obj9.go

     1  // cmd/9l/noop.c, cmd/9l/pass.c, cmd/9l/span.c from Vita Nuova.
     2  //
     3  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     4  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
     5  //	Portions Copyright © 1997-1999 Vita Nuova Limited
     6  //	Portions Copyright © 2000-2008 Vita Nuova Holdings Limited (www.vitanuova.com)
     7  //	Portions Copyright © 2004,2006 Bruce Ellis
     8  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
     9  //	Revisions Copyright © 2000-2008 Lucent Technologies Inc. and others
    10  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
    11  //
    12  // Permission is hereby granted, free of charge, to any person obtaining a copy
    13  // of this software and associated documentation files (the "Software"), to deal
    14  // in the Software without restriction, including without limitation the rights
    15  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    16  // copies of the Software, and to permit persons to whom the Software is
    17  // furnished to do so, subject to the following conditions:
    18  //
    19  // The above copyright notice and this permission notice shall be included in
    20  // all copies or substantial portions of the Software.
    21  //
    22  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    23  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    24  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    25  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    26  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    27  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    28  // THE SOFTWARE.
    29  
    30  package ppc64
    31  
    32  import (
    33  	"cmd/internal/obj"
    34  	"cmd/internal/objabi"
    35  	"cmd/internal/src"
    36  	"cmd/internal/sys"
    37  	"internal/abi"
    38  	"internal/buildcfg"
    39  	"log"
    40  	"math"
    41  	"math/bits"
    42  	"strings"
    43  )
    44  
    45  // Test if this value can encoded as a mask for
    46  // li -1, rx; rlic rx,rx,sh,mb.
    47  // Masks can also extend from the msb and wrap to
    48  // the lsb too. That is, the valid masks are 32 bit strings
    49  // of the form: 0..01..10..0 or 1..10..01..1 or 1...1
    50  func isPPC64DoublewordRotateMask(v64 int64) bool {
    51  	// Isolate rightmost 1 (if none 0) and add.
    52  	v := uint64(v64)
    53  	vp := (v & -v) + v
    54  	// Likewise, for the wrapping case.
    55  	vn := ^v
    56  	vpn := (vn & -vn) + vn
    57  	return (v&vp == 0 || vn&vpn == 0) && v != 0
    58  }
    59  
    60  // Encode a doubleword rotate mask into mb (mask begin) and
    61  // me (mask end, inclusive). Note, POWER ISA labels bits in
    62  // big endian order.
    63  func encodePPC64RLDCMask(mask int64) (mb, me int) {
    64  	// Determine boundaries and then decode them
    65  	mb = bits.LeadingZeros64(uint64(mask))
    66  	me = 64 - bits.TrailingZeros64(uint64(mask))
    67  	mbn := bits.LeadingZeros64(^uint64(mask))
    68  	men := 64 - bits.TrailingZeros64(^uint64(mask))
    69  	// Check for a wrapping mask (e.g bits at 0 and 63)
    70  	if mb == 0 && me == 64 {
    71  		// swap the inverted values
    72  		mb, me = men, mbn
    73  	}
    74  	// Note, me is inclusive.
    75  	return mb, me - 1
    76  }
    77  
    78  // Is this a symbol which should never have a TOC prologue generated?
    79  // These are special functions which should not have a TOC regeneration
    80  // prologue.
    81  func isNOTOCfunc(name string) bool {
    82  	switch {
    83  	case name == "runtime.duffzero":
    84  		return true
    85  	case name == "runtime.duffcopy":
    86  		return true
    87  	case strings.HasPrefix(name, "runtime.elf_"):
    88  		return true
    89  	default:
    90  		return false
    91  	}
    92  }
    93  
    94  // Try converting FMOVD/FMOVS to XXSPLTIDP. If it is converted,
    95  // return true.
    96  func convertFMOVtoXXSPLTIDP(p *obj.Prog) bool {
    97  	if p.From.Type != obj.TYPE_FCONST || buildcfg.GOPPC64 < 10 {
    98  		return false
    99  	}
   100  	v := p.From.Val.(float64)
   101  	if float64(float32(v)) != v {
   102  		return false
   103  	}
   104  	// Secondly, is this value a normal value?
   105  	ival := int64(math.Float32bits(float32(v)))
   106  	isDenorm := ival&0x7F800000 == 0 && ival&0x007FFFFF != 0
   107  	if !isDenorm {
   108  		p.As = AXXSPLTIDP
   109  		p.From.Type = obj.TYPE_CONST
   110  		p.From.Offset = ival
   111  		// Convert REG_Fx into equivalent REG_VSx
   112  		p.To.Reg = REG_VS0 + (p.To.Reg & 31)
   113  	}
   114  	return !isDenorm
   115  }
   116  
   117  func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
   118  	p.From.Class = 0
   119  	p.To.Class = 0
   120  
   121  	c := ctxt9{ctxt: ctxt, newprog: newprog}
   122  
   123  	// Rewrite BR/BL to symbol as TYPE_BRANCH.
   124  	switch p.As {
   125  	case ABR,
   126  		ABL,
   127  		obj.ARET,
   128  		obj.ADUFFZERO,
   129  		obj.ADUFFCOPY:
   130  		if p.To.Sym != nil {
   131  			p.To.Type = obj.TYPE_BRANCH
   132  		}
   133  	}
   134  
   135  	// Rewrite float constants to values stored in memory.
   136  	switch p.As {
   137  	case AFMOVS:
   138  		if p.From.Type == obj.TYPE_FCONST && !convertFMOVtoXXSPLTIDP(p) {
   139  			f32 := float32(p.From.Val.(float64))
   140  			p.From.Type = obj.TYPE_MEM
   141  			p.From.Sym = ctxt.Float32Sym(f32)
   142  			p.From.Name = obj.NAME_EXTERN
   143  			p.From.Offset = 0
   144  		}
   145  
   146  	case AFMOVD:
   147  		if p.From.Type == obj.TYPE_FCONST {
   148  			f64 := p.From.Val.(float64)
   149  			// Constant not needed in memory for float +/- 0
   150  			if f64 != 0 && !convertFMOVtoXXSPLTIDP(p) {
   151  				p.From.Type = obj.TYPE_MEM
   152  				p.From.Sym = ctxt.Float64Sym(f64)
   153  				p.From.Name = obj.NAME_EXTERN
   154  				p.From.Offset = 0
   155  			}
   156  		}
   157  
   158  	case AMOVW, AMOVWZ:
   159  		// Note, for backwards compatibility, MOVW $const, Rx and MOVWZ $const, Rx are identical.
   160  		if p.From.Type == obj.TYPE_CONST && p.From.Offset != 0 && p.From.Offset&0xFFFF == 0 {
   161  			// This is a constant shifted 16 bits to the left, convert it to ADDIS/ORIS $const,...
   162  			p.As = AADDIS
   163  			// Use ORIS for large constants which should not be sign extended.
   164  			if p.From.Offset >= 0x80000000 {
   165  				p.As = AORIS
   166  			}
   167  			p.Reg = REG_R0
   168  			p.From.Offset >>= 16
   169  		}
   170  
   171  	case AMOVD:
   172  		// Skip this opcode if it is not a constant load.
   173  		if p.From.Type != obj.TYPE_CONST || p.From.Name != obj.NAME_NONE || p.From.Reg != 0 {
   174  			break
   175  		}
   176  
   177  		// 32b constants (signed and unsigned) can be generated via 1 or 2 instructions. They can be assembled directly.
   178  		isS32 := int64(int32(p.From.Offset)) == p.From.Offset
   179  		isU32 := uint64(uint32(p.From.Offset)) == uint64(p.From.Offset)
   180  		// If prefixed instructions are supported, a 34b signed constant can be generated by one pli instruction.
