obj7.go

     1  // cmd/7l/noop.c, cmd/7l/obj.c, cmd/ld/pass.c from Vita Nuova.
     2  // https://bitbucket.org/plan9-from-bell-labs/9-cc/src/master/
     3  //
     4  // 	Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
     5  // 	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
     6  // 	Portions Copyright © 1997-1999 Vita Nuova Limited
     7  // 	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
     8  // 	Portions Copyright © 2004,2006 Bruce Ellis
     9  // 	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
    10  // 	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
    11  // 	Portions Copyright © 2009 The Go Authors. All rights reserved.
    12  //
    13  // Permission is hereby granted, free of charge, to any person obtaining a copy
    14  // of this software and associated documentation files (the "Software"), to deal
    15  // in the Software without restriction, including without limitation the rights
    16  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    17  // copies of the Software, and to permit persons to whom the Software is
    18  // furnished to do so, subject to the following conditions:
    19  //
    20  // The above copyright notice and this permission notice shall be included in
    21  // all copies or substantial portions of the Software.
    22  //
    23  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    24  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    25  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    26  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    27  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    28  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    29  // THE SOFTWARE.
    30  
    31  package arm64
    32  
    33  import (
    34  	"cmd/internal/obj"
    35  	"cmd/internal/objabi"
    36  	"cmd/internal/src"
    37  	"cmd/internal/sys"
    38  	"internal/abi"
    39  	"internal/buildcfg"
    40  	"log"
    41  	"math"
    42  )
    43  
    44  // zrReplace is the set of instructions for which $0 in the From operand
    45  // should be replaced with REGZERO.
    46  var zrReplace = map[obj.As]bool{
    47  	AMOVD:  true,
    48  	AMOVW:  true,
    49  	AMOVWU: true,
    50  	AMOVH:  true,
    51  	AMOVHU: true,
    52  	AMOVB:  true,
    53  	AMOVBU: true,
    54  	ASBC:   true,
    55  	ASBCW:  true,
    56  	ASBCS:  true,
    57  	ASBCSW: true,
    58  	AADC:   true,
    59  	AADCW:  true,
    60  	AADCS:  true,
    61  	AADCSW: true,
    62  	AFMOVD: true,
    63  	AFMOVS: true,
    64  	AMSR:   true,
    65  }
    66  
    67  func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
    68  	if c.ctxt.Flag_maymorestack != "" {
    69  		p = c.cursym.Func().SpillRegisterArgs(p, c.newprog)
    70  
    71  		// Save LR and make room for FP, REGCTXT. Leave room
    72  		// for caller's saved FP.
    73  		const frameSize = 32
    74  		p = obj.Appendp(p, c.newprog)
    75  		p.As = AMOVD
    76  		p.From.Type = obj.TYPE_REG
    77  		p.From.Reg = REGLINK
    78  		p.To.Type = obj.TYPE_MEM
    79  		p.Scond = C_XPRE
    80  		p.To.Offset = -frameSize
    81  		p.To.Reg = REGSP
    82  		p.Spadj = frameSize
    83  
    84  		// Save FP.
    85  		p = obj.Appendp(p, c.newprog)
    86  		p.As = AMOVD
    87  		p.From.Type = obj.TYPE_REG
    88  		p.From.Reg = REGFP
    89  		p.To.Type = obj.TYPE_MEM
    90  		p.To.Reg = REGSP
    91  		p.To.Offset = -8
    92  
    93  		p = obj.Appendp(p, c.newprog)
    94  		p.As = ASUB
    95  		p.From.Type = obj.TYPE_CONST
    96  		p.From.Offset = 8
    97  		p.Reg = REGSP
    98  		p.To.Type = obj.TYPE_REG
    99  		p.To.Reg = REGFP
   100  
   101  		// Save REGCTXT (for simplicity we do this whether or
   102  		// not we need it.)
   103  		p = obj.Appendp(p, c.newprog)
   104  		p.As = AMOVD
   105  		p.From.Type = obj.TYPE_REG
   106  		p.From.Reg = REGCTXT
   107  		p.To.Type = obj.TYPE_MEM
   108  		p.To.Reg = REGSP
   109  		p.To.Offset = 8
   110  
   111  		// BL maymorestack
   112  		p = obj.Appendp(p, c.newprog)
   113  		p.As = ABL
   114  		p.To.Type = obj.TYPE_BRANCH
   115  		// See ../x86/obj6.go
   116  		p.To.Sym = c.ctxt.LookupABI(c.ctxt.Flag_maymorestack, c.cursym.ABI())
   117  
   118  		// Restore REGCTXT.
   119  		p = obj.Appendp(p, c.newprog)
   120  		p.As = AMOVD
   121  		p.From.Type = obj.TYPE_MEM
   122  		p.From.Reg = REGSP
   123  		p.From.Offset = 8
   124  		p.To.Type = obj.TYPE_REG
   125  		p.To.Reg = REGCTXT
   126  
   127  		// Restore FP.
