liblink: create new library based on linker code

There is an enormous amount of code moving around in this CL,
but the code is the same, and it is invoked in the same ways.
This CL is preparation for the new linker structure, not the new
structure itself.

The new library's definition is in include/link.h.

The main change is the use of a Link structure to hold all the
linker-relevant state, replacing the smattering of global variables.
The Link structure should both make it clearer which state must
be carried around and make it possible to parallelize more easily
later.

The main body of the linker has moved into the architecture-independent
cmd/ld directory. That includes the list of known header types, so the
distinction between Hplan9x32 and Hplan9x64 is removed (no other
header type distinguished 32- and 64-bit formats), and code for unused
formats such as ipaq kernels has been deleted.

The code being deleted from 5l, 6l, and 8l reappears in liblink or in ld.
Because multiple files are being merged in the liblink directory,
it is not possible to show the diffs nicely in hg.

The Prog and Addr structures have been unified into an
architecture-independent form and moved to link.h, where they will
be shared by all tools: the assemblers, the compilers, and the linkers.
The unification makes it possible to write architecture-independent
traversal of Prog lists, among other benefits.

The Sym structures cannot be unified: they are too fundamentally
different between the linker and the compilers. Instead, liblink defines
an LSym - a linker Sym - to be used in the Prog and Addr structures,
and the linker now refers exclusively to LSyms. The compilers will
keep using their own syms but will fill out the corresponding LSyms in
the Prog and Addr structures.

Although code from 5l, 6l, and 8l is now in a single library, the
code has been arranged so that only one architecture needs to
be linked into a particular program: 5l will not contain the code
needed for x86 instruction layout, for example.

The object file writing code in liblink/obj.c is from cmd/gc/obj.c.

Preparation for golang.org/s/go13linker work.

This CL does not build by itself. It depends on 35740044
and will be submitted at the same time.

