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  	var p1 *obj.Prog
   810  	var p2 *obj.Prog
   811  	for p := c.cursym.Func().Text; p != nil; p = p.Link {
   812  		o := p.As
   813  		switch o {
   814  		case obj.ATEXT:
   815  			autosize = int32(textstksiz)
   816  
   817  			if p.Mark&LEAF != 0 && autosize == 0 {
   818  				// A leaf function with no locals has no frame.
   819  				p.From.Sym.Set(obj.AttrNoFrame, true)
   820  			}
   821  
   822  			if !p.From.Sym.NoFrame() {
   823  				// If there is a stack frame at all, it includes
   824  				// space to save the LR.
   825  				autosize += int32(c.ctxt.Arch.FixedFrameSize)
   826  			}
   827  
   828  			if p.Mark&LEAF != 0 && autosize < abi.StackSmall {
   829  				// A leaf function with a small stack can be marked
   830  				// NOSPLIT, avoiding a stack check.
   831  				p.From.Sym.Set(obj.AttrNoSplit, true)
   832  			}
   833  
   834  			p.To.Offset = int64(autosize)
   835  
   836  			q = p
   837  
   838  			if NeedTOCpointer(c.ctxt) && !isNOTOCfunc(c.cursym.Name) {
   839  				// When compiling Go into PIC, without PCrel support, all functions must start
   840  				// with instructions to load the TOC pointer into r2:
   841  				//
   842  				//	addis r2, r12, .TOC.-func@ha
   843  				//	addi r2, r2, .TOC.-func@l+4
   844  				//
   845  				// We could probably skip this prologue in some situations
   846  				// but it's a bit subtle. However, it is both safe and
   847  				// necessary to leave the prologue off duffzero and
   848  				// duffcopy as we rely on being able to jump to a specific
   849  				// instruction offset for them.
   850  				//
   851  				// These are AWORDS because there is no (afaict) way to
   852  				// generate the addis instruction except as part of the
   853  				// load of a large constant, and in that case there is no
   854  				// way to use r12 as the source.
   855  				//
   856  				// Note that the same condition is tested in
   857  				// putelfsym in cmd/link/internal/ld/symtab.go
   858  				// where we set the st_other field to indicate
   859  				// the presence of these instructions.
   860  				q = obj.Appendp(q, c.newprog)
   861  				q.As = AWORD
   862  				q.Pos = p.Pos
   863  				q.From.Type = obj.TYPE_CONST
   864  				q.From.Offset = 0x3c4c0000
   865  				q = obj.Appendp(q, c.newprog)
   866  				q.As = AWORD
   867  				q.Pos = p.Pos
   868  				q.From.Type = obj.TYPE_CONST
   869  				q.From.Offset = 0x38420000
   870  				rel := obj.Addrel(c.cursym)
   871  				rel.Off = 0
   872  				rel.Siz = 8
   873  				rel.Sym = c.ctxt.Lookup(".TOC.")
   874  				rel.Type = objabi.R_ADDRPOWER_PCREL
   875  			}
   876  
   877  			if !c.cursym.Func().Text.From.Sym.NoSplit() {
   878  				q = c.stacksplit(q, autosize) // emit split check
   879  			}
   880  
   881  			if autosize != 0 {
   882  				var prologueEnd *obj.Prog
   883  				// Save the link register and update the SP.  MOVDU is used unless
   884  				// the frame size is too large.  The link register must be saved
   885  				// even for non-empty leaf functions so that traceback works.
   886  				if autosize >= -BIG && autosize <= BIG {
   887  					// Use MOVDU to adjust R1 when saving R31, if autosize is small.
   888  					q = obj.Appendp(q, c.newprog)
   889  					q.As = AMOVD
   890  					q.Pos = p.Pos
   891  					q.From.Type = obj.TYPE_REG
   892  					q.From.Reg = REG_LR
   893  					q.To.Type = obj.TYPE_REG
   894  					q.To.Reg = REGTMP
   895  					prologueEnd = q
   896  
   897  					q = obj.Appendp(q, c.newprog)
   898  					q.As = AMOVDU
   899  					q.Pos = p.Pos
   900  					q.From.Type = obj.TYPE_REG
   901  					q.From.Reg = REGTMP
   902  					q.To.Type = obj.TYPE_MEM
   903  					q.To.Offset = int64(-autosize)
   904  					q.To.Reg = REGSP
   905  					q.Spadj = autosize
   906  				} else {
   907  					// Frame size is too large for a MOVDU instruction.
