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 that 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 && 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 // de-virtualize an InterCall
749 // 'sym' is the symbol for the itab
750 func devirt(v *Value, aux Aux, sym Sym, offset int64) *AuxCall {
752 n, ok := sym.(*obj.LSym)
756 lsym := f.fe.DerefItab(n, offset)
757 if f.pass.debug > 0 {
759 f.Warnl(v.Pos, "de-virtualizing call")
761 f.Warnl(v.Pos, "couldn't de-virtualize call")
768 return StaticAuxCall(lsym, va.args, va.results, va.abiInfo)
771 // de-virtualize an InterLECall
772 // 'sym' is the symbol for the itab
773 func devirtLESym(v *Value, aux Aux, sym Sym, offset int64) *obj.LSym {
774 n, ok := sym.(*obj.LSym)
780 lsym := f.fe.DerefItab(n, offset)
781 if f.pass.debug > 0 {
783 f.Warnl(v.Pos, "de-virtualizing call")
785 f.Warnl(v.Pos, "couldn't de-virtualize call")
794 func devirtLECall(v *Value, sym *obj.LSym) *Value {
795 v.Op = OpStaticLECall
796 v.Aux.(*AuxCall).Fn = sym
801 // isSamePtr reports whether p1 and p2 point to the same address.
802 func isSamePtr(p1, p2 *Value) bool {
811 return p1.AuxInt == p2.AuxInt && isSamePtr(p1.Args[0], p2.Args[0])
812 case OpAddr, OpLocalAddr:
813 // OpAddr's 0th arg is either OpSP or OpSB, which means that it is uniquely identified by its Op.
814 // Checking for value equality only works after [z]cse has run.
815 return p1.Aux == p2.Aux && p1.Args[0].Op == p2.Args[0].Op
817 return p1.Args[1] == p2.Args[1] && isSamePtr(p1.Args[0], p2.Args[0])
822 func isStackPtr(v *Value) bool {
823 for v.Op == OpOffPtr || v.Op == OpAddPtr {
826 return v.Op == OpSP || v.Op == OpLocalAddr
829 // disjoint reports whether the memory region specified by [p1:p1+n1)
830 // does not overlap with [p2:p2+n2).
831 // A return value of false does not imply the regions overlap.
832 func disjoint(p1 *Value, n1 int64, p2 *Value, n2 int64) bool {
833 if n1 == 0 || n2 == 0 {
839 baseAndOffset := func(ptr *Value) (base *Value, offset int64) {
840 base, offset = ptr, 0
841 for base.Op == OpOffPtr {
842 offset += base.AuxInt
847 p1, off1 := baseAndOffset(p1)
848 p2, off2 := baseAndOffset(p2)
849 if isSamePtr(p1, p2) {
850 return !overlap(off1, n1, off2, n2)
852 // p1 and p2 are not the same, so if they are both OpAddrs then
853 // they point to different variables.
854 // If one pointer is on the stack and the other is an argument
855 // then they can't overlap.
857 case OpAddr, OpLocalAddr:
858 if p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpSP {
861 return p2.Op == OpArg && p1.Args[0].Op == OpSP
863 if p2.Op == OpSP || p2.Op == OpLocalAddr {
867 return p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpArg || p2.Op == OpSP
872 // moveSize returns the number of bytes an aligned MOV instruction moves
873 func moveSize(align int64, c *Config) int64 {
875 case align%8 == 0 && c.PtrSize == 8:
885 // mergePoint finds a block among a's blocks which dominates b and is itself
886 // dominated by all of a's blocks. Returns nil if it can't find one.
887 // Might return nil even if one does exist.
888 func mergePoint(b *Block, a ...*Value) *Block {
889 // Walk backward from b looking for one of the a's blocks.
895 for _, x := range a {
900 if len(b.Preds) > 1 {
901 // Don't know which way to go back. Abort.
907 return nil // too far away
909 // At this point, r is the first value in a that we find by walking backwards.
910 // if we return anything, r will be it.
913 // Keep going, counting the other a's that we find. They must all dominate r.
916 for _, x := range a {
922 // Found all of a in a backwards walk. We can return r.
925 if len(b.Preds) > 1 {
932 return nil // too far away
935 // clobber invalidates values. Returns true.
936 // clobber is used by rewrite rules to:
937 // A) make sure the values are really dead and never used again.
938 // B) decrement use counts of the values' args.
939 func clobber(vv ...*Value) bool {
940 for _, v := range vv {
942 // Note: leave v.Block intact. The Block field is used after clobber.
947 // clobberIfDead resets v when use count is 1. Returns true.