   128  		p = obj.Appendp(p, c.newprog)
   129  		p.As = AMOVD
   130  		p.From.Type = obj.TYPE_MEM
   131  		p.From.Reg = REGSP
   132  		p.From.Offset = -8
   133  		p.To.Type = obj.TYPE_REG
   134  		p.To.Reg = REGFP
   135  
   136  		// Restore LR and SP.
   137  		p = obj.Appendp(p, c.newprog)
   138  		p.As = AMOVD
   139  		p.From.Type = obj.TYPE_MEM
   140  		p.Scond = C_XPOST
   141  		p.From.Offset = frameSize
   142  		p.From.Reg = REGSP
   143  		p.To.Type = obj.TYPE_REG
   144  		p.To.Reg = REGLINK
   145  		p.Spadj = -frameSize
   146  
   147  		p = c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
   148  	}
   149  
   150  	// Jump back to here after morestack returns.
   151  	startPred := p
   152  
   153  	// MOV	g_stackguard(g), RT1
   154  	p = obj.Appendp(p, c.newprog)
   155  
   156  	p.As = AMOVD
   157  	p.From.Type = obj.TYPE_MEM
   158  	p.From.Reg = REGG
   159  	p.From.Offset = 2 * int64(c.ctxt.Arch.PtrSize) // G.stackguard0
   160  	if c.cursym.CFunc() {
   161  		p.From.Offset = 3 * int64(c.ctxt.Arch.PtrSize) // G.stackguard1
   162  	}
   163  	p.To.Type = obj.TYPE_REG
   164  	p.To.Reg = REGRT1
   165  
   166  	// Mark the stack bound check and morestack call async nonpreemptible.
   167  	// If we get preempted here, when resumed the preemption request is
   168  	// cleared, but we'll still call morestack, which will double the stack
   169  	// unnecessarily. See issue #35470.
   170  	p = c.ctxt.StartUnsafePoint(p, c.newprog)
   171  
   172  	q := (*obj.Prog)(nil)
   173  	if framesize <= abi.StackSmall {
   174  		// small stack: SP < stackguard
   175  		//	CMP	stackguard, SP
   176  
   177  		p = obj.Appendp(p, c.newprog)
   178  		p.As = ACMP
   179  		p.From.Type = obj.TYPE_REG
   180  		p.From.Reg = REGRT1
   181  		p.Reg = REGSP
   182  	} else if framesize <= abi.StackBig {
   183  		// large stack: SP-framesize < stackguard-StackSmall
   184  		//	SUB	$(framesize-StackSmall), SP, RT2
   185  		//	CMP	stackguard, RT2
   186  		p = obj.Appendp(p, c.newprog)
   187  
   188  		p.As = ASUB
   189  		p.From.Type = obj.TYPE_CONST
   190  		p.From.Offset = int64(framesize) - abi.StackSmall
   191  		p.Reg = REGSP
   192  		p.To.Type = obj.TYPE_REG
   193  		p.To.Reg = REGRT2
   194  
   195  		p = obj.Appendp(p, c.newprog)
   196  		p.As = ACMP
   197  		p.From.Type = obj.TYPE_REG
   198  		p.From.Reg = REGRT1
   199  		p.Reg = REGRT2
   200  	} else {
   201  		// Such a large stack we need to protect against underflow.
   202  		// The runtime guarantees SP > objabi.StackBig, but
   203  		// framesize is large enough that SP-framesize may
   204  		// underflow, causing a direct comparison with the
   205  		// stack guard to incorrectly succeed. We explicitly
   206  		// guard against underflow.
   207  		//
   208  		//	SUBS	$(framesize-StackSmall), SP, RT2
   209  		//	// On underflow, jump to morestack
   210  		//	BLO	label_of_call_to_morestack
   211  		//	CMP	stackguard, RT2
   212  
   213  		p = obj.Appendp(p, c.newprog)
   214  		p.As = ASUBS
   215  		p.From.Type = obj.TYPE_CONST
   216  		p.From.Offset = int64(framesize) - abi.StackSmall
   217  		p.Reg = REGSP
   218  		p.To.Type = obj.TYPE_REG
   219  		p.To.Reg = REGRT2
   220  
   221  		p = obj.Appendp(p, c.newprog)
   222  		q = p
   223  		p.As = ABLO
   224  		p.To.Type = obj.TYPE_BRANCH
   225  
   226  		p = obj.Appendp(p, c.newprog)
   227  		p.As = ACMP
   228  		p.From.Type = obj.TYPE_REG
   229  		p.From.Reg = REGRT1
   230  		p.Reg = REGRT2
   231  	}
   232  
   233  	// BLS	do-morestack
   234  	bls := obj.Appendp(p, c.newprog)
   235  	bls.As = ABLS
   236  	bls.To.Type = obj.TYPE_BRANCH
   237  
   238  	end := c.ctxt.EndUnsafePoint(bls, c.newprog, -1)
   239  
   240  	var last *obj.Prog
   241  	for last = c.cursym.Func().Text; last.Link != nil; last = last.Link {
   242  	}
   243  
   244  	// Now we are at the end of the function, but logically
   245  	// we are still in function prologue. We need to fix the
   246  	// SP data and PCDATA.
