Source file src/cmd/internal/obj/ppc64/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  				c.cursym.AddRel(c.ctxt, obj.Reloc{
   871  					Type: objabi.R_ADDRPOWER_PCREL,
   872  					Off:  0,
   873  					Siz:  8,
   874  					Sym:  c.ctxt.Lookup(".TOC."),
   875  				})
   876  			}
   877  
   878  			if !c.cursym.Func().Text.From.Sym.NoSplit() {
   879  				q = c.stacksplit(q, autosize) // emit split check
   880  			}
   881  
   882  			if autosize != 0 {
   883  				var prologueEnd *obj.Prog
   884  				// Save the link register and update the SP.  MOVDU is used unless
   885  				// the frame size is too large.  The link register must be saved
   886  				// even for non-empty leaf functions so that traceback works.
   887  				if autosize >= -BIG && autosize <= BIG {
   888  					// Use MOVDU to adjust R1 when saving R31, if autosize is small.
   889  					q = obj.Appendp(q, c.newprog)
   890  					q.As = AMOVD
   891  					q.Pos = p.Pos
   892  					q.From.Type = obj.TYPE_REG
   893  					q.From.Reg = REG_LR
   894  					q.To.Type = obj.TYPE_REG
   895  					q.To.Reg = REGTMP
   896  					prologueEnd = q
   897  
   898  					q = obj.Appendp(q, c.newprog)
   899  					q.As = AMOVDU
   900  					q.Pos = p.Pos
   901  					q.From.Type = obj.TYPE_REG
   902  					q.From.Reg = REGTMP
   903  					q.To.Type = obj.TYPE_MEM
   904  					q.To.Offset = int64(-autosize)
   905  					q.To.Reg = REGSP
   906  					q.Spadj = autosize
   907  				} else {
   908  					// Frame size is too large for a MOVDU instruction.
   909  					// Store link register before decrementing SP, so if a signal comes
   910  					// during the execution of the function prologue, the traceback
   911  					// code will not see a half-updated stack frame.
   912  					// This sequence is not async preemptible, as if we open a frame
   913  					// at the current SP, it will clobber the saved LR.
   914  					q = obj.Appendp(q, c.newprog)
   915  					q.As = AMOVD
   916  					q.Pos = p.Pos
   917  					q.From.Type = obj.TYPE_REG
   918  					q.From.Reg = REG_LR
   919  					q.To.Type = obj.TYPE_REG
   920  					q.To.Reg = REG_R29 // REGTMP may be used to synthesize large offset in the next instruction
   921  
   922  					q = c.ctxt.StartUnsafePoint(q, c.newprog)
   923  
   924  					q = obj.Appendp(q, c.newprog)
   925  					q.As = AMOVD
   926  					q.Pos = p.Pos
   927  					q.From.Type = obj.TYPE_REG
   928  					q.From.Reg = REG_R29
   929  					q.To.Type = obj.TYPE_MEM
   930  					q.To.Offset = int64(-autosize)
   931  					q.To.Reg = REGSP
   932  
   933  					prologueEnd = q
   934  
   935  					q = obj.Appendp(q, c.newprog)
   936  					q.As = AADD
   937  					q.Pos = p.Pos
   938  					q.From.Type = obj.TYPE_CONST
   939  					q.From.Offset = int64(-autosize)
   940  					q.To.Type = obj.TYPE_REG
   941  					q.To.Reg = REGSP
   942  					q.Spadj = +autosize
   943  
   944  					q = c.ctxt.EndUnsafePoint(q, c.newprog, -1)
   945  				}
   946  				prologueEnd.Pos = prologueEnd.Pos.WithXlogue(src.PosPrologueEnd)
   947  			} else if c.cursym.Func().Text.Mark&LEAF == 0 {
   948  				// A very few functions that do not return to their caller
   949  				// (e.g. gogo) are not identified as leaves but still have
   950  				// no frame.