   908  					// Store link register before decrementing SP, so if a signal comes
   909  					// during the execution of the function prologue, the traceback
   910  					// code will not see a half-updated stack frame.
   911  					// This sequence is not async preemptible, as if we open a frame
   912  					// at the current SP, it will clobber the saved LR.
   913  					q = obj.Appendp(q, c.newprog)
   914  					q.As = AMOVD
   915  					q.Pos = p.Pos
   916  					q.From.Type = obj.TYPE_REG
   917  					q.From.Reg = REG_LR
   918  					q.To.Type = obj.TYPE_REG
   919  					q.To.Reg = REG_R29 // REGTMP may be used to synthesize large offset in the next instruction
   920  
   921  					q = c.ctxt.StartUnsafePoint(q, c.newprog)
   922  
   923  					q = obj.Appendp(q, c.newprog)
   924  					q.As = AMOVD
   925  					q.Pos = p.Pos
   926  					q.From.Type = obj.TYPE_REG
   927  					q.From.Reg = REG_R29
   928  					q.To.Type = obj.TYPE_MEM
   929  					q.To.Offset = int64(-autosize)
   930  					q.To.Reg = REGSP
   931  
   932  					prologueEnd = q
   933  
   934  					q = obj.Appendp(q, c.newprog)
   935  					q.As = AADD
   936  					q.Pos = p.Pos
   937  					q.From.Type = obj.TYPE_CONST
   938  					q.From.Offset = int64(-autosize)
   939  					q.To.Type = obj.TYPE_REG
   940  					q.To.Reg = REGSP
   941  					q.Spadj = +autosize
   942  
   943  					q = c.ctxt.EndUnsafePoint(q, c.newprog, -1)
   944  				}
   945  				prologueEnd.Pos = prologueEnd.Pos.WithXlogue(src.PosPrologueEnd)
   946  			} else if c.cursym.Func().Text.Mark&LEAF == 0 {
   947  				// A very few functions that do not return to their caller
   948  				// (e.g. gogo) are not identified as leaves but still have
   949  				// no frame.
   950  				c.cursym.Func().Text.Mark |= LEAF
   951  			}
   952  
   953  			if c.cursym.Func().Text.Mark&LEAF != 0 {
   954  				c.cursym.Set(obj.AttrLeaf, true)
   955  				break
   956  			}
   957  
   958  			if NeedTOCpointer(c.ctxt) {
   959  				q = obj.Appendp(q, c.newprog)
   960  				q.As = AMOVD
   961  				q.Pos = p.Pos
   962  				q.From.Type = obj.TYPE_REG
   963  				q.From.Reg = REG_R2
   964  				q.To.Type = obj.TYPE_MEM
   965  				q.To.Reg = REGSP
   966  				q.To.Offset = 24
   967  			}
   968  
   969  			if c.cursym.Func().Text.From.Sym.Wrapper() {
   970  				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
   971  				//
   972  				//	MOVD g_panic(g), R22
   973  				//	CMP R22, $0
   974  				//	BEQ end
   975  				//	MOVD panic_argp(R22), R23
   976  				//	ADD $(autosize+8), R1, R24
   977  				//	CMP R23, R24
   978  				//	BNE end
   979  				//	ADD $8, R1, R25
   980  				//	MOVD R25, panic_argp(R22)
   981  				// end:
   982  				//	NOP
   983  				//
   984  				// The NOP is needed to give the jumps somewhere to land.
   985  				// It is a liblink NOP, not a ppc64 NOP: it encodes to 0 instruction bytes.