   247  	spfix := obj.Appendp(last, c.newprog)
   248  	spfix.As = obj.ANOP
   249  	spfix.Spadj = -framesize
   250  
   251  	pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
   252  	pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
   253  
   254  	if q != nil {
   255  		q.To.SetTarget(pcdata)
   256  	}
   257  	bls.To.SetTarget(pcdata)
   258  
   259  	spill := c.cursym.Func().SpillRegisterArgs(pcdata, c.newprog)
   260  
   261  	// MOV	LR, R3
   262  	movlr := obj.Appendp(spill, c.newprog)
   263  	movlr.As = AMOVD
   264  	movlr.From.Type = obj.TYPE_REG
   265  	movlr.From.Reg = REGLINK
   266  	movlr.To.Type = obj.TYPE_REG
   267  	movlr.To.Reg = REG_R3
   268  
   269  	debug := movlr
   270  	if false {
   271  		debug = obj.Appendp(debug, c.newprog)
   272  		debug.As = AMOVD
   273  		debug.From.Type = obj.TYPE_CONST
   274  		debug.From.Offset = int64(framesize)
   275  		debug.To.Type = obj.TYPE_REG
   276  		debug.To.Reg = REGTMP
   277  	}
   278  
   279  	// BL	runtime.morestack(SB)
   280  	call := obj.Appendp(debug, c.newprog)
   281  	call.As = ABL
   282  	call.To.Type = obj.TYPE_BRANCH
   283  	morestack := "runtime.morestack"
   284  	switch {
   285  	case c.cursym.CFunc():
   286  		morestack = "runtime.morestackc"
   287  	case !c.cursym.Func().Text.From.Sym.NeedCtxt():
   288  		morestack = "runtime.morestack_noctxt"
   289  	}
   290  	call.To.Sym = c.ctxt.Lookup(morestack)
   291  
   292  	// The instructions which unspill regs should be preemptible.
   293  	pcdata = c.ctxt.EndUnsafePoint(call, c.newprog, -1)
   294  	unspill := c.cursym.Func().UnspillRegisterArgs(pcdata, c.newprog)
   295  
   296  	// B	start
   297  	jmp := obj.Appendp(unspill, c.newprog)
   298  	jmp.As = AB
   299  	jmp.To.Type = obj.TYPE_BRANCH
   300  	jmp.To.SetTarget(startPred.Link)
   301  	jmp.Spadj = +framesize
   302  
   303  	return end
   304  }
   305  
   306  func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
   307  	c := ctxt7{ctxt: ctxt, newprog: newprog}
   308  
   309  	p.From.Class = 0
   310  	p.To.Class = 0
   311  
   312  	// Previously we rewrote $0 to ZR, but we have now removed this change.
   313  	// In order to be compatible with some previous legal instruction formats,
   314  	// reserve the previous conversion for some specific instructions.
   315  	if p.From.Type == obj.TYPE_CONST && p.From.Offset == 0 && zrReplace[p.As] {
   316  		p.From.Type = obj.TYPE_REG
   317  		p.From.Reg = REGZERO
   318  	}
   319  
   320  	// Rewrite BR/BL to symbol as TYPE_BRANCH.
   321  	switch p.As {
   322  	case AB, ABL, obj.ARET:
   323  		if p.To.Sym != nil {
   324  			p.To.Type = obj.TYPE_BRANCH
   325  		}
   326  		break
   327  	}
   328  
   329  	// Rewrite float and vector constants to values stored in memory.
