check.go

     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.
     4  
     5  package ssa
     6  
     7  import (
     8  	"cmd/internal/obj/s390x"
     9  	"math"
    10  	"math/bits"
    11  )
    12  
    13  // checkFunc checks invariants of f.
    14  func checkFunc(f *Func) {
    15  	blockMark := make([]bool, f.NumBlocks())
    16  	valueMark := make([]bool, f.NumValues())
    17  
    18  	for _, b := range f.Blocks {
    19  		if blockMark[b.ID] {
    20  			f.Fatalf("block %s appears twice in %s!", b, f.Name)
    21  		}
    22  		blockMark[b.ID] = true
    23  		if b.Func != f {
    24  			f.Fatalf("%s.Func=%s, want %s", b, b.Func.Name, f.Name)
    25  		}
    26  
    27  		for i, e := range b.Preds {
    28  			if se := e.b.Succs[e.i]; se.b != b || se.i != i {
    29  				f.Fatalf("block pred/succ not crosslinked correctly %d:%s %d:%s", i, b, se.i, se.b)
    30  			}
    31  		}
    32  		for i, e := range b.Succs {
    33  			if pe := e.b.Preds[e.i]; pe.b != b || pe.i != i {
    34  				f.Fatalf("block succ/pred not crosslinked correctly %d:%s %d:%s", i, b, pe.i, pe.b)
    35  			}
    36  		}
    37  
    38  		switch b.Kind {
    39  		case BlockExit:
    40  			if len(b.Succs) != 0 {
    41  				f.Fatalf("exit block %s has successors", b)
    42  			}
    43  			if b.NumControls() != 1 {
    44  				f.Fatalf("exit block %s has no control value", b)
    45  			}
    46  			if !b.Controls[0].Type.IsMemory() {
    47  				f.Fatalf("exit block %s has non-memory control value %s", b, b.Controls[0].LongString())
    48  			}
    49  		case BlockRet:
    50  			if len(b.Succs) != 0 {
    51  				f.Fatalf("ret block %s has successors", b)
    52  			}
    53  			if b.NumControls() != 1 {
    54  				f.Fatalf("ret block %s has nil control", b)
    55  			}
    56  			if !b.Controls[0].Type.IsMemory() {
    57  				f.Fatalf("ret block %s has non-memory control value %s", b, b.Controls[0].LongString())
    58  			}
    59  		case BlockRetJmp:
    60  			if len(b.Succs) != 0 {
    61  				f.Fatalf("retjmp block %s len(Succs)==%d, want 0", b, len(b.Succs))
    62  			}
    63  			if b.NumControls() != 1 {
    64  				f.Fatalf("retjmp block %s has nil control", b)
    65  			}
    66  			if !b.Controls[0].Type.IsMemory() {
    67  				f.Fatalf("retjmp block %s has non-memory control value %s", b, b.Controls[0].LongString())
    68  			}
    69  		case BlockPlain:
    70  			if len(b.Succs) != 1 {
    71  				f.Fatalf("plain block %s len(Succs)==%d, want 1", b, len(b.Succs))
    72  			}
    73  			if b.NumControls() != 0 {
    74  				f.Fatalf("plain block %s has non-nil control %s", b, b.Controls[0].LongString())
    75  			}
    76  		case BlockIf:
    77  			if len(b.Succs) != 2 {
    78  				f.Fatalf("if block %s len(Succs)==%d, want 2", b, len(b.Succs))
    79  			}
    80  			if b.NumControls() != 1 {
    81  				f.Fatalf("if block %s has no control value", b)
    82  			}
    83  			if !b.Controls[0].Type.IsBoolean() {
    84  				f.Fatalf("if block %s has non-bool control value %s", b, b.Controls[0].LongString())
    85  			}
    86  		case BlockDefer:
    87  			if len(b.Succs) != 2 {
    88  				f.Fatalf("defer block %s len(Succs)==%d, want 2", b, len(b.Succs))
    89  			}
    90  			if b.NumControls() != 1 {
    91  				f.Fatalf("defer block %s has no control value", b)
    92  			}
    93  			if !b.Controls[0].Type.IsMemory() {
    94  				f.Fatalf("defer block %s has non-memory control value %s", b, b.Controls[0].LongString())
    95  			}
    96  		case BlockFirst:
    97  			if len(b.Succs) != 2 {
    98  				f.Fatalf("plain/dead block %s len(Succs)==%d, want 2", b, len(b.Succs))
    99  			}
   100  			if b.NumControls() != 0 {
   101  				f.Fatalf("plain/dead block %s has a control value", b)
   102  			}
   103  		}
   104  		if len(b.Succs) != 2 && b.Likely != BranchUnknown {
   105  			f.Fatalf("likeliness prediction %d for block %s with %d successors", b.Likely, b, len(b.Succs))
   106  		}
   107  
   108  		for _, v := range b.Values {
   109  			// Check to make sure argument count makes sense (argLen of -1 indicates
   110  			// variable length args)
   111  			nArgs := opcodeTable[v.Op].argLen
   112  			if nArgs != -1 && int32(len(v.Args)) != nArgs {
   113  				f.Fatalf("value %s has %d args, expected %d", v.LongString(),
   114  					len(v.Args), nArgs)
   115  			}
   116  
   117  			// Check to make sure aux values make sense.
