src/cmd/internal/obj/arm64/obj7.go

   1 // cmd/7l/noop.c, cmd/7l/obj.c, cmd/ld/pass.c from Vita Nuova.
   2 // https://code.google.com/p/ken-cc/source/browse/
   3 //
   4 //      Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
   5 //      Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
   6 //      Portions Copyright © 1997-1999 Vita Nuova Limited
   7 //      Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
   8 //      Portions Copyright © 2004,2006 Bruce Ellis
   9 //      Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
  10 //      Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
  11 //      Portions Copyright © 2009 The Go Authors. All rights reserved.
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining a copy
  14 // of this software and associated documentation files (the "Software"), to deal
  15 // in the Software without restriction, including without limitation the rights
  16 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  17 // copies of the Software, and to permit persons to whom the Software is
  18 // furnished to do so, subject to the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be included in
  21 // all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  24 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  25 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  26 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  27 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  28 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  29 // THE SOFTWARE.
  30
  31 package arm64
  32
  33 import (
  34         "cmd/internal/obj"
  35         "cmd/internal/objabi"
  36         "cmd/internal/src"
  37         "cmd/internal/sys"
  38         "math"
  39 )
  40
  41 var complements = []obj.As{
  42         AADD:  ASUB,
  43         AADDW: ASUBW,
  44         ASUB:  AADD,
  45         ASUBW: AADDW,
  46         ACMP:  ACMN,
  47         ACMPW: ACMNW,
  48         ACMN:  ACMP,
  49         ACMNW: ACMPW,
  50 }
  51
  52 func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
  53         // MOV  g_stackguard(g), R1
  54         p = obj.Appendp(p, c.newprog)
  55
  56         p.As = AMOVD
  57         p.From.Type = obj.TYPE_MEM
  58         p.From.Reg = REGG
  59         p.From.Offset = 2 * int64(c.ctxt.Arch.PtrSize) // G.stackguard0
  60         if c.cursym.CFunc() {
  61                 p.From.Offset = 3 * int64(c.ctxt.Arch.PtrSize) // G.stackguard1
  62         }
  63         p.To.Type = obj.TYPE_REG
  64         p.To.Reg = REG_R1
  65
  66         // Mark the stack bound check and morestack call async nonpreemptible.
  67         // If we get preempted here, when resumed the preemption request is
  68         // cleared, but we'll still call morestack, which will double the stack
  69         // unnecessarily. See issue #35470.
  70         p = c.ctxt.StartUnsafePoint(p, c.newprog)
  71
  72         q := (*obj.Prog)(nil)
  73         if framesize <= objabi.StackSmall {
  74                 // small stack: SP < stackguard
  75                 //      MOV     SP, R2
  76                 //      CMP     stackguard, R2
  77                 p = obj.Appendp(p, c.newprog)
  78
  79                 p.As = AMOVD
  80                 p.From.Type = obj.TYPE_REG
  81                 p.From.Reg = REGSP
  82                 p.To.Type = obj.TYPE_REG
  83                 p.To.Reg = REG_R2
  84
  85                 p = obj.Appendp(p, c.newprog)
  86                 p.As = ACMP
  87                 p.From.Type = obj.TYPE_REG
  88                 p.From.Reg = REG_R1
  89                 p.Reg = REG_R2
  90         } else if framesize <= objabi.StackBig {
  91                 // large stack: SP-framesize < stackguard-StackSmall
  92                 //      SUB     $(framesize-StackSmall), SP, R2
  93                 //      CMP     stackguard, R2
  94                 p = obj.Appendp(p, c.newprog)
  95
  96                 p.As = ASUB
  97                 p.From.Type = obj.TYPE_CONST
  98                 p.From.Offset = int64(framesize) - objabi.StackSmall
  99                 p.Reg = REGSP
 100                 p.To.Type = obj.TYPE_REG
 101                 p.To.Reg = REG_R2
 102
 103                 p = obj.Appendp(p, c.newprog)
 104                 p.As = ACMP
 105                 p.From.Type = obj.TYPE_REG
 106                 p.From.Reg = REG_R1
 107                 p.Reg = REG_R2
 108         } else {
 109                 // Such a large stack we need to protect against wraparound
 110                 // if SP is close to zero.
 111                 //      SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
 112                 // The +StackGuard on both sides is required to keep the left side positive:
 113                 // SP is allowed to be slightly below stackguard. See stack.h.