   330  	switch p.As {
   331  	case AVMOVS:
   332  		if p.From.Type == obj.TYPE_CONST {
   333  			p.From.Type = obj.TYPE_MEM
   334  			p.From.Sym = c.ctxt.Int32Sym(p.From.Offset)
   335  			p.From.Name = obj.NAME_EXTERN
   336  			p.From.Offset = 0
   337  		}
   338  
   339  	case AVMOVD:
   340  		if p.From.Type == obj.TYPE_CONST {
   341  			p.From.Type = obj.TYPE_MEM
   342  			p.From.Sym = c.ctxt.Int64Sym(p.From.Offset)
   343  			p.From.Name = obj.NAME_EXTERN
   344  			p.From.Offset = 0
   345  		}
   346  
   347  	case AVMOVQ:
   348  		if p.From.Type == obj.TYPE_CONST {
   349  			p.From.Type = obj.TYPE_MEM
   350  			p.From.Sym = c.ctxt.Int128Sym(p.GetFrom3().Offset, p.From.Offset)
   351  			p.From.Name = obj.NAME_EXTERN
   352  			p.From.Offset = 0
   353  			p.RestArgs = nil
   354  		}
   355  
   356  	case AFMOVS:
   357  		if p.From.Type == obj.TYPE_FCONST {
   358  			f64 := p.From.Val.(float64)
   359  			f32 := float32(f64)
   360  			if c.chipfloat7(f64) > 0 {
   361  				break
   362  			}
   363  			if math.Float32bits(f32) == 0 {
   364  				p.From.Type = obj.TYPE_REG
   365  				p.From.Reg = REGZERO
   366  				break
   367  			}
   368  			p.From.Type = obj.TYPE_MEM
   369  			p.From.Sym = c.ctxt.Float32Sym(f32)
   370  			p.From.Name = obj.NAME_EXTERN
   371  			p.From.Offset = 0
   372  		}
   373  
   374  	case AFMOVD:
   375  		if p.From.Type == obj.TYPE_FCONST {
   376  			f64 := p.From.Val.(float64)
   377  			if c.chipfloat7(f64) > 0 {
   378  				break
   379  			}
   380  			if math.Float64bits(f64) == 0 {
   381  				p.From.Type = obj.TYPE_REG
   382  				p.From.Reg = REGZERO
   383  				break
   384  			}
   385  			p.From.Type = obj.TYPE_MEM
   386  			p.From.Sym = c.ctxt.Float64Sym(f64)
   387  			p.From.Name = obj.NAME_EXTERN
   388  			p.From.Offset = 0
   389  		}
   390  	}
   391  
   392  	if c.ctxt.Flag_dynlink {
   393  		c.rewriteToUseGot(p)
   394  	}
   395  }
   396  
   397  // Rewrite p, if necessary, to access global data via the global offset table.
   398  func (c *ctxt7) rewriteToUseGot(p *obj.Prog) {
   399  
   400  	// We only care about global data: NAME_EXTERN means a global
   401  	// symbol in the Go sense, and p.Sym.Local is true for a few
   402  	// internally defined symbols.
   403  	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
   404  		// MOVD $sym, Rx becomes MOVD sym@GOT, Rx
   405  		// MOVD $sym+<off>, Rx becomes MOVD sym@GOT, Rx; ADD <off>, Rx
   406  		if p.As != AMOVD {
   407  			c.ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
   408  		}
   409  		if p.To.Type != obj.TYPE_REG {
   410  			c.ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
   411  		}
   412  		p.From.Type = obj.TYPE_MEM
   413  		p.From.Name = obj.NAME_GOTREF
   414  		if p.From.Offset != 0 {
   415  			q := obj.Appendp(p, c.newprog)
   416  			q.As = AADD
   417  			q.From.Type = obj.TYPE_CONST
   418  			q.From.Offset = p.From.Offset
   419  			q.To = p.To
   420  			p.From.Offset = 0
   421  		}
   422  	}
   423  	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
   424  		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
   425  	}
   426  	var source *obj.Addr
   427  	// MOVx sym, Ry becomes MOVD sym@GOT, REGTMP; MOVx (REGTMP), Ry
   428  	// MOVx Ry, sym becomes MOVD sym@GOT, REGTMP; MOVD Ry, (REGTMP)
   429  	// An addition may be inserted between the two MOVs if there is an offset.
   430  	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
   431  		if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
   432  			c.ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
   433  		}
   434  		source = &p.From
   435  	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
   436  		source = &p.To
   437  	} else {
   438  		return
   439  	}
   440  	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
   441  		return
   442  	}
   443  	if source.Sym.Type == objabi.STLSBSS {
   444  		return
   445  	}
   446  	if source.Type != obj.TYPE_MEM {
   447  		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
   448  	}
   449  	p1 := obj.Appendp(p, c.newprog)
   450  	p2 := obj.Appendp(p1, c.newprog)
   451  	p1.As = AMOVD
   452  	p1.From.Type = obj.TYPE_MEM
   453  	p1.From.Sym = source.Sym
   454  	p1.From.Name = obj.NAME_GOTREF
   455  	p1.To.Type = obj.TYPE_REG
   456  	p1.To.Reg = REGTMP
   457  
   458  	p2.As = p.As
   459  	p2.From = p.From
   460  	p2.To = p.To
   461  	if p.From.Name == obj.NAME_EXTERN {
   462  		p2.From.Reg = REGTMP
   463  		p2.From.Name = obj.NAME_NONE
   464  		p2.From.Sym = nil
   465  	} else if p.To.Name == obj.NAME_EXTERN {
   466  		p2.To.Reg = REGTMP
   467  		p2.To.Name = obj.NAME_NONE
   468  		p2.To.Sym = nil
   469  	} else {
   470  		return
   471  	}
   472  	obj.Nopout(p)
   473  }
   474  
   475  func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
   476  	if cursym.Func().Text == nil || cursym.Func().Text.Link == nil {
   477  		return
   478  	}
   479  
   480  	c := ctxt7{ctxt: ctxt, newprog: newprog, cursym: cursym}
   481  
   482  	p := c.cursym.Func().Text
   483  	textstksiz := p.To.Offset
   484  	if textstksiz == -8 {
   485  		// Historical way to mark NOFRAME.