   118  			canHaveAux := false
   119  			canHaveAuxInt := false
   120  			// TODO: enforce types of Aux in this switch (like auxString does below)
   121  			switch opcodeTable[v.Op].auxType {
   122  			case auxNone:
   123  			case auxBool:
   124  				if v.AuxInt < 0 || v.AuxInt > 1 {
   125  					f.Fatalf("bad bool AuxInt value for %v", v)
   126  				}
   127  				canHaveAuxInt = true
   128  			case auxInt8:
   129  				if v.AuxInt != int64(int8(v.AuxInt)) {
   130  					f.Fatalf("bad int8 AuxInt value for %v", v)
   131  				}
   132  				canHaveAuxInt = true
   133  			case auxInt16:
   134  				if v.AuxInt != int64(int16(v.AuxInt)) {
   135  					f.Fatalf("bad int16 AuxInt value for %v", v)
   136  				}
   137  				canHaveAuxInt = true
   138  			case auxInt32:
   139  				if v.AuxInt != int64(int32(v.AuxInt)) {
   140  					f.Fatalf("bad int32 AuxInt value for %v", v)
   141  				}
   142  				canHaveAuxInt = true
   143  			case auxInt64, auxARM64BitField:
   144  				canHaveAuxInt = true
   145  			case auxInt128:
   146  				// AuxInt must be zero, so leave canHaveAuxInt set to false.
   147  			case auxUInt8:
   148  				if v.AuxInt != int64(uint8(v.AuxInt)) {
   149  					f.Fatalf("bad uint8 AuxInt value for %v", v)
   150  				}
   151  				canHaveAuxInt = true
   152  			case auxFloat32:
   153  				canHaveAuxInt = true
   154  				if math.IsNaN(v.AuxFloat()) {
   155  					f.Fatalf("value %v has an AuxInt that encodes a NaN", v)
   156  				}
   157  				if !isExactFloat32(v.AuxFloat()) {
   158  					f.Fatalf("value %v has an AuxInt value that is not an exact float32", v)
   159  				}
   160  			case auxFloat64:
   161  				canHaveAuxInt = true
   162  				if math.IsNaN(v.AuxFloat()) {
   163  					f.Fatalf("value %v has an AuxInt that encodes a NaN", v)
   164  				}
   165  			case auxString:
   166  				if _, ok := v.Aux.(stringAux); !ok {
   167  					f.Fatalf("value %v has Aux type %T, want string", v, v.Aux)
   168  				}
   169  				canHaveAux = true
   170  			case auxCallOff:
   171  				canHaveAuxInt = true
   172  				fallthrough
   173  			case auxCall:
   174  				if ac, ok := v.Aux.(*AuxCall); ok {
   175  					if v.Op == OpStaticCall && ac.Fn == nil {
   176  						f.Fatalf("value %v has *AuxCall with nil Fn", v)
   177  					}
   178  				} else {
   179  					f.Fatalf("value %v has Aux type %T, want *AuxCall", v, v.Aux)
   180  				}
   181  				canHaveAux = true
   182  			case auxNameOffsetInt8:
   183  				if _, ok := v.Aux.(*AuxNameOffset); !ok {
   184  					f.Fatalf("value %v has Aux type %T, want *AuxNameOffset", v, v.Aux)
   185  				}
   186  				canHaveAux = true
   187  				canHaveAuxInt = true
   188  			case auxSym, auxTyp:
   189  				canHaveAux = true
   190  			case auxSymOff, auxSymValAndOff, auxTypSize:
   191  				canHaveAuxInt = true
   192  				canHaveAux = true
   193  			case auxCCop:
   194  				if opcodeTable[Op(v.AuxInt)].name == "OpInvalid" {