948 // clobberIfDead is used by rewrite rules to decrement
949 // use counts of v's args when v is dead and never used.
950 func clobberIfDead(v *Value) bool {
954 // Note: leave v.Block intact. The Block field is used after clobberIfDead.
958 // noteRule is an easy way to track if a rule is matched when writing
959 // new ones. Make the rule of interest also conditional on
960 // noteRule("note to self: rule of interest matched")
961 // and that message will print when the rule matches.
962 func noteRule(s string) bool {
967 // countRule increments Func.ruleMatches[key].
968 // If Func.ruleMatches is non-nil at the end
969 // of compilation, it will be printed to stdout.
970 // This is intended to make it easier to find which functions
971 // which contain lots of rules matches when developing new rules.
972 func countRule(v *Value, key string) bool {
974 if f.ruleMatches == nil {
975 f.ruleMatches = make(map[string]int)
981 // warnRule generates compiler debug output with string s when
982 // v is not in autogenerated code, cond is true and the rule has fired.
983 func warnRule(cond bool, v *Value, s string) bool {
984 if pos := v.Pos; pos.Line() > 1 && cond {
985 v.Block.Func.Warnl(pos, s)
990 // for a pseudo-op like (LessThan x), extract x
991 func flagArg(v *Value) *Value {
992 if len(v.Args) != 1 || !v.Args[0].Type.IsFlags() {
998 // arm64Negate finds the complement to an ARM64 condition code,
999 // for example !Equal -> NotEqual or !LessThan -> GreaterEqual
1001 // For floating point, it's more subtle because NaN is unordered. We do
1002 // !LessThanF -> NotLessThanF, the latter takes care of NaNs.
1003 func arm64Negate(op Op) Op {
1005 case OpARM64LessThan:
1006 return OpARM64GreaterEqual
1007 case OpARM64LessThanU:
1008 return OpARM64GreaterEqualU
1009 case OpARM64GreaterThan:
1010 return OpARM64LessEqual
1011 case OpARM64GreaterThanU:
1012 return OpARM64LessEqualU
1013 case OpARM64LessEqual:
1014 return OpARM64GreaterThan
1015 case OpARM64LessEqualU:
1016 return OpARM64GreaterThanU
1017 case OpARM64GreaterEqual:
1018 return OpARM64LessThan
1019 case OpARM64GreaterEqualU:
1020 return OpARM64LessThanU
1022 return OpARM64NotEqual
1023 case OpARM64NotEqual:
1025 case OpARM64LessThanF:
1026 return OpARM64NotLessThanF
1027 case OpARM64NotLessThanF:
1028 return OpARM64LessThanF
1029 case OpARM64LessEqualF:
1030 return OpARM64NotLessEqualF
1031 case OpARM64NotLessEqualF:
1032 return OpARM64LessEqualF
1033 case OpARM64GreaterThanF:
1034 return OpARM64NotGreaterThanF
1035 case OpARM64NotGreaterThanF:
1036 return OpARM64GreaterThanF
1037 case OpARM64GreaterEqualF:
1038 return OpARM64NotGreaterEqualF
1039 case OpARM64NotGreaterEqualF:
1040 return OpARM64GreaterEqualF
1042 panic("unreachable")
1046 // arm64Invert evaluates (InvertFlags op), which
1047 // is the same as altering the condition codes such
1048 // that the same result would be produced if the arguments
1049 // to the flag-generating instruction were reversed, e.g.
1050 // (InvertFlags (CMP x y)) -> (CMP y x)
1051 func arm64Invert(op Op) Op {
1053 case OpARM64LessThan:
1054 return OpARM64GreaterThan
1055 case OpARM64LessThanU:
1056 return OpARM64GreaterThanU
1057 case OpARM64GreaterThan:
1058 return OpARM64LessThan
1059 case OpARM64GreaterThanU:
1060 return OpARM64LessThanU
1061 case OpARM64LessEqual:
1062 return OpARM64GreaterEqual
1063 case OpARM64LessEqualU:
1064 return OpARM64GreaterEqualU
1065 case OpARM64GreaterEqual:
1066 return OpARM64LessEqual
1067 case OpARM64GreaterEqualU:
1068 return OpARM64LessEqualU
1069 case OpARM64Equal, OpARM64NotEqual:
1071 case OpARM64LessThanF:
1072 return OpARM64GreaterThanF
1073 case OpARM64GreaterThanF:
1074 return OpARM64LessThanF
1075 case OpARM64LessEqualF:
1076 return OpARM64GreaterEqualF
1077 case OpARM64GreaterEqualF:
1078 return OpARM64LessEqualF
1079 case OpARM64NotLessThanF:
1080 return OpARM64NotGreaterThanF
1081 case OpARM64NotGreaterThanF:
1082 return OpARM64NotLessThanF
1083 case OpARM64NotLessEqualF:
1084 return OpARM64NotGreaterEqualF
1085 case OpARM64NotGreaterEqualF:
1086 return OpARM64NotLessEqualF
1088 panic("unreachable")
1092 // evaluate an ARM64 op against a flags value
1093 // that is potentially constant; return 1 for true,
1094 // -1 for false, and 0 for not constant.