   951  				c.cursym.Func().Text.Mark |= LEAF
   952  			}
   953  
   954  			if c.cursym.Func().Text.Mark&LEAF != 0 {
   955  				c.cursym.Set(obj.AttrLeaf, true)
   956  				break
   957  			}
   958  
   959  			if NeedTOCpointer(c.ctxt) {
   960  				q = obj.Appendp(q, c.newprog)
   961  				q.As = AMOVD
   962  				q.Pos = p.Pos
   963  				q.From.Type = obj.TYPE_REG
   964  				q.From.Reg = REG_R2
   965  				q.To.Type = obj.TYPE_MEM
   966  				q.To.Reg = REGSP
   967  				q.To.Offset = 24
   968  			}
   969  
   970  			if c.cursym.Func().Text.From.Sym.Wrapper() {
   971  				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
   972  				//
   973  				//	MOVD g_panic(g), R22
   974  				//	CMP R22, $0
   975  				//	BEQ end
   976  				//	MOVD panic_argp(R22), R23
   977  				//	ADD $(autosize+8), R1, R24
   978  				//	CMP R23, R24
   979  				//	BNE end
   980  				//	ADD $8, R1, R25
   981  				//	MOVD R25, panic_argp(R22)
   982  				// end:
   983  				//	NOP
   984  				//
   985  				// The NOP is needed to give the jumps somewhere to land.
   986  				// It is a liblink NOP, not a ppc64 NOP: it encodes to 0 instruction bytes.
   987  
   988  				q = obj.Appendp(q, c.newprog)
   989  
   990  				q.As = AMOVD
   991  				q.From.Type = obj.TYPE_MEM
   992  				q.From.Reg = REGG
   993  				q.From.Offset = 4 * int64(c.ctxt.Arch.PtrSize) // G.panic
   994  				q.To.Type = obj.TYPE_REG
   995  				q.To.Reg = REG_R22
   996  
   997  				q = obj.Appendp(q, c.newprog)
   998  				q.As = ACMP
   999  				q.From.Type = obj.TYPE_REG
  1000  				q.From.Reg = REG_R22
  1001  				q.To.Type = obj.TYPE_CONST
  1002  				q.To.Offset = 0
  1003  
  1004  				q = obj.Appendp(q, c.newprog)
  1005  				q.As = ABEQ
  1006  				q.To.Type = obj.TYPE_BRANCH
  1007  				p1 = q
  1008  
  1009  				q = obj.Appendp(q, c.newprog)
  1010  				q.As = AMOVD
  1011  				q.From.Type = obj.TYPE_MEM
  1012  				q.From.Reg = REG_R22
  1013  				q.From.Offset = 0 // Panic.argp
  1014  				q.To.Type = obj.TYPE_REG
  1015  				q.To.Reg = REG_R23
  1016  
  1017  				q = obj.Appendp(q, c.newprog)
  1018  				q.As = AADD
  1019  				q.From.Type = obj.TYPE_CONST
  1020  				q.From.Offset = int64(autosize) + c.ctxt.Arch.FixedFrameSize
  1021  				q.Reg = REGSP
  1022  				q.To.Type = obj.TYPE_REG
  1023  				q.To.Reg = REG_R24
  1024  
  1025  				q = obj.Appendp(q, c.newprog)
  1026  				q.As = ACMP
  1027  				q.From.Type = obj.TYPE_REG
  1028  				q.From.Reg = REG_R23
  1029  				q.To.Type = obj.TYPE_REG
  1030  				q.To.Reg = REG_R24
  1031  
  1032  				q = obj.Appendp(q, c.newprog)
  1033  				q.As = ABNE
  1034  				q.To.Type = obj.TYPE_BRANCH
  1035  				p2 = q
  1036  
  1037  				q = obj.Appendp(q, c.newprog)
  1038  				q.As = AADD
  1039  				q.From.Type = obj.TYPE_CONST
  1040  				q.From.Offset = c.ctxt.Arch.FixedFrameSize
  1041  				q.Reg = REGSP
  1042  				q.To.Type = obj.TYPE_REG
  1043  				q.To.Reg = REG_R25
  1044  
  1045  				q = obj.Appendp(q, c.newprog)
  1046  				q.As = AMOVD