   195  					f.Fatalf("value %v has an AuxInt value that is a valid opcode", v)
   196  				}
   197  				canHaveAuxInt = true
   198  			case auxS390XCCMask:
   199  				if _, ok := v.Aux.(s390x.CCMask); !ok {
   200  					f.Fatalf("bad type %T for S390XCCMask in %v", v.Aux, v)
   201  				}
   202  				canHaveAux = true
   203  			case auxS390XRotateParams:
   204  				if _, ok := v.Aux.(s390x.RotateParams); !ok {
   205  					f.Fatalf("bad type %T for S390XRotateParams in %v", v.Aux, v)
   206  				}
   207  				canHaveAux = true
   208  			case auxFlagConstant:
   209  				if v.AuxInt < 0 || v.AuxInt > 15 {
   210  					f.Fatalf("bad FlagConstant AuxInt value for %v", v)
   211  				}
   212  				canHaveAuxInt = true
   213  			default:
   214  				f.Fatalf("unknown aux type for %s", v.Op)
   215  			}
   216  			if !canHaveAux && v.Aux != nil {
   217  				f.Fatalf("value %s has an Aux value %v but shouldn't", v.LongString(), v.Aux)
   218  			}
   219  			if !canHaveAuxInt && v.AuxInt != 0 {
   220  				f.Fatalf("value %s has an AuxInt value %d but shouldn't", v.LongString(), v.AuxInt)
   221  			}
   222  
   223  			for i, arg := range v.Args {
   224  				if arg == nil {
   225  					f.Fatalf("value %s has nil arg", v.LongString())
   226  				}
   227  				if v.Op != OpPhi {
   228  					// For non-Phi ops, memory args must be last, if present
   229  					if arg.Type.IsMemory() && i != len(v.Args)-1 {
   230  						f.Fatalf("value %s has non-final memory arg (%d < %d)", v.LongString(), i, len(v.Args)-1)
   231  					}
   232  				}
   233  			}
   234  
   235  			if valueMark[v.ID] {
   236  				f.Fatalf("value %s appears twice!", v.LongString())
   237  			}
   238  			valueMark[v.ID] = true
   239  
   240  			if v.Block != b {
   241  				f.Fatalf("%s.block != %s", v, b)
   242  			}
   243  			if v.Op == OpPhi && len(v.Args) != len(b.Preds) {
   244  				f.Fatalf("phi length %s does not match pred length %d for block %s", v.LongString(), len(b.Preds), b)
   245  			}
   246  
   247  			if v.Op == OpAddr {
   248  				if len(v.Args) == 0 {
   249  					f.Fatalf("no args for OpAddr %s", v.LongString())
   250  				}
   251  				if v.Args[0].Op != OpSB {
   252  					f.Fatalf("bad arg to OpAddr %v", v)
   253  				}
   254  			}
   255  
   256  			if v.Op == OpLocalAddr {
   257  				if len(v.Args) != 2 {
   258  					f.Fatalf("wrong # of args for OpLocalAddr %s", v.LongString())
   259  				}
   260  				if v.Args[0].Op != OpSP {
   261  					f.Fatalf("bad arg 0 to OpLocalAddr %v", v)
   262  				}
   263  				if !v.Args[1].Type.IsMemory() {
   264  					f.Fatalf("bad arg 1 to OpLocalAddr %v", v)
   265  				}
   266  			}
   267  
   268  			if f.RegAlloc != nil && f.Config.SoftFloat && v.Type.IsFloat() {
   269  				f.Fatalf("unexpected floating-point type %v", v.LongString())
   270  			}
   271  
   272  			// Check types.
   273  			// TODO: more type checks?
