 case OpAMD64MOVWQZX, OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVWloadidx2:
1280 return x.Type.Width == 2
1281 case OpPhi, OpSelect0, OpSelect1:
1282 // Phis can use each-other as an arguments, instead of tracking visited values,
1283 // just limit recursion depth.
1287 for i := range x.Args {
1288 if !zeroUpper48Bits(x.Args[i], depth-1) {
1298 // zeroUpper56Bits is similar to zeroUpper32Bits, but for upper 56 bits
1299 func zeroUpper56Bits(x *Value, depth int) bool {
1301 case OpAMD64MOVBQZX, OpAMD64MOVBload, OpAMD64MOVBloadidx1:
1304 return x.Type.Width == 1
1305 case OpPhi, OpSelect0, OpSelect1:
1306 // Phis can use each-other as an arguments, instead of tracking visited values,
1307 // just limit recursion depth.
1311 for i := range x.Args {
1312 if !zeroUpper56Bits(x.Args[i], depth-1) {
1322 // isInlinableMemmove reports whether the given arch performs a Move of the given size
1323 // faster than memmove. It will only return true if replacing the memmove with a Move is
1324 // safe, either because Move is small or because the arguments are disjoint.
1325 // This is used as a check for replacing memmove with Move ops.
1326 func isInlinableMemmove(dst, src *Value, sz int64, c *Config) bool {
1327 // It is always safe to convert memmove into Move when its arguments are disjoint.
1328 // Move ops may or may not be faster for large sizes depending on how the platform
1329 // lowers them, so we only perform this optimization on platforms that we know to
1330 // have fast Move ops.
1333 return sz <= 16 || (sz < 1024 && disjoint(dst, sz, src, sz))
1334 case "386", "arm64":
1336 case "s390x", "ppc64", "ppc64le":
1337 return sz <= 8 || disjoint(dst, sz, src, sz)
1338 case "arm", "mips", "mips64", "mipsle", "mips64le":
1344 // logLargeCopy logs the occurrence of a large copy.
1345 // The best place to do this is in the rewrite rules where the size of the move is easy to find.
1346 // "Large" is arbitrarily chosen to be 128 bytes; this may change.
1347 func logLargeCopy(v *Value, s int64) bool {
1351 if logopt.Enabled() {
1352 logopt.LogOpt(v.Pos, "copy", "lower", v.Block.Func.Name, fmt.Sprintf("%d bytes", s))
1357 // hasSmallRotate reports whether the architecture has rotate instructions
1358 // for sizes < 32-bit. This is used to decide whether to promote some rotations.
1359 func hasSmallRotate(c *Config) bool {
1361 case "amd64", "386":
1368 func newPPC64ShiftAuxInt(sh, mb, me, sz int64) int32 {
1369 if sh < 0 || sh >= sz {
1370 panic("PPC64 shift arg sh out of range")
1372 if mb < 0 || mb >= sz {
1373 panic("PPC64 shift arg mb out of range")
1375 if me < 0 || me >= sz {
1376 panic("PPC64 shift arg me out of range")
1378 return int32(sh<<16 | mb<<8 | me)
1381 func GetPPC64Shiftsh(auxint int64) int64 {
1382 return int64(int8(auxint >> 16))
1385 func GetPPC64Shiftmb(auxint int64) int64 {
1386 return int64(int8(auxint >> 8))
1389 func GetPPC64Shiftme(auxint int64) int64 {
1390 return int64(int8(auxint))
1393 // Test if this value can encoded as a mask for a rlwinm like
1394 // operation. Masks can also extend from the msb and wrap to
1395 // the lsb too. That is, the valid masks are 32 bit strings
1396 // of the form: 0..01..10..0 or 1..10..01..1 or 1...1
1397 func isPPC64WordRotateMask(v64 int64) bool {
1398 // Isolate rightmost 1 (if none 0) and add.
1401 // Likewise, for the wrapping case.
1403 vpn := (vn & -vn) + vn
1404 return (v&vp == 0 || vn&vpn == 0) && v != 0
1407 // Compress mask and shift into single value of the form
1408 // me | mb<<8 | rotate<<16 | nbits<<24 where me and mb can
1409 // be used to regenerate the input mask.