  1047  				q.From.Type = obj.TYPE_REG
  1048  				q.From.Reg = REG_R25
  1049  				q.To.Type = obj.TYPE_MEM
  1050  				q.To.Reg = REG_R22
  1051  				q.To.Offset = 0 // Panic.argp
  1052  
  1053  				q = obj.Appendp(q, c.newprog)
  1054  
  1055  				q.As = obj.ANOP
  1056  				p1.To.SetTarget(q)
  1057  				p2.To.SetTarget(q)
  1058  			}
  1059  
  1060  		case obj.ARET:
  1061  			if p.From.Type == obj.TYPE_CONST {
  1062  				c.ctxt.Diag("using BECOME (%v) is not supported!", p)
  1063  				break
  1064  			}
  1065  
  1066  			retTarget := p.To.Sym
  1067  
  1068  			if c.cursym.Func().Text.Mark&LEAF != 0 {
  1069  				if autosize == 0 {
  1070  					p.As = ABR
  1071  					p.From = obj.Addr{}
  1072  					if retTarget == nil {
  1073  						p.To.Type = obj.TYPE_REG
  1074  						p.To.Reg = REG_LR
  1075  					} else {
  1076  						p.To.Type = obj.TYPE_BRANCH
  1077  						p.To.Sym = retTarget
  1078  					}
  1079  					p.Mark |= BRANCH
  1080  					break
  1081  				}
  1082  
  1083  				p.As = AADD
  1084  				p.From.Type = obj.TYPE_CONST
  1085  				p.From.Offset = int64(autosize)
  1086  				p.To.Type = obj.TYPE_REG
  1087  				p.To.Reg = REGSP
  1088  				p.Spadj = -autosize
  1089  
  1090  				q = c.newprog()
  1091  				q.As = ABR
  1092  				q.Pos = p.Pos
  1093  				if retTarget == nil {
  1094  					q.To.Type = obj.TYPE_REG
  1095  					q.To.Reg = REG_LR
  1096  				} else {
  1097  					q.To.Type = obj.TYPE_BRANCH
  1098  					q.To.Sym = retTarget
  1099  				}
  1100  				q.Mark |= BRANCH
  1101  				q.Spadj = +autosize
  1102  
  1103  				q.Link = p.Link
  1104  				p.Link = q
  1105  				break
  1106  			}
  1107  
  1108  			p.As = AMOVD
  1109  			p.From.Type = obj.TYPE_MEM
  1110  			p.From.Offset = 0
  1111  			p.From.Reg = REGSP
  1112  			p.To.Type = obj.TYPE_REG
  1113  			p.To.Reg = REGTMP
  1114  
  1115  			q = c.newprog()
  1116  			q.As = AMOVD
  1117  			q.Pos = p.Pos
  1118  			q.From.Type = obj.TYPE_REG
  1119  			q.From.Reg = REGTMP
  1120  			q.To.Type = obj.TYPE_REG
  1121  			q.To.Reg = REG_LR
  1122  
  1123  			q.Link = p.Link
  1124  			p.Link = q
  1125  			p = q
  1126  
  1127  			if false {
  1128  				// Debug bad returns
  1129  				q = c.newprog()
  1130  
  1131  				q.As = AMOVD
  1132  				q.Pos = p.Pos
  1133  				q.From.Type = obj.TYPE_MEM
  1134  				q.From.Offset = 0
  1135  				q.From.Reg = REGTMP
  1136  				q.To.Type = obj.TYPE_REG
  1137  				q.To.Reg = REGTMP
  1138  
  1139  				q.Link = p.Link
  1140  				p.Link = q
  1141  				p = q
  1142  			}
  1143  			prev := p
  1144  			if autosize != 0 {
  1145  				q = c.newprog()
  1146  				q.As = AADD
  1147  				q.Pos = p.Pos
  1148  				q.From.Type = obj.TYPE_CONST
  1149  				q.From.Offset = int64(autosize)
  1150  				q.To.Type = obj.TYPE_REG
  1151  				q.To.Reg = REGSP
  1152  				q.Spadj = -autosize
  1153  
  1154  				q.Link = p.Link
  1155  				prev.Link = q
  1156  				prev = q
  1157  			}
  1158  
  1159  			q1 = c.newprog()
  1160  			q1.As = ABR