   274  			switch c := f.Config; v.Op {
   275  			case OpSP, OpSB:
   276  				if v.Type != c.Types.Uintptr {
   277  					f.Fatalf("bad %s type: want uintptr, have %s",
   278  						v.Op, v.Type.String())
   279  				}
   280  			case OpStringLen:
   281  				if v.Type != c.Types.Int {
   282  					f.Fatalf("bad %s type: want int, have %s",
   283  						v.Op, v.Type.String())
   284  				}
   285  			case OpLoad:
   286  				if !v.Args[1].Type.IsMemory() {
   287  					f.Fatalf("bad arg 1 type to %s: want mem, have %s",
   288  						v.Op, v.Args[1].Type.String())
   289  				}
   290  			case OpStore:
   291  				if !v.Type.IsMemory() {
   292  					f.Fatalf("bad %s type: want mem, have %s",
   293  						v.Op, v.Type.String())
   294  				}
   295  				if !v.Args[2].Type.IsMemory() {
   296  					f.Fatalf("bad arg 2 type to %s: want mem, have %s",
   297  						v.Op, v.Args[2].Type.String())
   298  				}
   299  			case OpCondSelect:
   300  				if !v.Args[2].Type.IsBoolean() {
   301  					f.Fatalf("bad arg 2 type to %s: want boolean, have %s",
   302  						v.Op, v.Args[2].Type.String())
   303  				}
   304  			case OpAddPtr:
   305  				if !v.Args[0].Type.IsPtrShaped() && v.Args[0].Type != c.Types.Uintptr {
   306  					f.Fatalf("bad arg 0 type to %s: want ptr, have %s", v.Op, v.Args[0].LongString())
   307  				}
   308  				if !v.Args[1].Type.IsInteger() {
   309  					f.Fatalf("bad arg 1 type to %s: want integer, have %s", v.Op, v.Args[1].LongString())
   310  				}
   311  
   312  			}
   313  
   314  			// TODO: check for cycles in values
   315  		}
   316  	}
   317  
   318  	// Check to make sure all Blocks referenced are in the function.
   319  	if !blockMark[f.Entry.ID] {
   320  		f.Fatalf("entry block %v is missing", f.Entry)
   321  	}
   322  	for _, b := range f.Blocks {
   323  		for _, c := range b.Preds {
   324  			if !blockMark[c.b.ID] {
   325  				f.Fatalf("predecessor block %v for %v is missing", c, b)
   326  			}
   327  		}
   328  		for _, c := range b.Succs {
   329  			if !blockMark[c.b.ID] {
   330  				f.Fatalf("successor block %v for %v is missing", c, b)
   331  			}
   332  		}
   333  	}
   334  
   335  	if len(f.Entry.Preds) > 0 {
   336  		f.Fatalf("entry block %s of %s has predecessor(s) %v", f.Entry, f.Name, f.Entry.Preds)
   337  	}
   338  
   339  	// Check to make sure all Values referenced are in the function.
   340  	for _, b := range f.Blocks {
   341  		for _, v := range b.Values {
   342  			for i, a := range v.Args {
   343  				if !valueMark[a.ID] {
   344  					f.Fatalf("%v, arg %d of %s, is missing", a, i, v.LongString())
   345  				}
   346  			}
   347  		}
   348  		for _, c := range b.ControlValues() {
   349  			if !valueMark[c.ID] {
   350  				f.Fatalf("control value for %s is missing: %v", b, c)
   351  			}
   352  		}
   353  	}
   354  	for b := f.freeBlocks; b != nil; b = b.succstorage[0].b {
   355  		if blockMark[b.ID] {
   356  			f.Fatalf("used block b%d in free list", b.ID)
   357  		}
   358  	}
   359  	for v := f.freeValues; v != nil; v = v.argstorage[0] {
   360  		if valueMark[v.ID] {
   361  			f.Fatalf("used value v%d in free list", v.ID)
   362  		}
   363  	}
   364  
   365  	// Check to make sure all args dominate uses.
   366  	if f.RegAlloc == nil {
   367  		// Note: regalloc introduces non-dominating args.
   368  		// See TODO in regalloc.go.