   486  		p.From.Sym.Set(obj.AttrNoFrame, true)
   487  		textstksiz = 0
   488  	}
   489  	if textstksiz < 0 {
   490  		c.ctxt.Diag("negative frame size %d - did you mean NOFRAME?", textstksiz)
   491  	}
   492  	if p.From.Sym.NoFrame() {
   493  		if textstksiz != 0 {
   494  			c.ctxt.Diag("NOFRAME functions must have a frame size of 0, not %d", textstksiz)
   495  		}
   496  	}
   497  
   498  	c.cursym.Func().Args = p.To.Val.(int32)
   499  	c.cursym.Func().Locals = int32(textstksiz)
   500  
   501  	/*
   502  	 * find leaf subroutines
   503  	 */
   504  	for p := c.cursym.Func().Text; p != nil; p = p.Link {
   505  		switch p.As {
   506  		case obj.ATEXT:
   507  			p.Mark |= LEAF
   508  
   509  		case ABL:
   510  			c.cursym.Func().Text.Mark &^= LEAF
   511  		}
   512  	}
   513  
   514  	var q *obj.Prog
   515  	var q1 *obj.Prog
   516  	for p := c.cursym.Func().Text; p != nil; p = p.Link {
   517  		o := p.As
   518  		switch o {
   519  		case obj.ATEXT:
   520  			c.cursym.Func().Text = p
   521  			c.autosize = int32(textstksiz)
   522  
   523  			if p.Mark&LEAF != 0 && c.autosize == 0 {
   524  				// A leaf function with no locals has no frame.
   525  				p.From.Sym.Set(obj.AttrNoFrame, true)
   526  			}
   527  
   528  			if !p.From.Sym.NoFrame() {
   529  				// If there is a stack frame at all, it includes
   530  				// space to save the LR.
   531  				c.autosize += 8
   532  			}
   533  
   534  			if c.autosize != 0 {
   535  				extrasize := int32(0)
   536  				if c.autosize%16 == 8 {
   537  					// Allocate extra 8 bytes on the frame top to save FP
   538  					extrasize = 8
   539  				} else if c.autosize&(16-1) == 0 {
   540  					// Allocate extra 16 bytes to save FP for the old frame whose size is 8 mod 16
   541  					extrasize = 16
   542  				} else {
   543  					c.ctxt.Diag("%v: unaligned frame size %d - must be 16 aligned", p, c.autosize-8)
   544  				}
   545  				c.autosize += extrasize
   546  				c.cursym.Func().Locals += extrasize
   547  
   548  				// low 32 bits for autosize
   549  				// high 32 bits for extrasize
   550  				p.To.Offset = int64(c.autosize) | int64(extrasize)<<32
   551  			} else {
   552  				// NOFRAME
   553  				p.To.Offset = 0
   554  			}
   555  
   556  			if c.autosize == 0 && c.cursym.Func().Text.Mark&LEAF == 0 {
   557  				if c.ctxt.Debugvlog {
   558  					c.ctxt.Logf("save suppressed in: %s\n", c.cursym.Func().Text.From.Sym.Name)
   559  				}
   560  				c.cursym.Func().Text.Mark |= LEAF
   561  			}
   562  
   563  			if cursym.Func().Text.Mark&LEAF != 0 {
   564  				cursym.Set(obj.AttrLeaf, true)
   565  				if p.From.Sym.NoFrame() {
   566  					break
   567  				}
   568  			}
   569  
   570  			if p.Mark&LEAF != 0 && c.autosize < abi.StackSmall {
   571  				// A leaf function with a small stack can be marked
   572  				// NOSPLIT, avoiding a stack check.
   573  				p.From.Sym.Set(obj.AttrNoSplit, true)
   574  			}
   575  
   576  			if !p.From.Sym.NoSplit() {
   577  				p = c.stacksplit(p, c.autosize) // emit split check
   578  			}
   579  
   580  			var prologueEnd *obj.Prog
   581  
   582  			aoffset := c.autosize
   583  			if aoffset > 0xf0 {
   584  				// MOVD.W offset variant range is -0x100 to 0xf8, SP should be 16-byte aligned.
   585  				// so the maximum aoffset value is 0xf0.
   586  				aoffset = 0xf0
   587  			}
   588  
   589  			// Frame is non-empty. Make sure to save link register, even if
   590  			// it is a leaf function, so that traceback works.