R=iant
CC=golang-dev
https://golang.org/cl/35790044

1 files changed, 1187 insertions, 0 deletions

diff --git a/src/liblink/obj5.c b/src/liblink/obj5.c
new file mode 100644
index 0000000000..e9c0b57318
--- /dev/null
+++ b/src/liblink/obj5.c
@@ -0,0 +1,1187 @@
+// Derived from Inferno utils/5c/swt.c
+// http://code.google.com/p/inferno-os/source/browse/utils/5c/swt.c
+//
+//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
+//	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
+//	Portions Copyright © 1997-1999 Vita Nuova Limited
+//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
+//	Portions Copyright © 2004,2006 Bruce Ellis
+//	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
+//	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
+//	Portions Copyright © 2009 The Go Authors.  All rights reserved.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <link.h>
+#include "../cmd/5l/5.out.h"
+#include "../pkg/runtime/stack.h"
+
+static Addr noaddr = {
+	.type = D_NONE,
+	.name = D_NONE,
+	.reg = NREG,
+};
+
+static Prog zprg = {
+	.as = AGOK,
+	.scond = 14,
+	.reg = NREG,
+	.from = {
+		.name = D_NONE,
+		.type = D_NONE,
+		.reg = NREG,
+	},
+	.to = {
+		.name = D_NONE,
+		.type = D_NONE,
+		.reg = NREG,
+	},
+};
+
+static void
+zname(Biobuf *b, LSym *s, int t)
+{
+	BPUTC(b, ANAME);	/* as */
+	BPUTC(b, t);		/* type */
+	BPUTC(b, s->symid);	/* sym */
+	Bwrite(b, s->name, strlen(s->name)+1);
+}
+
+static void
+zfile(Biobuf *b, char *p, int n)
+{
+	BPUTC(b, ANAME);
+	BPUTC(b, D_FILE);
+	BPUTC(b, 1);
+	BPUTC(b, '<');
+	Bwrite(b, p, n);
+	BPUTC(b, 0);
+}
+
+static void
+zaddr(Biobuf *b, Addr *a, int s, int gotype)
+{
+	int32 l;
+	uint64 e;
+	int i;
+	char *n;
+
+	switch(a->type) {
+	case D_STATIC:
+	case D_AUTO:
+	case D_EXTERN:
+	case D_PARAM:
+		// TODO(kaib): remove once everything seems to work
+		sysfatal("We should no longer generate these as types");
+
+	default:
+		BPUTC(b, a->type);
+		BPUTC(b, a->reg);
+		BPUTC(b, s);
+		BPUTC(b, a->name);
+		BPUTC(b, gotype);
+	}
+
+	switch(a->type) {
+	default:
+		print("unknown type %d in zaddr\n", a->type);
+
+	case D_NONE:
+	case D_REG:
+	case D_FREG:
+	case D_PSR:
+		break;
+
+	case D_CONST2:
+		l = a->offset2;
+		BPUTLE4(b, l); // fall through
+	case D_OREG:
+	case D_CONST:
+	case D_SHIFT:
+	case D_STATIC:
+	case D_AUTO:
+	case D_EXTERN:
+	case D_PARAM:
+		l = a->offset;
+		BPUTLE4(b, l);
+		break;
+
+	case D_BRANCH:
+		if(a->offset == 0 || a->u.branch != nil) {
+			if(a->u.branch == nil)
+				sysfatal("unpatched branch %D", a);
+			a->offset = a->u.branch->loc;
+		}
+		l = a->offset;
+		BPUTLE4(b, l);
+		break;
+
+	case D_SCONST:
+		n = a->u.sval;
+		for(i=0; i<NSNAME; i++) {
+			BPUTC(b, *n);
+			n++;
+		}
+		break;
+
+	case D_REGREG:
+	case D_REGREG2:
+		BPUTC(b, a->offset);
+		break;
+
+	case D_FCONST:
+		double2ieee(&e, a->u.dval);
+		BPUTLE4(b, e);
+		BPUTLE4(b, e >> 32);
+		break;
+	}
+}
+
+static void
+zhist(Biobuf *b, int line, vlong offset)
+{
+	Addr a;
+
+	BPUTC(b, AHISTORY);
+	BPUTC(b, C_SCOND_NONE);