   369  		sdom := f.Sdom()
   370  		for _, b := range f.Blocks {
   371  			for _, v := range b.Values {
   372  				for i, arg := range v.Args {
   373  					x := arg.Block
   374  					y := b
   375  					if v.Op == OpPhi {
   376  						y = b.Preds[i].b
   377  					}
   378  					if !domCheck(f, sdom, x, y) {
   379  						f.Fatalf("arg %d of value %s does not dominate, arg=%s", i, v.LongString(), arg.LongString())
   380  					}
   381  				}
   382  			}
   383  			for _, c := range b.ControlValues() {
   384  				if !domCheck(f, sdom, c.Block, b) {
   385  					f.Fatalf("control value %s for %s doesn't dominate", c, b)
   386  				}
   387  			}
   388  		}
   389  	}
   390  
   391  	// Check loop construction
   392  	if f.RegAlloc == nil && f.pass != nil { // non-nil pass allows better-targeted debug printing
   393  		ln := f.loopnest()
   394  		if !ln.hasIrreducible {
   395  			po := f.postorder() // use po to avoid unreachable blocks.
   396  			for _, b := range po {
   397  				for _, s := range b.Succs {
   398  					bb := s.Block()
   399  					if ln.b2l[b.ID] == nil && ln.b2l[bb.ID] != nil && bb != ln.b2l[bb.ID].header {
   400  						f.Fatalf("block %s not in loop branches to non-header block %s in loop", b.String(), bb.String())
   401  					}
   402  					if ln.b2l[b.ID] != nil && ln.b2l[bb.ID] != nil && bb != ln.b2l[bb.ID].header && !ln.b2l[b.ID].isWithinOrEq(ln.b2l[bb.ID]) {
   403  						f.Fatalf("block %s in loop branches to non-header block %s in non-containing loop", b.String(), bb.String())
   404  					}
   405  				}
   406  			}
   407  		}
   408  	}
   409  
   410  	// Check use counts
   411  	uses := make([]int32, f.NumValues())
   412  	for _, b := range f.Blocks {
   413  		for _, v := range b.Values {
   414  			for _, a := range v.Args {
   415  				uses[a.ID]++
   416  			}
   417  		}
   418  		for _, c := range b.ControlValues() {
   419  			uses[c.ID]++
   420  		}
   421  	}
   422  	for _, b := range f.Blocks {
   423  		for _, v := range b.Values {
   424  			if v.Uses != uses[v.ID] {
   425  				f.Fatalf("%s has %d uses, but has Uses=%d", v, uses[v.ID], v.Uses)
   426  			}
   427  		}
   428  	}
   429  
   430  	memCheck(f)
   431  }
   432  
   433  func memCheck(f *Func) {
   434  	// Check that if a tuple has a memory type, it is second.
   435  	for _, b := range f.Blocks {
   436  		for _, v := range b.Values {
   437  			if v.Type.IsTuple() && v.Type.FieldType(0).IsMemory() {
   438  				f.Fatalf("memory is first in a tuple: %s\n", v.LongString())
   439  			}
   440  		}
   441  	}
   442  
   443  	// Single live memory checks.
   444  	// These checks only work if there are no memory copies.
   445  	// (Memory copies introduce ambiguity about which mem value is really live.
   446  	// probably fixable, but it's easier to avoid the problem.)
   447  	// For the same reason, disable this check if some memory ops are unused.
   448  	for _, b := range f.Blocks {
   449  		for _, v := range b.Values {
   450  			if (v.Op == OpCopy || v.Uses == 0) && v.Type.IsMemory() {
   451  				return
   452  			}
   453  		}
   454  		if b != f.Entry && len(b.Preds) == 0 {
   455  			return
   456  		}
   457  	}
   458  
   459  	// Compute live memory at the end of each block.
   460  	lastmem := make([]*Value, f.NumBlocks())
   461  	ss := newSparseSet(f.NumValues())
   462  	for _, b := range f.Blocks {
   463  		// Mark overwritten memory values. Those are args of other
   464  		// ops that generate memory values.
   465  		ss.clear()
   466  		for _, v := range b.Values {
   467  			if v.Op == OpPhi || !v.Type.IsMemory() {
   468  				continue
   469  			}
   470  			if m := v.MemoryArg(); m != nil {
   471  				ss.add(m.ID)
   472  			}
   473  		}
   474  		// There should be at most one remaining unoverwritten memory value.