  1161  			q1.Pos = p.Pos
  1162  			if retTarget == nil {
  1163  				q1.To.Type = obj.TYPE_REG
  1164  				q1.To.Reg = REG_LR
  1165  			} else {
  1166  				q1.To.Type = obj.TYPE_BRANCH
  1167  				q1.To.Sym = retTarget
  1168  			}
  1169  			q1.Mark |= BRANCH
  1170  			q1.Spadj = +autosize
  1171  
  1172  			q1.Link = q.Link
  1173  			prev.Link = q1
  1174  		case AADD:
  1175  			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
  1176  				p.Spadj = int32(-p.From.Offset)
  1177  			}
  1178  		case AMOVDU:
  1179  			if p.To.Type == obj.TYPE_MEM && p.To.Reg == REGSP {
  1180  				p.Spadj = int32(-p.To.Offset)
  1181  			}
  1182  			if p.From.Type == obj.TYPE_MEM && p.From.Reg == REGSP {
  1183  				p.Spadj = int32(-p.From.Offset)
  1184  			}
  1185  		case obj.AGETCALLERPC:
  1186  			if cursym.Leaf() {
  1187  				/* MOVD LR, Rd */
  1188  				p.As = AMOVD
  1189  				p.From.Type = obj.TYPE_REG
  1190  				p.From.Reg = REG_LR
  1191  			} else {
  1192  				/* MOVD (RSP), Rd */
  1193  				p.As = AMOVD
  1194  				p.From.Type = obj.TYPE_MEM
  1195  				p.From.Reg = REGSP
  1196  			}
  1197  		}
  1198  
  1199  		if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.Spadj == 0 && p.As != ACMPU {
  1200  			f := c.cursym.Func()
  1201  			if f.FuncFlag&abi.FuncFlagSPWrite == 0 {
  1202  				c.cursym.Func().FuncFlag |= abi.FuncFlagSPWrite
  1203  				if ctxt.Debugvlog || !ctxt.IsAsm {
  1204  					ctxt.Logf("auto-SPWRITE: %s %v\n", c.cursym.Name, p)
  1205  					if !ctxt.IsAsm {
  1206  						ctxt.Diag("invalid auto-SPWRITE in non-assembly")
  1207  						ctxt.DiagFlush()
  1208  						log.Fatalf("bad SPWRITE")
  1209  					}
  1210  				}
  1211  			}
  1212  		}
  1213  	}
  1214  }
  1215  
  1216  /*
  1217  // instruction scheduling
  1218  
  1219  	if(debug['Q'] == 0)
  1220  		return;
  1221  
  1222  	curtext = nil;
  1223  	q = nil;	// p - 1
  1224  	q1 = firstp;	// top of block
  1225  	o = 0;		// count of instructions
  1226  	for(p = firstp; p != nil; p = p1) {
  1227  		p1 = p->link;
  1228  		o++;
  1229  		if(p->mark & NOSCHED){
  1230  			if(q1 != p){
  1231  				sched(q1, q);
  1232  			}
  1233  			for(; p != nil; p = p->link){
  1234  				if(!(p->mark & NOSCHED))
  1235  					break;
  1236  				q = p;
  1237  			}
  1238  			p1 = p;
  1239  			q1 = p;
  1240  			o = 0;
  1241  			continue;
  1242  		}
  1243  		if(p->mark & (LABEL|SYNC)) {
  1244  			if(q1 != p)
  1245  				sched(q1, q);
  1246  			q1 = p;
  1247  			o = 1;
  1248  		}
  1249  		if(p->mark & (BRANCH|SYNC)) {
  1250  			sched(q1, p);
  1251  			q1 = p1;
  1252  			o = 0;
  1253  		}
  1254  		if(o >= NSCHED) {
  1255  			sched(q1, p);
  1256  			q1 = p1;
  1257  			o = 0;
  1258  		}
  1259  		q = p;
  1260  	}
  1261  */
  1262  func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
  1263  	if c.ctxt.Flag_maymorestack != "" {
  1264  		if c.ctxt.Flag_shared || c.ctxt.Flag_dynlink {
  1265  			// See the call to morestack for why these are
  1266  			// complicated to support.