 114                 //      CMP     $StackPreempt, R1
 115                 //      BEQ     label_of_call_to_morestack
 116                 //      ADD     $StackGuard, SP, R2
 117                 //      SUB     R1, R2
 118                 //      MOV     $(framesize+(StackGuard-StackSmall)), R3
 119                 //      CMP     R3, R2
 120                 p = obj.Appendp(p, c.newprog)
 121
 122                 p.As = ACMP
 123                 p.From.Type = obj.TYPE_CONST
 124                 p.From.Offset = objabi.StackPreempt
 125                 p.Reg = REG_R1
 126
 127                 p = obj.Appendp(p, c.newprog)
 128                 q = p
 129                 p.As = ABEQ
 130                 p.To.Type = obj.TYPE_BRANCH
 131
 132                 p = obj.Appendp(p, c.newprog)
 133                 p.As = AADD
 134                 p.From.Type = obj.TYPE_CONST
 135                 p.From.Offset = int64(objabi.StackGuard)
 136                 p.Reg = REGSP
 137                 p.To.Type = obj.TYPE_REG
 138                 p.To.Reg = REG_R2
 139
 140                 p = obj.Appendp(p, c.newprog)
 141                 p.As = ASUB
 142                 p.From.Type = obj.TYPE_REG
 143                 p.From.Reg = REG_R1
 144                 p.To.Type = obj.TYPE_REG
 145                 p.To.Reg = REG_R2
 146
 147                 p = obj.Appendp(p, c.newprog)
 148                 p.As = AMOVD
 149                 p.From.Type = obj.TYPE_CONST
 150                 p.From.Offset = int64(framesize) + (int64(objabi.StackGuard) - objabi.StackSmall)
 151                 p.To.Type = obj.TYPE_REG
 152                 p.To.Reg = REG_R3
 153
 154                 p = obj.Appendp(p, c.newprog)
 155                 p.As = ACMP
 156                 p.From.Type = obj.TYPE_REG
 157                 p.From.Reg = REG_R3
 158                 p.Reg = REG_R2
 159         }
 160
 161         // BLS  do-morestack
 162         bls := obj.Appendp(p, c.newprog)
 163         bls.As = ABLS
 164         bls.To.Type = obj.TYPE_BRANCH
 165
 166         end := c.ctxt.EndUnsafePoint(bls, c.newprog, -1)
 167
 168         var last *obj.Prog
 169         for last = c.cursym.Func.Text; last.Link != nil; last = last.Link {
 170         }
 171
 172         // Now we are at the end of the function, but logically
 173         // we are still in function prologue. We need to fix the
 174         // SP data and PCDATA.
 175         spfix := obj.Appendp(last, c.newprog)
 176         spfix.As = obj.ANOP
 177         spfix.Spadj = -framesize
 178
 179         pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
 180         pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
 181
 182         // MOV  LR, R3
 183         movlr := obj.Appendp(pcdata, c.newprog)
 184         movlr.As = AMOVD
 185         movlr.From.Type = obj.TYPE_REG
 186         movlr.From.Reg = REGLINK
 187         movlr.To.Type = obj.TYPE_REG
 188         movlr.To.Reg = REG_R3
 189         if q != nil {
 190                 q.Pcond = movlr
 191         }
 192         bls.Pcond = movlr
 193
 194         debug := movlr
 195         if false {
 196                 debug = obj.Appendp(debug, c.newprog)
 197                 debug.As = AMOVD
 198                 debug.From.Type = obj.TYPE_CONST
 199                 debug.From.Offset = int64(framesize)
 200                 debug.To.Type = obj.TYPE_REG
 201                 debug.To.Reg = REGTMP
 202         }
 203
 204         // BL   runtime.morestack(SB)
 205         call := obj.Appendp(debug, c.newprog)
 206         call.As = ABL
 207         call.To.Type = obj.TYPE_BRANCH
 208         morestack := "runtime.morestack"
 209         switch {
 210         case c.cursym.CFunc():
 211                 morestack = "runtime.morestackc"
 212         case !c.cursym.Func.Text.From.Sym.NeedCtxt():
 213                 morestack = "runtime.morestack_noctxt"
 214         }
 215         call.To.Sym = c.ctxt.Lookup(morestack)
 216
 217         pcdata = c.ctxt.EndUnsafePoint(call, c.newprog, -1)
 218
 219         // B    start
 220         jmp := obj.Appendp(pcdata, c.newprog)
 221         jmp.As = AB
 222         jmp.To.Type = obj.TYPE_BRANCH
 223         jmp.Pcond = c.cursym.Func.Text.Link
 224         jmp.Spadj = +framesize
 225
 226         return end
 227 }
 228
 229 func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 230         c := ctxt7{ctxt: ctxt, newprog: newprog}
 231
 232         p.From.Class = 0
 233         p.To.Class = 0
 234
 235         // $0 results in C_ZCON, which matches both C_REG and various
 236         // C_xCON, however the C_REG cases in asmout don't expect a
 237         // constant, so they will use the register fields and assemble
 238         // a R0. To prevent that, rewrite $0 as ZR.
 239         if p.From.Type == obj.TYPE_CONST && p.From.Offset == 0 {
 240                 p.From.Type = obj.TYPE_REG
 241                 p.From.Reg = REGZERO
 242         }
 243         if p.To.Type == obj.TYPE_CONST && p.To.Offset == 0 {
 244                 p.To.Type = obj.TYPE_REG
 245                 p.To.Reg = REGZERO
 246         }
 247
 248         // Rewrite BR/BL to symbol as TYPE_BRANCH.
 249         switch p.As {
 250         case AB,
 251                 ABL,
 252                 obj.ARET,
 253                 obj.ADUFFZERO,
 254                 obj.ADUFFCOPY:
 255                 if p.To.Sym != nil {
 256                         p.To.Type = obj.TYPE_BRANCH
 257                 }
 258                 break
 259         }
 260
 261         // Rewrite float constants to values stored in memory.
