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)
40 var states map[string]bool
44 for _, b := range f.Blocks {
49 b0.Succs = append([]Edge{}, b.Succs...) // make a new copy, not aliasing
51 for i, c := range b.ControlValues() {
54 b.ReplaceControl(i, c)
60 fmt.Printf("rewriting %s -> %s\n", b0.LongString(), b.LongString())
63 for j, v := range b.Values {
68 v0.Args = append([]*Value{}, v.Args...) // make a new copy, not aliasing
70 if v.Uses == 0 && v.removeable() {
71 if v.Op != OpInvalid && deadcode == removeDeadValues {
72 // Reset any values that are now unused, so that we decrement
73 // the use count of all of its arguments.
74 // Not quite a deadcode pass, because it does not handle cycles.
75 // But it should help Uses==1 rules to fire.
79 // No point rewriting values which aren't used.
83 vchange := phielimValue(v)
84 if vchange && debug > 1 {
85 fmt.Printf("rewriting %s -> %s\n", v0.LongString(), v.LongString())
88 // Eliminate copy inputs.
89 // If any copy input becomes unused, mark it
90 // as invalid and discard its argument. Repeat
91 // recursively on the discarded argument.
92 // This phase helps remove phantom "dead copy" uses
93 // of a value so that a x.Uses==1 rule condition
95 for i, a := range v.Args {
101 // If a, a copy, has a line boundary indicator, attempt to find a new value
102 // to hold it. The first candidate is the value that will replace a (aa),
103 // if it shares the same block and line and is eligible.
104 // The second option is v, which has a as an input. Because aa is earlier in
105 // the data flow, it is the better choice.
106 if a.Pos.IsStmt() == src.PosIsStmt {
107 if aa.Block == a.Block && aa.Pos.Line() == a.Pos.Line() && aa.Pos.IsStmt() != src.PosNotStmt {
108 aa.Pos = aa.Pos.WithIsStmt()
109 } else if v.Block == a.Block && v.Pos.Line() == a.Pos.Line() && v.Pos.IsStmt() != src.PosNotStmt {
110 v.Pos = v.Pos.WithIsStmt()
112 // Record the lost line and look for a new home after all rewrites are complete.
113 // TODO: it's possible (in FOR loops, in particular) for statement boundaries for the same
114 // line to appear in more than one block, but only one block is stored, so if both end
115 // up here, then one will be lost.
116 pendingLines.set(a.Pos, int32(a.Block.ID))
118 a.Pos = a.Pos.WithNotStmt()
127 if vchange && debug > 1 {
128 fmt.Printf("rewriting %s -> %s\n", v0.LongString(), v.LongString())
131 // apply rewrite function
134 // If value changed to a poor choice for a statement boundary, move the boundary
135 if v.Pos.IsStmt() == src.PosIsStmt {
136 if k := nextGoodStatementIndex(v, j, b); k != j {
137 v.Pos = v.Pos.WithNotStmt()
138 b.Values[k].Pos = b.Values[k].Pos.WithIsStmt()
143 change = change || vchange
144 if vchange && debug > 1 {
145 fmt.Printf("rewriting %s -> %s\n", v0.LongString(), v.LongString())
149 if !change && !deadChange {
153 if (iters > 1000 || debug >= 2) && change {
154 // We've done a suspiciously large number of rewrites (or we're in debug mode).
155 // As of Sep 2021, 90% of rewrites complete in 4 iterations or fewer
156 // and the maximum value encountered during make.bash is 12.
157 // Start checking for cycles. (This is too expensive to do routinely.)
158 // Note: we avoid this path for deadChange-only iterations, to fix #51639.
160 states = make(map[string]bool)
163 if _, ok := states[h]; ok {
164 // We've found a cycle.
165 // To diagnose it, set debug to 2 and start again,
166 // so that we'll print all rules applied until we complete another cycle.
167 // If debug is already >= 2, we've already done that, so it's time to crash.
170 states = make(map[string]bool)
172 f.Fatalf("rewrite cycle detected")
178 // remove clobbered values
179 for _, b := range f.Blocks {
181 for i, v := range b.Values {
183 if v.Op == OpInvalid {
184 if v.Pos.IsStmt() == src.PosIsStmt {
185 pendingLines.set(vl, int32(b.ID))
190 if v.Pos.IsStmt() != src.PosNotStmt && !notStmtBoundary(v.Op) && pendingLines.get(vl) == int32(b.ID) {
191 pendingLines.remove(vl)
192 v.Pos = v.Pos.WithIsStmt()
199 if pendingLines.get(b.Pos) == int32(b.ID) {
200 b.Pos = b.Pos.WithIsStmt()
201 pendingLines.remove(b.Pos)
207 // Common functions called from rewriting rules
209 func is64BitFloat(t *types.Type) bool {
210 return t.Size() == 8 && t.IsFloat()
213 func is32BitFloat(t *types.Type) bool {
214 return t.Size() == 4 && t.IsFloat()
217 func is64BitInt(t *types.Type) bool {
218 return t.Size() == 8 && t.IsInteger()
221 func is32BitInt(t *types.Type) bool {
222 return t.Size() == 4 && t.IsInteger()
225 func is16BitInt(t *types.Type) bool {
226 return t.Size() == 2 && t.IsInteger()
229 func is8BitInt(t *types.Type) bool {
230 return t.Size() == 1 && t.IsInteger()
233 func isPtr(t *types.Type) bool {
234 return t.IsPtrShaped()
237 func isSigned(t *types.Type) bool {
241 // mergeSym merges two symbolic offsets. There is no real merging of
242 // offsets, we just pick the non-nil one.
243 func mergeSym(x, y Sym) Sym {
250 panic(fmt.Sprintf("mergeSym with two non-nil syms %v %v", x, y))
253 func canMergeSym(x, y Sym) bool {
254 return x == nil || y == nil
257 // canMergeLoadClobber reports whether the load can be merged into target without
258 // invalidating the schedule.
259 // It also checks that the other non-load argument x is something we
260 // are ok with clobbering.
261 func canMergeLoadClobber(target, load, x *Value) bool {
262 // The register containing x is going to get clobbered.
263 // Don't merge if we still need the value of x.
264 // We don't have liveness information here, but we can
265 // approximate x dying with:
266 // 1) target is x's only use.
267 // 2) target is not in a deeper loop than x.
271 loopnest := x.Block.Func.loopnest()
272 loopnest.calculateDepths()
273 if loopnest.depth(target.Block.ID) > loopnest.depth(x.Block.ID) {
276 return canMergeLoad(target, load)
279 // canMergeLoad reports whether the load can be merged into target without
280 // invalidating the schedule.
281 func canMergeLoad(target, load *Value) bool {
282 if target.Block.ID != load.Block.ID {
283 // If the load is in a different block do not merge it.
287 // We can't merge the load into the target if the load
288 // has more than one use.
293 mem := load.MemoryArg()
295 // We need the load's memory arg to still be alive at target. That
296 // can't be the case if one of target's args depends on a memory
297 // state that is a successor of load's memory arg.