1410 func encodePPC64RotateMask(rotate, mask, nbits int64) int64 {
1411 var mb, me, mbn, men int
1413 // Determine boundaries and then decode them
1414 if mask == 0 || ^mask == 0 || rotate >= nbits {
1415 panic("Invalid PPC64 rotate mask")
1416 } else if nbits == 32 {
1417 mb = bits.LeadingZeros32(uint32(mask))
1418 me = 32 - bits.TrailingZeros32(uint32(mask))
1419 mbn = bits.LeadingZeros32(^uint32(mask))
1420 men = 32 - bits.TrailingZeros32(^uint32(mask))
1422 mb = bits.LeadingZeros64(uint64(mask))
1423 me = 64 - bits.TrailingZeros64(uint64(mask))
1424 mbn = bits.LeadingZeros64(^uint64(mask))
1425 men = 64 - bits.TrailingZeros64(^uint64(mask))
1427 // Check for a wrapping mask (e.g bits at 0 and 63)
1428 if mb == 0 && me == int(nbits) {
1429 // swap the inverted values
1433 return int64(me) | int64(mb<<8) | int64(rotate<<16) | int64(nbits<<24)
1436 // The inverse operation of encodePPC64RotateMask. The values returned as
1437 // mb and me satisfy the POWER ISA definition of MASK(x,y) where MASK(mb,me) = mask.
1438 func DecodePPC64RotateMask(sauxint int64) (rotate, mb, me int64, mask uint64) {
1439 auxint := uint64(sauxint)
1440 rotate = int64((auxint >> 16) & 0xFF)
1441 mb = int64((auxint >> 8) & 0xFF)
1442 me = int64((auxint >> 0) & 0xFF)
1443 nbits := int64((auxint >> 24) & 0xFF)
1444 mask = ((1 << uint(nbits-mb)) - 1) ^ ((1 << uint(nbits-me)) - 1)
1449 mask = uint64(uint32(mask))
1452 // Fixup ME to match ISA definition. The second argument to MASK(..,me)
1454 me = (me - 1) & (nbits - 1)
1458 // This verifies that the mask is a set of
1459 // consecutive bits including the least
1461 func isPPC64ValidShiftMask(v int64) bool {
1462 if (v != 0) && ((v+1)&v) == 0 {
1468 func getPPC64ShiftMaskLength(v int64) int64 {
1469 return int64(bits.Len64(uint64(v)))
1472 // Decompose a shift right into an equivalent rotate/mask,
1473 // and return mask & m.
1474 func mergePPC64RShiftMask(m, s, nbits int64) int64 {
1475 smask := uint64((1<<uint(nbits))-1) >> uint(s)
1476 return m & int64(smask)
1479 // Combine (ANDconst [m] (SRWconst [s])) into (RLWINM [y]) or return 0
1480 func mergePPC64AndSrwi(m, s int64) int64 {
1481 mask := mergePPC64RShiftMask(m, s, 32)
1482 if !isPPC64WordRotateMask(mask) {
1485 return encodePPC64RotateMask((32-s)&31, mask, 32)
1488 // Test if a shift right feeding into a CLRLSLDI can be merged into RLWINM.
1489 // Return the encoded RLWINM constant, or 0 if they cannot be merged.
1490 func mergePPC64ClrlsldiSrw(sld, srw int64) int64 {
1491 mask_1 := uint64(0xFFFFFFFF >> uint(srw))
1492 // for CLRLSLDI, it's more convient to think of it as a mask left bits then rotate left.
1493 mask_2 := uint64(0xFFFFFFFFFFFFFFFF) >> uint(GetPPC64Shiftmb(int64(sld)))
1495 // Rewrite mask to apply after the final left shift.
1496 mask_3 := (mask_1 & mask_2) << uint(GetPPC64Shiftsh(sld))
1499 r_2 := GetPPC64Shiftsh(sld)
1500 r_3 := (r_1 + r_2) & 31 // This can wrap.
1502 if uint64(uint32(mask_3)) != mask_3 || mask_3 == 0 {
1505 return encodePPC64RotateMask(int64(r_3), int64(mask_3), 32)
1508 // Test if a RLWINM feeding into a CLRLSLDI can be merged into RLWINM. Return
1509 // the encoded RLWINM constant, or 0 if they cannot be merged.
1510 func mergePPC64ClrlsldiRlwinm(sld int32, rlw int64) int64 {
1511 r_1, _, _, mask_1 := DecodePPC64RotateMask(rlw)
1512 // for CLRLSLDI, it's more convient to think of it as a mask left bits then rotate left.