1095 func ccARM64Eval(op Op, flags *Value) int {
1097 if fop == OpARM64InvertFlags {
1098 return -ccARM64Eval(op, flags.Args[0])
1100 if fop != OpARM64FlagConstant {
1103 fc := flagConstant(flags.AuxInt)
1104 b2i := func(b bool) int {
1113 case OpARM64NotEqual:
1115 case OpARM64LessThan:
1117 case OpARM64LessThanU:
1118 return b2i(fc.ult())
1119 case OpARM64GreaterThan:
1121 case OpARM64GreaterThanU:
1122 return b2i(fc.ugt())
1123 case OpARM64LessEqual:
1125 case OpARM64LessEqualU:
1126 return b2i(fc.ule())
1127 case OpARM64GreaterEqual:
1129 case OpARM64GreaterEqualU:
1130 return b2i(fc.uge())
1135 // logRule logs the use of the rule s. This will only be enabled if
1136 // rewrite rules were generated with the -log option, see gen/rulegen.go.
1137 func logRule(s string) {
1138 if ruleFile == nil {
1139 // Open a log file to write log to. We open in append
1140 // mode because all.bash runs the compiler lots of times,
1141 // and we want the concatenation of all of those logs.
1142 // This means, of course, that users need to rm the old log
1143 // to get fresh data.
1144 // TODO: all.bash runs compilers in parallel. Need to synchronize logging somehow?
1145 w, err := os.OpenFile(filepath.Join(os.Getenv("GOROOT"), "src", "rulelog"),
1146 os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
1152 _, err := fmt.Fprintln(ruleFile, s)
1158 var ruleFile io.Writer
1160 func min(x, y int64) int64 {
1167 func isConstZero(v *Value) bool {
1171 case OpConst64, OpConst32, OpConst16, OpConst8, OpConstBool, OpConst32F, OpConst64F:
1172 return v.AuxInt == 0
1177 // reciprocalExact64 reports whether 1/c is exactly representable.
1178 func reciprocalExact64(c float64) bool {
1179 b := math.Float64bits(c)
1180 man := b & (1<<52 - 1)
1182 return false // not a power of 2, denormal, or NaN
1184 exp := b >> 52 & (1<<11 - 1)
1185 // exponent bias is 0x3ff. So taking the reciprocal of a number
1186 // changes the exponent to 0x7fe-exp.
1191 return false // ±inf
1193 return false // exponent is not representable
1199 // reciprocalExact32 reports whether 1/c is exactly representable.
1200 func reciprocalExact32(c float32) bool {
1201 b := math.Float32bits(c)
1202 man := b & (1<<23 - 1)
1204 return false // not a power of 2, denormal, or NaN
1206 exp := b >> 23 & (1<<8 - 1)
1207 // exponent bias is 0x7f. So taking the reciprocal of a number
1208 // changes the exponent to 0xfe-exp.
1213 return false // ±inf
1215 return false // exponent is not representable
1221 // check if an immediate can be directly encoded into an ARM's instruction
1222 func isARMImmRot(v uint32) bool {
1223 for i := 0; i < 16; i++ {
1233 // overlap reports whether the ranges given by the given offset and
1234 // size pairs overlap.
1235 func overlap(offset1, size1, offset2, size2 int64) bool {
1236 if offset1 >= offset2 && offset2+size2 > offset1 {
1239 if offset2 >= offset1 && offset1+size1 > offset2 {
1245 func areAdjacentOffsets(off1, off2, size int64) bool {
1246 return off1+size == off2 || off1 == off2+size
1249 // check if value zeroes out upper 32-bit of 64-bit register.
1250 // depth limits recursion depth. In AMD64.rules 3 is used as limit,
1251 // because it catches same amount of cases as 4.