+	BPUTC(b, NREG);
+	BPUTLE4(b, line);
+	zaddr(b, &noaddr, 0, 0);
+	a = noaddr;
+	if(offset != 0) {
+		a.offset = offset;
+		a.type = D_CONST;
+	}
+	zaddr(b, &a, 0, 0);
+}
+
+static int
+symtype(Addr *a)
+{
+	return a->name;
+}
+
+static void
+zprog(Link *ctxt, Biobuf *b, Prog *p, int sf, int gf, int st, int gt)
+{
+	USED(ctxt);
+
+	BPUTC(b, p->as);
+	BPUTC(b, p->scond);
+ 	BPUTC(b, p->reg);
+	BPUTLE4(b, p->lineno);
+	zaddr(b, &p->from, sf, gf);
+	zaddr(b, &p->to, st, gt);
+}
+
+static int
+isdata(Prog *p)
+{
+	return p->as == ADATA || p->as == AGLOBL;
+}
+
+static int
+iscall(Prog *p)
+{
+	return p->as == ABL;
+}
+
+static int
+datasize(Prog *p)
+{
+	return p->reg;
+}
+
+static int
+textflag(Prog *p)
+{
+	return p->reg;
+}
+
+static void
+settextflag(Prog *p, int f)
+{
+	p->reg = f;
+}
+
+static Prog*
+prg(void)
+{
+	Prog *p;
+
+	p = emallocz(sizeof(*p));
+	*p = zprg;
+	return p;
+}
+
+static	Prog*	stacksplit(Link*, Prog*, int32);
+static	void		initdiv(Link*);
+static	void	softfloat(Link*, LSym*);
+
+// Prog.mark
+enum
+{
+	FOLL = 1<<0,
+	LABEL = 1<<1,
+	LEAF = 1<<2,
+};
+
+static void
+linkcase(Prog *casep)
+{
+	Prog *p;
+
+	for(p = casep; p != nil; p = p->link){
+		if(p->as == ABCASE) {
+			for(; p != nil && p->as == ABCASE; p = p->link)
+				p->pcrel = casep;
+			break;
+		}
+	}
+}
+
+static void
+nocache(Prog *p)
+{
+	p->optab = 0;
+	p->from.class = 0;
+	p->to.class = 0;
+}
+
+static void
+addstacksplit(Link *ctxt, LSym *cursym)
+{
+	Prog *p, *pl, *q, *q1, *q2;
+	int o;
+	LSym *tlsfallback;
+	int32 autosize, autoffset;
+	
+	autosize = 0;
+
+	if(ctxt->symmorestack[0] == nil)
+		ctxt->symmorestack[0] = linklookup(ctxt, "runtime.morestack", 0);
+	
+	tlsfallback = linklookup(ctxt, "runtime.read_tls_fallback", 0);
+	ctxt->gmsym = nil;
+	if(ctxt->linkmode == LinkExternal)
+		ctxt->gmsym = linklookup(ctxt, "runtime.tlsgm", 0);
+	q = nil;
+	
+	ctxt->cursym = cursym;
+
+	if(cursym->text == nil || cursym->text->link == nil)
+		return;				
+
+	softfloat(ctxt, cursym);
+
+	if(ctxt->debugzerostack) {
+		p = cursym->text;
+		autoffset = p->to.offset;
+		if(autoffset < 0)
+			autoffset = 0;
+		if(autoffset && !(p->reg&NOSPLIT)) {
+			// MOVW $4(R13), R1
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->from.type = D_CONST;
+			p->from.reg = 13;
+			p->from.offset = 4;
+			p->to.type = D_REG;
+			p->to.reg = 1;
+	
+			// MOVW $n(R13), R2
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->from.type = D_CONST;
+			p->from.reg = 13;
+			p->from.offset = 4 + autoffset;
+			p->to.type = D_REG;
+			p->to.reg = 2;
+	
+			// MOVW $0, R3
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->from.type = D_CONST;
+			p->from.offset = 0;
+			p->to.type = D_REG;
+			p->to.reg = 3;
+	
+			// L:
+			//	MOVW.nil R3, 0(R1) +4
+			//	CMP R1, R2
+			//	BNE L
+			p = pl = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->from.type = D_REG;
+			p->from.reg = 3;
+			p->to.type = D_OREG;
+			p->to.reg = 1;
+			p->to.offset = 4;
+			p->scond |= C_PBIT;
+	
+			p = appendp(ctxt, p);
+			p->as = ACMP;