   181  		isS34 := pfxEnabled && (p.From.Offset<<30)>>30 == p.From.Offset
   182  
   183  		// Try converting MOVD $const,Rx into ADDIS/ORIS $s32>>16,R0,Rx
   184  		switch {
   185  		case isS32 && p.From.Offset&0xFFFF == 0 && p.From.Offset != 0:
   186  			p.As = AADDIS
   187  			p.From.Offset >>= 16
   188  			p.Reg = REG_R0
   189  
   190  		case isU32 && p.From.Offset&0xFFFF == 0 && p.From.Offset != 0:
   191  			p.As = AORIS
   192  			p.From.Offset >>= 16
   193  			p.Reg = REG_R0
   194  
   195  		case isS32 || isU32 || isS34:
   196  			// The assembler can generate this opcode in 1 (on Power10) or 2 opcodes.
   197  
   198  		// Otherwise, see if the large constant can be generated with 2 instructions. If not, load it from memory.
   199  		default:
   200  			// Is this a shifted 16b constant? If so, rewrite it to avoid a creating and loading a constant.
   201  			val := p.From.Offset
   202  			shift := bits.TrailingZeros64(uint64(val))
   203  			mask := int64(0xFFFF) << shift
   204  			if val&mask == val || (val>>(shift+16) == -1 && (val>>shift)<<shift == val) {
   205  				// Rewrite this value into MOVD $const>>shift, Rto; SLD $shift, Rto
   206  				q := obj.Appendp(p, c.newprog)
   207  				q.As = ASLD
   208  				q.From.SetConst(int64(shift))
   209  				q.To = p.To
   210  				p.From.Offset >>= shift
   211  				p = q
   212  			} else if isPPC64DoublewordRotateMask(val) {
   213  				// This constant is a mask value, generate MOVD $-1, Rto; RLDIC Rto, ^me, mb, Rto
   214  				mb, me := encodePPC64RLDCMask(val)
   215  				q := obj.Appendp(p, c.newprog)
   216  				q.As = ARLDC
   217  				q.AddRestSourceConst((^int64(me)) & 0x3F)
   218  				q.AddRestSourceConst(int64(mb))
   219  				q.From = p.To
   220  				q.To = p.To
   221  				p.From.Offset = -1
   222  				p = q
   223  			} else {
   224  				// Load the constant from memory.
   225  				p.From.Type = obj.TYPE_MEM
   226  				p.From.Sym = ctxt.Int64Sym(p.From.Offset)
   227  				p.From.Name = obj.NAME_EXTERN
   228  				p.From.Offset = 0
   229  			}
   230  		}
   231  	}
   232  
   233  	switch p.As {
   234  	// Rewrite SUB constants into ADD.
   235  	case ASUBC:
   236  		if p.From.Type == obj.TYPE_CONST {
   237  			p.From.Offset = -p.From.Offset
   238  			p.As = AADDC
   239  		}
   240  
   241  	case ASUBCCC:
   242  		if p.From.Type == obj.TYPE_CONST {
   243  			p.From.Offset = -p.From.Offset
   244  			p.As = AADDCCC
   245  		}
   246  
   247  	case ASUB:
   248  		if p.From.Type != obj.TYPE_CONST {
   249  			break
   250  		}
   251  		// Rewrite SUB $const,... into ADD $-const,...
   252  		p.From.Offset = -p.From.Offset
   253  		p.As = AADD
   254  		// This is now an ADD opcode, try simplifying it below.
   255  		fallthrough
   256  
   257  	// Rewrite ADD/OR/XOR/ANDCC $const,... forms into ADDIS/ORIS/XORIS/ANDISCC
   258  	case AADD:
   259  		// Don't rewrite if this is not adding a constant value, or is not an int32
   260  		if p.From.Type != obj.TYPE_CONST || p.From.Offset == 0 || int64(int32(p.From.Offset)) != p.From.Offset {
   261  			break
   262  		}
   263  		if p.From.Offset&0xFFFF == 0 {
   264  			// The constant can be added using ADDIS
   265  			p.As = AADDIS
   266  			p.From.Offset >>= 16
   267  		} else if buildcfg.GOPPC64 >= 10 {
   268  			// Let the assembler generate paddi for large constants.
   269  			break
   270  		} else if (p.From.Offset < -0x8000 && int64(int32(p.From.Offset)) == p.From.Offset) || (p.From.Offset > 0xFFFF && p.From.Offset < 0x7FFF8000) {
   271  			// For a constant x, 0xFFFF (UINT16_MAX) < x < 0x7FFF8000 or -0x80000000 (INT32_MIN) <= x < -0x8000 (INT16_MIN)
   272  			// This is not done for 0x7FFF < x < 0x10000; the assembler will generate a slightly faster instruction sequence.
   273  			//
   274  			// The constant x can be rewritten as ADDIS + ADD as follows:
   275  			//     ADDIS $x>>16 + (x>>15)&1, rX, rY
   276  			//     ADD   $int64(int16(x)), rY, rY
   277  			// The range is slightly asymmetric as 0x7FFF8000 and above overflow the sign bit, whereas for
   278  			// negative values, this would happen with constant values between -1 and -32768 which can
   279  			// assemble into a single addi.
   280  			is := p.From.Offset>>16 + (p.From.Offset>>15)&1
   281  			i := int64(int16(p.From.Offset))
   282  			p.As = AADDIS
   283  			p.From.Offset = is
   284  			q := obj.Appendp(p, c.newprog)
   285  			q.As = AADD
   286  			q.From.SetConst(i)
   287  			q.Reg = p.To.Reg
   288  			q.To = p.To
   289  			p = q
   290  		}
   291  	case AOR:
   292  		if p.From.Type == obj.TYPE_CONST && uint64(p.From.Offset)&0xFFFFFFFF0000FFFF == 0 && p.From.Offset != 0 {
   293  			p.As = AORIS
   294  			p.From.Offset >>= 16
   295  		}
   296  	case AXOR:
   297  		if p.From.Type == obj.TYPE_CONST && uint64(p.From.Offset)&0xFFFFFFFF0000FFFF == 0 && p.From.Offset != 0 {
   298  			p.As = AXORIS
   299  			p.From.Offset >>= 16
   300  		}
   301  	case AANDCC:
   302  		if p.From.Type == obj.TYPE_CONST && uint64(p.From.Offset)&0xFFFFFFFF0000FFFF == 0 && p.From.Offset != 0 {
   303  			p.As = AANDISCC
   304  			p.From.Offset >>= 16
   305  		}
   306  
   307  	// To maintain backwards compatibility, we accept some 4 argument usage of
   308  	// several opcodes which was likely not intended, but did work. These are not
   309  	// added to optab to avoid the chance this behavior might be used with newer
   310  	// instructions.
   311  	//
   312  	// Rewrite argument ordering like "ADDEX R3, $3, R4, R5" into
   313  	//                                "ADDEX R3, R4, $3, R5"
   314  	case AVSHASIGMAW, AVSHASIGMAD, AADDEX, AXXSLDWI, AXXPERMDI:
   315  		if len(p.RestArgs) == 2 && p.Reg == 0 && p.RestArgs[0].Addr.Type == obj.TYPE_CONST && p.RestArgs[1].Addr.Type == obj.TYPE_REG {
   316  			p.Reg = p.RestArgs[1].Addr.Reg
   317  			p.RestArgs = p.RestArgs[:1]
   318  		}
   319  	}
   320  
   321  	if c.ctxt.Headtype == objabi.Haix {
   322  		c.rewriteToUseTOC(p)
   323  	} else if c.ctxt.Flag_dynlink {
   324  		c.rewriteToUseGot(p)
   325  	}
   326  }
   327  
   328  // Rewrite p, if necessary, to access a symbol using its TOC anchor.
   329  // This code is for AIX only.
   330  func (c *ctxt9) rewriteToUseTOC(p *obj.Prog) {
   331  	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
   332  		return
   333  	}
   334  
   335  	if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
   336  		// ADUFFZERO/ADUFFCOPY is considered as an ABL except in dynamic
   337  		// link where it should be an indirect call.