1513 mask_2 := uint64(0xFFFFFFFFFFFFFFFF) >> uint(GetPPC64Shiftmb(int64(sld)))
1515 // combine the masks, and adjust for the final left shift.
1516 mask_3 := (mask_1 & mask_2) << uint(GetPPC64Shiftsh(int64(sld)))
1517 r_2 := GetPPC64Shiftsh(int64(sld))
1518 r_3 := (r_1 + r_2) & 31 // This can wrap.
1520 // Verify the result is still a valid bitmask of <= 32 bits.
1521 if !isPPC64WordRotateMask(int64(mask_3)) || uint64(uint32(mask_3)) != mask_3 {
1524 return encodePPC64RotateMask(r_3, int64(mask_3), 32)
1527 // Compute the encoded RLWINM constant from combining (SLDconst [sld] (SRWconst [srw] x)),
1528 // or return 0 if they cannot be combined.
1529 func mergePPC64SldiSrw(sld, srw int64) int64 {
1530 if sld > srw || srw >= 32 {
1533 mask_r := uint32(0xFFFFFFFF) >> uint(srw)
1534 mask_l := uint32(0xFFFFFFFF) >> uint(sld)
1535 mask := (mask_r & mask_l) << uint(sld)
1536 return encodePPC64RotateMask((32-srw+sld)&31, int64(mask), 32)
1539 // Convenience function to rotate a 32 bit constant value by another constant.
1540 func rotateLeft32(v, rotate int64) int64 {
1541 return int64(bits.RotateLeft32(uint32(v), int(rotate)))
1544 // encodes the lsb and width for arm(64) bitfield ops into the expected auxInt format.
1545 func armBFAuxInt(lsb, width int64) arm64BitField {
1546 if lsb < 0 || lsb > 63 {
1547 panic("ARM(64) bit field lsb constant out of range")
1549 if width < 1 || width > 64 {
1550 panic("ARM(64) bit field width constant out of range")
1552 return arm64BitField(width | lsb<<8)
1555 // returns the lsb part of the auxInt field of arm64 bitfield ops.
1556 func (bfc arm64BitField) getARM64BFlsb() int64 {
1557 return int64(uint64(bfc) >> 8)
1560 // returns the width part of the auxInt field of arm64 bitfield ops.
1561 func (bfc arm64BitField) getARM64BFwidth() int64 {
1562 return int64(bfc) & 0xff
1565 // checks if mask >> rshift applied at lsb is a valid arm64 bitfield op mask.
1566 func isARM64BFMask(lsb, mask, rshift int64) bool {
1567 shiftedMask := int64(uint64(mask) >> uint64(rshift))
1568 return shiftedMask != 0 && isPowerOfTwo64(shiftedMask+1) && nto(shiftedMask)+lsb < 64
1571 // returns the bitfield width of mask >> rshift for arm64 bitfield ops
1572 func arm64BFWidth(mask, rshift int64) int64 {
1573 shiftedMask := int64(uint64(mask) >> uint64(rshift))
1574 if shiftedMask == 0 {
1575 panic("ARM64 BF mask is zero")
1577 return nto(shiftedMask)
1580 // sizeof returns the size of t in bytes.
1581 // It will panic if t is not a *types.Type.
1582 func sizeof(t interface{}) int64 {
1583 return t.(*types.Type).Size()
1586 // registerizable reports whether t is a primitive type that fits in
1587 // a register. It assumes float64 values will always fit into registers
1588 // even if that isn't strictly true.
1589 func registerizable(b *Block, typ *types.Type) bool {
1590 if typ.IsPtrShaped() || typ.IsFloat() {
1593 if typ.IsInteger() {
1594 return typ.Size() <= b.Func.Config.RegSize
1599 // needRaceCleanup reports whether this call to racefuncenter/exit isn't needed.
1600 func needRaceCleanup(sym *AuxCall, v *Value) bool {
1605 if !isSameCall(sym, "runtime.racefuncenter") && !isSameCall(sym, "runtime.racefuncexit") {
1608 for _, b := range f.Blocks {
1609 for _, v := range b.Values {
1611 case OpStaticCall, OpStaticLECall:
1612 // Check for racefuncenter will encounter racefuncexit and vice versa.