   986  
   987  				q = obj.Appendp(q, c.newprog)
   988  
   989  				q.As = AMOVD
   990  				q.From.Type = obj.TYPE_MEM
   991  				q.From.Reg = REGG
   992  				q.From.Offset = 4 * int64(c.ctxt.Arch.PtrSize) // G.panic
   993  				q.To.Type = obj.TYPE_REG
   994  				q.To.Reg = REG_R22
   995  
   996  				q = obj.Appendp(q, c.newprog)
   997  				q.As = ACMP
   998  				q.From.Type = obj.TYPE_REG
   999  				q.From.Reg = REG_R22
  1000  				q.To.Type = obj.TYPE_CONST
  1001  				q.To.Offset = 0
  1002  
  1003  				q = obj.Appendp(q, c.newprog)
  1004  				q.As = ABEQ
  1005  				q.To.Type = obj.TYPE_BRANCH
  1006  				p1 = q
  1007  
  1008  				q = obj.Appendp(q, c.newprog)
  1009  				q.As = AMOVD
  1010  				q.From.Type = obj.TYPE_MEM
  1011  				q.From.Reg = REG_R22
  1012  				q.From.Offset = 0 // Panic.argp
  1013  				q.To.Type = obj.TYPE_REG
  1014  				q.To.Reg = REG_R23
  1015  
  1016  				q = obj.Appendp(q, c.newprog)
  1017  				q.As = AADD
  1018  				q.From.Type = obj.TYPE_CONST
  1019  				q.From.Offset = int64(autosize) + c.ctxt.Arch.FixedFrameSize
  1020  				q.Reg = REGSP
  1021  				q.To.Type = obj.TYPE_REG
  1022  				q.To.Reg = REG_R24
  1023  
  1024  				q = obj.Appendp(q, c.newprog)
  1025  				q.As = ACMP
  1026  				q.From.Type = obj.TYPE_REG
  1027  				q.From.Reg = REG_R23
  1028  				q.To.Type = obj.TYPE_REG
  1029  				q.To.Reg = REG_R24
  1030  
  1031  				q = obj.Appendp(q, c.newprog)
  1032  				q.As = ABNE
  1033  				q.To.Type = obj.TYPE_BRANCH
  1034  				p2 = q
  1035  
  1036  				q = obj.Appendp(q, c.newprog)
  1037  				q.As = AADD
  1038  				q.From.Type = obj.TYPE_CONST
  1039  				q.From.Offset = c.ctxt.Arch.FixedFrameSize
  1040  				q.Reg = REGSP
  1041  				q.To.Type = obj.TYPE_REG
  1042  				q.To.Reg = REG_R25
  1043  
  1044  				q = obj.Appendp(q, c.newprog)
  1045  				q.As = AMOVD
  1046  				q.From.Type = obj.TYPE_REG
  1047  				q.From.Reg = REG_R25
  1048  				q.To.Type = obj.TYPE_MEM
  1049  				q.To.Reg = REG_R22
  1050  				q.To.Offset = 0 // Panic.argp
  1051  
  1052  				q = obj.Appendp(q, c.newprog)
  1053  
  1054  				q.As = obj.ANOP
  1055  				p1.To.SetTarget(q)
  1056  				p2.To.SetTarget(q)
  1057  			}
  1058  
  1059  		case obj.ARET:
  1060  			if p.From.Type == obj.TYPE_CONST {
  1061  				c.ctxt.Diag("using BECOME (%v) is not supported!", p)
  1062  				break
  1063  			}
  1064  
  1065  			retTarget := p.To.Sym
  1066  
  1067  			if c.cursym.Func().Text.Mark&LEAF != 0 {
  1068  				if autosize == 0 {
  1069  					p.As = ABR
  1070  					p.From = obj.Addr{}
  1071  					if retTarget == nil {
  1072  						p.To.Type = obj.TYPE_REG
  1073  						p.To.Reg = REG_LR
  1074  					} else {
  1075  						p.To.Type = obj.TYPE_BRANCH
  1076  						p.To.Sym = retTarget
  1077  					}
  1078  					p.Mark |= BRANCH
  1079  					break
  1080  				}
  1081  
  1082  				p.As = AADD
  1083  				p.From.Type = obj.TYPE_CONST
  1084  				p.From.Offset = int64(autosize)
  1085  				p.To.Type = obj.TYPE_REG
  1086  				p.To.Reg = REGSP
  1087  				p.Spadj = -autosize
  1088  
  1089  				q = c.newprog()
  1090  				q.As = ABR
  1091  				q.Pos = p.Pos
  1092  				if retTarget == nil {
  1093  					q.To.Type = obj.TYPE_REG
  1094  					q.To.Reg = REG_LR
  1095  				} else {
  1096  					q.To.Type = obj.TYPE_BRANCH
  1097  					q.To.Sym = retTarget
  1098  				}
  1099  				q.Mark |= BRANCH
  1100  				q.Spadj = +autosize
  1101  
  1102  				q.Link = p.Link