  1267  			c.ctxt.Diag("maymorestack with -shared or -dynlink is not supported")
  1268  		}
  1269  
  1270  		// Spill arguments. This has to happen before we open
  1271  		// any more frame space.
  1272  		p = c.cursym.Func().SpillRegisterArgs(p, c.newprog)
  1273  
  1274  		// Save LR and REGCTXT
  1275  		frameSize := 8 + c.ctxt.Arch.FixedFrameSize
  1276  
  1277  		// MOVD LR, REGTMP
  1278  		p = obj.Appendp(p, c.newprog)
  1279  		p.As = AMOVD
  1280  		p.From.Type = obj.TYPE_REG
  1281  		p.From.Reg = REG_LR
  1282  		p.To.Type = obj.TYPE_REG
  1283  		p.To.Reg = REGTMP
  1284  		// MOVDU REGTMP, -16(SP)
  1285  		p = obj.Appendp(p, c.newprog)
  1286  		p.As = AMOVDU
  1287  		p.From.Type = obj.TYPE_REG
  1288  		p.From.Reg = REGTMP
  1289  		p.To.Type = obj.TYPE_MEM
  1290  		p.To.Offset = -frameSize
  1291  		p.To.Reg = REGSP
  1292  		p.Spadj = int32(frameSize)
  1293  
  1294  		// MOVD REGCTXT, 8(SP)
  1295  		p = obj.Appendp(p, c.newprog)
  1296  		p.As = AMOVD
  1297  		p.From.Type = obj.TYPE_REG
  1298  		p.From.Reg = REGCTXT
  1299  		p.To.Type = obj.TYPE_MEM
  1300  		p.To.Offset = 8
  1301  		p.To.Reg = REGSP
  1302  
  1303  		// BL maymorestack
  1304  		p = obj.Appendp(p, c.newprog)
  1305  		p.As = ABL
  1306  		p.To.Type = obj.TYPE_BRANCH
  1307  		// See ../x86/obj6.go
  1308  		p.To.Sym = c.ctxt.LookupABI(c.ctxt.Flag_maymorestack, c.cursym.ABI())
  1309  
  1310  		// Restore LR and REGCTXT
  1311  
  1312  		// MOVD 8(SP), REGCTXT
  1313  		p = obj.Appendp(p, c.newprog)
  1314  		p.As = AMOVD
  1315  		p.From.Type = obj.TYPE_MEM
  1316  		p.From.Offset = 8
  1317  		p.From.Reg = REGSP
  1318  		p.To.Type = obj.TYPE_REG
  1319  		p.To.Reg = REGCTXT
  1320  
  1321  		// MOVD 0(SP), REGTMP
  1322  		p = obj.Appendp(p, c.newprog)
  1323  		p.As = AMOVD
  1324  		p.From.Type = obj.TYPE_MEM
  1325  		p.From.Offset = 0
  1326  		p.From.Reg = REGSP
  1327  		p.To.Type = obj.TYPE_REG
  1328  		p.To.Reg = REGTMP
  1329  
  1330  		// MOVD REGTMP, LR
  1331  		p = obj.Appendp(p, c.newprog)
  1332  		p.As = AMOVD
  1333  		p.From.Type = obj.TYPE_REG
  1334  		p.From.Reg = REGTMP
  1335  		p.To.Type = obj.TYPE_REG
  1336  		p.To.Reg = REG_LR
  1337  
  1338  		// ADD $16, SP
  1339  		p = obj.Appendp(p, c.newprog)
  1340  		p.As = AADD
  1341  		p.From.Type = obj.TYPE_CONST
  1342  		p.From.Offset = frameSize
  1343  		p.To.Type = obj.TYPE_REG
  1344  		p.To.Reg = REGSP
  1345  		p.Spadj = -int32(frameSize)
  1346  
  1347  		// Unspill arguments.