   338  		if !c.ctxt.Flag_dynlink {
   339  			return
   340  		}
   341  		//     ADUFFxxx $offset
   342  		// becomes
   343  		//     MOVD runtime.duffxxx@TOC, R12
   344  		//     ADD $offset, R12
   345  		//     MOVD R12, LR
   346  		//     BL (LR)
   347  		var sym *obj.LSym
   348  		if p.As == obj.ADUFFZERO {
   349  			sym = c.ctxt.Lookup("runtime.duffzero")
   350  		} else {
   351  			sym = c.ctxt.Lookup("runtime.duffcopy")
   352  		}
   353  		// Retrieve or create the TOC anchor.
   354  		symtoc := c.ctxt.LookupInit("TOC."+sym.Name, func(s *obj.LSym) {
   355  			s.Type = objabi.SDATA
   356  			s.Set(obj.AttrDuplicateOK, true)
   357  			s.Set(obj.AttrStatic, true)
   358  			c.ctxt.Data = append(c.ctxt.Data, s)
   359  			s.WriteAddr(c.ctxt, 0, 8, sym, 0)
   360  		})
   361  
   362  		offset := p.To.Offset
   363  		p.As = AMOVD
   364  		p.From.Type = obj.TYPE_MEM
   365  		p.From.Name = obj.NAME_TOCREF
   366  		p.From.Sym = symtoc
   367  		p.To.Type = obj.TYPE_REG
   368  		p.To.Reg = REG_R12
   369  		p.To.Name = obj.NAME_NONE
   370  		p.To.Offset = 0
   371  		p.To.Sym = nil
   372  		p1 := obj.Appendp(p, c.newprog)
   373  		p1.As = AADD
   374  		p1.From.Type = obj.TYPE_CONST
   375  		p1.From.Offset = offset
   376  		p1.To.Type = obj.TYPE_REG
   377  		p1.To.Reg = REG_R12
   378  		p2 := obj.Appendp(p1, c.newprog)
   379  		p2.As = AMOVD
   380  		p2.From.Type = obj.TYPE_REG
   381  		p2.From.Reg = REG_R12
   382  		p2.To.Type = obj.TYPE_REG
   383  		p2.To.Reg = REG_LR
   384  		p3 := obj.Appendp(p2, c.newprog)
   385  		p3.As = obj.ACALL
   386  		p3.To.Type = obj.TYPE_REG
   387  		p3.To.Reg = REG_LR
   388  	}
   389  
   390  	var source *obj.Addr
   391  	if p.From.Name == obj.NAME_EXTERN || p.From.Name == obj.NAME_STATIC {
   392  		if p.From.Type == obj.TYPE_ADDR {
   393  			if p.As == ADWORD {
   394  				// ADWORD $sym doesn't need TOC anchor
   395  				return
   396  			}
   397  			if p.As != AMOVD {
   398  				c.ctxt.Diag("do not know how to handle TYPE_ADDR in %v", p)
   399  				return
   400  			}
   401  			if p.To.Type != obj.TYPE_REG {
   402  				c.ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v", p)
   403  				return
   404  			}
   405  		} else if p.From.Type != obj.TYPE_MEM {
   406  			c.ctxt.Diag("do not know how to handle %v without TYPE_MEM", p)
   407  			return
   408  		}
   409  		source = &p.From
   410  
   411  	} else if p.To.Name == obj.NAME_EXTERN || p.To.Name == obj.NAME_STATIC {
   412  		if p.To.Type != obj.TYPE_MEM {
   413  			c.ctxt.Diag("do not know how to handle %v without TYPE_MEM", p)
   414  			return
   415  		}
   416  		if source != nil {
   417  			c.ctxt.Diag("cannot handle symbols on both sides in %v", p)
   418  			return
   419  		}
   420  		source = &p.To
   421  	} else {
   422  		return
   423  
   424  	}
   425  
   426  	if source.Sym == nil {
   427  		c.ctxt.Diag("do not know how to handle nil symbol in %v", p)
   428  		return
   429  	}
   430  
   431  	if source.Sym.Type == objabi.STLSBSS {
   432  		return
   433  	}
   434  
   435  	// Retrieve or create the TOC anchor.
   436  	symtoc := c.ctxt.LookupInit("TOC."+source.Sym.Name, func(s *obj.LSym) {
   437  		s.Type = objabi.SDATA
   438  		s.Set(obj.AttrDuplicateOK, true)
   439  		s.Set(obj.AttrStatic, true)
   440  		c.ctxt.Data = append(c.ctxt.Data, s)
   441  		s.WriteAddr(c.ctxt, 0, 8, source.Sym, 0)
   442  	})
   443  
   444  	if source.Type == obj.TYPE_ADDR {
   445  		// MOVD $sym, Rx becomes MOVD symtoc, Rx
   446  		// MOVD $sym+<off>, Rx becomes MOVD symtoc, Rx; ADD <off>, Rx
   447  		p.From.Type = obj.TYPE_MEM
   448  		p.From.Sym = symtoc
   449  		p.From.Name = obj.NAME_TOCREF
   450  
   451  		if p.From.Offset != 0 {
   452  			q := obj.Appendp(p, c.newprog)
   453  			q.As = AADD
   454  			q.From.Type = obj.TYPE_CONST
   455  			q.From.Offset = p.From.Offset
   456  			p.From.Offset = 0
   457  			q.To = p.To
   458  		}
   459  		return
   460  
   461  	}
   462  
   463  	// MOVx sym, Ry becomes MOVD symtoc, REGTMP; MOVx (REGTMP), Ry
   464  	// MOVx Ry, sym becomes MOVD symtoc, REGTMP; MOVx Ry, (REGTMP)
   465  	// An addition may be inserted between the two MOVs if there is an offset.
   466  
   467  	q := obj.Appendp(p, c.newprog)
   468  	q.As = AMOVD
   469  	q.From.Type = obj.TYPE_MEM
   470  	q.From.Sym = symtoc
   471  	q.From.Name = obj.NAME_TOCREF
   472  	q.To.Type = obj.TYPE_REG
   473  	q.To.Reg = REGTMP
   474  
   475  	q = obj.Appendp(q, c.newprog)
   476  	q.As = p.As
   477  	q.From = p.From
   478  	q.To = p.To
   479  	if p.From.Name != obj.NAME_NONE {
   480  		q.From.Type = obj.TYPE_MEM
   481  		q.From.Reg = REGTMP
   482  		q.From.Name = obj.NAME_NONE
   483  		q.From.Sym = nil
   484  	} else if p.To.Name != obj.NAME_NONE {
   485  		q.To.Type = obj.TYPE_MEM
   486  		q.To.Reg = REGTMP
   487  		q.To.Name = obj.NAME_NONE
   488  		q.To.Sym = nil
   489  	} else {
   490  		c.ctxt.Diag("unreachable case in rewriteToUseTOC with %v", p)
   491  	}
   492  
   493  	obj.Nopout(p)
   494  }
   495  
   496  // Rewrite p, if necessary, to access global data via the global offset table.
   497  func (c *ctxt9) rewriteToUseGot(p *obj.Prog) {
   498  	if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
   499  		//     ADUFFxxx $offset
   500  		// becomes
   501  		//     MOVD runtime.duffxxx@GOT, R12
   502  		//     ADD $offset, R12
   503  		//     MOVD R12, LR
   504  		//     BL (LR)
   505  		var sym *obj.LSym
   506  		if p.As == obj.ADUFFZERO {
   507  			sym = c.ctxt.LookupABI("runtime.duffzero", obj.ABIInternal)
   508  		} else {
   509  			sym = c.ctxt.LookupABI("runtime.duffcopy", obj.ABIInternal)
   510  		}
   511  		offset := p.To.Offset
   512  		p.As = AMOVD
   513  		p.From.Type = obj.TYPE_MEM
   514  		p.From.Name = obj.NAME_GOTREF
   515  		p.From.Sym = sym
   516  		p.To.Type = obj.TYPE_REG
   517  		p.To.Reg = REG_R12
   518  		p.To.Name = obj.NAME_NONE
   519  		p.To.Offset = 0
   520  		p.To.Sym = nil
   521  		p1 := obj.Appendp(p, c.newprog)
   522  		p1.As = AADD
   523  		p1.From.Type = obj.TYPE_CONST
   524  		p1.From.Offset = offset
   525  		p1.To.Type = obj.TYPE_REG
   526  		p1.To.Reg = REG_R12
   527  		p2 := obj.Appendp(p1, c.newprog)
   528  		p2.As = AMOVD
   529  		p2.From.Type = obj.TYPE_REG
   530  		p2.From.Reg = REG_R12
   531  		p2.To.Type = obj.TYPE_REG
   532  		p2.To.Reg = REG_LR
   533  		p3 := obj.Appendp(p2, c.newprog)
   534  		p3.As = obj.ACALL
   535  		p3.To.Type = obj.TYPE_REG
   536  		p3.To.Reg = REG_LR
   537  	}
   538  
   539  	// We only care about global data: NAME_EXTERN means a global
   540  	// symbol in the Go sense, and p.Sym.Local is true for a few
   541  	// internally defined symbols.