299 // For example, it would be invalid to merge load into target in
300 // the following situation because newmem has killed oldmem
301 // before target is reached:
302 // load = read ... oldmem
303 // newmem = write ... oldmem
304 // arg0 = read ... newmem
305 // target = add arg0 load
307 // If the argument comes from a different block then we can exclude
308 // it immediately because it must dominate load (which is in the
309 // same block as target).
311 for _, a := range target.Args {
312 if a != load && a.Block.ID == target.Block.ID {
313 args = append(args, a)
317 // memPreds contains memory states known to be predecessors of load's
318 // memory state. It is lazily initialized.
319 var memPreds map[*Value]bool
320 for i := 0; len(args) > 0; i++ {
323 // Give up if we have done a lot of iterations.
326 v := args[len(args)-1]
327 args = args[:len(args)-1]
328 if target.Block.ID != v.Block.ID {
329 // Since target and load are in the same block
330 // we can stop searching when we leave the block.
334 // A Phi implies we have reached the top of the block.
335 // The memory phi, if it exists, is always
336 // the first logical store in the block.
339 if v.Type.IsTuple() && v.Type.FieldType(1).IsMemory() {
340 // We could handle this situation however it is likely
344 if v.Op.SymEffect()&SymAddr != 0 {
345 // This case prevents an operation that calculates the
346 // address of a local variable from being forced to schedule
347 // before its corresponding VarDef.
353 // We don't want to combine the CMPQ with the load, because
354 // that would force the CMPQ to schedule before the VARDEF, which
355 // in turn requires the LEAQ to schedule before the VARDEF.
358 if v.Type.IsMemory() {
360 // Initialise a map containing memory states
361 // known to be predecessors of load's memory
363 memPreds = make(map[*Value]bool)
366 for i := 0; i < limit; i++ {
368 // The memory phi, if it exists, is always
369 // the first logical store in the block.
372 if m.Block.ID != target.Block.ID {
375 if !m.Type.IsMemory() {
379 if len(m.Args) == 0 {
386 // We can merge if v is a predecessor of mem.
388 // For example, we can merge load into target in the
389 // following scenario:
392 // load = read ... mem
393 // target = add x load
399 if len(v.Args) > 0 && v.Args[len(v.Args)-1] == mem {
400 // If v takes mem as an input then we know mem
401 // is valid at this point.
404 for _, a := range v.Args {
405 if target.Block.ID == a.Block.ID {
406 args = append(args, a)
414 // isSameCall reports whether sym is the same as the given named symbol
415 func isSameCall(sym interface{}, name string) bool {
416 fn := sym.(*AuxCall).Fn
417 return fn != nil && fn.String() == name
420 // canLoadUnaligned reports if the achitecture supports unaligned load operations
421 func canLoadUnaligned(c *Config) bool {
422 return c.ctxt.Arch.Alignment == 1
425 // nlz returns the number of leading zeros.
426 func nlz64(x int64) int { return bits.LeadingZeros64(uint64(x)) }
427 func nlz32(x int32) int { return bits.LeadingZeros32(uint32(x)) }
428 func nlz16(x int16) int { return bits.LeadingZeros16(uint16(x)) }
429 func nlz8(x int8) int { return bits.LeadingZeros8(uint8(x)) }
431 // ntzX returns the number of trailing zeros.
432 func ntz64(x int64) int { return bits.TrailingZeros64(uint64(x)) }
433 func ntz32(x int32) int { return bits.TrailingZeros32(uint32(x)) }
434 func ntz16(x int16) int { return bits.TrailingZeros16(uint16(x)) }
435 func ntz8(x int8) int { return bits.TrailingZeros8(uint8(x)) }
437 func oneBit(x int64) bool { return x&(x-1) == 0 && x != 0 }
438 func oneBit8(x int8) bool { return x&(x-1) == 0 && x != 0 }
439 func oneBit16(x int16) bool { return x&(x-1) == 0 && x != 0 }
440 func oneBit32(x int32) bool { return x&(x-1) == 0 && x != 0 }
441 func oneBit64(x int64) bool { return x&(x-1) == 0 && x != 0 }
443 // nto returns the number of trailing ones.
444 func nto(x int64) int64 {
445 return int64(ntz64(^x))
448 // logX returns logarithm of n base 2.
449 // n must be a positive power of 2 (isPowerOfTwoX returns true).
450 func log8(n int8) int64 {
451 return int64(bits.Len8(uint8(n))) - 1
453 func log16(n int16) int64 {
454 return int64(bits.Len16(uint16(n))) - 1
456 func log32(n int32) int64 {
457 return int64(bits.Len32(uint32(n))) - 1
459 func log64(n int64) int64 {
460 return int64(bits.Len64(uint64(n))) - 1
463 // log2uint32 returns logarithm in base 2 of uint32(n), with log2(0) = -1.
465 func log2uint32(n int64) int64 {
466 return int64(bits.Len32(uint32(n))) - 1
469 // isPowerOfTwo functions report whether n is a power of 2.
470 func isPowerOfTwo8(n int8) bool {
471 return n > 0 && n&(n-1) == 0
473 func isPowerOfTwo16(n int16) bool {
474 return n > 0 && n&(n-1) == 0
476 func isPowerOfTwo32(n int32) bool {
477 return n > 0 && n&(n-1) == 0
479 func isPowerOfTwo64(n int64) bool {
480 return n > 0 && n&(n-1) == 0
483 // isUint64PowerOfTwo reports whether uint64(n) is a power of 2.
484 func isUint64PowerOfTwo(in int64) bool {
486 return n > 0 && n&(n-1) == 0
489 // isUint32PowerOfTwo reports whether uint32(n) is a power of 2.
490 func isUint32PowerOfTwo(in int64) bool {
491 n := uint64(uint32(in))
492 return n > 0 && n&(n-1) == 0
495 // is32Bit reports whether n can be represented as a signed 32 bit integer.
496 func is32Bit(n int64) bool {
497 return n == int64(int32(n))
500 // is16Bit reports whether n can be represented as a signed 16 bit integer.
501 func is16Bit(n int64) bool {
502 return n == int64(int16(n))
505 // is8Bit reports whether n can be represented as a signed 8 bit integer.
506 func is8Bit(n int64) bool {
507 return n == int64(int8(n))
510 // isU8Bit reports whether n can be represented as an unsigned 8 bit integer.
511 func isU8Bit(n int64) bool {
512 return n == int64(uint8(n))
515 // isU12Bit reports whether n can be represented as an unsigned 12 bit integer.
516 func isU12Bit(n int64) bool {
517 return 0 <= n && n < (1<<12)
520 // isU16Bit reports whether n can be represented as an unsigned 16 bit integer.
521 func isU16Bit(n int64) bool {
522 return n == int64(uint16(n))
525 // isU32Bit reports whether n can be represented as an unsigned 32 bit integer.
526 func isU32Bit(n int64) bool {
527 return n == int64(uint32(n))
530 // is20Bit reports whether n can be represented as a signed 20 bit integer.
531 func is20Bit(n int64) bool {
532 return -(1<<19) <= n && n < (1<<19)
535 // b2i translates a boolean value to 0 or 1 for assigning to auxInt.
536 func b2i(b bool) int64 {
543 // b2i32 translates a boolean value to 0 or 1.
544 func b2i32(b bool) int32 {
551 // shiftIsBounded reports whether (left/right) shift Value v is known to be bounded.