 262         switch p.As {
 263         case AFMOVS:
 264                 if p.From.Type == obj.TYPE_FCONST {
 265                         f64 := p.From.Val.(float64)
 266                         f32 := float32(f64)
 267                         if c.chipfloat7(f64) > 0 {
 268                                 break
 269                         }
 270                         if math.Float32bits(f32) == 0 {
 271                                 p.From.Type = obj.TYPE_REG
 272                                 p.From.Reg = REGZERO
 273                                 break
 274                         }
 275                         p.From.Type = obj.TYPE_MEM
 276                         p.From.Sym = c.ctxt.Float32Sym(f32)
 277                         p.From.Name = obj.NAME_EXTERN
 278                         p.From.Offset = 0
 279                 }
 280
 281         case AFMOVD:
 282                 if p.From.Type == obj.TYPE_FCONST {
 283                         f64 := p.From.Val.(float64)
 284                         if c.chipfloat7(f64) > 0 {
 285                                 break
 286                         }
 287                         if math.Float64bits(f64) == 0 {
 288                                 p.From.Type = obj.TYPE_REG
 289                                 p.From.Reg = REGZERO
 290                                 break
 291                         }
 292                         p.From.Type = obj.TYPE_MEM
 293                         p.From.Sym = c.ctxt.Float64Sym(f64)
 294                         p.From.Name = obj.NAME_EXTERN
 295                         p.From.Offset = 0
 296                 }
 297
 298                 break
 299         }
 300
 301         // Rewrite negative immediates as positive immediates with
 302         // complementary instruction.
 303         switch p.As {
 304         case AADD, ASUB, ACMP, ACMN:
 305                 if p.From.Type == obj.TYPE_CONST && p.From.Offset < 0 && p.From.Offset != -1<<63 {
 306                         p.From.Offset = -p.From.Offset
 307                         p.As = complements[p.As]
 308                 }
 309         case AADDW, ASUBW, ACMPW, ACMNW:
 310                 if p.From.Type == obj.TYPE_CONST && p.From.Offset < 0 && int32(p.From.Offset) != -1<<31 {
 311                         p.From.Offset = -p.From.Offset
 312                         p.As = complements[p.As]
 313                 }
 314         }
 315
 316         // For 32-bit logical instruction with constant,
 317         // rewrite the high 32-bit to be a repetition of
 318         // the low 32-bit, so that the BITCON test can be
 319         // shared for both 32-bit and 64-bit. 32-bit ops
 320         // will zero the high 32-bit of the destination
 321         // register anyway.
 322         if isANDWop(p.As) && p.From.Type == obj.TYPE_CONST {
 323                 v := p.From.Offset & 0xffffffff
 324                 p.From.Offset = v | v<<32
 325         }
 326
 327         if c.ctxt.Flag_dynlink {
 328                 c.rewriteToUseGot(p)
 329         }
 330 }
 331
 332 // Rewrite p, if necessary, to access global data via the global offset table.
 333 func (c *ctxt7) rewriteToUseGot(p *obj.Prog) {
 334         if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
 335                 //     ADUFFxxx $offset
 336                 // becomes
 337                 //     MOVD runtime.duffxxx@GOT, REGTMP
 338                 //     ADD $offset, REGTMP
 339                 //     CALL REGTMP
 340                 var sym *obj.LSym
 341                 if p.As == obj.ADUFFZERO {
 342                         sym = c.ctxt.Lookup("runtime.duffzero")
 343                 } else {
 344                         sym = c.ctxt.Lookup("runtime.duffcopy")
 345                 }
 346                 offset := p.To.Offset
 347                 p.As = AMOVD
 348                 p.From.Type = obj.TYPE_MEM
 349                 p.From.Name = obj.NAME_GOTREF
 350                 p.From.Sym = sym
 351                 p.To.Type = obj.TYPE_REG
 352                 p.To.Reg = REGTMP
 353                 p.To.Name = obj.NAME_NONE
 354                 p.To.Offset = 0
 355                 p.To.Sym = nil
 356                 p1 := obj.Appendp(p, c.newprog)
 357                 p1.As = AADD
 358                 p1.From.Type = obj.TYPE_CONST
 359                 p1.From.Offset = offset
 360                 p1.To.Type = obj.TYPE_REG
 361                 p1.To.Reg = REGTMP
 362                 p2 := obj.Appendp(p1, c.newprog)
 363                 p2.As = obj.ACALL
 364                 p2.To.Type = obj.TYPE_REG
 365                 p2.To.Reg = REGTMP
 366         }
 367
 368         // We only care about global data: NAME_EXTERN means a global
 369         // symbol in the Go sense, and p.Sym.Local is true for a few
 370         // internally defined symbols.