   542  	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
   543  		// MOVD $sym, Rx becomes MOVD sym@GOT, Rx
   544  		// MOVD $sym+<off>, Rx becomes MOVD sym@GOT, Rx; ADD <off>, Rx
   545  		if p.As != AMOVD {
   546  			c.ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
   547  		}
   548  		if p.To.Type != obj.TYPE_REG {
   549  			c.ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
   550  		}
   551  		p.From.Type = obj.TYPE_MEM
   552  		p.From.Name = obj.NAME_GOTREF
   553  		if p.From.Offset != 0 {
   554  			q := obj.Appendp(p, c.newprog)
   555  			q.As = AADD
   556  			q.From.Type = obj.TYPE_CONST
   557  			q.From.Offset = p.From.Offset
   558  			q.To = p.To
   559  			p.From.Offset = 0
   560  		}
   561  	}
   562  	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
   563  		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
   564  	}
   565  	var source *obj.Addr
   566  	// MOVx sym, Ry becomes MOVD sym@GOT, REGTMP; MOVx (REGTMP), Ry
   567  	// MOVx Ry, sym becomes MOVD sym@GOT, REGTMP; MOVx Ry, (REGTMP)
   568  	// An addition may be inserted between the two MOVs if there is an offset.
   569  	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
   570  		if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
   571  			c.ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
   572  		}
   573  		source = &p.From
   574  	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
   575  		source = &p.To
   576  	} else {
   577  		return
   578  	}
   579  	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
   580  		return
   581  	}
   582  	if source.Sym.Type == objabi.STLSBSS {
   583  		return
   584  	}
   585  	if source.Type != obj.TYPE_MEM {
   586  		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
   587  	}
   588  	p1 := obj.Appendp(p, c.newprog)
   589  	p2 := obj.Appendp(p1, c.newprog)
   590  
   591  	p1.As = AMOVD
   592  	p1.From.Type = obj.TYPE_MEM
   593  	p1.From.Sym = source.Sym
   594  	p1.From.Name = obj.NAME_GOTREF
   595  	p1.To.Type = obj.TYPE_REG
   596  	p1.To.Reg = REGTMP
   597  
   598  	p2.As = p.As
   599  	p2.From = p.From
   600  	p2.To = p.To
   601  	if p.From.Name == obj.NAME_EXTERN {
   602  		p2.From.Reg = REGTMP
   603  		p2.From.Name = obj.NAME_NONE
   604  		p2.From.Sym = nil
   605  	} else if p.To.Name == obj.NAME_EXTERN {
   606  		p2.To.Reg = REGTMP
   607  		p2.To.Name = obj.NAME_NONE
   608  		p2.To.Sym = nil
   609  	} else {
   610  		return
   611  	}
   612  	obj.Nopout(p)
   613  }
   614  
   615  func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
   616  	// TODO(minux): add morestack short-cuts with small fixed frame-size.
   617  	if cursym.Func().Text == nil || cursym.Func().Text.Link == nil {
   618  		return
   619  	}
   620  
   621  	c := ctxt9{ctxt: ctxt, cursym: cursym, newprog: newprog}
   622  
   623  	p := c.cursym.Func().Text
   624  	textstksiz := p.To.Offset
   625  	if textstksiz == -8 {
   626  		// Compatibility hack.
   627  		p.From.Sym.Set(obj.AttrNoFrame, true)
   628  		textstksiz = 0
   629  	}
   630  	if textstksiz%8 != 0 {
   631  		c.ctxt.Diag("frame size %d not a multiple of 8", textstksiz)
   632  	}
   633  	if p.From.Sym.NoFrame() {
   634  		if textstksiz != 0 {
   635  			c.ctxt.Diag("NOFRAME functions must have a frame size of 0, not %d", textstksiz)
   636  		}
   637  	}
   638  
   639  	c.cursym.Func().Args = p.To.Val.(int32)
   640  	c.cursym.Func().Locals = int32(textstksiz)
   641  
   642  	/*
   643  	 * find leaf subroutines
   644  	 * expand RET
   645  	 * expand BECOME pseudo
   646  	 */
   647  
   648  	var q *obj.Prog
   649  	var q1 *obj.Prog
   650  	for p := c.cursym.Func().Text; p != nil; p = p.Link {
   651  		switch p.As {
   652  		/* too hard, just leave alone */
   653  		case obj.ATEXT:
   654  			q = p
   655  
   656  			p.Mark |= LABEL | LEAF | SYNC
   657  			if p.Link != nil {
   658  				p.Link.Mark |= LABEL
   659  			}
   660  
   661  		case ANOR:
   662  			q = p
   663  			if p.To.Type == obj.TYPE_REG {
   664  				if p.To.Reg == REGZERO {
   665  					p.Mark |= LABEL | SYNC
   666  				}
   667  			}
   668  
   669  		case ALWAR,
   670  			ALBAR,
   671  			ASTBCCC,
   672  			ASTWCCC,
   673  			AEIEIO,
   674  			AICBI,
   675  			AISYNC,
   676  			ATLBIE,
   677  			ATLBIEL,
   678  			ASLBIA,
   679  			ASLBIE,
   680  			ASLBMFEE,
   681  			ASLBMFEV,
   682  			ASLBMTE,
   683  			ADCBF,
   684  			ADCBI,
   685  			ADCBST,
   686  			ADCBT,
   687  			ADCBTST,
   688  			ADCBZ,
   689  			ASYNC,
   690  			ATLBSYNC,
   691  			APTESYNC,
   692  			ALWSYNC,
   693  			ATW,
   694  			AWORD,
   695  			ARFI,
   696  			ARFCI,
   697  			ARFID,
   698  			AHRFID:
   699  			q = p
   700  			p.Mark |= LABEL | SYNC
   701  			continue
   702  
   703  		case AMOVW, AMOVWZ, AMOVD:
   704  			q = p
   705  			if p.From.Reg >= REG_SPECIAL || p.To.Reg >= REG_SPECIAL {
   706  				p.Mark |= LABEL | SYNC
   707  			}
   708  			continue
   709  
   710  		case AFABS,
   711  			AFABSCC,
   712  			AFADD,
   713  			AFADDCC,
   714  			AFCTIW,
   715  			AFCTIWCC,
   716  			AFCTIWZ,
   717  			AFCTIWZCC,
   718  			AFDIV,
   719  			AFDIVCC,
   720  			AFMADD,
   721  			AFMADDCC,
   722  			AFMOVD,
   723  			AFMOVDU,
   724  			/* case AFMOVDS: */
   725  			AFMOVS,
   726  			AFMOVSU,
   727  
   728  			/* case AFMOVSD: */
   729  			AFMSUB,
   730  			AFMSUBCC,
   731  			AFMUL,
   732  			AFMULCC,
   733  			AFNABS,
   734  			AFNABSCC,
   735  			AFNEG,
   736  			AFNEGCC,
   737  			AFNMADD,
   738  			AFNMADDCC,
   739  			AFNMSUB,
   740  			AFNMSUBCC,
   741  			AFRSP,
   742  			AFRSPCC,
   743  			AFSUB,
   744  			AFSUBCC:
   745  			q = p
   746  
   747  			p.Mark |= FLOAT
   748  			continue
   749  
   750  		case ABL,
   751  			ABCL,
   752  			obj.ADUFFZERO,
   753  			obj.ADUFFCOPY:
   754  			c.cursym.Func().Text.Mark &^= LEAF
   755  			fallthrough
   756  
   757  		case ABC,
   758  			ABEQ,
   759  			ABGE,
   760  			ABGT,
   761  			ABLE,
   762  			ABLT,
   763  			ABNE,
   764  			ABR,
   765  			ABVC,
   766  			ABVS:
   767  			p.Mark |= BRANCH
   768  			q = p
   769  			q1 = p.To.Target()
   770  			if q1 != nil {
   771  				// NOPs are not removed due to #40689.