552 // A shift is bounded if it is shifting by less than the width of the shifted value.
553 func shiftIsBounded(v *Value) bool {
557 // canonLessThan returns whether x is "ordered" less than y, for purposes of normalizing
558 // generated code as much as possible.
559 func canonLessThan(x, y *Value) bool {
563 if !x.Pos.SameFileAndLine(y.Pos) {
564 return x.Pos.Before(y.Pos)
569 // truncate64Fto32F converts a float64 value to a float32 preserving the bit pattern
570 // of the mantissa. It will panic if the truncation results in lost information.
571 func truncate64Fto32F(f float64) float32 {
572 if !isExactFloat32(f) {
573 panic("truncate64Fto32F: truncation is not exact")
578 // NaN bit patterns aren't necessarily preserved across conversion
579 // instructions so we need to do the conversion manually.
580 b := math.Float64bits(f)
581 m := b & ((1 << 52) - 1) // mantissa (a.k.a. significand)
582 // | sign | exponent | mantissa |
583 r := uint32(((b >> 32) & (1 << 31)) | 0x7f800000 | (m >> (52 - 23)))
584 return math.Float32frombits(r)
587 // extend32Fto64F converts a float32 value to a float64 value preserving the bit
588 // pattern of the mantissa.
589 func extend32Fto64F(f float32) float64 {
590 if !math.IsNaN(float64(f)) {
593 // NaN bit patterns aren't necessarily preserved across conversion
594 // instructions so we need to do the conversion manually.
595 b := uint64(math.Float32bits(f))
596 // | sign | exponent | mantissa |
597 r := ((b << 32) & (1 << 63)) | (0x7ff << 52) | ((b & 0x7fffff) << (52 - 23))
598 return math.Float64frombits(r)
601 // DivisionNeedsFixUp reports whether the division needs fix-up code.
602 func DivisionNeedsFixUp(v *Value) bool {
606 // auxFrom64F encodes a float64 value so it can be stored in an AuxInt.
607 func auxFrom64F(f float64) int64 {
609 panic("can't encode a NaN in AuxInt field")
611 return int64(math.Float64bits(f))
614 // auxFrom32F encodes a float32 value so it can be stored in an AuxInt.
615 func auxFrom32F(f float32) int64 {
617 panic("can't encode a NaN in AuxInt field")
619 return int64(math.Float64bits(extend32Fto64F(f)))
622 // auxTo32F decodes a float32 from the AuxInt value provided.
623 func auxTo32F(i int64) float32 {
624 return truncate64Fto32F(math.Float64frombits(uint64(i)))
627 // auxTo64F decodes a float64 from the AuxInt value provided.
628 func auxTo64F(i int64) float64 {
629 return math.Float64frombits(uint64(i))
632 func auxIntToBool(i int64) bool {
638 func auxIntToInt8(i int64) int8 {
641 func auxIntToInt16(i int64) int16 {
644 func auxIntToInt32(i int64) int32 {
647 func auxIntToInt64(i int64) int64 {
650 func auxIntToUint8(i int64) uint8 {
653 func auxIntToFloat32(i int64) float32 {
654 return float32(math.Float64frombits(uint64(i)))
656 func auxIntToFloat64(i int64) float64 {
657 return math.Float64frombits(uint64(i))
659 func auxIntToValAndOff(i int64) ValAndOff {
662 func auxIntToArm64BitField(i int64) arm64BitField {
663 return arm64BitField(i)
665 func auxIntToInt128(x int64) int128 {
667 panic("nonzero int128 not allowed")
671 func auxIntToFlagConstant(x int64) flagConstant {
672 return flagConstant(x)
675 func auxIntToOp(cc int64) Op {
679 func boolToAuxInt(b bool) int64 {
685 func int8ToAuxInt(i int8) int64 {
688 func int16ToAuxInt(i int16) int64 {
691 func int32ToAuxInt(i int32) int64 {
694 func int64ToAuxInt(i int64) int64 {
697 func uint8ToAuxInt(i uint8) int64 {
698 return int64(int8(i))
700 func float32ToAuxInt(f float32) int64 {
701 return int64(math.Float64bits(float64(f)))
703 func float64ToAuxInt(f float64) int64 {
704 return int64(math.Float64bits(f))
706 func valAndOffToAuxInt(v ValAndOff) int64 {
709 func arm64BitFieldToAuxInt(v arm64BitField) int64 {
712 func int128ToAuxInt(x int128) int64 {
714 panic("nonzero int128 not allowed")
718 func flagConstantToAuxInt(x flagConstant) int64 {
722 func opToAuxInt(o Op) int64 {
726 // Aux is an interface to hold miscellaneous data in Blocks and Values.
731 // stringAux wraps string values for use in Aux.
732 type stringAux string
734 func (stringAux) CanBeAnSSAAux() {}
736 func auxToString(i Aux) string {
737 return string(i.(stringAux))
739 func auxToSym(i Aux) Sym {
740 // TODO: kind of a hack - allows nil interface through
744 func auxToType(i Aux) *types.Type {
745 return i.(*types.Type)
747 func auxToCall(i Aux) *AuxCall {
750 func auxToS390xCCMask(i Aux) s390x.CCMask {
751 return i.(s390x.CCMask)
753 func auxToS390xRotateParams(i Aux) s390x.RotateParams {
754 return i.(s390x.RotateParams)
757 func StringToAux(s string) Aux {
760 func symToAux(s Sym) Aux {
763 func callToAux(s *AuxCall) Aux {
766 func typeToAux(t *types.Type) Aux {
769 func s390xCCMaskToAux(c s390x.CCMask) Aux {
772 func s390xRotateParamsToAux(r s390x.RotateParams) Aux {
776 // uaddOvf reports whether unsigned a+b would overflow.
777 func uaddOvf(a, b int64) bool {
778 return uint64(a)+uint64(b) < uint64(a)
781 // loadLSymOffset simulates reading a word at an offset into a
782 // read-only symbol's runtime memory. If it would read a pointer to
783 // another symbol, that symbol is returned. Otherwise, it returns nil.
784 func loadLSymOffset(lsym *obj.LSym, offset int64) *obj.LSym {
785 if lsym.Type != objabi.SRODATA {
789 for _, r := range lsym.R {
790 if int64(r.Off) == offset && r.Type&^objabi.R_WEAK == objabi.R_ADDR && r.Add == 0 {
798 // de-virtualize an InterLECall
799 // 'sym' is the symbol for the itab
800 func devirtLESym(v *Value, aux Aux, sym Sym, offset int64) *obj.LSym {
801 n, ok := sym.(*obj.LSym)
806 lsym := loadLSymOffset(n, offset)
807 if f := v.Block.Func; f.pass.debug > 0 {
809 f.Warnl(v.Pos, "de-virtualizing call")
811 f.Warnl(v.Pos, "couldn't de-virtualize call")
817 func devirtLECall(v *Value, sym *obj.LSym) *Value {
818 v.Op = OpStaticLECall
819 auxcall := v.Aux.(*AuxCall)
823 copy(v.Args[0:], v.Args[1:])
824 v.Args[len(v.Args)-1] = nil // aid GC
825 v.Args = v.Args[:len(v.Args)-1]
829 // isSamePtr reports whether p1 and p2 point to the same address.