1252 func zeroUpper32Bits(x *Value, depth int) bool {
1254 case OpAMD64MOVLconst, OpAMD64MOVLload, OpAMD64MOVLQZX, OpAMD64MOVLloadidx1,
1255 OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVBload, OpAMD64MOVBloadidx1,
1256 OpAMD64MOVLloadidx4, OpAMD64ADDLload, OpAMD64SUBLload, OpAMD64ANDLload,
1257 OpAMD64ORLload, OpAMD64XORLload, OpAMD64CVTTSD2SL,
1258 OpAMD64ADDL, OpAMD64ADDLconst, OpAMD64SUBL, OpAMD64SUBLconst,
1259 OpAMD64ANDL, OpAMD64ANDLconst, OpAMD64ORL, OpAMD64ORLconst,
1260 OpAMD64XORL, OpAMD64XORLconst, OpAMD64NEGL, OpAMD64NOTL,
1261 OpAMD64SHRL, OpAMD64SHRLconst, OpAMD64SARL, OpAMD64SARLconst,
1262 OpAMD64SHLL, OpAMD64SHLLconst:
1265 return x.Type.Width == 4
1266 case OpPhi, OpSelect0, OpSelect1:
1267 // Phis can use each-other as an arguments, instead of tracking visited values,
1268 // just limit recursion depth.
1272 for i := range x.Args {
1273 if !zeroUpper32Bits(x.Args[i], depth-1) {
1283 // zeroUpper48Bits is similar to zeroUpper32Bits, but for upper 48 bits
1284 func zeroUpper48Bits(x *Value, depth int) bool {
1286 case OpAMD64MOVWQZX, OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVWloadidx2:
1289 return x.Type.Width == 2
1290 case OpPhi, OpSelect0, OpSelect1:
1291 // Phis can use each-other as an arguments, instead of tracking visited values,
1292 // just limit recursion depth.
1296 for i := range x.Args {
1297 if !zeroUpper48Bits(x.Args[i], depth-1) {
1307 // zeroUpper56Bits is similar to zeroUpper32Bits, but for upper 56 bits
1308 func zeroUpper56Bits(x *Value, depth int) bool {
1310 case OpAMD64MOVBQZX, OpAMD64MOVBload, OpAMD64MOVBloadidx1:
1313 return x.Type.Width == 1
1314 case OpPhi, OpSelect0, OpSelect1:
1315 // Phis can use each-other as an arguments, instead of tracking visited values,
1316 // just limit recursion depth.
1320 for i := range x.Args {
1321 if !zeroUpper56Bits(x.Args[i], depth-1) {
1331 // isInlinableMemmove reports whether the given arch performs a Move of the given size
1332 // faster than memmove. It will only return true if replacing the memmove with a Move is
1333 // safe, either because Move is small or because the arguments are disjoint.
1334 // This is used as a check for replacing memmove with Move ops.
1335 func isInlinableMemmove(dst, src *Value, sz int64, c *Config) bool {
1336 // It is always safe to convert memmove into Move when its arguments are disjoint.
1337 // Move ops may or may not be faster for large sizes depending on how the platform
1338 // lowers them, so we only perform this optimization on platforms that we know to
1339 // have fast Move ops.
1342 return sz <= 16 || (sz < 1024 && disjoint(dst, sz, src, sz))
1343 case "386", "arm64":
1345 case "s390x", "ppc64", "ppc64le":
1346 return sz <= 8 || disjoint(dst, sz, src, sz)
1347 case "arm", "mips", "mips64", "mipsle", "mips64le":
1353 // logLargeCopy logs the occurrence of a large copy.
1354 // The best place to do this is in the rewrite rules where the size of the move is easy to find.
1355 // "Large" is arbitrarily chosen to be 128 bytes; this may change.
1356 func logLargeCopy(v *Value, s int64) bool {
1360 if logopt.Enabled() {
1361 logopt.LogOpt(v.Pos, "copy", "lower", v.Block.Func.Name, fmt.Sprintf("%d bytes", s))
1366 // hasSmallRotate reports whether the architecture has rotate instructions
1367 // for sizes < 32-bit. This is used to decide whether to promote some rotations.
1368 func hasSmallRotate(c *Config) bool {
1370 case "amd64", "386":
1377 func newPPC64ShiftAuxInt(sh, mb, me, sz int64) int32 {
1378 if sh < 0 || sh >= sz {
1379 panic("PPC64 shift arg sh out of range")
1381 if mb < 0 || mb >= sz {
1382 panic("PPC64 shift arg mb out of range")
1384 if me < 0 || me >= sz {
1385 panic("PPC64 shift arg me out of range")
1387 return int32(sh<<16 | mb<<8 | me)
1390 func GetPPC64Shiftsh(auxint int64) int64 {
1391 return int64(int8(auxint >> 16))
1394 func GetPPC64Shiftmb(auxint int64) int64 {
1395 return int64(int8(auxint >> 8))
1398 func GetPPC64Shiftme(auxint int64) int64 {
1399 return int64(int8(auxint))
1402 // Test if this value can encoded as a mask for a rlwinm like
1403 // operation. Masks can also extend from the msb and wrap to
1404 // the lsb too. That is, the valid masks are 32 bit strings
1405 // of the form: 0..01..10..0 or 1..10..01..1 or 1...1
1406 func isPPC64WordRotateMask(v64 int64) bool {
1407 // Isolate rightmost 1 (if none 0) and add.