  1103  				p.Link = q
  1104  				break
  1105  			}
  1106  
  1107  			p.As = AMOVD
  1108  			p.From.Type = obj.TYPE_MEM
  1109  			p.From.Offset = 0
  1110  			p.From.Reg = REGSP
  1111  			p.To.Type = obj.TYPE_REG
  1112  			p.To.Reg = REGTMP
  1113  
  1114  			q = c.newprog()
  1115  			q.As = AMOVD
  1116  			q.Pos = p.Pos
  1117  			q.From.Type = obj.TYPE_REG
  1118  			q.From.Reg = REGTMP
  1119  			q.To.Type = obj.TYPE_REG
  1120  			q.To.Reg = REG_LR
  1121  
  1122  			q.Link = p.Link
  1123  			p.Link = q
  1124  			p = q
  1125  
  1126  			if false {
  1127  				// Debug bad returns
  1128  				q = c.newprog()
  1129  
  1130  				q.As = AMOVD
  1131  				q.Pos = p.Pos
  1132  				q.From.Type = obj.TYPE_MEM
  1133  				q.From.Offset = 0
  1134  				q.From.Reg = REGTMP
  1135  				q.To.Type = obj.TYPE_REG
  1136  				q.To.Reg = REGTMP
  1137  
  1138  				q.Link = p.Link
  1139  				p.Link = q
  1140  				p = q
  1141  			}
  1142  			prev := p
  1143  			if autosize != 0 {
  1144  				q = c.newprog()
  1145  				q.As = AADD
  1146  				q.Pos = p.Pos
  1147  				q.From.Type = obj.TYPE_CONST
  1148  				q.From.Offset = int64(autosize)
  1149  				q.To.Type = obj.TYPE_REG
  1150  				q.To.Reg = REGSP
  1151  				q.Spadj = -autosize
  1152  
  1153  				q.Link = p.Link
  1154  				prev.Link = q
  1155  				prev = q
  1156  			}
  1157  
  1158  			q1 = c.newprog()
  1159  			q1.As = ABR
  1160  			q1.Pos = p.Pos
  1161  			if retTarget == nil {
  1162  				q1.To.Type = obj.TYPE_REG
  1163  				q1.To.Reg = REG_LR
  1164  			} else {
  1165  				q1.To.Type = obj.TYPE_BRANCH
  1166  				q1.To.Sym = retTarget
  1167  			}
  1168  			q1.Mark |= BRANCH
  1169  			q1.Spadj = +autosize
  1170  
  1171  			q1.Link = q.Link
  1172  			prev.Link = q1
  1173  		case AADD:
  1174  			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
  1175  				p.Spadj = int32(-p.From.Offset)
  1176  			}
  1177  		case AMOVDU:
  1178  			if p.To.Type == obj.TYPE_MEM && p.To.Reg == REGSP {
  1179  				p.Spadj = int32(-p.To.Offset)
  1180  			}
  1181  			if p.From.Type == obj.TYPE_MEM && p.From.Reg == REGSP {
  1182  				p.Spadj = int32(-p.From.Offset)
  1183  			}
  1184  		case obj.AGETCALLERPC:
  1185  			if cursym.Leaf() {
  1186  				/* MOVD LR, Rd */
  1187  				p.As = AMOVD
  1188  				p.From.Type = obj.TYPE_REG
  1189  				p.From.Reg = REG_LR
  1190  			} else {
  1191  				/* MOVD (RSP), Rd */
  1192  				p.As = AMOVD
  1193  				p.From.Type = obj.TYPE_MEM
  1194  				p.From.Reg = REGSP
  1195  			}
  1196  		}
  1197  
  1198  		if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.Spadj == 0 && p.As != ACMPU {
  1199  			f := c.cursym.Func()
  1200  			if f.FuncFlag&abi.FuncFlagSPWrite == 0 {
  1201  				c.cursym.Func().FuncFlag |= abi.FuncFlagSPWrite
  1202  				if ctxt.Debugvlog || !ctxt.IsAsm {
  1203  					ctxt.Logf("auto-SPWRITE: %s %v\n", c.cursym.Name, p)
  1204  					if !ctxt.IsAsm {
  1205  						ctxt.Diag("invalid auto-SPWRITE in non-assembly")
  1206  						ctxt.DiagFlush()
  1207  						log.Fatalf("bad SPWRITE")
  1208  					}
  1209  				}
  1210  			}
  1211  		}
  1212  	}
  1213  }
  1214  
  1215  /*
  1216  // instruction scheduling
  1217  
  1218  	if(debug['Q'] == 0)
  1219  		return;
  1220  
  1221  	curtext = nil;
  1222  	q = nil;	// p - 1
  1223  	q1 = firstp;	// top of block
  1224  	o = 0;		// count of instructions
  1225  	for(p = firstp; p != nil; p = p1) {
  1226  		p1 = p->link;
  1227  		o++;