+			p->from.type = D_REG;
+			p->from.reg = 1;
+			p->reg = 2;
+	
+			p = appendp(ctxt, p);
+			p->as = ABNE;
+			p->to.type = D_BRANCH;
+			p->pcond = pl;
+		}
+	}
+
+	/*
+	 * find leaf subroutines
+	 * strip NOPs
+	 * expand RET
+	 * expand BECOME pseudo
+	 * fixup TLS
+	 */
+
+	for(p = cursym->text; p != nil; p = p->link) {
+		switch(p->as) {
+		case ACASE:
+			if(ctxt->flag_shared)
+				linkcase(p);
+			break;
+
+		case ATEXT:
+			p->mark |= LEAF;
+			break;
+
+		case ARET:
+			break;
+
+		case ADIV:
+		case ADIVU:
+		case AMOD:
+		case AMODU:
+			q = p;
+			if(ctxt->sym_div == nil)
+				initdiv(ctxt);
+			cursym->text->mark &= ~LEAF;
+			continue;
+
+		case ANOP:
+			q1 = p->link;
+			q->link = q1;		/* q is non-nop */
+			if(q1 != nil)
+				q1->mark |= p->mark;
+			continue;
+
+		case ABL:
+		case ABX:
+			cursym->text->mark &= ~LEAF;
+
+		case ABCASE:
+		case AB:
+
+		case ABEQ:
+		case ABNE:
+		case ABCS:
+		case ABHS:
+		case ABCC:
+		case ABLO:
+		case ABMI:
+		case ABPL:
+		case ABVS:
+		case ABVC:
+		case ABHI:
+		case ABLS:
+		case ABGE:
+		case ABLT:
+		case ABGT:
+		case ABLE:
+			q1 = p->pcond;
+			if(q1 != nil) {
+				while(q1->as == ANOP) {
+					q1 = q1->link;
+					p->pcond = q1;
+				}
+			}
+			break;
+		case AWORD:
+			// Rewrite TLS register fetch: MRC 15, 0, <reg>, C13, C0, 3
+			if((p->to.offset & 0xffff0fff) == 0xee1d0f70) {
+				if(ctxt->headtype == Hopenbsd) {
+					p->as = ARET;
+				} else if(ctxt->goarm < 7) {
+					if(tlsfallback->type != STEXT) {
+						ctxt->diag("runtime·read_tls_fallback not defined");
+						sysfatal("tlsfallback");
+					}
+					// BL runtime.read_tls_fallback(SB)
+					p->as = ABL;
+					p->to.type = D_BRANCH;
+					p->to.sym = tlsfallback;
+					p->pcond = tlsfallback->text;
+					p->to.offset = 0;
+					cursym->text->mark &= ~LEAF;
+				}
+				if(ctxt->linkmode == LinkExternal) {
+					// runtime.tlsgm is relocated with R_ARM_TLS_LE32
+					// and $runtime.tlsgm will contain the TLS offset.
+					//
+					// MOV $runtime.tlsgm+ctxt->tlsoffset(SB), REGTMP
+					// ADD REGTMP, <reg>
+					//
+					// In shared mode, runtime.tlsgm is relocated with
+					// R_ARM_TLS_IE32 and runtime.tlsgm(SB) will point
+					// to the GOT entry containing the TLS offset.
+					//
+					// MOV runtime.tlsgm(SB), REGTMP
+					// ADD REGTMP, <reg>
+					// SUB -ctxt->tlsoffset, <reg>
+					//
+					// The SUB compensates for ctxt->tlsoffset
+					// used in runtime.save_gm and runtime.load_gm.
+					q = p;
+					p = appendp(ctxt, p);
+					p->as = AMOVW;
+					p->scond = 14;
+					p->reg = NREG;
+					if(ctxt->flag_shared) {
+						p->from.type = D_OREG;
+						p->from.offset = 0;
+					} else {
+						p->from.type = D_CONST;
+						p->from.offset = ctxt->tlsoffset;
+					}
+					p->from.sym = ctxt->gmsym;
+					p->from.name = D_EXTERN;
+					p->to.type = D_REG;
+					p->to.reg = REGTMP;
+					p->to.offset = 0;
+
+					p = appendp(ctxt, p);
+					p->as = AADD;
+					p->scond = 14;
+					p->reg = NREG;
+					p->from.type = D_REG;