1410 // Likewise, for the wrapping case.
1412 vpn := (vn & -vn) + vn
1413 return (v&vp == 0 || vn&vpn == 0) && v != 0
1416 // Compress mask and and shift into single value of the form
1417 // me | mb<<8 | rotate<<16 | nbits<<24 where me and mb can
1418 // be used to regenerate the input mask.
1419 func encodePPC64RotateMask(rotate, mask, nbits int64) int64 {
1420 var mb, me, mbn, men int
1422 // Determine boundaries and then decode them
1423 if mask == 0 || ^mask == 0 || rotate >= nbits {
1424 panic("Invalid PPC64 rotate mask")
1425 } else if nbits == 32 {
1426 mb = bits.LeadingZeros32(uint32(mask))
1427 me = 32 - bits.TrailingZeros32(uint32(mask))
1428 mbn = bits.LeadingZeros32(^uint32(mask))
1429 men = 32 - bits.TrailingZeros32(^uint32(mask))
1431 mb = bits.LeadingZeros64(uint64(mask))
1432 me = 64 - bits.TrailingZeros64(uint64(mask))
1433 mbn = bits.LeadingZeros64(^uint64(mask))
1434 men = 64 - bits.TrailingZeros64(^uint64(mask))
1436 // Check for a wrapping mask (e.g bits at 0 and 63)
1437 if mb == 0 && me == int(nbits) {
1438 // swap the inverted values
1442 return int64(me) | int64(mb<<8) | int64(rotate<<16) | int64(nbits<<24)
1445 // The inverse operation of encodePPC64RotateMask. The values returned as
1446 // mb and me satisfy the POWER ISA definition of MASK(x,y) where MASK(mb,me) = mask.
1447 func DecodePPC64RotateMask(sauxint int64) (rotate, mb, me int64, mask uint64) {
1448 auxint := uint64(sauxint)
1449 rotate = int64((auxint >> 16) & 0xFF)
1450 mb = int64((auxint >> 8) & 0xFF)
1451 me = int64((auxint >> 0) & 0xFF)
1452 nbits := int64((auxint >> 24) & 0xFF)
1453 mask = ((1 << uint(nbits-mb)) - 1) ^ ((1 << uint(nbits-me)) - 1)
1458 mask = uint64(uint32(mask))
1461 // Fixup ME to match ISA definition. The second argument to MASK(..,me)
1463 me = (me - 1) & (nbits - 1)
1467 // This verifies that the mask is a set of
1468 // consecutive bits including the least
1470 func isPPC64ValidShiftMask(v int64) bool {
1471 if (v != 0) && ((v+1)&v) == 0 {
1477 func getPPC64ShiftMaskLength(v int64) int64 {
1478 return int64(bits.Len64(uint64(v)))
1481 // Decompose a shift right into an equivalent rotate/mask,
1482 // and return mask & m.
1483 func mergePPC64RShiftMask(m, s, nbits int64) int64 {
1484 smask := uint64((1<<uint(nbits))-1) >> uint(s)
1485 return m & int64(smask)
1488 // Combine (ANDconst [m] (SRWconst [s])) into (RLWINM [y]) or return 0
1489 func mergePPC64AndSrwi(m, s int64) int64 {
1490 mask := mergePPC64RShiftMask(m, s, 32)
1491 if !isPPC64WordRotateMask(mask) {
1494 return encodePPC64RotateMask(32-s, mask, 32)
1497 // Test if a shift right feeding into a CLRLSLDI can be merged into RLWINM.
1498 // Return the encoded RLWINM constant, or 0 if they cannot be merged.
1499 func mergePPC64ClrlsldiSrw(sld, srw int64) int64 {
1500 mask_1 := uint64(0xFFFFFFFF >> uint(srw))
1501 // for CLRLSLDI, it's more convient to think of it as a mask left bits then rotate left.
1502 mask_2 := uint64(0xFFFFFFFFFFFFFFFF) >> uint(GetPPC64Shiftmb(int64(sld)))
1504 // Rewrite mask to apply after the final left shift.