  1348  		p = c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
  1349  	}
  1350  
  1351  	// save entry point, but skipping the two instructions setting R2 in shared mode and maymorestack
  1352  	startPred := p
  1353  
  1354  	// MOVD	g_stackguard(g), R22
  1355  	p = obj.Appendp(p, c.newprog)
  1356  
  1357  	p.As = AMOVD
  1358  	p.From.Type = obj.TYPE_MEM
  1359  	p.From.Reg = REGG
  1360  	p.From.Offset = 2 * int64(c.ctxt.Arch.PtrSize) // G.stackguard0
  1361  	if c.cursym.CFunc() {
  1362  		p.From.Offset = 3 * int64(c.ctxt.Arch.PtrSize) // G.stackguard1
  1363  	}
  1364  	p.To.Type = obj.TYPE_REG
  1365  	p.To.Reg = REG_R22
  1366  
  1367  	// Mark the stack bound check and morestack call async nonpreemptible.
  1368  	// If we get preempted here, when resumed the preemption request is
  1369  	// cleared, but we'll still call morestack, which will double the stack
  1370  	// unnecessarily. See issue #35470.
  1371  	p = c.ctxt.StartUnsafePoint(p, c.newprog)
  1372  
  1373  	var q *obj.Prog
  1374  	if framesize <= abi.StackSmall {
  1375  		// small stack: SP < stackguard
  1376  		//	CMP	stackguard, SP
  1377  		p = obj.Appendp(p, c.newprog)
  1378  
  1379  		p.As = ACMPU
  1380  		p.From.Type = obj.TYPE_REG
  1381  		p.From.Reg = REG_R22
  1382  		p.To.Type = obj.TYPE_REG
  1383  		p.To.Reg = REGSP
  1384  	} else {
  1385  		// large stack: SP-framesize < stackguard-StackSmall
  1386  		offset := int64(framesize) - abi.StackSmall
  1387  		if framesize > abi.StackBig {
  1388  			// Such a large stack we need to protect against underflow.
  1389  			// The runtime guarantees SP > objabi.StackBig, but
  1390  			// framesize is large enough that SP-framesize may
  1391  			// underflow, causing a direct comparison with the
  1392  			// stack guard to incorrectly succeed. We explicitly
  1393  			// guard against underflow.
  1394  			//
  1395  			//	CMPU	SP, $(framesize-StackSmall)
  1396  			//	BLT	label-of-call-to-morestack
  1397  			if offset <= 0xffff {
  1398  				p = obj.Appendp(p, c.newprog)
  1399  				p.As = ACMPU
  1400  				p.From.Type = obj.TYPE_REG
  1401  				p.From.Reg = REGSP
  1402  				p.To.Type = obj.TYPE_CONST
  1403  				p.To.Offset = offset
  1404  			} else {
  1405  				// Constant is too big for CMPU.
  1406  				p = obj.Appendp(p, c.newprog)
  1407  				p.As = AMOVD
  1408  				p.From.Type = obj.TYPE_CONST
  1409  				p.From.Offset = offset
  1410  				p.To.Type = obj.TYPE_REG
  1411  				p.To.Reg = REG_R23
  1412  
  1413  				p = obj.Appendp(p, c.newprog)
  1414  				p.As = ACMPU
  1415  				p.From.Type = obj.TYPE_REG
  1416  				p.From.Reg = REGSP
  1417  				p.To.Type = obj.TYPE_REG
  1418  				p.To.Reg = REG_R23
  1419  			}
  1420  
  1421  			p = obj.Appendp(p, c.newprog)
  1422  			q = p
  1423  			p.As = ABLT
  1424  			p.To.Type = obj.TYPE_BRANCH
  1425  		}
  1426  
  1427  		// Check against the stack guard. We've ensured this won't underflow.