830 func isSamePtr(p1, p2 *Value) bool {
839 return p1.AuxInt == p2.AuxInt && isSamePtr(p1.Args[0], p2.Args[0])
840 case OpAddr, OpLocalAddr:
841 // OpAddr's 0th arg is either OpSP or OpSB, which means that it is uniquely identified by its Op.
842 // Checking for value equality only works after [z]cse has run.
843 return p1.Aux == p2.Aux && p1.Args[0].Op == p2.Args[0].Op
845 return p1.Args[1] == p2.Args[1] && isSamePtr(p1.Args[0], p2.Args[0])
850 func isStackPtr(v *Value) bool {
851 for v.Op == OpOffPtr || v.Op == OpAddPtr {
854 return v.Op == OpSP || v.Op == OpLocalAddr
857 // disjoint reports whether the memory region specified by [p1:p1+n1)
858 // does not overlap with [p2:p2+n2).
859 // A return value of false does not imply the regions overlap.
860 func disjoint(p1 *Value, n1 int64, p2 *Value, n2 int64) bool {
861 if n1 == 0 || n2 == 0 {
867 baseAndOffset := func(ptr *Value) (base *Value, offset int64) {
868 base, offset = ptr, 0
869 for base.Op == OpOffPtr {
870 offset += base.AuxInt
875 p1, off1 := baseAndOffset(p1)
876 p2, off2 := baseAndOffset(p2)
877 if isSamePtr(p1, p2) {
878 return !overlap(off1, n1, off2, n2)
880 // p1 and p2 are not the same, so if they are both OpAddrs then
881 // they point to different variables.
882 // If one pointer is on the stack and the other is an argument
883 // then they can't overlap.
885 case OpAddr, OpLocalAddr:
886 if p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpSP {
889 return (p2.Op == OpArg || p2.Op == OpArgIntReg) && p1.Args[0].Op == OpSP
890 case OpArg, OpArgIntReg:
891 if p2.Op == OpSP || p2.Op == OpLocalAddr {
895 return p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpArg || p2.Op == OpArgIntReg || p2.Op == OpSP
900 // moveSize returns the number of bytes an aligned MOV instruction moves
901 func moveSize(align int64, c *Config) int64 {
903 case align%8 == 0 && c.PtrSize == 8:
913 // mergePoint finds a block among a's blocks which dominates b and is itself
914 // dominated by all of a's blocks. Returns nil if it can't find one.
915 // Might return nil even if one does exist.
916 func mergePoint(b *Block, a ...*Value) *Block {
917 // Walk backward from b looking for one of the a's blocks.
923 for _, x := range a {
928 if len(b.Preds) > 1 {
929 // Don't know which way to go back. Abort.
935 return nil // too far away
937 // At this point, r is the first value in a that we find by walking backwards.
938 // if we return anything, r will be it.
941 // Keep going, counting the other a's that we find. They must all dominate r.
944 for _, x := range a {
950 // Found all of a in a backwards walk. We can return r.
953 if len(b.Preds) > 1 {
960 return nil // too far away
963 // clobber invalidates values. Returns true.
964 // clobber is used by rewrite rules to:
965 // A) make sure the values are really dead and never used again.
966 // B) decrement use counts of the values' args.
967 func clobber(vv ...*Value) bool {
968 for _, v := range vv {
970 // Note: leave v.Block intact. The Block field is used after clobber.
975 // clobberIfDead resets v when use count is 1. Returns true.
976 // clobberIfDead is used by rewrite rules to decrement
977 // use counts of v's args when v is dead and never used.
978 func clobberIfDead(v *Value) bool {
982 // Note: leave v.Block intact. The Block field is used after clobberIfDead.
986 // noteRule is an easy way to track if a rule is matched when writing
987 // new ones. Make the rule of interest also conditional on
988 // noteRule("note to self: rule of interest matched")
989 // and that message will print when the rule matches.
990 func noteRule(s string) bool {
995 // countRule increments Func.ruleMatches[key].
996 // If Func.ruleMatches is non-nil at the end
997 // of compilation, it will be printed to stdout.
998 // This is intended to make it easier to find which functions
999 // which contain lots of rules matches when developing new rules.
1000 func countRule(v *Value, key string) bool {
1002 if f.ruleMatches == nil {
1003 f.ruleMatches = make(map[string]int)
1005 f.ruleMatches[key]++
1009 // warnRule generates compiler debug output with string s when
1010 // v is not in autogenerated code, cond is true and the rule has fired.
1011 func warnRule(cond bool, v *Value, s string) bool {
1012 if pos := v.Pos; pos.Line() > 1 && cond {
1013 v.Block.Func.Warnl(pos, s)
1018 // for a pseudo-op like (LessThan x), extract x
1019 func flagArg(v *Value) *Value {
1020 if len(v.Args) != 1 || !v.Args[0].Type.IsFlags() {
1026 // arm64Negate finds the complement to an ARM64 condition code,
1027 // for example !Equal -> NotEqual or !LessThan -> GreaterEqual
1029 // For floating point, it's more subtle because NaN is unordered. We do
1030 // !LessThanF -> NotLessThanF, the latter takes care of NaNs.
1031 func arm64Negate(op Op) Op {
1033 case OpARM64LessThan:
1034 return OpARM64GreaterEqual
1035 case OpARM64LessThanU:
1036 return OpARM64GreaterEqualU
1037 case OpARM64GreaterThan:
1038 return OpARM64LessEqual
1039 case OpARM64GreaterThanU:
1040 return OpARM64LessEqualU
1041 case OpARM64LessEqual:
1042 return OpARM64GreaterThan
1043 case OpARM64LessEqualU:
1044 return OpARM64GreaterThanU
1045 case OpARM64GreaterEqual:
1046 return OpARM64LessThan
1047 case OpARM64GreaterEqualU:
1048 return OpARM64LessThanU
1050 return OpARM64NotEqual
1051 case OpARM64NotEqual:
1053 case OpARM64LessThanF:
1054 return OpARM64NotLessThanF
1055 case OpARM64NotLessThanF:
1056 return OpARM64LessThanF
1057 case OpARM64LessEqualF:
1058 return OpARM64NotLessEqualF
1059 case OpARM64NotLessEqualF:
1060 return OpARM64LessEqualF
1061 case OpARM64GreaterThanF:
1062 return OpARM64NotGreaterThanF
1063 case OpARM64NotGreaterThanF:
1064 return OpARM64GreaterThanF
1065 case OpARM64GreaterEqualF:
1066 return OpARM64NotGreaterEqualF
1067 case OpARM64NotGreaterEqualF:
1068 return OpARM64GreaterEqualF
1070 panic("unreachable")
1074 // arm64Invert evaluates (InvertFlags op), which
1075 // is the same as altering the condition codes such
1076 // that the same result would be produced if the arguments
1077 // to the flag-generating instruction were reversed, e.g.