 371         if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
 372                 // MOVD $sym, Rx becomes MOVD sym@GOT, Rx
 373                 // MOVD $sym+<off>, Rx becomes MOVD sym@GOT, Rx; ADD <off>, Rx
 374                 if p.As != AMOVD {
 375                         c.ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
 376                 }
 377                 if p.To.Type != obj.TYPE_REG {
 378                         c.ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
 379                 }
 380                 p.From.Type = obj.TYPE_MEM
 381                 p.From.Name = obj.NAME_GOTREF
 382                 if p.From.Offset != 0 {
 383                         q := obj.Appendp(p, c.newprog)
 384                         q.As = AADD
 385                         q.From.Type = obj.TYPE_CONST
 386                         q.From.Offset = p.From.Offset
 387                         q.To = p.To
 388                         p.From.Offset = 0
 389                 }
 390         }
 391         if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
 392                 c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
 393         }
 394         var source *obj.Addr
 395         // MOVx sym, Ry becomes MOVD sym@GOT, REGTMP; MOVx (REGTMP), Ry
 396         // MOVx Ry, sym becomes MOVD sym@GOT, REGTMP; MOVD Ry, (REGTMP)
 397         // An addition may be inserted between the two MOVs if there is an offset.
 398         if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local() {
 399                 if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
 400                         c.ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
 401                 }
 402                 source = &p.From
 403         } else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local() {
 404                 source = &p.To
 405         } else {
 406                 return
 407         }
 408         if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
 409                 return
 410         }
 411         if source.Sym.Type == objabi.STLSBSS {
 412                 return
 413         }
 414         if source.Type != obj.TYPE_MEM {
 415                 c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
 416         }
 417         p1 := obj.Appendp(p, c.newprog)
 418         p2 := obj.Appendp(p1, c.newprog)
 419         p1.As = AMOVD
 420         p1.From.Type = obj.TYPE_MEM
 421         p1.From.Sym = source.Sym
 422         p1.From.Name = obj.NAME_GOTREF
 423         p1.To.Type = obj.TYPE_REG
 424         p1.To.Reg = REGTMP
 425
 426         p2.As = p.As
 427         p2.From = p.From
 428         p2.To = p.To
 429         if p.From.Name == obj.NAME_EXTERN {
 430                 p2.From.Reg = REGTMP
 431                 p2.From.Name = obj.NAME_NONE
 432                 p2.From.Sym = nil
 433         } else if p.To.Name == obj.NAME_EXTERN {
 434                 p2.To.Reg = REGTMP
 435                 p2.To.Name = obj.NAME_NONE
 436                 p2.To.Sym = nil
 437         } else {
 438                 return
 439         }
 440         obj.Nopout(p)
 441 }
 442
 443 func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 444         if cursym.Func.Text == nil || cursym.Func.Text.Link == nil {
 445                 return
 446         }
 447
 448         c := ctxt7{ctxt: ctxt, newprog: newprog, cursym: cursym}
 449
 450         p := c.cursym.Func.Text
 451         textstksiz := p.To.Offset
 452         if textstksiz == -8 {
 453                 // Historical way to mark NOFRAME.
 454                 p.From.Sym.Set(obj.AttrNoFrame, true)
 455                 textstksiz = 0
 456         }
 457         if textstksiz < 0 {
 458                 c.ctxt.Diag("negative frame size %d - did you mean NOFRAME?", textstksiz)
 459         }
 460         if p.From.Sym.NoFrame() {
 461                 if textstksiz != 0 {
 462                         c.ctxt.Diag("NOFRAME functions must have a frame size of 0, not %d", textstksiz)
 463                 }
 464         }
 465
 466         c.cursym.Func.Args = p.To.Val.(int32)
 467         c.cursym.Func.Locals = int32(textstksiz)
 468
 469         /*
 470          * find leaf subroutines
 471          */
 472         for p := c.cursym.Func.Text; p != nil; p = p.Link {
 473                 switch p.As {
 474                 case obj.ATEXT:
 475                         p.Mark |= LEAF
 476
 477                 case ABL,
 478                         obj.ADUFFZERO,
 479                         obj.ADUFFCOPY:
 480                         c.cursym.Func.Text.Mark &^= LEAF
 481                 }
 482         }
 483
 484         var q *obj.Prog
 485         var q1 *obj.Prog
 486         var retjmp *obj.LSym
 487         for p := c.cursym.Func.Text; p != nil; p = p.Link {
 488                 o := p.As
 489                 switch o {
 490                 case obj.ATEXT:
 491                         c.cursym.Func.Text = p
 492                         c.autosize = int32(textstksiz)
 493
 494                         if p.Mark&LEAF != 0 && c.autosize == 0 {
 495                                 // A leaf function with no locals has no frame.
 496                                 p.From.Sym.Set(obj.AttrNoFrame, true)
 497                         }
 498
 499                         if !p.From.Sym.NoFrame() {
 500                                 // If there is a stack frame at all, it includes
 501                                 // space to save the LR.