  1228  		if(p->mark & NOSCHED){
  1229  			if(q1 != p){
  1230  				sched(q1, q);
  1231  			}
  1232  			for(; p != nil; p = p->link){
  1233  				if(!(p->mark & NOSCHED))
  1234  					break;
  1235  				q = p;
  1236  			}
  1237  			p1 = p;
  1238  			q1 = p;
  1239  			o = 0;
  1240  			continue;
  1241  		}
  1242  		if(p->mark & (LABEL|SYNC)) {
  1243  			if(q1 != p)
  1244  				sched(q1, q);
  1245  			q1 = p;
  1246  			o = 1;
  1247  		}
  1248  		if(p->mark & (BRANCH|SYNC)) {
  1249  			sched(q1, p);
  1250  			q1 = p1;
  1251  			o = 0;
  1252  		}
  1253  		if(o >= NSCHED) {
  1254  			sched(q1, p);
  1255  			q1 = p1;
  1256  			o = 0;
  1257  		}
  1258  		q = p;
  1259  	}
  1260  */
  1261  func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
  1262  	if c.ctxt.Flag_maymorestack != "" {
  1263  		if c.ctxt.Flag_shared || c.ctxt.Flag_dynlink {
  1264  			// See the call to morestack for why these are
  1265  			// complicated to support.
  1266  			c.ctxt.Diag("maymorestack with -shared or -dynlink is not supported")
  1267  		}
  1268  
  1269  		// Spill arguments. This has to happen before we open
  1270  		// any more frame space.
  1271  		p = c.cursym.Func().SpillRegisterArgs(p, c.newprog)
  1272  
  1273  		// Save LR and REGCTXT
  1274  		frameSize := 8 + c.ctxt.Arch.FixedFrameSize
  1275  
  1276  		// MOVD LR, REGTMP
  1277  		p = obj.Appendp(p, c.newprog)
  1278  		p.As = AMOVD
  1279  		p.From.Type = obj.TYPE_REG
  1280  		p.From.Reg = REG_LR
  1281  		p.To.Type = obj.TYPE_REG
  1282  		p.To.Reg = REGTMP
  1283  		// MOVDU REGTMP, -16(SP)
  1284  		p = obj.Appendp(p, c.newprog)
  1285  		p.As = AMOVDU
  1286  		p.From.Type = obj.TYPE_REG
  1287  		p.From.Reg = REGTMP
  1288  		p.To.Type = obj.TYPE_MEM
  1289  		p.To.Offset = -frameSize
  1290  		p.To.Reg = REGSP
  1291  		p.Spadj = int32(frameSize)
  1292  
  1293  		// MOVD REGCTXT, 8(SP)
  1294  		p = obj.Appendp(p, c.newprog)
  1295  		p.As = AMOVD
  1296  		p.From.Type = obj.TYPE_REG
  1297  		p.From.Reg = REGCTXT
  1298  		p.To.Type = obj.TYPE_MEM
  1299  		p.To.Offset = 8
  1300  		p.To.Reg = REGSP
  1301  
  1302  		// BL maymorestack
  1303  		p = obj.Appendp(p, c.newprog)
  1304  		p.As = ABL
  1305  		p.To.Type = obj.TYPE_BRANCH
  1306  		// See ../x86/obj6.go
  1307  		p.To.Sym = c.ctxt.LookupABI(c.ctxt.Flag_maymorestack, c.cursym.ABI())
  1308  
  1309  		// Restore LR and REGCTXT
  1310  
  1311  		// MOVD 8(SP), REGCTXT
  1312  		p = obj.Appendp(p, c.newprog)
  1313  		p.As = AMOVD
  1314  		p.From.Type = obj.TYPE_MEM
  1315  		p.From.Offset = 8
  1316  		p.From.Reg = REGSP
  1317  		p.To.Type = obj.TYPE_REG
  1318  		p.To.Reg = REGCTXT
  1319  
  1320  		// MOVD 0(SP), REGTMP
  1321  		p = obj.Appendp(p, c.newprog)
  1322  		p.As = AMOVD
  1323  		p.From.Type = obj.TYPE_MEM
  1324  		p.From.Offset = 0
  1325  		p.From.Reg = REGSP
  1326  		p.To.Type = obj.TYPE_REG
  1327  		p.To.Reg = REGTMP
  1328  
  1329  		// MOVD REGTMP, LR
  1330  		p = obj.Appendp(p, c.newprog)
  1331  		p.As = AMOVD
  1332  		p.From.Type = obj.TYPE_REG
  1333  		p.From.Reg = REGTMP
  1334  		p.To.Type = obj.TYPE_REG
  1335  		p.To.Reg = REG_LR
  1336  
  1337  		// ADD $16, SP
  1338  		p = obj.Appendp(p, c.newprog)
  1339  		p.As = AADD
  1340  		p.From.Type = obj.TYPE_CONST
  1341  		p.From.Offset = frameSize
  1342  		p.To.Type = obj.TYPE_REG
  1343  		p.To.Reg = REGSP
  1344  		p.Spadj = -int32(frameSize)
  1345  
  1346  		// Unspill arguments.