1078 // (InvertFlags (CMP x y)) -> (CMP y x)
1079 func arm64Invert(op Op) Op {
1081 case OpARM64LessThan:
1082 return OpARM64GreaterThan
1083 case OpARM64LessThanU:
1084 return OpARM64GreaterThanU
1085 case OpARM64GreaterThan:
1086 return OpARM64LessThan
1087 case OpARM64GreaterThanU:
1088 return OpARM64LessThanU
1089 case OpARM64LessEqual:
1090 return OpARM64GreaterEqual
1091 case OpARM64LessEqualU:
1092 return OpARM64GreaterEqualU
1093 case OpARM64GreaterEqual:
1094 return OpARM64LessEqual
1095 case OpARM64GreaterEqualU:
1096 return OpARM64LessEqualU
1097 case OpARM64Equal, OpARM64NotEqual:
1099 case OpARM64LessThanF:
1100 return OpARM64GreaterThanF
1101 case OpARM64GreaterThanF:
1102 return OpARM64LessThanF
1103 case OpARM64LessEqualF:
1104 return OpARM64GreaterEqualF
1105 case OpARM64GreaterEqualF:
1106 return OpARM64LessEqualF
1107 case OpARM64NotLessThanF:
1108 return OpARM64NotGreaterThanF
1109 case OpARM64NotGreaterThanF:
1110 return OpARM64NotLessThanF
1111 case OpARM64NotLessEqualF:
1112 return OpARM64NotGreaterEqualF
1113 case OpARM64NotGreaterEqualF:
1114 return OpARM64NotLessEqualF
1116 panic("unreachable")
1120 // evaluate an ARM64 op against a flags value
1121 // that is potentially constant; return 1 for true,
1122 // -1 for false, and 0 for not constant.
1123 func ccARM64Eval(op Op, flags *Value) int {
1125 if fop == OpARM64InvertFlags {
1126 return -ccARM64Eval(op, flags.Args[0])
1128 if fop != OpARM64FlagConstant {
1131 fc := flagConstant(flags.AuxInt)
1132 b2i := func(b bool) int {
1141 case OpARM64NotEqual:
1143 case OpARM64LessThan:
1145 case OpARM64LessThanU:
1146 return b2i(fc.ult())
1147 case OpARM64GreaterThan:
1149 case OpARM64GreaterThanU:
1150 return b2i(fc.ugt())
1151 case OpARM64LessEqual:
1153 case OpARM64LessEqualU:
1154 return b2i(fc.ule())
1155 case OpARM64GreaterEqual:
1157 case OpARM64GreaterEqualU:
1158 return b2i(fc.uge())
1163 // logRule logs the use of the rule s. This will only be enabled if
1164 // rewrite rules were generated with the -log option, see gen/rulegen.go.
1165 func logRule(s string) {
1166 if ruleFile == nil {
1167 // Open a log file to write log to. We open in append
1168 // mode because all.bash runs the compiler lots of times,
1169 // and we want the concatenation of all of those logs.
1170 // This means, of course, that users need to rm the old log
1171 // to get fresh data.
1172 // TODO: all.bash runs compilers in parallel. Need to synchronize logging somehow?
1173 w, err := os.OpenFile(filepath.Join(os.Getenv("GOROOT"), "src", "rulelog"),
1174 os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
1180 _, err := fmt.Fprintln(ruleFile, s)
1186 var ruleFile io.Writer
1188 func min(x, y int64) int64 {
1195 func isConstZero(v *Value) bool {
1199 case OpConst64, OpConst32, OpConst16, OpConst8, OpConstBool, OpConst32F, OpConst64F:
1200 return v.AuxInt == 0
1205 // reciprocalExact64 reports whether 1/c is exactly representable.
1206 func reciprocalExact64(c float64) bool {
1207 b := math.Float64bits(c)
1208 man := b & (1<<52 - 1)
1210 return false // not a power of 2, denormal, or NaN
1212 exp := b >> 52 & (1<<11 - 1)
1213 // exponent bias is 0x3ff. So taking the reciprocal of a number
1214 // changes the exponent to 0x7fe-exp.
1219 return false // ±inf
1221 return false // exponent is not representable
1227 // reciprocalExact32 reports whether 1/c is exactly representable.
1228 func reciprocalExact32(c float32) bool {
1229 b := math.Float32bits(c)
1230 man := b & (1<<23 - 1)
1232 return false // not a power of 2, denormal, or NaN
1234 exp := b >> 23 & (1<<8 - 1)
1235 // exponent bias is 0x7f. So taking the reciprocal of a number
1236 // changes the exponent to 0xfe-exp.
1241 return false // ±inf
1243 return false // exponent is not representable
1249 // check if an immediate can be directly encoded into an ARM's instruction
1250 func isARMImmRot(v uint32) bool {
1251 for i := 0; i < 16; i++ {
1261 // overlap reports whether the ranges given by the given offset and
1262 // size pairs overlap.
1263 func overlap(offset1, size1, offset2, size2 int64) bool {
1264 if offset1 >= offset2 && offset2+size2 > offset1 {
1267 if offset2 >= offset1 && offset1+size1 > offset2 {
1273 func areAdjacentOffsets(off1, off2, size int64) bool {
1274 return off1+size == off2 || off1 == off2+size
1277 // check if value zeroes out upper 32-bit of 64-bit register.
1278 // depth limits recursion depth. In AMD64.rules 3 is used as limit,
1279 // because it catches same amount of cases as 4.
1280 func zeroUpper32Bits(x *Value, depth int) bool {
1282 case OpAMD64MOVLconst, OpAMD64MOVLload, OpAMD64MOVLQZX, OpAMD64MOVLloadidx1,
1283 OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVBload, OpAMD64MOVBloadidx1,
1284 OpAMD64MOVLloadidx4, OpAMD64ADDLload, OpAMD64SUBLload, OpAMD64ANDLload,
1285 OpAMD64ORLload, OpAMD64XORLload, OpAMD64CVTTSD2SL,
1286 OpAMD64ADDL, OpAMD64ADDLconst, OpAMD64SUBL, OpAMD64SUBLconst,
1287 OpAMD64ANDL, OpAMD64ANDLconst, OpAMD64ORL, OpAMD64ORLconst,
1288 OpAMD64XORL, OpAMD64XORLconst, OpAMD64NEGL, OpAMD64NOTL,
1289 OpAMD64SHRL, OpAMD64SHRLconst, OpAMD64SARL, OpAMD64SARLconst,
1290 OpAMD64SHLL, OpAMD64SHLLconst:
1293 return x.Type.Size() == 4
1294 case OpPhi, OpSelect0, OpSelect1:
1295 // Phis can use each-other as an arguments, instead of tracking visited values,
1296 // just limit recursion depth.
1300 for i := range x.Args {
1301 if !zeroUpper32Bits(x.Args[i], depth-1) {
1311 // zeroUpper48Bits is similar to zeroUpper32Bits, but for upper 48 bits
1312 func zeroUpper48Bits(x *Value, depth int) bool {
1314 case OpAMD64MOVWQZX, OpAMD64MOVWload, OpAMD64MOVWloadidx1, OpAMD64MOVWloadidx2:
1317 return x.Type.Size() == 2
1318 case OpPhi, OpSelect0, OpSelect1:
1319 // Phis can use each-other as an arguments, instead of tracking visited values,
1320 // just limit recursion depth.