   772  
   773  				if q1.Mark&LEAF == 0 {
   774  					q1.Mark |= LABEL
   775  				}
   776  			} else {
   777  				p.Mark |= LABEL
   778  			}
   779  			q1 = p.Link
   780  			if q1 != nil {
   781  				q1.Mark |= LABEL
   782  			}
   783  			continue
   784  
   785  		case AFCMPO, AFCMPU:
   786  			q = p
   787  			p.Mark |= FCMP | FLOAT
   788  			continue
   789  
   790  		case obj.ARET:
   791  			q = p
   792  			if p.Link != nil {
   793  				p.Link.Mark |= LABEL
   794  			}
   795  			continue
   796  
   797  		case obj.ANOP:
   798  			// NOPs are not removed due to
   799  			// #40689
   800  			continue
   801  
   802  		default:
   803  			q = p
   804  			continue
   805  		}
   806  	}
   807  
   808  	autosize := int32(0)
   809  	for p := c.cursym.Func().Text; p != nil; p = p.Link {
   810  		o := p.As
   811  		switch o {
   812  		case obj.ATEXT:
   813  			autosize = int32(textstksiz)
   814  
   815  			if p.Mark&LEAF != 0 && autosize == 0 {
   816  				// A leaf function with no locals has no frame.
   817  				p.From.Sym.Set(obj.AttrNoFrame, true)
   818  			}
   819  
   820  			if !p.From.Sym.NoFrame() {
   821  				// If there is a stack frame at all, it includes
   822  				// space to save the LR.
   823  				autosize += int32(c.ctxt.Arch.FixedFrameSize)
   824  			}
   825  
   826  			if p.Mark&LEAF != 0 && autosize < abi.StackSmall {
   827  				// A leaf function with a small stack can be marked
   828  				// NOSPLIT, avoiding a stack check.
   829  				p.From.Sym.Set(obj.AttrNoSplit, true)
   830  			}
   831  
   832  			p.To.Offset = int64(autosize)
   833  
   834  			q = p
   835  
   836  			if NeedTOCpointer(c.ctxt) && !isNOTOCfunc(c.cursym.Name) {
   837  				// When compiling Go into PIC, without PCrel support, all functions must start
   838  				// with instructions to load the TOC pointer into r2:
   839  				//
   840  				//	addis r2, r12, .TOC.-func@ha
   841  				//	addi r2, r2, .TOC.-func@l+4
   842  				//
   843  				// We could probably skip this prologue in some situations
   844  				// but it's a bit subtle. However, it is both safe and
   845  				// necessary to leave the prologue off duffzero and
   846  				// duffcopy as we rely on being able to jump to a specific
   847  				// instruction offset for them.
   848  				//
   849  				// These are AWORDS because there is no (afaict) way to
   850  				// generate the addis instruction except as part of the
   851  				// load of a large constant, and in that case there is no
   852  				// way to use r12 as the source.
   853  				//
   854  				// Note that the same condition is tested in
   855  				// putelfsym in cmd/link/internal/ld/symtab.go
   856  				// where we set the st_other field to indicate
   857  				// the presence of these instructions.
   858  				q = obj.Appendp(q, c.newprog)
   859  				q.As = AWORD
   860  				q.Pos = p.Pos
   861  				q.From.Type = obj.TYPE_CONST
   862  				q.From.Offset = 0x3c4c0000
   863  				q = obj.Appendp(q, c.newprog)
   864  				q.As = AWORD
   865  				q.Pos = p.Pos
   866  				q.From.Type = obj.TYPE_CONST
   867  				q.From.Offset = 0x38420000
   868  				c.cursym.AddRel(c.ctxt, obj.Reloc{
   869  					Type: objabi.R_ADDRPOWER_PCREL,
   870  					Off:  0,
   871  					Siz:  8,
   872  					Sym:  c.ctxt.Lookup(".TOC."),
   873  				})
   874  			}
   875  
   876  			if !c.cursym.Func().Text.From.Sym.NoSplit() {
   877  				q = c.stacksplit(q, autosize) // emit split check
   878  			}
   879  
   880  			if autosize != 0 {
   881  				var prologueEnd *obj.Prog
   882  				// Save the link register and update the SP.  MOVDU is used unless
   883  				// the frame size is too large.  The link register must be saved
   884  				// even for non-empty leaf functions so that traceback works.
   885  				if autosize >= -BIG && autosize <= BIG {
   886  					// Use MOVDU to adjust R1 when saving R31, if autosize is small.
   887  					q = obj.Appendp(q, c.newprog)
   888  					q.As = AMOVD
   889  					q.Pos = p.Pos
   890  					q.From.Type = obj.TYPE_REG
   891  					q.From.Reg = REG_LR
   892  					q.To.Type = obj.TYPE_REG
   893  					q.To.Reg = REGTMP
   894  					prologueEnd = q
   895  
   896  					q = obj.Appendp(q, c.newprog)
   897  					q.As = AMOVDU
   898  					q.Pos = p.Pos
   899  					q.From.Type = obj.TYPE_REG
   900  					q.From.Reg = REGTMP
   901  					q.To.Type = obj.TYPE_MEM
   902  					q.To.Offset = int64(-autosize)
   903  					q.To.Reg = REGSP
   904  					q.Spadj = autosize
   905  				} else {
   906  					// Frame size is too large for an stdu MOVDU instruction, use stdux MOVDU.
   907  					q = obj.Appendp(q, c.newprog)
   908  					q.As = AMOVD
   909  					q.Pos = p.Pos
   910  					q.From.Type = obj.TYPE_REG
   911  					q.From.Reg = REG_LR
   912  					q.To.Type = obj.TYPE_REG
   913  					q.To.Reg = REG_R29
   914  
   915  					// Create stack adjustment in REGTMP
   916  					q = obj.Appendp(q, c.newprog)
   917  					q.As = AMOVD
   918  					q.Pos = p.Pos
   919  					q.From.Type = obj.TYPE_CONST
   920  					q.From.Offset = int64(-autosize)
   921  					q.To.Type = obj.TYPE_REG
   922  					q.To.Reg = REGTMP
   923  
   924  					prologueEnd = q
   925  
   926  					// MOVDU R29, R31(R1)
   927  					q = obj.Appendp(q, c.newprog)
   928  					q.As = AMOVDU
   929  					q.Pos = p.Pos
   930  					q.From.Type = obj.TYPE_REG
   931  					q.From.Reg = REG_R29
   932  					q.To.Type = obj.TYPE_MEM
   933  					q.To.Reg = REGTMP
   934  					q.To.Index = REGSP
   935  					q.Spadj = autosize
   936  				}
   937  
   938  				prologueEnd.Pos = prologueEnd.Pos.WithXlogue(src.PosPrologueEnd)
   939  			} else if c.cursym.Func().Text.Mark&LEAF == 0 {
   940  				// A very few functions that do not return to their caller
   941  				// (e.g. gogo) are not identified as leaves but still have
   942  				// no frame.