  1347  		p = c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
  1348  	}
  1349  
  1350  	// save entry point, but skipping the two instructions setting R2 in shared mode and maymorestack
  1351  	startPred := p
  1352  
  1353  	// MOVD	g_stackguard(g), R22
  1354  	p = obj.Appendp(p, c.newprog)
  1355  
  1356  	p.As = AMOVD
  1357  	p.From.Type = obj.TYPE_MEM
  1358  	p.From.Reg = REGG
  1359  	p.From.Offset = 2 * int64(c.ctxt.Arch.PtrSize) // G.stackguard0
  1360  	if c.cursym.CFunc() {
  1361  		p.From.Offset = 3 * int64(c.ctxt.Arch.PtrSize) // G.stackguard1
  1362  	}
  1363  	p.To.Type = obj.TYPE_REG
  1364  	p.To.Reg = REG_R22
  1365  
  1366  	// Mark the stack bound check and morestack call async nonpreemptible.
  1367  	// If we get preempted here, when resumed the preemption request is
  1368  	// cleared, but we'll still call morestack, which will double the stack
  1369  	// unnecessarily. See issue #35470.
  1370  	p = c.ctxt.StartUnsafePoint(p, c.newprog)
  1371  
  1372  	var q *obj.Prog
  1373  	if framesize <= abi.StackSmall {
  1374  		// small stack: SP < stackguard
  1375  		//	CMP	stackguard, SP
  1376  		p = obj.Appendp(p, c.newprog)
  1377  
  1378  		p.As = ACMPU
  1379  		p.From.Type = obj.TYPE_REG
  1380  		p.From.Reg = REG_R22
  1381  		p.To.Type = obj.TYPE_REG
  1382  		p.To.Reg = REGSP
  1383  	} else {
  1384  		// large stack: SP-framesize < stackguard-StackSmall
  1385  		offset := int64(framesize) - abi.StackSmall
  1386  		if framesize > abi.StackBig {
  1387  			// Such a large stack we need to protect against underflow.
  1388  			// The runtime guarantees SP > objabi.StackBig, but
  1389  			// framesize is large enough that SP-framesize may
  1390  			// underflow, causing a direct comparison with the
  1391  			// stack guard to incorrectly succeed. We explicitly
  1392  			// guard against underflow.
  1393  			//
  1394  			//	CMPU	SP, $(framesize-StackSmall)
  1395  			//	BLT	label-of-call-to-morestack
  1396  			if offset <= 0xffff {
  1397  				p = obj.Appendp(p, c.newprog)
  1398  				p.As = ACMPU
  1399  				p.From.Type = obj.TYPE_REG
  1400  				p.From.Reg = REGSP
  1401  				p.To.Type = obj.TYPE_CONST
  1402  				p.To.Offset = offset
  1403  			} else {
  1404  				// Constant is too big for CMPU.