+					p->from.reg = REGTMP;
+					p->to.type = D_REG;
+					p->to.reg = (q->to.offset & 0xf000) >> 12;
+					p->to.offset = 0;
+
+					if(ctxt->flag_shared) {
+						p = appendp(ctxt, p);
+						p->as = ASUB;
+						p->scond = 14;
+						p->reg = NREG;
+						p->from.type = D_CONST;
+						p->from.offset = -ctxt->tlsoffset;
+						p->to.type = D_REG;
+						p->to.reg = (q->to.offset & 0xf000) >> 12;
+						p->to.offset = 0;
+					}
+				}
+			}
+		}
+		q = p;
+	}
+
+	for(p = cursym->text; p != nil; p = p->link) {
+		o = p->as;
+		switch(o) {
+		case ATEXT:
+			autosize = p->to.offset + 4;
+			if(autosize <= 4)
+			if(cursym->text->mark & LEAF) {
+				p->to.offset = -4;
+				autosize = 0;
+			}
+
+			if(!autosize && !(cursym->text->mark & LEAF)) {
+				if(ctxt->debugvlog) {
+					Bprint(ctxt->bso, "save suppressed in: %s\n",
+						cursym->name);
+					Bflush(ctxt->bso);
+				}
+				cursym->text->mark |= LEAF;
+			}
+			if(cursym->text->mark & LEAF) {
+				cursym->leaf = 1;
+				if(!autosize)
+					break;
+			}
+
+			if(!(p->reg & NOSPLIT))
+				p = stacksplit(ctxt, p, autosize); // emit split check
+			
+			// MOVW.W		R14,$-autosize(SP)
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->scond |= C_WBIT;
+			p->from.type = D_REG;
+			p->from.reg = REGLINK;
+			p->to.type = D_OREG;
+			p->to.offset = -autosize;
+			p->to.reg = REGSP;
+			p->spadj = autosize;
+			
+			if(cursym->text->reg & WRAPPER) {
+				// g->panicwrap += autosize;
+				// MOVW panicwrap_offset(g), R3
+				// ADD $autosize, R3
+				// MOVW R3 panicwrap_offset(g)
+				p = appendp(ctxt, p);
+				p->as = AMOVW;
+				p->from.type = D_OREG;
+				p->from.reg = REGG;
+				p->from.offset = 2*ctxt->arch->ptrsize;
+				p->to.type = D_REG;
+				p->to.reg = 3;
+			
+				p = appendp(ctxt, p);
+				p->as = AADD;
+				p->from.type = D_CONST;
+				p->from.offset = autosize;
+				p->to.type = D_REG;
+				p->to.reg = 3;
+				
+				p = appendp(ctxt, p);
+				p->as = AMOVW;
+				p->from.type = D_REG;
+				p->from.reg = 3;
+				p->to.type = D_OREG;
+				p->to.reg = REGG;
+				p->to.offset = 2*ctxt->arch->ptrsize;
+			}
+			break;
+
+		case ARET:
+			nocache(p);
+			if(cursym->text->mark & LEAF) {
+				if(!autosize) {
+					p->as = AB;
+					p->from = zprg.from;
+					if(p->to.sym) { // retjmp
+						p->to.type = D_BRANCH;
+						p->pcond = p->to.sym->text;
+					} else {
+						p->to.type = D_OREG;
+						p->to.offset = 0;
+						p->to.reg = REGLINK;
+					}
+					break;
+				}
+			}
+
+			if(cursym->text->reg & WRAPPER) {
+				int scond;
+				
+				// Preserve original RET's cond, to allow RET.EQ
+				// in the implementation of reflect.call.
+				scond = p->scond;
+				p->scond = C_SCOND_NONE;
+
+				// g->panicwrap -= autosize;
+				// MOVW panicwrap_offset(g), R3
+				// SUB $autosize, R3
+				// MOVW R3 panicwrap_offset(g)
+				p->as = AMOVW;
+				p->from.type = D_OREG;
+				p->from.reg = REGG;
+				p->from.offset = 2*ctxt->arch->ptrsize;
+				p->to.type = D_REG;
+				p->to.reg = 3;
+				p = appendp(ctxt, p);
+			