   943  				c.cursym.Func().Text.Mark |= LEAF
   944  			}
   945  
   946  			if c.cursym.Func().Text.Mark&LEAF != 0 {
   947  				c.cursym.Set(obj.AttrLeaf, true)
   948  				break
   949  			}
   950  
   951  			if NeedTOCpointer(c.ctxt) {
   952  				q = obj.Appendp(q, c.newprog)
   953  				q.As = AMOVD
   954  				q.Pos = p.Pos
   955  				q.From.Type = obj.TYPE_REG
   956  				q.From.Reg = REG_R2
   957  				q.To.Type = obj.TYPE_MEM
   958  				q.To.Reg = REGSP
   959  				q.To.Offset = 24
   960  			}
   961  
   962  		case obj.ARET:
   963  			if p.From.Type == obj.TYPE_CONST {
   964  				c.ctxt.Diag("using BECOME (%v) is not supported!", p)
   965  				break
   966  			}
   967  
   968  			retTarget := p.To.Sym
   969  
   970  			if c.cursym.Func().Text.Mark&LEAF != 0 {
   971  				if autosize == 0 {
   972  					p.As = ABR
   973  					p.From = obj.Addr{}
   974  					if retTarget == nil {
   975  						p.To.Type = obj.TYPE_REG
   976  						p.To.Reg = REG_LR
   977  					} else {
   978  						p.To.Type = obj.TYPE_BRANCH
   979  						p.To.Sym = retTarget
   980  					}
   981  					p.Mark |= BRANCH
   982  					break
   983  				}
   984  
   985  				p.As = AADD
   986  				p.From.Type = obj.TYPE_CONST
   987  				p.From.Offset = int64(autosize)
   988  				p.To.Type = obj.TYPE_REG
   989  				p.To.Reg = REGSP
   990  				p.Spadj = -autosize
   991  
   992  				q = c.newprog()
   993  				q.As = ABR
   994  				q.Pos = p.Pos
   995  				if retTarget == nil {
   996  					q.To.Type = obj.TYPE_REG
   997  					q.To.Reg = REG_LR
   998  				} else {
   999  					q.To.Type = obj.TYPE_BRANCH
  1000  					q.To.Sym = retTarget
  1001  				}
  1002  				q.Mark |= BRANCH
  1003  				q.Spadj = +autosize
  1004  
  1005  				q.Link = p.Link
  1006  				p.Link = q
  1007  				break
  1008  			}
  1009  
  1010  			p.As = AMOVD
  1011  			p.From.Type = obj.TYPE_MEM
  1012  			p.From.Offset = 0
  1013  			p.From.Reg = REGSP
  1014  			p.To.Type = obj.TYPE_REG
  1015  			p.To.Reg = REGTMP
  1016  
  1017  			q = c.newprog()
  1018  			q.As = AMOVD
  1019  			q.Pos = p.Pos
  1020  			q.From.Type = obj.TYPE_REG
  1021  			q.From.Reg = REGTMP
  1022  			q.To.Type = obj.TYPE_REG
  1023  			q.To.Reg = REG_LR
  1024  
  1025  			q.Link = p.Link
  1026  			p.Link = q
  1027  			p = q
  1028  
  1029  			if false {
  1030  				// Debug bad returns
  1031  				q = c.newprog()
  1032  
  1033  				q.As = AMOVD
  1034  				q.Pos = p.Pos
  1035  				q.From.Type = obj.TYPE_MEM
  1036  				q.From.Offset = 0
  1037  				q.From.Reg = REGTMP
  1038  				q.To.Type = obj.TYPE_REG
  1039  				q.To.Reg = REGTMP
  1040  
  1041  				q.Link = p.Link
  1042  				p.Link = q
  1043  				p = q
  1044  			}
  1045  			prev := p
  1046  			if autosize != 0 {
  1047  				q = c.newprog()
  1048  				q.As = AADD
  1049  				q.Pos = p.Pos
  1050  				q.From.Type = obj.TYPE_CONST
  1051  				q.From.Offset = int64(autosize)
  1052  				q.To.Type = obj.TYPE_REG
  1053  				q.To.Reg = REGSP
  1054  				q.Spadj = -autosize
  1055  
  1056  				q.Link = p.Link
  1057  				prev.Link = q
  1058  				prev = q
  1059  			}
  1060  
  1061  			q1 = c.newprog()
  1062  			q1.As = ABR
  1063  			q1.Pos = p.Pos
  1064  			if retTarget == nil {
  1065  				q1.To.Type = obj.TYPE_REG
  1066  				q1.To.Reg = REG_LR
  1067  			} else {
  1068  				q1.To.Type = obj.TYPE_BRANCH
  1069  				q1.To.Sym = retTarget
  1070  			}
  1071  			q1.Mark |= BRANCH
  1072  			q1.Spadj = +autosize
  1073  
  1074  			q1.Link = q.Link
  1075  			prev.Link = q1
  1076  		case AADD:
  1077  			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
  1078  				p.Spadj = int32(-p.From.Offset)
  1079  			}
  1080  		case AMOVDU:
  1081  			if p.To.Type == obj.TYPE_MEM && p.To.Reg == REGSP {
  1082  				p.Spadj = int32(-p.To.Offset)
  1083  			}
  1084  			if p.From.Type == obj.TYPE_MEM && p.From.Reg == REGSP {
  1085  				p.Spadj = int32(-p.From.Offset)
  1086  			}
  1087  		case obj.AGETCALLERPC:
  1088  			if cursym.Leaf() {
  1089  				/* MOVD LR, Rd */
  1090  				p.As = AMOVD
  1091  				p.From.Type = obj.TYPE_REG
  1092  				p.From.Reg = REG_LR
  1093  			} else {
  1094  				/* MOVD (RSP), Rd */
  1095  				p.As = AMOVD
  1096  				p.From.Type = obj.TYPE_MEM
  1097  				p.From.Reg = REGSP
  1098  			}
  1099  		}
  1100  
  1101  		if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.Spadj == 0 && p.As != ACMPU {
  1102  			f := c.cursym.Func()
  1103  			if f.FuncFlag&abi.FuncFlagSPWrite == 0 {
  1104  				c.cursym.Func().FuncFlag |= abi.FuncFlagSPWrite
  1105  				if ctxt.Debugvlog || !ctxt.IsAsm {
  1106  					ctxt.Logf("auto-SPWRITE: %s %v\n", c.cursym.Name, p)
  1107  					if !ctxt.IsAsm {
  1108  						ctxt.Diag("invalid auto-SPWRITE in non-assembly")
  1109  						ctxt.DiagFlush()
  1110  						log.Fatalf("bad SPWRITE")
  1111  					}
  1112  				}
  1113  			}
  1114  		}
  1115  	}
  1116  }
  1117  
  1118  /*
  1119  // instruction scheduling
  1120  
  1121  	if(debug['Q'] == 0)
  1122  		return;
  1123  
  1124  	curtext = nil;
  1125  	q = nil;	// p - 1
  1126  	q1 = firstp;	// top of block
  1127  	o = 0;		// count of instructions
  1128  	for(p = firstp; p != nil; p = p1) {
  1129  		p1 = p->link;
  1130  		o++;
  1131  		if(p->mark & NOSCHED){
  1132  			if(q1 != p){
  1133  				sched(q1, q);
  1134  			}
  1135  			for(; p != nil; p = p->link){
  1136  				if(!(p->mark & NOSCHED))
  1137  					break;
  1138  				q = p;
  1139  			}
  1140  			p1 = p;
  1141  			q1 = p;
  1142  			o = 0;
  1143  			continue;
  1144  		}
  1145  		if(p->mark & (LABEL|SYNC)) {
  1146  			if(q1 != p)
  1147  				sched(q1, q);
  1148  			q1 = p;
  1149  			o = 1;
  1150  		}
  1151  		if(p->mark & (BRANCH|SYNC)) {
  1152  			sched(q1, p);
  1153  			q1 = p1;
  1154  			o = 0;
  1155  		}
  1156  		if(o >= NSCHED) {
  1157  			sched(q1, p);
  1158  			q1 = p1;
  1159  			o = 0;
  1160  		}
  1161  		q = p;
  1162  	}
  1163  */
  1164  func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
  1165  	if c.ctxt.Flag_maymorestack != "" {
  1166  		if c.ctxt.Flag_shared || c.ctxt.Flag_dynlink {
  1167  			// See the call to morestack for why these are
  1168  			// complicated to support.