1613 // Allow calls to panic*
1614 s := v.Aux.(*AuxCall).Fn.String()
1616 case "runtime.racefuncenter", "runtime.racefuncexit",
1617 "runtime.panicdivide", "runtime.panicwrap",
1618 "runtime.panicshift":
1621 // If we encountered any call, we need to keep racefunc*,
1622 // for accurate stacktraces.
1624 case OpPanicBounds, OpPanicExtend:
1625 // Note: these are panic generators that are ok (like the static calls above).
1626 case OpClosureCall, OpInterCall, OpClosureLECall, OpInterLECall:
1627 // We must keep the race functions if there are any other call types.
1632 if isSameCall(sym, "runtime.racefuncenter") {
1633 // TODO REGISTER ABI this needs to be cleaned up.
1634 // If we're removing racefuncenter, remove its argument as well.
1635 if v.Args[0].Op != OpStore {
1636 if v.Op == OpStaticLECall {
1637 // there is no store, yet.
1642 mem := v.Args[0].Args[2]
1643 v.Args[0].reset(OpCopy)
1644 v.Args[0].AddArg(mem)
1649 // symIsRO reports whether sym is a read-only global.
1650 func symIsRO(sym interface{}) bool {
1651 lsym := sym.(*obj.LSym)
1652 return lsym.Type == objabi.SRODATA && len(lsym.R) == 0
1655 // symIsROZero reports whether sym is a read-only global whose data contains all zeros.
1656 func symIsROZero(sym Sym) bool {
1657 lsym := sym.(*obj.LSym)
1658 if lsym.Type != objabi.SRODATA || len(lsym.R) != 0 {
1661 for _, b := range lsym.P {
1669 // read8 reads one byte from the read-only global sym at offset off.
1670 func read8(sym interface{}, off int64) uint8 {
1671 lsym := sym.(*obj.LSym)
1672 if off >= int64(len(lsym.P)) || off < 0 {
1673 // Invalid index into the global sym.
1674 // This can happen in dead code, so we don't want to panic.
1675 // Just return any value, it will eventually get ignored.
1682 // read16 reads two bytes from the read-only global sym at offset off.
1683 func read16(sym interface{}, off int64, byteorder binary.ByteOrder) uint16 {
1684 lsym := sym.(*obj.LSym)
1685 // lsym.P is written lazily.
1686 // Bytes requested after the end of lsym.P are 0.
1688 if 0 <= off && off < int64(len(lsym.P)) {
1691 buf := make([]byte, 2)
1693 return byteorder.Uint16(buf)
1696 // read32 reads four bytes from the read-only global sym at offset off.
1697 func read32(sym interface{}, off int64, byteorder binary.ByteOrder) uint32 {
1698 lsym := sym.(*obj.LSym)
1700 if 0 <= off && off < int64(len(lsym.P)) {
1703 buf := make([]byte, 4)
1705 return byteorder.Uint32(buf)
1708 // read64 reads eight bytes from the read-only global sym at offset off.
1709 func read64(sym interface{}, off int64, byteorder binary.ByteOrder) uint64 {
1710 lsym := sym.(*obj.LSym)
1712 if 0 <= off && off < int64(len(lsym.P)) {
1715 buf := make([]byte, 8)
1717 return byteorder.Uint64(buf)
1720 // sequentialAddresses reports true if it can prove that x + n == y
1721 func sequentialAddresses(x, y *Value, n int64) bool {
1722 if x.Op == Op386ADDL && y.Op == Op386LEAL1 && y.AuxInt == n && y.Aux == nil &&
1723 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1724 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1727 if x.Op == Op386LEAL1 && y.Op == Op386LEAL1 && y.AuxInt == x.AuxInt+n && x.Aux == y.Aux &&
1728 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1729 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1732 if x.Op == OpAMD64ADDQ && y.Op == OpAMD64LEAQ1 && y.AuxInt == n && y.Aux == nil &&
1733 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1734 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1737 if x.Op == OpAMD64LEAQ1 && y.Op == OpAMD64LEAQ1 && y.AuxInt == x.AuxInt+n && x.Aux == y.Aux &&
1738 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1739 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1745 // flagConstant represents the result of a compile-time comparison.
1746 // The sense of these flags does not necessarily represent the hardware's notion
1747 // of a flags register - these are just a compile-time construct.
1748 // We happen to match the semantics to those of arm/arm64.
1749 // Note that these semantics differ from x86: the carry flag has the opposite
1750 // sense on a subtraction!
1751 // On amd64, C=1 represents a borrow, e.g. SBB on amd64 does x - y - C.