1324 for i := range x.Args {
1325 if !zeroUpper48Bits(x.Args[i], depth-1) {
1335 // zeroUpper56Bits is similar to zeroUpper32Bits, but for upper 56 bits
1336 func zeroUpper56Bits(x *Value, depth int) bool {
1338 case OpAMD64MOVBQZX, OpAMD64MOVBload, OpAMD64MOVBloadidx1:
1341 return x.Type.Size() == 1
1342 case OpPhi, OpSelect0, OpSelect1:
1343 // Phis can use each-other as an arguments, instead of tracking visited values,
1344 // just limit recursion depth.
1348 for i := range x.Args {
1349 if !zeroUpper56Bits(x.Args[i], depth-1) {
1359 // isInlinableMemmove reports whether the given arch performs a Move of the given size
1360 // faster than memmove. It will only return true if replacing the memmove with a Move is
1361 // safe, either because Move is small or because the arguments are disjoint.
1362 // This is used as a check for replacing memmove with Move ops.
1363 func isInlinableMemmove(dst, src *Value, sz int64, c *Config) bool {
1364 // It is always safe to convert memmove into Move when its arguments are disjoint.
1365 // Move ops may or may not be faster for large sizes depending on how the platform
1366 // lowers them, so we only perform this optimization on platforms that we know to
1367 // have fast Move ops.
1370 return sz <= 16 || (sz < 1024 && disjoint(dst, sz, src, sz))
1371 case "386", "arm64":
1373 case "s390x", "ppc64", "ppc64le":
1374 return sz <= 8 || disjoint(dst, sz, src, sz)
1375 case "arm", "mips", "mips64", "mipsle", "mips64le":
1381 // logLargeCopy logs the occurrence of a large copy.
1382 // The best place to do this is in the rewrite rules where the size of the move is easy to find.
1383 // "Large" is arbitrarily chosen to be 128 bytes; this may change.
1384 func logLargeCopy(v *Value, s int64) bool {
1388 if logopt.Enabled() {
1389 logopt.LogOpt(v.Pos, "copy", "lower", v.Block.Func.Name, fmt.Sprintf("%d bytes", s))
1394 // hasSmallRotate reports whether the architecture has rotate instructions
1395 // for sizes < 32-bit. This is used to decide whether to promote some rotations.
1396 func hasSmallRotate(c *Config) bool {
1398 case "amd64", "386":
1405 func newPPC64ShiftAuxInt(sh, mb, me, sz int64) int32 {
1406 if sh < 0 || sh >= sz {
1407 panic("PPC64 shift arg sh out of range")
1409 if mb < 0 || mb >= sz {
1410 panic("PPC64 shift arg mb out of range")
1412 if me < 0 || me >= sz {
1413 panic("PPC64 shift arg me out of range")
1415 return int32(sh<<16 | mb<<8 | me)
1418 func GetPPC64Shiftsh(auxint int64) int64 {
1419 return int64(int8(auxint >> 16))
1422 func GetPPC64Shiftmb(auxint int64) int64 {
1423 return int64(int8(auxint >> 8))
1426 func GetPPC64Shiftme(auxint int64) int64 {
1427 return int64(int8(auxint))
1430 // Test if this value can encoded as a mask for a rlwinm like
1431 // operation. Masks can also extend from the msb and wrap to
1432 // the lsb too. That is, the valid masks are 32 bit strings
1433 // of the form: 0..01..10..0 or 1..10..01..1 or 1...1
1434 func isPPC64WordRotateMask(v64 int64) bool {
1435 // Isolate rightmost 1 (if none 0) and add.
1438 // Likewise, for the wrapping case.
1440 vpn := (vn & -vn) + vn
1441 return (v&vp == 0 || vn&vpn == 0) && v != 0
1444 // Compress mask and shift into single value of the form
1445 // me | mb<<8 | rotate<<16 | nbits<<24 where me and mb can
1446 // be used to regenerate the input mask.
1447 func encodePPC64RotateMask(rotate, mask, nbits int64) int64 {
1448 var mb, me, mbn, men int
1450 // Determine boundaries and then decode them
1451 if mask == 0 || ^mask == 0 || rotate >= nbits {
1452 panic("Invalid PPC64 rotate mask")
1453 } else if nbits == 32 {
1454 mb = bits.LeadingZeros32(uint32(mask))
1455 me = 32 - bits.TrailingZeros32(uint32(mask))
1456 mbn = bits.LeadingZeros32(^uint32(mask))
1457 men = 32 - bits.TrailingZeros32(^uint32(mask))
1459 mb = bits.LeadingZeros64(uint64(mask))
1460 me = 64 - bits.TrailingZeros64(uint64(mask))
1461 mbn = bits.LeadingZeros64(^uint64(mask))
1462 men = 64 - bits.TrailingZeros64(^uint64(mask))
1464 // Check for a wrapping mask (e.g bits at 0 and 63)
1465 if mb == 0 && me == int(nbits) {
1466 // swap the inverted values
1470 return int64(me) | int64(mb<<8) | int64(rotate<<16) | int64(nbits<<24)
1473 // The inverse operation of encodePPC64RotateMask. The values returned as
1474 // mb and me satisfy the POWER ISA definition of MASK(x,y) where MASK(mb,me) = mask.
1475 func DecodePPC64RotateMask(sauxint int64) (rotate, mb, me int64, mask uint64) {
1476 auxint := uint64(sauxint)
1477 rotate = int64((auxint >> 16) & 0xFF)
1478 mb = int64((auxint >> 8) & 0xFF)
1479 me = int64((auxint >> 0) & 0xFF)
1480 nbits := int64((auxint >> 24) & 0xFF)
1481 mask = ((1 << uint(nbits-mb)) - 1) ^ ((1 << uint(nbits-me)) - 1)
1486 mask = uint64(uint32(mask))
1489 // Fixup ME to match ISA definition. The second argument to MASK(..,me)
1491 me = (me - 1) & (nbits - 1)
1495 // This verifies that the mask is a set of
1496 // consecutive bits including the least
1498 func isPPC64ValidShiftMask(v int64) bool {
1499 if (v != 0) && ((v+1)&v) == 0 {
1505 func getPPC64ShiftMaskLength(v int64) int64 {
1506 return int64(bits.Len64(uint64(v)))
1509 // Decompose a shift right into an equivalent rotate/mask,
1510 // and return mask & m.
1511 func mergePPC64RShiftMask(m, s, nbits int64) int64 {
1512 smask := uint64((1<<uint(nbits))-1) >> uint(s)
1513 return m & int64(smask)
1516 // Combine (ANDconst [m] (SRWconst [s])) into (RLWINM [y]) or return 0
1517 func mergePPC64AndSrwi(m, s int64) int64 {
1518 mask := mergePPC64RShiftMask(m, s, 32)
1519 if !isPPC64WordRotateMask(mask) {
1522 return encodePPC64RotateMask((32-s)&31, mask, 32)
1525 // Test if a shift right feeding into a CLRLSLDI can be merged into RLWINM.
1526 // Return the encoded RLWINM constant, or 0 if they cannot be merged.
1527 func mergePPC64ClrlsldiSrw(sld, srw int64) int64 {
1528 mask_1 := uint64(0xFFFFFFFF >> uint(srw))
1529 // for CLRLSLDI, it's more convient to think of it as a mask left bits then rotate left.