   591  			q = p
   592  			if c.autosize > aoffset {
   593  				// Frame size is too large for a MOVD.W instruction. Store the frame pointer
   594  				// register and link register before decrementing SP, so if a signal comes
   595  				// during the execution of the function prologue, the traceback code will
   596  				// not see a half-updated stack frame.
   597  
   598  				// SUB $autosize, RSP, R20
   599  				q1 = obj.Appendp(q, c.newprog)
   600  				q1.Pos = p.Pos
   601  				q1.As = ASUB
   602  				q1.From.Type = obj.TYPE_CONST
   603  				q1.From.Offset = int64(c.autosize)
   604  				q1.Reg = REGSP
   605  				q1.To.Type = obj.TYPE_REG
   606  				q1.To.Reg = REG_R20
   607  
   608  				prologueEnd = q1
   609  
   610  				// STP (R29, R30), -8(R20)
   611  				q1 = obj.Appendp(q1, c.newprog)
   612  				q1.Pos = p.Pos
   613  				q1.As = ASTP
   614  				q1.From.Type = obj.TYPE_REGREG
   615  				q1.From.Reg = REGFP
   616  				q1.From.Offset = REGLINK
   617  				q1.To.Type = obj.TYPE_MEM
   618  				q1.To.Reg = REG_R20
   619  				q1.To.Offset = -8
   620  
   621  				// This is not async preemptible, as if we open a frame
   622  				// at the current SP, it will clobber the saved LR.
   623  				q1 = c.ctxt.StartUnsafePoint(q1, c.newprog)
   624  
   625  				// MOVD R20, RSP
   626  				q1 = obj.Appendp(q1, c.newprog)
   627  				q1.Pos = p.Pos
   628  				q1.As = AMOVD
   629  				q1.From.Type = obj.TYPE_REG
   630  				q1.From.Reg = REG_R20
   631  				q1.To.Type = obj.TYPE_REG
   632  				q1.To.Reg = REGSP
   633  				q1.Spadj = c.autosize
   634  
   635  				q1 = c.ctxt.EndUnsafePoint(q1, c.newprog, -1)
   636  
   637  				if buildcfg.GOOS == "ios" {
   638  					// iOS does not support SA_ONSTACK. We will run the signal handler
   639  					// on the G stack. If we write below SP, it may be clobbered by
   640  					// the signal handler. So we save FP and LR after decrementing SP.
   641  					// STP (R29, R30), -8(RSP)
   642  					q1 = obj.Appendp(q1, c.newprog)
   643  					q1.Pos = p.Pos
   644  					q1.As = ASTP
   645  					q1.From.Type = obj.TYPE_REGREG
   646  					q1.From.Reg = REGFP
   647  					q1.From.Offset = REGLINK
   648  					q1.To.Type = obj.TYPE_MEM
   649  					q1.To.Reg = REGSP
   650  					q1.To.Offset = -8
   651  				}
   652  			} else {
   653  				// small frame, update SP and save LR in a single MOVD.W instruction.
   654  				// So if a signal comes during the execution of the function prologue,
   655  				// the traceback code will not see a half-updated stack frame.
   656  				// Also, on Linux, in a cgo binary we may get a SIGSETXID signal
   657  				// early on before the signal stack is set, as glibc doesn't allow
   658  				// us to block SIGSETXID. So it is important that we don't write below
   659  				// the SP until the signal stack is set.
   660  				// Luckily, all the functions from thread entry to setting the signal
   661  				// stack have small frames.
   662  				q1 = obj.Appendp(q, c.newprog)
   663  				q1.As = AMOVD
   664  				q1.Pos = p.Pos
   665  				q1.From.Type = obj.TYPE_REG
   666  				q1.From.Reg = REGLINK
   667  				q1.To.Type = obj.TYPE_MEM
   668  				q1.Scond = C_XPRE
   669  				q1.To.Offset = int64(-aoffset)
   670  				q1.To.Reg = REGSP
   671  				q1.Spadj = aoffset
   672  
   673  				prologueEnd = q1
   674  
   675  				// Frame pointer.