  1169  			c.ctxt.Diag("maymorestack with -shared or -dynlink is not supported")
  1170  		}
  1171  
  1172  		// Spill arguments. This has to happen before we open
  1173  		// any more frame space.
  1174  		p = c.cursym.Func().SpillRegisterArgs(p, c.newprog)
  1175  
  1176  		// Save LR and REGCTXT
  1177  		frameSize := 8 + c.ctxt.Arch.FixedFrameSize
  1178  
  1179  		// MOVD LR, REGTMP
  1180  		p = obj.Appendp(p, c.newprog)
  1181  		p.As = AMOVD
  1182  		p.From.Type = obj.TYPE_REG
  1183  		p.From.Reg = REG_LR
  1184  		p.To.Type = obj.TYPE_REG
  1185  		p.To.Reg = REGTMP
  1186  		// MOVDU REGTMP, -16(SP)
  1187  		p = obj.Appendp(p, c.newprog)
  1188  		p.As = AMOVDU
  1189  		p.From.Type = obj.TYPE_REG
  1190  		p.From.Reg = REGTMP
  1191  		p.To.Type = obj.TYPE_MEM
  1192  		p.To.Offset = -frameSize
  1193  		p.To.Reg = REGSP
  1194  		p.Spadj = int32(frameSize)
  1195  
  1196  		// MOVD REGCTXT, 8(SP)
  1197  		p = obj.Appendp(p, c.newprog)
  1198  		p.As = AMOVD
  1199  		p.From.Type = obj.TYPE_REG
  1200  		p.From.Reg = REGCTXT
  1201  		p.To.Type = obj.TYPE_MEM
  1202  		p.To.Offset = 8
  1203  		p.To.Reg = REGSP
  1204  
  1205  		// BL maymorestack
  1206  		p = obj.Appendp(p, c.newprog)
  1207  		p.As = ABL
  1208  		p.To.Type = obj.TYPE_BRANCH
  1209  		// See ../x86/obj6.go
  1210  		p.To.Sym = c.ctxt.LookupABI(c.ctxt.Flag_maymorestack, c.cursym.ABI())
  1211  
  1212  		// Restore LR and REGCTXT
  1213  
  1214  		// MOVD 8(SP), REGCTXT
  1215  		p = obj.Appendp(p, c.newprog)
  1216  		p.As = AMOVD
  1217  		p.From.Type = obj.TYPE_MEM
  1218  		p.From.Offset = 8
  1219  		p.From.Reg = REGSP
  1220  		p.To.Type = obj.TYPE_REG
  1221  		p.To.Reg = REGCTXT
  1222  
  1223  		// MOVD 0(SP), REGTMP
  1224  		p = obj.Appendp(p, c.newprog)
  1225  		p.As = AMOVD
  1226  		p.From.Type = obj.TYPE_MEM
  1227  		p.From.Offset = 0
  1228  		p.From.Reg = REGSP
  1229  		p.To.Type = obj.TYPE_REG
  1230  		p.To.Reg = REGTMP
  1231  
  1232  		// MOVD REGTMP, LR
  1233  		p = obj.Appendp(p, c.newprog)
  1234  		p.As = AMOVD
  1235  		p.From.Type = obj.TYPE_REG
  1236  		p.From.Reg = REGTMP
  1237  		p.To.Type = obj.TYPE_REG
  1238  		p.To.Reg = REG_LR
  1239  
  1240  		// ADD $16, SP
  1241  		p = obj.Appendp(p, c.newprog)
  1242  		p.As = AADD
  1243  		p.From.Type = obj.TYPE_CONST
  1244  		p.From.Offset = frameSize
  1245  		p.To.Type = obj.TYPE_REG
  1246  		p.To.Reg = REGSP
  1247  		p.Spadj = -int32(frameSize)
  1248  
  1249  		// Unspill arguments.
  1250  		p = c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
  1251  	}
  1252  
  1253  	// save entry point, but skipping the two instructions setting R2 in shared mode and maymorestack
  1254  	startPred := p
  1255  
  1256  	// MOVD	g_stackguard(g), R22
  1257  	p = obj.Appendp(p, c.newprog)
  1258  
  1259  	p.As = AMOVD
  1260  	p.From.Type = obj.TYPE_MEM
  1261  	p.From.Reg = REGG
  1262  	p.From.Offset = 2 * int64(c.ctxt.Arch.PtrSize) // G.stackguard0
  1263  	if c.cursym.CFunc() {
  1264  		p.From.Offset = 3 * int64(c.ctxt.Arch.PtrSize) // G.stackguard1
  1265  	}
  1266  	p.To.Type = obj.TYPE_REG
  1267  	p.To.Reg = REG_R22
  1268  
  1269  	// Mark the stack bound check and morestack call async nonpreemptible.
  1270  	// If we get preempted here, when resumed the preemption request is
  1271  	// cleared, but we'll still call morestack, which will double the stack
  1272  	// unnecessarily. See issue #35470.
  1273  	p = c.ctxt.StartUnsafePoint(p, c.newprog)
  1274  
  1275  	var q *obj.Prog
  1276  	if framesize <= abi.StackSmall {
  1277  		// small stack: SP < stackguard
  1278  		//	CMP	stackguard, SP
  1279  		p = obj.Appendp(p, c.newprog)
  1280  
  1281  		p.As = ACMPU
  1282  		p.From.Type = obj.TYPE_REG
  1283  		p.From.Reg = REG_R22
  1284  		p.To.Type = obj.TYPE_REG
  1285  		p.To.Reg = REGSP
  1286  	} else {
  1287  		// large stack: SP-framesize < stackguard-StackSmall
  1288  		offset := int64(framesize) - abi.StackSmall
  1289  		if framesize > abi.StackBig {
  1290  			// Such a large stack we need to protect against underflow.
  1291  			// The runtime guarantees SP > objabi.StackBig, but
  1292  			// framesize is large enough that SP-framesize may
  1293  			// underflow, causing a direct comparison with the
  1294  			// stack guard to incorrectly succeed. We explicitly
  1295  			// guard against underflow.
  1296  			//
  1297  			//	CMPU	SP, $(framesize-StackSmall)
  1298  			//	BLT	label-of-call-to-morestack
  1299  			if offset <= 0xffff {
  1300  				p = obj.Appendp(p, c.newprog)
  1301  				p.As = ACMPU
  1302  				p.From.Type = obj.TYPE_REG
  1303  				p.From.Reg = REGSP
  1304  				p.To.Type = obj.TYPE_CONST
  1305  				p.To.Offset = offset
  1306  			} else {
  1307  				// Constant is too big for CMPU.
  1308  				p = obj.Appendp(p, c.newprog)
  1309  				p.As = AMOVD
  1310  				p.From.Type = obj.TYPE_CONST
  1311  				p.From.Offset = offset
  1312  				p.To.Type = obj.TYPE_REG
  1313  				p.To.Reg = REG_R23
  1314  
  1315  				p = obj.Appendp(p, c.newprog)
  1316  				p.As = ACMPU
  1317  				p.From.Type = obj.TYPE_REG
  1318  				p.From.Reg = REGSP
  1319  				p.To.Type = obj.TYPE_REG
  1320  				p.To.Reg = REG_R23
  1321  			}
  1322  
  1323  			p = obj.Appendp(p, c.newprog)
  1324  			q = p
  1325  			p.As = ABLT
  1326  			p.To.Type = obj.TYPE_BRANCH
  1327  		}
  1328  
  1329  		// Check against the stack guard. We've ensured this won't underflow.