1505 mask_3 := (mask_1 & mask_2) << uint(GetPPC64Shiftsh(sld))
1508 r_2 := GetPPC64Shiftsh(sld)
1509 r_3 := (r_1 + r_2) & 31 // This can wrap.
1511 if uint64(uint32(mask_3)) != mask_3 || mask_3 == 0 {
1514 return encodePPC64RotateMask(int64(r_3), int64(mask_3), 32)
1517 // Test if a RLWINM feeding into a CLRLSLDI can be merged into RLWINM. Return
1518 // the encoded RLWINM constant, or 0 if they cannot be merged.
1519 func mergePPC64ClrlsldiRlwinm(sld int32, rlw int64) int64 {
1520 r_1, _, _, mask_1 := DecodePPC64RotateMask(rlw)
1521 // for CLRLSLDI, it's more convient to think of it as a mask left bits then rotate left.
1522 mask_2 := uint64(0xFFFFFFFFFFFFFFFF) >> uint(GetPPC64Shiftmb(int64(sld)))
1524 // combine the masks, and adjust for the final left shift.
1525 mask_3 := (mask_1 & mask_2) << uint(GetPPC64Shiftsh(int64(sld)))
1526 r_2 := GetPPC64Shiftsh(int64(sld))
1527 r_3 := (r_1 + r_2) & 31 // This can wrap.
1529 // Verify the result is still a valid bitmask of <= 32 bits.
1530 if !isPPC64WordRotateMask(int64(mask_3)) || uint64(uint32(mask_3)) != mask_3 {
1533 return encodePPC64RotateMask(r_3, int64(mask_3), 32)
1536 // Compute the encoded RLWINM constant from combining (SLDconst [sld] (SRWconst [srw] x)),
1537 // or return 0 if they cannot be combined.
1538 func mergePPC64SldiSrw(sld, srw int64) int64 {
1539 if sld > srw || srw >= 32 {
1542 mask_r := uint32(0xFFFFFFFF) >> uint(srw)
1543 mask_l := uint32(0xFFFFFFFF) >> uint(sld)
1544 mask := (mask_r & mask_l) << uint(sld)
1545 return encodePPC64RotateMask((32-srw+sld)&31, int64(mask), 32)
1548 // Convenience function to rotate a 32 bit constant value by another constant.
1549 func rotateLeft32(v, rotate int64) int64 {
1550 return int64(bits.RotateLeft32(uint32(v), int(rotate)))
1553 // encodes the lsb and width for arm(64) bitfield ops into the expected auxInt format.
1554 func armBFAuxInt(lsb, width int64) arm64BitField {
1555 if lsb < 0 || lsb > 63 {
1556 panic("ARM(64) bit field lsb constant out of range")
1558 if width < 1 || width > 64 {
1559 panic("ARM(64) bit field width constant out of range")
1561 return arm64BitField(width | lsb<<8)
1564 // returns the lsb part of the auxInt field of arm64 bitfield ops.
1565 func (bfc arm64BitField) getARM64BFlsb() int64 {
1566 return int64(uint64(bfc) >> 8)
1569 // returns the width part of the auxInt field of arm64 bitfield ops.
1570 func (bfc arm64BitField) getARM64BFwidth() int64 {
1571 return int64(bfc) & 0xff
1574 // checks if mask >> rshift applied at lsb is a valid arm64 bitfield op mask.
1575 func isARM64BFMask(lsb, mask, rshift int64) bool {
1576 shiftedMask := int64(uint64(mask) >> uint64(rshift))
1577 return shiftedMask != 0 && isPowerOfTwo64(shiftedMask+1) && nto(shiftedMask)+lsb < 64
1580 // returns the bitfield width of mask >> rshift for arm64 bitfield ops
1581 func arm64BFWidth(mask, rshift int64) int64 {
1582 shiftedMask := int64(uint64(mask) >> uint64(rshift))
1583 if shiftedMask == 0 {
1584 panic("ARM64 BF mask is zero")
1586 return nto(shiftedMask)
1589 // sizeof returns the size of t in bytes.
1590 // It will panic if t is not a *types.Type.
1591 func sizeof(t interface{}) int64 {
1592 return t.(*types.Type).Size()
1595 // registerizable reports whether t is a primitive type that fits in
1596 // a register. It assumes float64 values will always fit into registers
1597 // even if that isn't strictly true.
1598 func registerizable(b *Block, typ *types.Type) bool {
1599 if typ.IsPtrShaped() || typ.IsFloat() {
1602 if typ.IsInteger() {
1603 return typ.Size() <= b.Func.Config.RegSize
1608 // needRaceCleanup reports whether this call to racefuncenter/exit isn't needed.