1752 // On arm64, C=0 represents a borrow, e.g. SBC on arm64 does x - y - ^C.
1753 // (because it does x + ^y + C).
1754 // See https://en.wikipedia.org/wiki/Carry_flag#Vs._borrow_flag
1755 type flagConstant uint8
1757 // N reports whether the result of an operation is negative (high bit set).
1758 func (fc flagConstant) N() bool {
1762 // Z reports whether the result of an operation is 0.
1763 func (fc flagConstant) Z() bool {
1767 // C reports whether an unsigned add overflowed (carry), or an
1768 // unsigned subtract did not underflow (borrow).
1769 func (fc flagConstant) C() bool {
1773 // V reports whether a signed operation overflowed or underflowed.
1774 func (fc flagConstant) V() bool {
1778 func (fc flagConstant) eq() bool {
1781 func (fc flagConstant) ne() bool {
1784 func (fc flagConstant) lt() bool {
1785 return fc.N() != fc.V()
1787 func (fc flagConstant) le() bool {
1788 return fc.Z() || fc.lt()
1790 func (fc flagConstant) gt() bool {
1791 return !fc.Z() && fc.ge()
1793 func (fc flagConstant) ge() bool {
1794 return fc.N() == fc.V()
1796 func (fc flagConstant) ult() bool {
1799 func (fc flagConstant) ule() bool {
1800 return fc.Z() || fc.ult()
1802 func (fc flagConstant) ugt() bool {
1803 return !fc.Z() && fc.uge()
1805 func (fc flagConstant) uge() bool {
1809 func (fc flagConstant) ltNoov() bool {
1810 return fc.lt() && !fc.V()
1812 func (fc flagConstant) leNoov() bool {
1813 return fc.le() && !fc.V()
1815 func (fc flagConstant) gtNoov() bool {
1816 return fc.gt() && !fc.V()
1818 func (fc flagConstant) geNoov() bool {
1819 return fc.ge() && !fc.V()
1822 func (fc flagConstant) String() string {
1823 return fmt.Sprintf("N=%v,Z=%v,C=%v,V=%v", fc.N(), fc.Z(), fc.C(), fc.V())
1826 type flagConstantBuilder struct {
1833 func (fcs flagConstantBuilder) encode() flagConstant {
1850 // Note: addFlags(x,y) != subFlags(x,-y) in some situations:
1851 // - the results of the C flag are different
1852 // - the results of the V flag when y==minint are different
1854 // addFlags64 returns the flags that would be set from computing x+y.
1855 func addFlags64(x, y int64) flagConstant {
1856 var fcb flagConstantBuilder
1859 fcb.C = uint64(x+y) < uint64(x)
1860 fcb.V = x >= 0 && y >= 0 && x+y < 0 || x < 0 && y < 0 && x+y >= 0
1864 // subFlags64 returns the flags that would be set from computing x-y.
1865 func subFlags64(x, y int64) flagConstant {
1866 var fcb flagConstantBuilder
1869 fcb.C = uint64(y) <= uint64(x) // This code follows the arm carry flag model.
1870 fcb.V = x >= 0 && y < 0 && x-y < 0 || x < 0 && y >= 0 && x-y >= 0
1874 // addFlags32 returns the flags that would be set from computing x+y.
1875 func addFlags32(x, y int32) flagConstant {
1876 var fcb flagConstantBuilder
1879 fcb.C = uint32(x+y) < uint32(x)
1880 fcb.V = x >= 0 && y >= 0 && x+y < 0 || x < 0 && y < 0 && x+y >= 0
1884 // subFlags32 returns the flags that would be set from computing x-y.
1885 func subFlags32(x, y int32) flagConstant {
1886 var fcb flagConstantBuilder
1889 fcb.C = uint32(y) <= uint32(x) // This code follows the arm carry flag model.
1890 fcb.V = x >= 0 && y < 0 && x-y < 0 || x < 0 && y >= 0 && x-y >= 0
1894 // logicFlags64 returns flags set to the sign/zeroness of x.
1895 // C and V are set to false.
1896 func logicFlags64(x int64) flagConstant {
1897 var fcb flagConstantBuilder
1903 // logicFlags32 returns flags set to the sign/zeroness of x.
1904 // C and V are set to false.
1905 func logicFlags32(x int32) flagConstant {
1906 var fcb flagConstantBuilder