 502                                 c.autosize += 8
 503                         }
 504
 505                         if c.autosize != 0 {
 506                                 extrasize := int32(0)
 507                                 if c.autosize%16 == 8 {
 508                                         // Allocate extra 8 bytes on the frame top to save FP
 509                                         extrasize = 8
 510                                 } else if c.autosize&(16-1) == 0 {
 511                                         // Allocate extra 16 bytes to save FP for the old frame whose size is 8 mod 16
 512                                         extrasize = 16
 513                                 } else {
 514                                         c.ctxt.Diag("%v: unaligned frame size %d - must be 16 aligned", p, c.autosize-8)
 515                                 }
 516                                 c.autosize += extrasize
 517                                 c.cursym.Func.Locals += extrasize
 518
 519                                 // low 32 bits for autosize
 520                                 // high 32 bits for extrasize
 521                                 p.To.Offset = int64(c.autosize) | int64(extrasize)<<32
 522                         } else {
 523                                 // NOFRAME
 524                                 p.To.Offset = 0
 525                         }
 526
 527                         if c.autosize == 0 && c.cursym.Func.Text.Mark&LEAF == 0 {
 528                                 if c.ctxt.Debugvlog {
 529                                         c.ctxt.Logf("save suppressed in: %s\n", c.cursym.Func.Text.From.Sym.Name)
 530                                 }
 531                                 c.cursym.Func.Text.Mark |= LEAF
 532                         }
 533
 534                         if cursym.Func.Text.Mark&LEAF != 0 {
 535                                 cursym.Set(obj.AttrLeaf, true)
 536                                 if p.From.Sym.NoFrame() {
 537                                         break
 538                                 }
 539                         }
 540
 541                         if !p.From.Sym.NoSplit() {
 542                                 p = c.stacksplit(p, c.autosize) // emit split check
 543                         }
 544
 545                         var prologueEnd *obj.Prog
 546
 547                         aoffset := c.autosize
 548                         if aoffset > 0xF0 {
 549                                 aoffset = 0xF0
 550                         }
 551
 552                         // Frame is non-empty. Make sure to save link register, even if
 553                         // it is a leaf function, so that traceback works.
 554                         q = p
 555                         if c.autosize > aoffset {
 556                                 // Frame size is too large for a MOVD.W instruction.
 557                                 // Store link register before decrementing SP, so if a signal comes
 558                                 // during the execution of the function prologue, the traceback
 559                                 // code will not see a half-updated stack frame.
 560                                 // This sequence is not async preemptible, as if we open a frame
 561                                 // at the current SP, it will clobber the saved LR.
 562                                 q = c.ctxt.StartUnsafePoint(q, c.newprog)
 563
 564                                 q = obj.Appendp(q, c.newprog)
 565                                 q.Pos = p.Pos
 566                                 q.As = ASUB
 567                                 q.From.Type = obj.TYPE_CONST
 568                                 q.From.Offset = int64(c.autosize)
 569                                 q.Reg = REGSP
 570                                 q.To.Type = obj.TYPE_REG
 571                                 q.To.Reg = REGTMP
 572
 573                                 prologueEnd = q
 574
 575                                 q = obj.Appendp(q, c.newprog)
 576                                 q.Pos = p.Pos
 577                                 q.As = AMOVD
 578                                 q.From.Type = obj.TYPE_REG
 579                                 q.From.Reg = REGLINK
 580                                 q.To.Type = obj.TYPE_MEM
 581                                 q.To.Reg = REGTMP
 582
 583                                 q1 = obj.Appendp(q, c.newprog)
 584                                 q1.Pos = p.Pos
 585                                 q1.As = AMOVD
 586                                 q1.From.Type = obj.TYPE_REG
 587                                 q1.From.Reg = REGTMP
 588                                 q1.To.Type = obj.TYPE_REG
 589                                 q1.To.Reg = REGSP
 590                                 q1.Spadj = c.autosize
 591
 592                                 if c.ctxt.Headtype == objabi.Hdarwin {
 593                                         // iOS does not support SA_ONSTACK. We will run the signal handler
 594                                         // on the G stack. If we write below SP, it may be clobbered by
 595                                         // the signal handler. So we save LR after decrementing SP.
 596                                         q1 = obj.Appendp(q1, c.newprog)
 597                                         q1.Pos = p.Pos
 598                                         q1.As = AMOVD
 599                                         q1.From.Type = obj.TYPE_REG
 600                                         q1.From.Reg = REGLINK
 601                                         q1.To.Type = obj.TYPE_MEM
 602                                         q1.To.Reg = REGSP
 603                                 }
 604
 605                                 q1 = c.ctxt.EndUnsafePoint(q1, c.newprog, -1)
 606                         } else {
 607                                 // small frame, update SP and save LR in a single MOVD.W instruction
 608                                 q1 = obj.Appendp(q, c.newprog)
 609                                 q1.As = AMOVD
 610                                 q1.Pos = p.Pos
 611                                 q1.From.Type = obj.TYPE_REG
 612                                 q1.From.Reg = REGLINK
 613                                 q1.To.Type = obj.TYPE_MEM
 614                                 q1.Scond = C_XPRE
 615                                 q1.To.Offset = int64(-aoffset)
 616                                 q1.To.Reg = REGSP
 617                                 q1.Spadj = aoffset
 618
 619                                 prologueEnd = q1
 620                         }
 621
 622                         prologueEnd.Pos = prologueEnd.Pos.WithXlogue(src.PosPrologueEnd)
 623
 624                         if objabi.Framepointer_enabled(objabi.GOOS, objabi.GOARCH) {
 625                                 q1 = obj.Appendp(q1, c.newprog)
 626                                 q1.Pos = p.Pos
 627                                 q1.As = AMOVD
 628                                 q1.From.Type = obj.TYPE_REG
 629                                 q1.From.Reg = REGFP
 630                                 q1.To.Type = obj.TYPE_MEM
 631                                 q1.To.Reg = REGSP
 632                                 q1.To.Offset = -8
 633
 634                                 q1 = obj.Appendp(q1, c.newprog)
 635                                 q1.Pos = p.Pos
 636                                 q1.As = ASUB
 637                                 q1.From.Type = obj.TYPE_CONST
 638                                 q1.From.Offset = 8
 639                                 q1.Reg = REGSP
 640                                 q1.To.Type = obj.TYPE_REG
 641                                 q1.To.Reg = REGFP
 642                         }
 643
 644                         if c.cursym.Func.Text.From.Sym.Wrapper() {
 645                                 // if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
 646                                 //
 647                                 //      MOV  g_panic(g), R1
 648                                 //      CBNZ checkargp
 649                                 // end:
 650                                 //      NOP
 651                                 // ... function body ...