1609 func needRaceCleanup(sym *AuxCall, v *Value) bool {
1614 if !isSameCall(sym, "runtime.racefuncenter") && !isSameCall(sym, "runtime.racefuncenterfp") && !isSameCall(sym, "runtime.racefuncexit") {
1617 for _, b := range f.Blocks {
1618 for _, v := range b.Values {
1621 // Check for racefuncenter/racefuncenterfp will encounter racefuncexit and vice versa.
1622 // Allow calls to panic*
1623 s := v.Aux.(*AuxCall).Fn.String()
1625 case "runtime.racefuncenter", "runtime.racefuncenterfp", "runtime.racefuncexit",
1626 "runtime.panicdivide", "runtime.panicwrap",
1627 "runtime.panicshift":
1630 // If we encountered any call, we need to keep racefunc*,
1631 // for accurate stacktraces.
1633 case OpPanicBounds, OpPanicExtend:
1634 // Note: these are panic generators that are ok (like the static calls above).
1635 case OpClosureCall, OpInterCall:
1636 // We must keep the race functions if there are any other call types.
1641 if isSameCall(sym, "runtime.racefuncenter") {
1642 // If we're removing racefuncenter, remove its argument as well.
1643 if v.Args[0].Op != OpStore {
1646 mem := v.Args[0].Args[2]
1647 v.Args[0].reset(OpCopy)
1648 v.Args[0].AddArg(mem)
1653 // symIsRO reports whether sym is a read-only global.
1654 func symIsRO(sym interface{}) bool {
1655 lsym := sym.(*obj.LSym)
1656 return lsym.Type == objabi.SRODATA && len(lsym.R) == 0
1659 // symIsROZero reports whether sym is a read-only global whose data contains all zeros.
1660 func symIsROZero(sym Sym) bool {
1661 lsym := sym.(*obj.LSym)
1662 if lsym.Type != objabi.SRODATA || len(lsym.R) != 0 {
1665 for _, b := range lsym.P {
1673 // read8 reads one byte from the read-only global sym at offset off.
1674 func read8(sym interface{}, off int64) uint8 {
1675 lsym := sym.(*obj.LSym)
1676 if off >= int64(len(lsym.P)) || off < 0 {
1677 // Invalid index into the global sym.
1678 // This can happen in dead code, so we don't want to panic.
1679 // Just return any value, it will eventually get ignored.
1686 // read16 reads two bytes from the read-only global sym at offset off.
1687 func read16(sym interface{}, off int64, byteorder binary.ByteOrder) uint16 {
1688 lsym := sym.(*obj.LSym)
1689 // lsym.P is written lazily.
1690 // Bytes requested after the end of lsym.P are 0.
1692 if 0 <= off && off < int64(len(lsym.P)) {
1695 buf := make([]byte, 2)
1697 return byteorder.Uint16(buf)
1700 // read32 reads four bytes from the read-only global sym at offset off.
1701 func read32(sym interface{}, off int64, byteorder binary.ByteOrder) uint32 {
1702 lsym := sym.(*obj.LSym)
1704 if 0 <= off && off < int64(len(lsym.P)) {
1707 buf := make([]byte, 4)
1709 return byteorder.Uint32(buf)
1712 // read64 reads eight bytes from the read-only global sym at offset off.
1713 func read64(sym interface{}, off int64, byteorder binary.ByteOrder) uint64 {
1714 lsym := sym.(*obj.LSym)
1716 if 0 <= off && off < int64(len(lsym.P)) {
1719 buf := make([]byte, 8)
1721 return byteorder.Uint64(buf)
1724 // sequentialAddresses reports true if it can prove that x + n == y
1725 func sequentialAddresses(x, y *Value, n int64) bool {
1726 if x.Op == Op386ADDL && y.Op == Op386LEAL1 && y.AuxInt == n && y.Aux == nil &&
1727 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1728 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1731 if x.Op == Op386LEAL1 && y.Op == Op386LEAL1 && y.AuxInt == x.AuxInt+n && x.Aux == y.Aux &&
1732 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1733 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1736 if x.Op == OpAMD64ADDQ && y.Op == OpAMD64LEAQ1 && y.AuxInt == n && y.Aux == nil &&
1737 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1738 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1741 if x.Op == OpAMD64LEAQ1 && y.Op == OpAMD64LEAQ1 && y.AuxInt == x.AuxInt+n && x.Aux == y.Aux &&
1742 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1743 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1749 // flagConstant represents the result of a compile-time comparison.
1750 // The sense of these flags does not necessarily represent the hardware's notion
1751 // of a flags register - these are just a compile-time construct.