  1330  		//	ADD  $-(framesize-StackSmall), SP, R4
  1331  		//	CMPU stackguard, R4
  1332  		p = obj.Appendp(p, c.newprog)
  1333  
  1334  		p.As = AADD
  1335  		p.From.Type = obj.TYPE_CONST
  1336  		p.From.Offset = -offset
  1337  		p.Reg = REGSP
  1338  		p.To.Type = obj.TYPE_REG
  1339  		p.To.Reg = REG_R23
  1340  
  1341  		p = obj.Appendp(p, c.newprog)
  1342  		p.As = ACMPU
  1343  		p.From.Type = obj.TYPE_REG
  1344  		p.From.Reg = REG_R22
  1345  		p.To.Type = obj.TYPE_REG
  1346  		p.To.Reg = REG_R23
  1347  	}
  1348  
  1349  	// q1: BLT	done
  1350  	p = obj.Appendp(p, c.newprog)
  1351  	q1 := p
  1352  
  1353  	p.As = ABLT
  1354  	p.To.Type = obj.TYPE_BRANCH
  1355  
  1356  	p = obj.Appendp(p, c.newprog)
  1357  	p.As = obj.ANOP // zero-width place holder
  1358  
  1359  	if q != nil {
  1360  		q.To.SetTarget(p)
  1361  	}
  1362  
  1363  	// Spill the register args that could be clobbered by the
  1364  	// morestack code.
  1365  
  1366  	spill := c.cursym.Func().SpillRegisterArgs(p, c.newprog)
  1367  
  1368  	// MOVD LR, R5
  1369  	p = obj.Appendp(spill, c.newprog)
  1370  	p.As = AMOVD
  1371  	p.From.Type = obj.TYPE_REG
  1372  	p.From.Reg = REG_LR
  1373  	p.To.Type = obj.TYPE_REG
  1374  	p.To.Reg = REG_R5
  1375  
  1376  	p = c.ctxt.EmitEntryStackMap(c.cursym, p, c.newprog)
  1377  
  1378  	var morestacksym *obj.LSym
  1379  	if c.cursym.CFunc() {
  1380  		morestacksym = c.ctxt.Lookup("runtime.morestackc")
  1381  	} else if !c.cursym.Func().Text.From.Sym.NeedCtxt() {
  1382  		morestacksym = c.ctxt.Lookup("runtime.morestack_noctxt")
  1383  	} else {
  1384  		morestacksym = c.ctxt.Lookup("runtime.morestack")
  1385  	}
  1386  
  1387  	if NeedTOCpointer(c.ctxt) {
  1388  		// In PPC64 PIC code, R2 is used as TOC pointer derived from R12
  1389  		// which is the address of function entry point when entering
  1390  		// the function. We need to preserve R2 across call to morestack.
  1391  		// Fortunately, in shared mode, 8(SP) and 16(SP) are reserved in
  1392  		// the caller's frame, but not used (0(SP) is caller's saved LR,
  1393  		// 24(SP) is caller's saved R2). Use 8(SP) to save this function's R2.
  1394  		// MOVD R2, 8(SP)
  1395  		p = obj.Appendp(p, c.newprog)
  1396  		p.As = AMOVD
  1397  		p.From.Type = obj.TYPE_REG
  1398  		p.From.Reg = REG_R2
  1399  		p.To.Type = obj.TYPE_MEM
  1400  		p.To.Reg = REGSP
  1401  		p.To.Offset = 8
  1402  	}
  1403  
  1404  	if c.ctxt.Flag_dynlink {
  1405  		// Avoid calling morestack via a PLT when dynamically linking. The
  1406  		// PLT stubs generated by the system linker on ppc64le when "std r2,
  1407  		// 24(r1)" to save the TOC pointer in their callers stack
  1408  		// frame. Unfortunately (and necessarily) morestack is called before
  1409  		// the function that calls it sets up its frame and so the PLT ends
  1410  		// up smashing the saved TOC pointer for its caller's caller.
  1411  		//
  1412  		// According to the ABI documentation there is a mechanism to avoid
  1413  		// the TOC save that the PLT stub does (put a R_PPC64_TOCSAVE
  1414  		// relocation on the nop after the call to morestack) but at the time
  1415  		// of writing it is not supported at all by gold and my attempt to
  1416  		// use it with ld.bfd caused an internal linker error. So this hack
  1417  		// seems preferable.
  1418  
  1419  		// MOVD $runtime.morestack(SB), R12
  1420  		p = obj.Appendp(p, c.newprog)
  1421  		p.As = AMOVD
  1422  		p.From.Type = obj.TYPE_MEM
  1423  		p.From.Sym = morestacksym
  1424  		p.From.Name = obj.NAME_GOTREF
  1425  		p.To.Type = obj.TYPE_REG
  1426  		p.To.Reg = REG_R12
  1427  
  1428  		// MOVD R12, LR
  1429  		p = obj.Appendp(p, c.newprog)
  1430  		p.As = AMOVD
  1431  		p.From.Type = obj.TYPE_REG
  1432  		p.From.Reg = REG_R12
  1433  		p.To.Type = obj.TYPE_REG
  1434  		p.To.Reg = REG_LR
  1435  
  1436  		// BL LR
  1437  		p = obj.Appendp(p, c.newprog)
  1438  		p.As = obj.ACALL
  1439  		p.To.Type = obj.TYPE_REG
  1440  		p.To.Reg = REG_LR
  1441  	} else {
  1442  		// BL	runtime.morestack(SB)
  1443  		p = obj.Appendp(p, c.newprog)
  1444  
  1445  		p.As = ABL
  1446  		p.To.Type = obj.TYPE_BRANCH
  1447  		p.To.Sym = morestacksym
  1448  	}
  1449  
  1450  	if NeedTOCpointer(c.ctxt) {
  1451  		// MOVD 8(SP), R2
  1452  		p = obj.Appendp(p, c.newprog)
  1453  		p.As = AMOVD
  1454  		p.From.Type = obj.TYPE_MEM
  1455  		p.From.Reg = REGSP
  1456  		p.From.Offset = 8
  1457  		p.To.Type = obj.TYPE_REG
  1458  		p.To.Reg = REG_R2
  1459  	}
  1460  
  1461  	// The instructions which unspill regs should be preemptible.
  1462  	p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
  1463  	unspill := c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
  1464  
  1465  	// BR	start
  1466  	p = obj.Appendp(unspill, c.newprog)
  1467  	p.As = ABR
  1468  	p.To.Type = obj.TYPE_BRANCH
  1469  	p.To.SetTarget(startPred.Link)
  1470  
  1471  	// placeholder for q1's jump target
  1472  	p = obj.Appendp(p, c.newprog)
  1473  
  1474  	p.As = obj.ANOP // zero-width place holder
  1475  	q1.To.SetTarget(p)
  1476  
  1477  	return p
  1478  }
  1479  
  1480  // MMA accumulator to/from instructions are slightly ambiguous since
  1481  // the argument represents both source and destination, specified as
  1482  // an accumulator. It is treated as a unary destination to simplify
  1483  // the code generation in ppc64map.
  1484  var unaryDst = map[obj.As]bool{
  1485  	AXXSETACCZ: true,
  1486  	AXXMTACC:   true,
  1487  	AXXMFACC:   true,
  1488  }
  1489  
  1490  var Linkppc64 = obj.LinkArch{
  1491  	Arch:           sys.ArchPPC64,
  1492  	Init:           buildop,
  1493  	Preprocess:     preprocess,
  1494  	Assemble:       span9,
  1495  	Progedit:       progedit,
  1496  	UnaryDst:       unaryDst,
  1497  	DWARFRegisters: PPC64DWARFRegisters,
  1498  }
  1499  
  1500  var Linkppc64le = obj.LinkArch{
  1501  	Arch:           sys.ArchPPC64LE,
  1502  	Init:           buildop,
  1503  	Preprocess:     preprocess,
  1504  	Assemble:       span9,
  1505  	Progedit:       progedit,
  1506  	UnaryDst:       unaryDst,
  1507  	DWARFRegisters: PPC64DWARFRegisters,
  1508  }
  1509
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