   676  				q1 = obj.Appendp(q1, c.newprog)
   677  				q1.Pos = p.Pos
   678  				q1.As = AMOVD
   679  				q1.From.Type = obj.TYPE_REG
   680  				q1.From.Reg = REGFP
   681  				q1.To.Type = obj.TYPE_MEM
   682  				q1.To.Reg = REGSP
   683  				q1.To.Offset = -8
   684  			}
   685  
   686  			prologueEnd.Pos = prologueEnd.Pos.WithXlogue(src.PosPrologueEnd)
   687  
   688  			q1 = obj.Appendp(q1, c.newprog)
   689  			q1.Pos = p.Pos
   690  			q1.As = ASUB
   691  			q1.From.Type = obj.TYPE_CONST
   692  			q1.From.Offset = 8
   693  			q1.Reg = REGSP
   694  			q1.To.Type = obj.TYPE_REG
   695  			q1.To.Reg = REGFP
   696  
   697  		case obj.ARET:
   698  			nocache(p)
   699  			if p.From.Type == obj.TYPE_CONST {
   700  				c.ctxt.Diag("using BECOME (%v) is not supported!", p)
   701  				break
   702  			}
   703  
   704  			retJMP, retReg := p.To.Sym, p.To.Reg
   705  			if retReg == 0 {
   706  				retReg = REGLINK
   707  			}
   708  			p.To = obj.Addr{}
   709  			aoffset := c.autosize
   710  			if c.cursym.Func().Text.Mark&LEAF != 0 {
   711  				if aoffset != 0 {
   712  					// Restore frame pointer.
   713  					// ADD $framesize-8, RSP, R29
   714  					p.As = AADD
   715  					p.From.Type = obj.TYPE_CONST
   716  					p.From.Offset = int64(c.autosize) - 8
   717  					p.Reg = REGSP
   718  					p.To.Type = obj.TYPE_REG
   719  					p.To.Reg = REGFP
   720  
   721  					// Pop stack frame.
   722  					// ADD $framesize, RSP, RSP
   723  					p = obj.Appendp(p, c.newprog)
   724  					p.As = AADD
   725  					p.From.Type = obj.TYPE_CONST
   726  					p.From.Offset = int64(c.autosize)
   727  					p.To.Type = obj.TYPE_REG
   728  					p.To.Reg = REGSP
   729  					p.Spadj = -c.autosize
   730  				}
   731  			} else if aoffset <= 0xF0 {
   732  				// small frame, restore LR and update SP in a single MOVD.P instruction.
   733  				// There is no correctness issue to use a single LDP for LR and FP,
   734  				// but the instructions are not pattern matched with the prologue's
   735  				// MOVD.W and MOVD, which may cause performance issue in
   736  				// store-forwarding.
   737  
   738  				// MOVD -8(RSP), R29
   739  				p.As = AMOVD
   740  				p.From.Type = obj.TYPE_MEM
   741  				p.From.Reg = REGSP
   742  				p.From.Offset = -8
   743  				p.To.Type = obj.TYPE_REG
   744  				p.To.Reg = REGFP
   745  				p = obj.Appendp(p, c.newprog)
   746  
   747  				// MOVD.P offset(RSP), R30
   748  				p.As = AMOVD
   749  				p.From.Type = obj.TYPE_MEM
   750  				p.Scond = C_XPOST
   751  				p.From.Offset = int64(aoffset)
   752  				p.From.Reg = REGSP
   753  				p.To.Type = obj.TYPE_REG
   754  				p.To.Reg = REGLINK
   755  				p.Spadj = -aoffset
   756  			} else {
   757  				// LDP -8(RSP), (R29, R30)
   758  				p.As = ALDP
   759  				p.From.Type = obj.TYPE_MEM
   760  				p.From.Offset = -8
   761  				p.From.Reg = REGSP
   762  				p.To.Type = obj.TYPE_REGREG
   763  				p.To.Reg = REGFP
   764  				p.To.Offset = REGLINK
   765  
   766  				if aoffset < 1<<12 {
   767  					// ADD $aoffset, RSP, RSP
   768  					q = newprog()
   769  					q.As = AADD
   770  					q.From.Type = obj.TYPE_CONST
   771  					q.From.Offset = int64(aoffset)
   772  					q.To.Type = obj.TYPE_REG
   773  					q.To.Reg = REGSP
   774  					q.Spadj = -aoffset
   775  					q.Pos = p.Pos
   776  					q.Link = p.Link
   777  					p.Link = q
   778  					p = q
   779  				} else {
   780  					// Put frame size in a separate register and
   781  					// add it in with a single instruction,
   782  					// so we never have a partial frame during
   783  					// the epilog. See issue 73259.
   784  
   785  					// MOVD $aoffset, REGTMP
   786  					q = newprog()
   787  					q.As = AMOVD
   788  					q.From.Type = obj.TYPE_CONST
   789  					q.From.Offset = int64(aoffset)
   790  					q.To.Type = obj.TYPE_REG
   791  					q.To.Reg = REGTMP
   792  					q.Pos = p.Pos
   793  					q.Link = p.Link
   794  					p.Link = q
   795  					p = q
   796  					// ADD REGTMP, RSP, RSP
   797  					q = newprog()
   798  					q.As = AADD
   799  					q.From.Type = obj.TYPE_REG
   800  					q.From.Reg = REGTMP
   801  					q.To.Type = obj.TYPE_REG
   802  					q.To.Reg = REGSP
   803  					q.Spadj = -aoffset
   804  					q.Pos = p.Pos
   805  					q.Link = p.Link
   806  					p.Link = q
   807  					p = q
   808  				}
   809  			}
   810  
   811  			// If enabled, this code emits 'MOV PC, R27' before every 'MOV LR, PC',
   812  			// so that if you are debugging a low-level crash where PC and LR are zero,
   813  			// you can look at R27 to see what jumped to the zero.
