github.com/tidwall/go@v0.0.0-20170415222209-6694a6888b7d/src/cmd/compile/internal/arm64/ggen.go (about)

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package arm64
     6  
     7  import (
     8  	"cmd/compile/internal/gc"
     9  	"cmd/internal/obj"
    10  	"cmd/internal/obj/arm64"
    11  )
    12  
    13  func defframe(pp *gc.Progs, fn *gc.Node, sz int64) {
    14  	// fill in argument size, stack size
    15  	pp.Text.To.Type = obj.TYPE_TEXTSIZE
    16  
    17  	pp.Text.To.Val = int32(gc.Rnd(fn.Type.ArgWidth(), int64(gc.Widthptr)))
    18  	frame := uint32(gc.Rnd(sz, int64(gc.Widthreg)))
    19  
    20  	// arm64 requires that the frame size (not counting saved LR)
    21  	// be empty or be 8 mod 16. If not, pad it.
    22  	if frame != 0 && frame%16 != 8 {
    23  		frame += 8
    24  	}
    25  
    26  	pp.Text.To.Offset = int64(frame)
    27  
    28  	// insert code to zero ambiguously live variables
    29  	// so that the garbage collector only sees initialized values
    30  	// when it looks for pointers.
    31  	p := pp.Text
    32  
    33  	hi := int64(0)
    34  	lo := hi
    35  
    36  	// iterate through declarations - they are sorted in decreasing xoffset order.
    37  	for _, n := range fn.Func.Dcl {
    38  		if !n.Name.Needzero() {
    39  			continue
    40  		}
    41  		if n.Class != gc.PAUTO {
    42  			gc.Fatalf("needzero class %d", n.Class)
    43  		}
    44  		if n.Type.Width%int64(gc.Widthptr) != 0 || n.Xoffset%int64(gc.Widthptr) != 0 || n.Type.Width == 0 {
    45  			gc.Fatalf("var %L has size %d offset %d", n, int(n.Type.Width), int(n.Xoffset))
    46  		}
    47  
    48  		if lo != hi && n.Xoffset+n.Type.Width >= lo-int64(2*gc.Widthreg) {
    49  			// merge with range we already have
    50  			lo = n.Xoffset
    51  
    52  			continue
    53  		}
    54  
    55  		// zero old range
    56  		p = zerorange(pp, p, int64(frame), lo, hi)
    57  
    58  		// set new range
    59  		hi = n.Xoffset + n.Type.Width
    60  
    61  		lo = n.Xoffset
    62  	}
    63  
    64  	// zero final range
    65  	zerorange(pp, p, int64(frame), lo, hi)
    66  }
    67  
    68  var darwin = obj.GOOS == "darwin"
    69  
    70  func zerorange(pp *gc.Progs, p *obj.Prog, frame int64, lo int64, hi int64) *obj.Prog {
    71  	cnt := hi - lo
    72  	if cnt == 0 {
    73  		return p
    74  	}
    75  	if cnt < int64(4*gc.Widthptr) {
    76  		for i := int64(0); i < cnt; i += int64(gc.Widthptr) {
    77  			p = pp.Appendpp(p, arm64.AMOVD, obj.TYPE_REG, arm64.REGZERO, 0, obj.TYPE_MEM, arm64.REGSP, 8+frame+lo+i)
    78  		}
    79  	} else if cnt <= int64(128*gc.Widthptr) && !darwin { // darwin ld64 cannot handle BR26 reloc with non-zero addend
    80  		p = pp.Appendpp(p, arm64.AMOVD, obj.TYPE_REG, arm64.REGSP, 0, obj.TYPE_REG, arm64.REGRT1, 0)
    81  		p = pp.Appendpp(p, arm64.AADD, obj.TYPE_CONST, 0, 8+frame+lo-8, obj.TYPE_REG, arm64.REGRT1, 0)
    82  		p.Reg = arm64.REGRT1
    83  		p = pp.Appendpp(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_MEM, 0, 0)
    84  		p.To.Name = obj.NAME_EXTERN
    85  		p.To.Sym = gc.Duffzero
    86  		p.To.Offset = 4 * (128 - cnt/int64(gc.Widthptr))
    87  	} else {
    88  		p = pp.Appendpp(p, arm64.AMOVD, obj.TYPE_CONST, 0, 8+frame+lo-8, obj.TYPE_REG, arm64.REGTMP, 0)
    89  		p = pp.Appendpp(p, arm64.AMOVD, obj.TYPE_REG, arm64.REGSP, 0, obj.TYPE_REG, arm64.REGRT1, 0)
    90  		p = pp.Appendpp(p, arm64.AADD, obj.TYPE_REG, arm64.REGTMP, 0, obj.TYPE_REG, arm64.REGRT1, 0)
    91  		p.Reg = arm64.REGRT1
    92  		p = pp.Appendpp(p, arm64.AMOVD, obj.TYPE_CONST, 0, cnt, obj.TYPE_REG, arm64.REGTMP, 0)
    93  		p = pp.Appendpp(p, arm64.AADD, obj.TYPE_REG, arm64.REGTMP, 0, obj.TYPE_REG, arm64.REGRT2, 0)
    94  		p.Reg = arm64.REGRT1
    95  		p = pp.Appendpp(p, arm64.AMOVD, obj.TYPE_REG, arm64.REGZERO, 0, obj.TYPE_MEM, arm64.REGRT1, int64(gc.Widthptr))
    96  		p.Scond = arm64.C_XPRE
    97  		p1 := p
    98  		p = pp.Appendpp(p, arm64.ACMP, obj.TYPE_REG, arm64.REGRT1, 0, obj.TYPE_NONE, 0, 0)
    99  		p.Reg = arm64.REGRT2
   100  		p = pp.Appendpp(p, arm64.ABNE, obj.TYPE_NONE, 0, 0, obj.TYPE_BRANCH, 0, 0)
   101  		gc.Patch(p, p1)
   102  	}
   103  
   104  	return p
   105  }
   106  
   107  func ginsnop(pp *gc.Progs) {
   108  	p := pp.Prog(arm64.AHINT)
   109  	p.From.Type = obj.TYPE_CONST
   110  }