 652                                 // checkargp:
 653                                 //      MOV  panic_argp(R1), R2
 654                                 //      ADD  $(autosize+8), RSP, R3
 655                                 //      CMP  R2, R3
 656                                 //      BNE  end
 657                                 //      ADD  $8, RSP, R4
 658                                 //      MOVD R4, panic_argp(R1)
 659                                 //      B    end
 660                                 //
 661                                 // The NOP is needed to give the jumps somewhere to land.
 662                                 // It is a liblink NOP, not an ARM64 NOP: it encodes to 0 instruction bytes.
 663                                 q = q1
 664
 665                                 // MOV g_panic(g), R1
 666                                 q = obj.Appendp(q, c.newprog)
 667                                 q.As = AMOVD
 668                                 q.From.Type = obj.TYPE_MEM
 669                                 q.From.Reg = REGG
 670                                 q.From.Offset = 4 * int64(c.ctxt.Arch.PtrSize) // G.panic
 671                                 q.To.Type = obj.TYPE_REG
 672                                 q.To.Reg = REG_R1
 673
 674                                 // CBNZ R1, checkargp
 675                                 cbnz := obj.Appendp(q, c.newprog)
 676                                 cbnz.As = ACBNZ
 677                                 cbnz.From.Type = obj.TYPE_REG
 678                                 cbnz.From.Reg = REG_R1
 679                                 cbnz.To.Type = obj.TYPE_BRANCH
 680
 681                                 // Empty branch target at the top of the function body
 682                                 end := obj.Appendp(cbnz, c.newprog)
 683                                 end.As = obj.ANOP
 684
 685                                 // find the end of the function
 686                                 var last *obj.Prog
 687                                 for last = end; last.Link != nil; last = last.Link {
 688                                 }
 689
 690                                 // MOV panic_argp(R1), R2
 691                                 mov := obj.Appendp(last, c.newprog)
 692                                 mov.As = AMOVD
 693                                 mov.From.Type = obj.TYPE_MEM
 694                                 mov.From.Reg = REG_R1
 695                                 mov.From.Offset = 0 // Panic.argp
 696                                 mov.To.Type = obj.TYPE_REG
 697                                 mov.To.Reg = REG_R2
 698
 699                                 // CBNZ branches to the MOV above
 700                                 cbnz.Pcond = mov
 701
 702                                 // ADD $(autosize+8), SP, R3
 703                                 q = obj.Appendp(mov, c.newprog)
 704                                 q.As = AADD
 705                                 q.From.Type = obj.TYPE_CONST
 706                                 q.From.Offset = int64(c.autosize) + 8
 707                                 q.Reg = REGSP
 708                                 q.To.Type = obj.TYPE_REG
 709                                 q.To.Reg = REG_R3
 710
 711                                 // CMP R2, R3
 712                                 q = obj.Appendp(q, c.newprog)
 713                                 q.As = ACMP
 714                                 q.From.Type = obj.TYPE_REG
 715                                 q.From.Reg = REG_R2
 716                                 q.Reg = REG_R3
 717
 718                                 // BNE end
 719                                 q = obj.Appendp(q, c.newprog)
 720                                 q.As = ABNE
 721                                 q.To.Type = obj.TYPE_BRANCH
 722                                 q.Pcond = end
 723
 724                                 // ADD $8, SP, R4
 725                                 q = obj.Appendp(q, c.newprog)
 726                                 q.As = AADD
 727                                 q.From.Type = obj.TYPE_CONST
 728                                 q.From.Offset = 8
 729                                 q.Reg = REGSP
 730                                 q.To.Type = obj.TYPE_REG
 731                                 q.To.Reg = REG_R4
 732
 733                                 // MOV R4, panic_argp(R1)
 734                                 q = obj.Appendp(q, c.newprog)
 735                                 q.As = AMOVD
 736                                 q.From.Type = obj.TYPE_REG
 737                                 q.From.Reg = REG_R4
 738                                 q.To.Type = obj.TYPE_MEM
 739                                 q.To.Reg = REG_R1
 740                                 q.To.Offset = 0 // Panic.argp
 741
 742                                 // B end
 743                                 q = obj.Appendp(q, c.newprog)
 744                                 q.As = AB
 745                                 q.To.Type = obj.TYPE_BRANCH
 746                                 q.Pcond = end
 747                         }
 748
 749                 case obj.ARET:
 750                         nocache(p)
 751                         if p.From.Type == obj.TYPE_CONST {
 752                                 c.ctxt.Diag("using BECOME (%v) is not supported!", p)
 753                                 break
 754                         }
 755
 756                         retjmp = p.To.Sym
 757                         p.To = obj.Addr{}
 758                         if c.cursym.Func.Text.Mark&LEAF != 0 {
 759                                 if c.autosize != 0 {
 760                                         p.As = AADD
 761                                         p.From.Type = obj.TYPE_CONST