1530 mask_2 := uint64(0xFFFFFFFFFFFFFFFF) >> uint(GetPPC64Shiftmb(int64(sld)))
1532 // Rewrite mask to apply after the final left shift.
1533 mask_3 := (mask_1 & mask_2) << uint(GetPPC64Shiftsh(sld))
1536 r_2 := GetPPC64Shiftsh(sld)
1537 r_3 := (r_1 + r_2) & 31 // This can wrap.
1539 if uint64(uint32(mask_3)) != mask_3 || mask_3 == 0 {
1542 return encodePPC64RotateMask(int64(r_3), int64(mask_3), 32)
1545 // Test if a RLWINM feeding into a CLRLSLDI can be merged into RLWINM. Return
1546 // the encoded RLWINM constant, or 0 if they cannot be merged.
1547 func mergePPC64ClrlsldiRlwinm(sld int32, rlw int64) int64 {
1548 r_1, _, _, mask_1 := DecodePPC64RotateMask(rlw)
1549 // for CLRLSLDI, it's more convient to think of it as a mask left bits then rotate left.
1550 mask_2 := uint64(0xFFFFFFFFFFFFFFFF) >> uint(GetPPC64Shiftmb(int64(sld)))
1552 // combine the masks, and adjust for the final left shift.
1553 mask_3 := (mask_1 & mask_2) << uint(GetPPC64Shiftsh(int64(sld)))
1554 r_2 := GetPPC64Shiftsh(int64(sld))
1555 r_3 := (r_1 + r_2) & 31 // This can wrap.
1557 // Verify the result is still a valid bitmask of <= 32 bits.
1558 if !isPPC64WordRotateMask(int64(mask_3)) || uint64(uint32(mask_3)) != mask_3 {
1561 return encodePPC64RotateMask(r_3, int64(mask_3), 32)
1564 // Compute the encoded RLWINM constant from combining (SLDconst [sld] (SRWconst [srw] x)),
1565 // or return 0 if they cannot be combined.
1566 func mergePPC64SldiSrw(sld, srw int64) int64 {
1567 if sld > srw || srw >= 32 {
1570 mask_r := uint32(0xFFFFFFFF) >> uint(srw)
1571 mask_l := uint32(0xFFFFFFFF) >> uint(sld)
1572 mask := (mask_r & mask_l) << uint(sld)
1573 return encodePPC64RotateMask((32-srw+sld)&31, int64(mask), 32)
1576 // Convenience function to rotate a 32 bit constant value by another constant.
1577 func rotateLeft32(v, rotate int64) int64 {
1578 return int64(bits.RotateLeft32(uint32(v), int(rotate)))
1581 func rotateRight64(v, rotate int64) int64 {
1582 return int64(bits.RotateLeft64(uint64(v), int(-rotate)))
1585 // encodes the lsb and width for arm(64) bitfield ops into the expected auxInt format.
1586 func armBFAuxInt(lsb, width int64) arm64BitField {
1587 if lsb < 0 || lsb > 63 {
1588 panic("ARM(64) bit field lsb constant out of range")
1590 if width < 1 || lsb+width > 64 {
1591 panic("ARM(64) bit field width constant out of range")
1593 return arm64BitField(width | lsb<<8)
1596 // returns the lsb part of the auxInt field of arm64 bitfield ops.
1597 func (bfc arm64BitField) getARM64BFlsb() int64 {
1598 return int64(uint64(bfc) >> 8)
1601 // returns the width part of the auxInt field of arm64 bitfield ops.
1602 func (bfc arm64BitField) getARM64BFwidth() int64 {
1603 return int64(bfc) & 0xff
1606 // checks if mask >> rshift applied at lsb is a valid arm64 bitfield op mask.
1607 func isARM64BFMask(lsb, mask, rshift int64) bool {
1608 shiftedMask := int64(uint64(mask) >> uint64(rshift))
1609 return shiftedMask != 0 && isPowerOfTwo64(shiftedMask+1) && nto(shiftedMask)+lsb < 64
1612 // returns the bitfield width of mask >> rshift for arm64 bitfield ops
1613 func arm64BFWidth(mask, rshift int64) int64 {
1614 shiftedMask := int64(uint64(mask) >> uint64(rshift))
1615 if shiftedMask == 0 {
1616 panic("ARM64 BF mask is zero")
1618 return nto(shiftedMask)
1621 // sizeof returns the size of t in bytes.
1622 // It will panic if t is not a *types.Type.
1623 func sizeof(t interface{}) int64 {
1624 return t.(*types.Type).Size()
1627 // registerizable reports whether t is a primitive type that fits in
1628 // a register. It assumes float64 values will always fit into registers
1629 // even if that isn't strictly true.
1630 func registerizable(b *Block, typ *types.Type) bool {
1631 if typ.IsPtrShaped() || typ.IsFloat() {
1634 if typ.IsInteger() {
1635 return typ.Size() <= b.Func.Config.RegSize
1640 // needRaceCleanup reports whether this call to racefuncenter/exit isn't needed.
1641 func needRaceCleanup(sym *AuxCall, v *Value) bool {
1646 if !isSameCall(sym, "runtime.racefuncenter") && !isSameCall(sym, "runtime.racefuncexit") {
1649 for _, b := range f.Blocks {
1650 for _, v := range b.Values {
1652 case OpStaticCall, OpStaticLECall:
1653 // Check for racefuncenter will encounter racefuncexit and vice versa.
1654 // Allow calls to panic*
1655 s := v.Aux.(*AuxCall).Fn.String()
1657 case "runtime.racefuncenter", "runtime.racefuncexit",
1658 "runtime.panicdivide", "runtime.panicwrap",
1659 "runtime.panicshift":
1662 // If we encountered any call, we need to keep racefunc*,
1663 // for accurate stacktraces.
1665 case OpPanicBounds, OpPanicExtend:
1666 // Note: these are panic generators that are ok (like the static calls above).
1667 case OpClosureCall, OpInterCall, OpClosureLECall, OpInterLECall:
1668 // We must keep the race functions if there are any other call types.
1673 if isSameCall(sym, "runtime.racefuncenter") {
1674 // TODO REGISTER ABI this needs to be cleaned up.
1675 // If we're removing racefuncenter, remove its argument as well.
1676 if v.Args[0].Op != OpStore {
1677 if v.Op == OpStaticLECall {
1678 // there is no store, yet.
1683 mem := v.Args[0].Args[2]
1684 v.Args[0].reset(OpCopy)
1685 v.Args[0].AddArg(mem)
1690 // symIsRO reports whether sym is a read-only global.
1691 func symIsRO(sym interface{}) bool {
1692 lsym := sym.(*obj.LSym)
1693 return lsym.Type == objabi.SRODATA && len(lsym.R) == 0
1696 // symIsROZero reports whether sym is a read-only global whose data contains all zeros.
1697 func symIsROZero(sym Sym) bool {
1698 lsym := sym.(*obj.LSym)
1699 if lsym.Type != objabi.SRODATA || len(lsym.R) != 0 {
1702 for _, b := range lsym.P {
1710 // read8 reads one byte from the read-only global sym at offset off.