1752 // We happen to match the semantics to those of arm/arm64.
1753 // Note that these semantics differ from x86: the carry flag has the opposite
1754 // sense on a subtraction!
1755 // On amd64, C=1 represents a borrow, e.g. SBB on amd64 does x - y - C.
1756 // On arm64, C=0 represents a borrow, e.g. SBC on arm64 does x - y - ^C.
1757 // (because it does x + ^y + C).
1758 // See https://en.wikipedia.org/wiki/Carry_flag#Vs._borrow_flag
1759 type flagConstant uint8
1761 // N reports whether the result of an operation is negative (high bit set).
1762 func (fc flagConstant) N() bool {
1766 // Z reports whether the result of an operation is 0.
1767 func (fc flagConstant) Z() bool {
1771 // C reports whether an unsigned add overflowed (carry), or an
1772 // unsigned subtract did not underflow (borrow).
1773 func (fc flagConstant) C() bool {
1777 // V reports whether a signed operation overflowed or underflowed.
1778 func (fc flagConstant) V() bool {
1782 func (fc flagConstant) eq() bool {
1785 func (fc flagConstant) ne() bool {
1788 func (fc flagConstant) lt() bool {
1789 return fc.N() != fc.V()
1791 func (fc flagConstant) le() bool {
1792 return fc.Z() || fc.lt()
1794 func (fc flagConstant) gt() bool {
1795 return !fc.Z() && fc.ge()
1797 func (fc flagConstant) ge() bool {
1798 return fc.N() == fc.V()
1800 func (fc flagConstant) ult() bool {
1803 func (fc flagConstant) ule() bool {
1804 return fc.Z() || fc.ult()
1806 func (fc flagConstant) ugt() bool {
1807 return !fc.Z() && fc.uge()
1809 func (fc flagConstant) uge() bool {
1813 func (fc flagConstant) ltNoov() bool {
1814 return fc.lt() && !fc.V()
1816 func (fc flagConstant) leNoov() bool {
1817 return fc.le() && !fc.V()
1819 func (fc flagConstant) gtNoov() bool {
1820 return fc.gt() && !fc.V()
1822 func (fc flagConstant) geNoov() bool {
1823 return fc.ge() && !fc.V()
1826 func (fc flagConstant) String() string {
1827 return fmt.Sprintf("N=%v,Z=%v,C=%v,V=%v", fc.N(), fc.Z(), fc.C(), fc.V())
1830 type flagConstantBuilder struct {
1837 func (fcs flagConstantBuilder) encode() flagConstant {
1854 // Note: addFlags(x,y) != subFlags(x,-y) in some situations:
1855 // - the results of the C flag are different
1856 // - the results of the V flag when y==minint are different
1858 // addFlags64 returns the flags that would be set from computing x+y.
1859 func addFlags64(x, y int64) flagConstant {
1860 var fcb flagConstantBuilder
1863 fcb.C = uint64(x+y) < uint64(x)
1864 fcb.V = x >= 0 && y >= 0 && x+y < 0 || x < 0 && y < 0 && x+y >= 0
1868 // subFlags64 returns the flags that would be set from computing x-y.
1869 func subFlags64(x, y int64) flagConstant {
1870 var fcb flagConstantBuilder
1873 fcb.C = uint64(y) <= uint64(x) // This code follows the arm carry flag model.
1874 fcb.V = x >= 0 && y < 0 && x-y < 0 || x < 0 && y >= 0 && x-y >= 0
1878 // addFlags32 returns the flags that would be set from computing x+y.
1879 func addFlags32(x, y int32) flagConstant {
1880 var fcb flagConstantBuilder
1883 fcb.C = uint32(x+y) < uint32(x)
1884 fcb.V = x >= 0 && y >= 0 && x+y < 0 || x < 0 && y < 0 && x+y >= 0
1888 // subFlags32 returns the flags that would be set from computing x-y.
1889 func subFlags32(x, y int32) flagConstant {
1890 var fcb flagConstantBuilder
1893 fcb.C = uint32(y) <= uint32(x) // This code follows the arm carry flag model.
1894 fcb.V = x >= 0 && y < 0 && x-y < 0 || x < 0 && y >= 0 && x-y >= 0
1898 // logicFlags64 returns flags set to the sign/zeroness of x.
1899 // C and V are set to false.
1900 func logicFlags64(x int64) flagConstant {
1901 var fcb flagConstantBuilder
1907 // logicFlags32 returns flags set to the sign/zeroness of x.
1908 // C and V are set to false.
1909 func logicFlags32(x int32) flagConstant {
1910 var fcb flagConstantBuilder