  1428  		//	ADD  $-(framesize-StackSmall), SP, R4
  1429  		//	CMPU stackguard, R4
  1430  		p = obj.Appendp(p, c.newprog)
  1431  
  1432  		p.As = AADD
  1433  		p.From.Type = obj.TYPE_CONST
  1434  		p.From.Offset = -offset
  1435  		p.Reg = REGSP
  1436  		p.To.Type = obj.TYPE_REG
  1437  		p.To.Reg = REG_R23
  1438  
  1439  		p = obj.Appendp(p, c.newprog)
  1440  		p.As = ACMPU
  1441  		p.From.Type = obj.TYPE_REG
  1442  		p.From.Reg = REG_R22
  1443  		p.To.Type = obj.TYPE_REG
  1444  		p.To.Reg = REG_R23
  1445  	}
  1446  
  1447  	// q1: BLT	done
  1448  	p = obj.Appendp(p, c.newprog)
  1449  	q1 := p
  1450  
  1451  	p.As = ABLT
  1452  	p.To.Type = obj.TYPE_BRANCH
  1453  
  1454  	p = obj.Appendp(p, c.newprog)
  1455  	p.As = obj.ANOP // zero-width place holder
  1456  
  1457  	if q != nil {
  1458  		q.To.SetTarget(p)
  1459  	}
  1460  
  1461  	// Spill the register args that could be clobbered by the
  1462  	// morestack code.
  1463  
  1464  	spill := c.cursym.Func().SpillRegisterArgs(p, c.newprog)
  1465  
  1466  	// MOVD LR, R5
  1467  	p = obj.Appendp(spill, c.newprog)
  1468  	p.As = AMOVD
  1469  	p.From.Type = obj.TYPE_REG
  1470  	p.From.Reg = REG_LR
  1471  	p.To.Type = obj.TYPE_REG
  1472  	p.To.Reg = REG_R5
  1473  
  1474  	p = c.ctxt.EmitEntryStackMap(c.cursym, p, c.newprog)
  1475  
  1476  	var morestacksym *obj.LSym
  1477  	if c.cursym.CFunc() {
  1478  		morestacksym = c.ctxt.Lookup("runtime.morestackc")
  1479  	} else if !c.cursym.Func().Text.From.Sym.NeedCtxt() {
  1480  		morestacksym = c.ctxt.Lookup("runtime.morestack_noctxt")
  1481  	} else {
  1482  		morestacksym = c.ctxt.Lookup("runtime.morestack")
  1483  	}
  1484  
  1485  	if NeedTOCpointer(c.ctxt) {
  1486  		// In PPC64 PIC code, R2 is used as TOC pointer derived from R12
  1487  		// which is the address of function entry point when entering
  1488  		// the function. We need to preserve R2 across call to morestack.
  1489  		// Fortunately, in shared mode, 8(SP) and 16(SP) are reserved in
  1490  		// the caller's frame, but not used (0(SP) is caller's saved LR,
  1491  		// 24(SP) is caller's saved R2). Use 8(SP) to save this function's R2.
  1492  		// MOVD R2, 8(SP)
  1493  		p = obj.Appendp(p, c.newprog)
  1494  		p.As = AMOVD
  1495  		p.From.Type = obj.TYPE_REG
  1496  		p.From.Reg = REG_R2
  1497  		p.To.Type = obj.TYPE_MEM
  1498  		p.To.Reg = REGSP
  1499  		p.To.Offset = 8
  1500  	}
  1501  
  1502  	if c.ctxt.Flag_dynlink {
  1503  		// Avoid calling morestack via a PLT when dynamically linking. The
  1504  		// PLT stubs generated by the system linker on ppc64le when "std r2,
  1505  		// 24(r1)" to save the TOC pointer in their callers stack
  1506  		// frame. Unfortunately (and necessarily) morestack is called before
  1507  		// the function that calls it sets up its frame and so the PLT ends
  1508  		// up smashing the saved TOC pointer for its caller's caller.
  1509  		//
  1510  		// According to the ABI documentation there is a mechanism to avoid
  1511  		// the TOC save that the PLT stub does (put a R_PPC64_TOCSAVE
  1512  		// relocation on the nop after the call to morestack) but at the time
  1513  		// of writing it is not supported at all by gold and my attempt to
  1514  		// use it with ld.bfd caused an internal linker error. So this hack
  1515  		// seems preferable.