   814  			// This is useful when bringing up Go on a new system.
   815  			// (There is similar code in ../ppc64/obj9.go:/if.false.)
   816  			const debugRETZERO = false
   817  			if debugRETZERO {
   818  				if p.As != obj.ARET {
   819  					q = newprog()
   820  					q.Pos = p.Pos
   821  					q.Link = p.Link
   822  					p.Link = q
   823  					p = q
   824  				}
   825  				p.As = AADR
   826  				p.From.Type = obj.TYPE_BRANCH
   827  				p.From.Offset = 0
   828  				p.To.Type = obj.TYPE_REG
   829  				p.To.Reg = REGTMP
   830  
   831  			}
   832  
   833  			if p.As != obj.ARET {
   834  				q = newprog()
   835  				q.Pos = p.Pos
   836  				q.Link = p.Link
   837  				p.Link = q
   838  				p = q
   839  			}
   840  
   841  			if retJMP != nil {
   842  				p.As = AB
   843  				p.To.Type = obj.TYPE_BRANCH
   844  				p.To.Sym = retJMP
   845  				p.Spadj = +c.autosize
   846  				break
   847  			}
   848  
   849  			p.As = obj.ARET
   850  			p.To.Type = obj.TYPE_MEM
   851  			p.To.Offset = 0
   852  			p.To.Reg = retReg
   853  			p.Spadj = +c.autosize
   854  
   855  		case AADD, ASUB:
   856  			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
   857  				if p.As == AADD {
   858  					p.Spadj = int32(-p.From.Offset)
   859  				} else {
   860  					p.Spadj = int32(+p.From.Offset)
   861  				}
   862  			}
   863  
   864  		case obj.AGETCALLERPC:
   865  			if cursym.Leaf() {
   866  				/* MOVD LR, Rd */
   867  				p.As = AMOVD
   868  				p.From.Type = obj.TYPE_REG
   869  				p.From.Reg = REGLINK
   870  			} else {
   871  				/* MOVD (RSP), Rd */
   872  				p.As = AMOVD
   873  				p.From.Type = obj.TYPE_MEM
   874  				p.From.Reg = REGSP
   875  			}
   876  		}
   877  		if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.Spadj == 0 {
   878  			f := c.cursym.Func()
   879  			if f.FuncFlag&abi.FuncFlagSPWrite == 0 {
   880  				c.cursym.Func().FuncFlag |= abi.FuncFlagSPWrite
   881  				if ctxt.Debugvlog || !ctxt.IsAsm {
   882  					ctxt.Logf("auto-SPWRITE: %s %v\n", c.cursym.Name, p)
   883  					if !ctxt.IsAsm {
   884  						ctxt.Diag("invalid auto-SPWRITE in non-assembly")
   885  						ctxt.DiagFlush()
   886  						log.Fatalf("bad SPWRITE")
   887  					}
   888  				}
   889  			}
   890  		}
   891  		if p.From.Type == obj.TYPE_SHIFT && (p.To.Reg == REG_RSP || p.Reg == REG_RSP) {
   892  			offset := p.From.Offset
   893  			op := offset & (3 << 22)
   894  			if op != SHIFT_LL {
   895  				ctxt.Diag("illegal combination: %v", p)
   896  			}
   897  			r := (offset >> 16) & 31
   898  			shift := (offset >> 10) & 63
   899  			if shift > 4 {
   900  				// the shift amount is out of range, in order to avoid repeated error
   901  				// reportings, don't call ctxt.Diag, because asmout case 27 has the
   902  				// same check.
   903  				shift = 7
   904  			}
   905  			p.From.Type = obj.TYPE_REG
   906  			p.From.Reg = int16(REG_LSL + r + (shift&7)<<5)
   907  			p.From.Offset = 0
   908  		}
   909  	}
   910  }
   911  
   912  func nocache(p *obj.Prog) {
   913  	p.Optab = 0
   914  	p.From.Class = 0
   915  	p.To.Class = 0
   916  }
   917  
   918  var unaryDst = map[obj.As]bool{
   919  	AWORD:  true,
   920  	ADWORD: true,
   921  	ABL:    true,
   922  	AB:     true,
   923  	ACLREX: true,
   924  }
   925  
   926  var Linkarm64 = obj.LinkArch{
   927  	Arch:           sys.ArchARM64,
   928  	Init:           buildop,
   929  	Preprocess:     preprocess,
   930  	Assemble:       span7,
   931  	Progedit:       progedit,
   932  	UnaryDst:       unaryDst,
   933  	DWARFRegisters: ARM64DWARFRegisters,
   934  }
   935
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