  1405  				p = obj.Appendp(p, c.newprog)
  1406  				p.As = AMOVD
  1407  				p.From.Type = obj.TYPE_CONST
  1408  				p.From.Offset = offset
  1409  				p.To.Type = obj.TYPE_REG
  1410  				p.To.Reg = REG_R23
  1411  
  1412  				p = obj.Appendp(p, c.newprog)
  1413  				p.As = ACMPU
  1414  				p.From.Type = obj.TYPE_REG
  1415  				p.From.Reg = REGSP
  1416  				p.To.Type = obj.TYPE_REG
  1417  				p.To.Reg = REG_R23
  1418  			}
  1419  
  1420  			p = obj.Appendp(p, c.newprog)
  1421  			q = p
  1422  			p.As = ABLT
  1423  			p.To.Type = obj.TYPE_BRANCH
  1424  		}
  1425  
  1426  		// Check against the stack guard. We've ensured this won't underflow.
  1427  		//	ADD  $-(framesize-StackSmall), SP, R4
  1428  		//	CMPU stackguard, R4
  1429  		p = obj.Appendp(p, c.newprog)
  1430  
  1431  		p.As = AADD
  1432  		p.From.Type = obj.TYPE_CONST
  1433  		p.From.Offset = -offset
  1434  		p.Reg = REGSP
  1435  		p.To.Type = obj.TYPE_REG
  1436  		p.To.Reg = REG_R23
  1437  
  1438  		p = obj.Appendp(p, c.newprog)
  1439  		p.As = ACMPU
  1440  		p.From.Type = obj.TYPE_REG
  1441  		p.From.Reg = REG_R22
  1442  		p.To.Type = obj.TYPE_REG
  1443  		p.To.Reg = REG_R23
  1444  	}
  1445  
  1446  	// q1: BLT	done
  1447  	p = obj.Appendp(p, c.newprog)
  1448  	q1 := p
  1449  
  1450  	p.As = ABLT
  1451  	p.To.Type = obj.TYPE_BRANCH
  1452  
  1453  	p = obj.Appendp(p, c.newprog)
  1454  	p.As = obj.ANOP // zero-width place holder
  1455  
  1456  	if q != nil {
  1457  		q.To.SetTarget(p)
  1458  	}
  1459  
  1460  	// Spill the register args that could be clobbered by the
  1461  	// morestack code.
  1462  
  1463  	spill := c.cursym.Func().SpillRegisterArgs(p, c.newprog)
  1464  
  1465  	// MOVD LR, R5
  1466  	p = obj.Appendp(spill, c.newprog)
  1467  	p.As = AMOVD
  1468  	p.From.Type = obj.TYPE_REG
  1469  	p.From.Reg = REG_LR
  1470  	p.To.Type = obj.TYPE_REG
  1471  	p.To.Reg = REG_R5
  1472  
  1473  	p = c.ctxt.EmitEntryStackMap(c.cursym, p, c.newprog)
  1474  
  1475  	var morestacksym *obj.LSym
  1476  	if c.cursym.CFunc() {
  1477  		morestacksym = c.ctxt.Lookup("runtime.morestackc")
  1478  	} else if !c.cursym.Func().Text.From.Sym.NeedCtxt() {
  1479  		morestacksym = c.ctxt.Lookup("runtime.morestack_noctxt")
  1480  	} else {
  1481  		morestacksym = c.ctxt.Lookup("runtime.morestack")
  1482  	}
  1483  
  1484  	if NeedTOCpointer(c.ctxt) {
  1485  		// In PPC64 PIC code, R2 is used as TOC pointer derived from R12
  1486  		// which is the address of function entry point when entering
  1487  		// the function. We need to preserve R2 across call to morestack.
  1488  		// Fortunately, in shared mode, 8(SP) and 16(SP) are reserved in
  1489  		// the caller's frame, but not used (0(SP) is caller's saved LR,
  1490  		// 24(SP) is caller's saved R2). Use 8(SP) to save this function's R2.
  1491  		// MOVD R2, 8(SP)
  1492  		p = obj.Appendp(p, c.newprog)
  1493  		p.As = AMOVD
  1494  		p.From.Type = obj.TYPE_REG
  1495  		p.From.Reg = REG_R2
  1496  		p.To.Type = obj.TYPE_MEM
  1497  		p.To.Reg = REGSP
  1498  		p.To.Offset = 8
  1499  	}
  1500  
  1501  	if c.ctxt.Flag_dynlink {
  1502  		// Avoid calling morestack via a PLT when dynamically linking. The
  1503  		// PLT stubs generated by the system linker on ppc64le when "std r2,
  1504  		// 24(r1)" to save the TOC pointer in their callers stack
  1505  		// frame. Unfortunately (and necessarily) morestack is called before
  1506  		// the function that calls it sets up its frame and so the PLT ends
  1507  		// up smashing the saved TOC pointer for its caller's caller.