  1516  
  1517  		// MOVD $runtime.morestack(SB), R12
  1518  		p = obj.Appendp(p, c.newprog)
  1519  		p.As = AMOVD
  1520  		p.From.Type = obj.TYPE_MEM
  1521  		p.From.Sym = morestacksym
  1522  		p.From.Name = obj.NAME_GOTREF
  1523  		p.To.Type = obj.TYPE_REG
  1524  		p.To.Reg = REG_R12
  1525  
  1526  		// MOVD R12, LR
  1527  		p = obj.Appendp(p, c.newprog)
  1528  		p.As = AMOVD
  1529  		p.From.Type = obj.TYPE_REG
  1530  		p.From.Reg = REG_R12
  1531  		p.To.Type = obj.TYPE_REG
  1532  		p.To.Reg = REG_LR
  1533  
  1534  		// BL LR
  1535  		p = obj.Appendp(p, c.newprog)
  1536  		p.As = obj.ACALL
  1537  		p.To.Type = obj.TYPE_REG
  1538  		p.To.Reg = REG_LR
  1539  	} else {
  1540  		// BL	runtime.morestack(SB)
  1541  		p = obj.Appendp(p, c.newprog)
  1542  
  1543  		p.As = ABL
  1544  		p.To.Type = obj.TYPE_BRANCH
  1545  		p.To.Sym = morestacksym
  1546  	}
  1547  
  1548  	if NeedTOCpointer(c.ctxt) {
  1549  		// MOVD 8(SP), R2
  1550  		p = obj.Appendp(p, c.newprog)
  1551  		p.As = AMOVD
  1552  		p.From.Type = obj.TYPE_MEM
  1553  		p.From.Reg = REGSP
  1554  		p.From.Offset = 8
  1555  		p.To.Type = obj.TYPE_REG
  1556  		p.To.Reg = REG_R2
  1557  	}
  1558  
  1559  	// The instructions which unspill regs should be preemptible.
  1560  	p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
  1561  	unspill := c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
  1562  
  1563  	// BR	start
  1564  	p = obj.Appendp(unspill, c.newprog)
  1565  	p.As = ABR
  1566  	p.To.Type = obj.TYPE_BRANCH
  1567  	p.To.SetTarget(startPred.Link)
  1568  
  1569  	// placeholder for q1's jump target
  1570  	p = obj.Appendp(p, c.newprog)
  1571  
  1572  	p.As = obj.ANOP // zero-width place holder
  1573  	q1.To.SetTarget(p)
  1574  
  1575  	return p
  1576  }
  1577  
  1578  // MMA accumulator to/from instructions are slightly ambiguous since
  1579  // the argument represents both source and destination, specified as
  1580  // an accumulator. It is treated as a unary destination to simplify
  1581  // the code generation in ppc64map.
  1582  var unaryDst = map[obj.As]bool{
  1583  	AXXSETACCZ: true,
  1584  	AXXMTACC:   true,
  1585  	AXXMFACC:   true,
  1586  }
  1587  
  1588  var Linkppc64 = obj.LinkArch{
  1589  	Arch:           sys.ArchPPC64,
  1590  	Init:           buildop,
  1591  	Preprocess:     preprocess,
  1592  	Assemble:       span9,
  1593  	Progedit:       progedit,
  1594  	UnaryDst:       unaryDst,
  1595  	DWARFRegisters: PPC64DWARFRegisters,
  1596  }
  1597  
  1598  var Linkppc64le = obj.LinkArch{
  1599  	Arch:           sys.ArchPPC64LE,
  1600  	Init:           buildop,
  1601  	Preprocess:     preprocess,
  1602  	Assemble:       span9,
  1603  	Progedit:       progedit,
  1604  	UnaryDst:       unaryDst,
  1605  	DWARFRegisters: PPC64DWARFRegisters,
  1606  }
  1607  

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