   475  		for _, v := range b.Values {
   476  			if !v.Type.IsMemory() {
   477  				continue
   478  			}
   479  			if ss.contains(v.ID) {
   480  				continue
   481  			}
   482  			if lastmem[b.ID] != nil {
   483  				f.Fatalf("two live memory values in %s: %s and %s", b, lastmem[b.ID], v)
   484  			}
   485  			lastmem[b.ID] = v
   486  		}
   487  		// If there is no remaining memory value, that means there was no memory update.
   488  		// Take any memory arg.
   489  		if lastmem[b.ID] == nil {
   490  			for _, v := range b.Values {
   491  				if v.Op == OpPhi {
   492  					continue
   493  				}
   494  				m := v.MemoryArg()
   495  				if m == nil {
   496  					continue
   497  				}
   498  				if lastmem[b.ID] != nil && lastmem[b.ID] != m {
   499  					f.Fatalf("two live memory values in %s: %s and %s", b, lastmem[b.ID], m)
   500  				}
   501  				lastmem[b.ID] = m
   502  			}
   503  		}
   504  	}
   505  	// Propagate last live memory through storeless blocks.
   506  	for {
   507  		changed := false
   508  		for _, b := range f.Blocks {
   509  			if lastmem[b.ID] != nil {
   510  				continue
   511  			}
   512  			for _, e := range b.Preds {
   513  				p := e.b
   514  				if lastmem[p.ID] != nil {
   515  					lastmem[b.ID] = lastmem[p.ID]
   516  					changed = true
   517  					break
   518  				}
   519  			}
   520  		}
   521  		if !changed {
   522  			break
   523  		}
   524  	}
   525  	// Check merge points.
   526  	for _, b := range f.Blocks {
   527  		for _, v := range b.Values {
   528  			if v.Op == OpPhi && v.Type.IsMemory() {
   529  				for i, a := range v.Args {
   530  					if a != lastmem[b.Preds[i].b.ID] {
   531  						f.Fatalf("inconsistent memory phi %s %d %s %s", v.LongString(), i, a, lastmem[b.Preds[i].b.ID])
   532  					}
   533  				}
   534  			}
   535  		}
   536  	}
   537  
   538  	// Check that only one memory is live at any point.
   539  	if f.scheduled {
   540  		for _, b := range f.Blocks {
   541  			var mem *Value // the current live memory in the block
   542  			for _, v := range b.Values {
   543  				if v.Op == OpPhi {
   544  					if v.Type.IsMemory() {
   545  						mem = v
   546  					}
   547  					continue
   548  				}
   549  				if mem == nil && len(b.Preds) > 0 {
   550  					// If no mem phi, take mem of any predecessor.
   551  					mem = lastmem[b.Preds[0].b.ID]
   552  				}
   553  				for _, a := range v.Args {
   554  					if a.Type.IsMemory() && a != mem {
   555  						f.Fatalf("two live mems @ %s: %s and %s", v, mem, a)
   556  					}
   557  				}
   558  				if v.Type.IsMemory() {
   559  					mem = v
   560  				}
   561  			}
   562  		}
   563  	}
   564  
   565  	// Check that after scheduling, phis are always first in the block.
   566  	if f.scheduled {
   567  		for _, b := range f.Blocks {
   568  			seenNonPhi := false
   569  			for _, v := range b.Values {
   570  				switch v.Op {
   571  				case OpPhi:
   572  					if seenNonPhi {
   573  						f.Fatalf("phi after non-phi @ %s: %s", b, v)
   574  					}
   575  				default:
   576  					seenNonPhi = true
   577  				}
   578  			}
   579  		}
   580  	}
   581  }
   582  
   583  // domCheck reports whether x dominates y (including x==y).
   584  func domCheck(f *Func, sdom SparseTree, x, y *Block) bool {
   585  	if !sdom.IsAncestorEq(f.Entry, y) {
   586  		// unreachable - ignore
   587  		return true
   588  	}
   589  	return sdom.IsAncestorEq(x, y)
   590  }
   591  
   592  // isExactFloat32 reports whether x can be exactly represented as a float32.
   593  func isExactFloat32(x float64) bool {
   594  	// Check the mantissa is in range.
   595  	if bits.TrailingZeros64(math.Float64bits(x)) < 52-23 {
   596  		return false
   597  	}
   598  	// Check the exponent is in range. The mantissa check above is sufficient for NaN values.
   599  	return math.IsNaN(x) || x == float64(float32(x))
   600  }
   601
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