 762                                         p.From.Offset = int64(c.autosize)
 763                                         p.To.Type = obj.TYPE_REG
 764                                         p.To.Reg = REGSP
 765                                         p.Spadj = -c.autosize
 766
 767                                         if objabi.Framepointer_enabled(objabi.GOOS, objabi.GOARCH) {
 768                                                 p = obj.Appendp(p, c.newprog)
 769                                                 p.As = ASUB
 770                                                 p.From.Type = obj.TYPE_CONST
 771                                                 p.From.Offset = 8
 772                                                 p.Reg = REGSP
 773                                                 p.To.Type = obj.TYPE_REG
 774                                                 p.To.Reg = REGFP
 775                                         }
 776                                 }
 777                         } else {
 778                                 /* want write-back pre-indexed SP+autosize -> SP, loading REGLINK*/
 779
 780                                 if objabi.Framepointer_enabled(objabi.GOOS, objabi.GOARCH) {
 781                                         p.As = AMOVD
 782                                         p.From.Type = obj.TYPE_MEM
 783                                         p.From.Reg = REGSP
 784                                         p.From.Offset = -8
 785                                         p.To.Type = obj.TYPE_REG
 786                                         p.To.Reg = REGFP
 787                                         p = obj.Appendp(p, c.newprog)
 788                                 }
 789
 790                                 aoffset := c.autosize
 791
 792                                 if aoffset <= 0xF0 {
 793                                         p.As = AMOVD
 794                                         p.From.Type = obj.TYPE_MEM
 795                                         p.Scond = C_XPOST
 796                                         p.From.Offset = int64(aoffset)
 797                                         p.From.Reg = REGSP
 798                                         p.To.Type = obj.TYPE_REG
 799                                         p.To.Reg = REGLINK
 800                                         p.Spadj = -aoffset
 801                                 } else {
 802                                         p.As = AMOVD
 803                                         p.From.Type = obj.TYPE_MEM
 804                                         p.From.Offset = 0
 805                                         p.From.Reg = REGSP
 806                                         p.To.Type = obj.TYPE_REG
 807                                         p.To.Reg = REGLINK
 808
 809                                         q = newprog()
 810                                         q.As = AADD
 811                                         q.From.Type = obj.TYPE_CONST
 812                                         q.From.Offset = int64(aoffset)
 813                                         q.To.Type = obj.TYPE_REG
 814                                         q.To.Reg = REGSP
 815                                         q.Link = p.Link
 816                                         q.Spadj = int32(-q.From.Offset)
 817                                         q.Pos = p.Pos
 818                                         p.Link = q
 819                                         p = q
 820                                 }
 821                         }
 822
 823                         if p.As != obj.ARET {
 824                                 q = newprog()
 825                                 q.Pos = p.Pos
 826                                 q.Link = p.Link
 827                                 p.Link = q
 828                                 p = q
 829                         }
 830
 831                         if retjmp != nil { // retjmp
 832                                 p.As = AB
 833                                 p.To.Type = obj.TYPE_BRANCH
 834                                 p.To.Sym = retjmp
 835                                 p.Spadj = +c.autosize
 836                                 break
 837                         }
 838
 839                         p.As = obj.ARET
 840                         p.To.Type = obj.TYPE_MEM
 841                         p.To.Offset = 0
 842                         p.To.Reg = REGLINK
 843                         p.Spadj = +c.autosize
 844
 845                 case AADD, ASUB:
 846                         if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
 847                                 if p.As == AADD {
 848                                         p.Spadj = int32(-p.From.Offset)
 849                                 } else {
 850                                         p.Spadj = int32(+p.From.Offset)
 851                                 }
 852                         }
 853
 854                 case obj.AGETCALLERPC:
 855                         if cursym.Leaf() {
 856                                 /* MOVD LR, Rd */
 857                                 p.As = AMOVD
 858                                 p.From.Type = obj.TYPE_REG
 859                                 p.From.Reg = REGLINK
 860                         } else {
 861                                 /* MOVD (RSP), Rd */
 862                                 p.As = AMOVD
 863                                 p.From.Type = obj.TYPE_MEM
 864                                 p.From.Reg = REGSP
 865                         }
 866
 867                 case obj.ADUFFCOPY:
 868                         if objabi.Framepointer_enabled(objabi.GOOS, objabi.GOARCH) {
 869                                 //  ADR ret_addr, R27
 870                                 //  STP (FP, R27), -24(SP)