  1508  		//
  1509  		// According to the ABI documentation there is a mechanism to avoid
  1510  		// the TOC save that the PLT stub does (put a R_PPC64_TOCSAVE
  1511  		// relocation on the nop after the call to morestack) but at the time
  1512  		// of writing it is not supported at all by gold and my attempt to
  1513  		// use it with ld.bfd caused an internal linker error. So this hack
  1514  		// seems preferable.
  1515  
  1516  		// MOVD $runtime.morestack(SB), R12
  1517  		p = obj.Appendp(p, c.newprog)
  1518  		p.As = AMOVD
  1519  		p.From.Type = obj.TYPE_MEM
  1520  		p.From.Sym = morestacksym
  1521  		p.From.Name = obj.NAME_GOTREF
  1522  		p.To.Type = obj.TYPE_REG
  1523  		p.To.Reg = REG_R12
  1524  
  1525  		// MOVD R12, LR
  1526  		p = obj.Appendp(p, c.newprog)
  1527  		p.As = AMOVD
  1528  		p.From.Type = obj.TYPE_REG
  1529  		p.From.Reg = REG_R12
  1530  		p.To.Type = obj.TYPE_REG
  1531  		p.To.Reg = REG_LR
  1532  
  1533  		// BL LR
  1534  		p = obj.Appendp(p, c.newprog)
  1535  		p.As = obj.ACALL
  1536  		p.To.Type = obj.TYPE_REG
  1537  		p.To.Reg = REG_LR
  1538  	} else {
  1539  		// BL	runtime.morestack(SB)
  1540  		p = obj.Appendp(p, c.newprog)
  1541  
  1542  		p.As = ABL
  1543  		p.To.Type = obj.TYPE_BRANCH
  1544  		p.To.Sym = morestacksym
  1545  	}
  1546  
  1547  	if NeedTOCpointer(c.ctxt) {
  1548  		// MOVD 8(SP), R2
  1549  		p = obj.Appendp(p, c.newprog)
  1550  		p.As = AMOVD
  1551  		p.From.Type = obj.TYPE_MEM
  1552  		p.From.Reg = REGSP
  1553  		p.From.Offset = 8
  1554  		p.To.Type = obj.TYPE_REG
  1555  		p.To.Reg = REG_R2
  1556  	}
  1557  
  1558  	// The instructions which unspill regs should be preemptible.
  1559  	p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
  1560  	unspill := c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
  1561  
  1562  	// BR	start
  1563  	p = obj.Appendp(unspill, c.newprog)
  1564  	p.As = ABR
  1565  	p.To.Type = obj.TYPE_BRANCH
  1566  	p.To.SetTarget(startPred.Link)
  1567  
  1568  	// placeholder for q1's jump target
  1569  	p = obj.Appendp(p, c.newprog)
  1570  
  1571  	p.As = obj.ANOP // zero-width place holder
  1572  	q1.To.SetTarget(p)
  1573  
  1574  	return p
  1575  }
  1576  
  1577  // MMA accumulator to/from instructions are slightly ambiguous since
  1578  // the argument represents both source and destination, specified as
  1579  // an accumulator. It is treated as a unary destination to simplify
  1580  // the code generation in ppc64map.
  1581  var unaryDst = map[obj.As]bool{
  1582  	AXXSETACCZ: true,
  1583  	AXXMTACC:   true,
  1584  	AXXMFACC:   true,
  1585  }
  1586  
  1587  var Linkppc64 = obj.LinkArch{
  1588  	Arch:           sys.ArchPPC64,
  1589  	Init:           buildop,
  1590  	Preprocess:     preprocess,
  1591  	Assemble:       span9,
  1592  	Progedit:       progedit,
  1593  	UnaryDst:       unaryDst,
  1594  	DWARFRegisters: PPC64DWARFRegisters,
  1595  }
  1596  
  1597  var Linkppc64le = obj.LinkArch{
  1598  	Arch:           sys.ArchPPC64LE,
  1599  	Init:           buildop,
  1600  	Preprocess:     preprocess,
  1601  	Assemble:       span9,
  1602  	Progedit:       progedit,
  1603  	UnaryDst:       unaryDst,
  1604  	DWARFRegisters: PPC64DWARFRegisters,
  1605  }
  1606
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