1711 func read8(sym interface{}, off int64) uint8 {
1712 lsym := sym.(*obj.LSym)
1713 if off >= int64(len(lsym.P)) || off < 0 {
1714 // Invalid index into the global sym.
1715 // This can happen in dead code, so we don't want to panic.
1716 // Just return any value, it will eventually get ignored.
1723 // read16 reads two bytes from the read-only global sym at offset off.
1724 func read16(sym interface{}, off int64, byteorder binary.ByteOrder) uint16 {
1725 lsym := sym.(*obj.LSym)
1726 // lsym.P is written lazily.
1727 // Bytes requested after the end of lsym.P are 0.
1729 if 0 <= off && off < int64(len(lsym.P)) {
1732 buf := make([]byte, 2)
1734 return byteorder.Uint16(buf)
1737 // read32 reads four bytes from the read-only global sym at offset off.
1738 func read32(sym interface{}, off int64, byteorder binary.ByteOrder) uint32 {
1739 lsym := sym.(*obj.LSym)
1741 if 0 <= off && off < int64(len(lsym.P)) {
1744 buf := make([]byte, 4)
1746 return byteorder.Uint32(buf)
1749 // read64 reads eight bytes from the read-only global sym at offset off.
1750 func read64(sym interface{}, off int64, byteorder binary.ByteOrder) uint64 {
1751 lsym := sym.(*obj.LSym)
1753 if 0 <= off && off < int64(len(lsym.P)) {
1756 buf := make([]byte, 8)
1758 return byteorder.Uint64(buf)
1761 // sequentialAddresses reports true if it can prove that x + n == y
1762 func sequentialAddresses(x, y *Value, n int64) bool {
1763 if x.Op == Op386ADDL && y.Op == Op386LEAL1 && y.AuxInt == n && y.Aux == nil &&
1764 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1765 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1768 if x.Op == Op386LEAL1 && y.Op == Op386LEAL1 && y.AuxInt == x.AuxInt+n && x.Aux == y.Aux &&
1769 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1770 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1773 if x.Op == OpAMD64ADDQ && y.Op == OpAMD64LEAQ1 && y.AuxInt == n && y.Aux == nil &&
1774 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1775 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1778 if x.Op == OpAMD64LEAQ1 && y.Op == OpAMD64LEAQ1 && y.AuxInt == x.AuxInt+n && x.Aux == y.Aux &&
1779 (x.Args[0] == y.Args[0] && x.Args[1] == y.Args[1] ||
1780 x.Args[0] == y.Args[1] && x.Args[1] == y.Args[0]) {
1786 // flagConstant represents the result of a compile-time comparison.
1787 // The sense of these flags does not necessarily represent the hardware's notion
1788 // of a flags register - these are just a compile-time construct.
1789 // We happen to match the semantics to those of arm/arm64.
1790 // Note that these semantics differ from x86: the carry flag has the opposite
1791 // sense on a subtraction!
1792 // On amd64, C=1 represents a borrow, e.g. SBB on amd64 does x - y - C.
1793 // On arm64, C=0 represents a borrow, e.g. SBC on arm64 does x - y - ^C.
1794 // (because it does x + ^y + C).
1795 // See https://en.wikipedia.org/wiki/Carry_flag#Vs._borrow_flag
1796 type flagConstant uint8
1798 // N reports whether the result of an operation is negative (high bit set).
1799 func (fc flagConstant) N() bool {
1803 // Z reports whether the result of an operation is 0.
1804 func (fc flagConstant) Z() bool {
1808 // C reports whether an unsigned add overflowed (carry), or an
1809 // unsigned subtract did not underflow (borrow).
1810 func (fc flagConstant) C() bool {
1814 // V reports whether a signed operation overflowed or underflowed.
1815 func (fc flagConstant) V() bool {
1819 func (fc flagConstant) eq() bool {
1822 func (fc flagConstant) ne() bool {
1825 func (fc flagConstant) lt() bool {
1826 return fc.N() != fc.V()
1828 func (fc flagConstant) le() bool {
1829 return fc.Z() || fc.lt()
1831 func (fc flagConstant) gt() bool {
1832 return !fc.Z() && fc.ge()
1834 func (fc flagConstant) ge() bool {
1835 return fc.N() == fc.V()
1837 func (fc flagConstant) ult() bool {
1840 func (fc flagConstant) ule() bool {
1841 return fc.Z() || fc.ult()
1843 func (fc flagConstant) ugt() bool {
1844 return !fc.Z() && fc.uge()
1846 func (fc flagConstant) uge() bool {
1850 func (fc flagConstant) ltNoov() bool {
1851 return fc.lt() && !fc.V()
1853 func (fc flagConstant) leNoov() bool {
1854 return fc.le() && !fc.V()
1856 func (fc flagConstant) gtNoov() bool {
1857 return fc.gt() && !fc.V()
1859 func (fc flagConstant) geNoov() bool {
1860 return fc.ge() && !fc.V()
1863 func (fc flagConstant) String() string {
1864 return fmt.Sprintf("N=%v,Z=%v,C=%v,V=%v", fc.N(), fc.Z(), fc.C(), fc.V())
1867 type flagConstantBuilder struct {
1874 func (fcs flagConstantBuilder) encode() flagConstant {
1891 // Note: addFlags(x,y) != subFlags(x,-y) in some situations:
1892 // - the results of the C flag are different
1893 // - the results of the V flag when y==minint are different
1895 // addFlags64 returns the flags that would be set from computing x+y.
1896 func addFlags64(x, y int64) flagConstant {
1897 var fcb flagConstantBuilder
1900 fcb.C = uint64(x+y) < uint64(x)
1901 fcb.V = x >= 0 && y >= 0 && x+y < 0 || x < 0 && y < 0 && x+y >= 0
1905 // subFlags64 returns the flags that would be set from computing x-y.
1906 func subFlags64(x, y int64) flagConstant {
1907 var fcb flagConstantBuilder
1910 fcb.C = uint64(y) <= uint64(x) // This code follows the arm carry flag model.
1911 fcb.V = x >= 0 && y < 0 && x-y < 0 || x < 0 && y >= 0 && x-y >= 0
1915 // addFlags32 returns the flags that would be set from computing x+y.
1916 func addFlags32(x, y int32) flagConstant {
1917 var fcb flagConstantBuilder
1920 fcb.C = uint32(x+y) < uint32(x)
1921 fcb.V = x >= 0 && y >= 0 && x+y < 0 || x < 0 && y < 0 && x+y >= 0
1925 // subFlags32 returns the flags that would be set from computing x-y.
1926 func subFlags32(x, y int32) flagConstant {
1927 var fcb flagConstantBuilder
1930 fcb.C = uint32(y) <= uint32(x) // This code follows the arm carry flag model.
1931 fcb.V = x >= 0 && y < 0 && x-y < 0 || x < 0 && y >= 0 && x-y >= 0
1935 // logicFlags64 returns flags set to the sign/zeroness of x.
1936 // C and V are set to false.
1937 func logicFlags64(x int64) flagConstant {
1938 var fcb flagConstantBuilder
1944 // logicFlags32 returns flags set to the sign/zeroness of x.
1945 // C and V are set to false.
1946 func logicFlags32(x int32) flagConstant {
1947 var fcb flagConstantBuilder