 871                                 //  SUB 24, SP, FP
 872                                 //  DUFFCOPY
 873                                 // ret_addr:
 874                                 //  SUB 8, SP, FP
 875
 876                                 q1 := p
 877                                 // copy DUFFCOPY from q1 to q4
 878                                 q4 := obj.Appendp(p, c.newprog)
 879                                 q4.Pos = p.Pos
 880                                 q4.As = obj.ADUFFCOPY
 881                                 q4.To = p.To
 882
 883                                 q1.As = AADR
 884                                 q1.From.Type = obj.TYPE_BRANCH
 885                                 q1.To.Type = obj.TYPE_REG
 886                                 q1.To.Reg = REG_R27
 887
 888                                 q2 := obj.Appendp(q1, c.newprog)
 889                                 q2.Pos = p.Pos
 890                                 q2.As = ASTP
 891                                 q2.From.Type = obj.TYPE_REGREG
 892                                 q2.From.Reg = REGFP
 893                                 q2.From.Offset = int64(REG_R27)
 894                                 q2.To.Type = obj.TYPE_MEM
 895                                 q2.To.Reg = REGSP
 896                                 q2.To.Offset = -24
 897
 898                                 // maintaine FP for DUFFCOPY
 899                                 q3 := obj.Appendp(q2, c.newprog)
 900                                 q3.Pos = p.Pos
 901                                 q3.As = ASUB
 902                                 q3.From.Type = obj.TYPE_CONST
 903                                 q3.From.Offset = 24
 904                                 q3.Reg = REGSP
 905                                 q3.To.Type = obj.TYPE_REG
 906                                 q3.To.Reg = REGFP
 907
 908                                 q5 := obj.Appendp(q4, c.newprog)
 909                                 q5.Pos = p.Pos
 910                                 q5.As = ASUB
 911                                 q5.From.Type = obj.TYPE_CONST
 912                                 q5.From.Offset = 8
 913                                 q5.Reg = REGSP
 914                                 q5.To.Type = obj.TYPE_REG
 915                                 q5.To.Reg = REGFP
 916                                 q1.Pcond = q5
 917                                 p = q5
 918                         }
 919
 920                 case obj.ADUFFZERO:
 921                         if objabi.Framepointer_enabled(objabi.GOOS, objabi.GOARCH) {
 922                                 //  ADR ret_addr, R27
 923                                 //  STP (FP, R27), -24(SP)
 924                                 //  SUB 24, SP, FP
 925                                 //  DUFFZERO
 926                                 // ret_addr:
 927                                 //  SUB 8, SP, FP
 928
 929                                 q1 := p
 930                                 // copy DUFFZERO from q1 to q4
 931                                 q4 := obj.Appendp(p, c.newprog)
 932                                 q4.Pos = p.Pos
 933                                 q4.As = obj.ADUFFZERO
 934                                 q4.To = p.To
 935
 936                                 q1.As = AADR
 937                                 q1.From.Type = obj.TYPE_BRANCH
 938                                 q1.To.Type = obj.TYPE_REG
 939                                 q1.To.Reg = REG_R27
 940
 941                                 q2 := obj.Appendp(q1, c.newprog)
 942                                 q2.Pos = p.Pos
 943                                 q2.As = ASTP
 944                                 q2.From.Type = obj.TYPE_REGREG
 945                                 q2.From.Reg = REGFP
 946                                 q2.From.Offset = int64(REG_R27)
 947                                 q2.To.Type = obj.TYPE_MEM
 948                                 q2.To.Reg = REGSP
 949                                 q2.To.Offset = -24
 950
 951                                 // maintaine FP for DUFFZERO
 952                                 q3 := obj.Appendp(q2, c.newprog)
 953                                 q3.Pos = p.Pos
 954                                 q3.As = ASUB
 955                                 q3.From.Type = obj.TYPE_CONST
 956                                 q3.From.Offset = 24
 957                                 q3.Reg = REGSP
 958                                 q3.To.Type = obj.TYPE_REG
 959                                 q3.To.Reg = REGFP
 960
 961                                 q5 := obj.Appendp(q4, c.newprog)
 962                                 q5.Pos = p.Pos
 963                                 q5.As = ASUB
 964                                 q5.From.Type = obj.TYPE_CONST
 965                                 q5.From.Offset = 8
 966                                 q5.Reg = REGSP
 967                                 q5.To.Type = obj.TYPE_REG
 968                                 q5.To.Reg = REGFP
 969                                 q1.Pcond = q5
 970                                 p = q5
 971                         }
 972                 }
 973         }
 974 }
 975
 976 func nocache(p *obj.Prog) {
 977         p.Optab = 0
 978         p.From.Class = 0
 979         p.To.Class = 0
 980 }
 981
 982 var unaryDst = map[obj.As]bool{
 983         AWORD:  true,
 984         ADWORD: true,
 985         ABL:    true,
 986         AB:     true,
 987         ACLREX: true,
 988 }
 989
 990 var Linkarm64 = obj.LinkArch{
 991         Arch:           sys.ArchARM64,
 992         Init:           buildop,
 993         Preprocess:     preprocess,
 994         Assemble:       span7,
 995         Progedit:       progedit,
 996         UnaryDst:       unaryDst,
 997         DWARFRegisters: ARM64DWARFRegisters,
 998 }