+				p->as = ASUB;
+				p->from.type = D_CONST;
+				p->from.offset = autosize;
+				p->to.type = D_REG;
+				p->to.reg = 3;
+				p = appendp(ctxt, p);
+
+				p->as = AMOVW;
+				p->from.type = D_REG;
+				p->from.reg = 3;
+				p->to.type = D_OREG;
+				p->to.reg = REGG;
+				p->to.offset = 2*ctxt->arch->ptrsize;
+				p = appendp(ctxt, p);
+
+				p->scond = scond;
+			}
+
+			p->as = AMOVW;
+			p->scond |= C_PBIT;
+			p->from.type = D_OREG;
+			p->from.offset = autosize;
+			p->from.reg = REGSP;
+			p->to.type = D_REG;
+			p->to.reg = REGPC;
+			// If there are instructions following
+			// this ARET, they come from a branch
+			// with the same stackframe, so no spadj.
+			
+			if(p->to.sym) { // retjmp
+				p->to.reg = REGLINK;
+				q2 = appendp(ctxt, p);
+				q2->as = AB;
+				q2->to.type = D_BRANCH;
+				q2->to.sym = p->to.sym;
+				q2->pcond = p->to.sym->text;
+				p->to.sym = nil;
+				p = q2;
+			}
+			break;
+
+		case AADD:
+			if(p->from.type == D_CONST && p->from.reg == NREG && p->to.type == D_REG && p->to.reg == REGSP)
+				p->spadj = -p->from.offset;
+			break;
+
+		case ASUB:
+			if(p->from.type == D_CONST && p->from.reg == NREG && p->to.type == D_REG && p->to.reg == REGSP)
+				p->spadj = p->from.offset;
+			break;
+
+		case ADIV:
+		case ADIVU:
+		case AMOD:
+		case AMODU:
+			if(ctxt->debugdivmod)
+				break;
+			if(p->from.type != D_REG)
+				break;
+			if(p->to.type != D_REG)
+				break;
+			q1 = p;
+
+			/* MOV a,4(SP) */
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->lineno = q1->lineno;
+			p->from.type = D_REG;
+			p->from.reg = q1->from.reg;
+			p->to.type = D_OREG;
+			p->to.reg = REGSP;
+			p->to.offset = 4;
+
+			/* MOV b,REGTMP */
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->lineno = q1->lineno;
+			p->from.type = D_REG;
+			p->from.reg = q1->reg;
+			if(q1->reg == NREG)
+				p->from.reg = q1->to.reg;
+			p->to.type = D_REG;
+			p->to.reg = REGTMP;
+			p->to.offset = 0;
+
+			/* CALL appropriate */
+			p = appendp(ctxt, p);
+			p->as = ABL;
+			p->lineno = q1->lineno;
+			p->to.type = D_BRANCH;
+			p->pcond = p;
+			switch(o) {
+			case ADIV:
+				p->to.sym = ctxt->sym_div;
+				break;
+			case ADIVU:
+				p->to.sym = ctxt->sym_divu;
+				break;
+			case AMOD:
+				p->to.sym = ctxt->sym_mod;
+				break;
+			case AMODU:
+				p->to.sym = ctxt->sym_modu;
+				break;
+			}
+
+			/* MOV REGTMP, b */
+			p = appendp(ctxt, p);
+			p->as = AMOVW;
+			p->lineno = q1->lineno;
+			p->from.type = D_REG;
+			p->from.reg = REGTMP;
+			p->from.offset = 0;
+			p->to.type = D_REG;
+			p->to.reg = q1->to.reg;
+
+			/* ADD $8,SP */
+			p = appendp(ctxt, p);
+			p->as = AADD;
+			p->lineno = q1->lineno;
+			p->from.type = D_CONST;
+			p->from.reg = NREG;
+			p->from.offset = 8;
+			p->reg = NREG;
+			p->to.type = D_REG;
+			p->to.reg = REGSP;
+			p->spadj = -8;
+
+			/* Keep saved LR at 0(SP) after SP change. */
+			/* MOVW 0(SP), REGTMP; MOVW REGTMP, -8!(SP) */
+			/* TODO: Remove SP adjustments; see issue 6699. */
+			q1->as = AMOVW;
+			q1->from.type = D_OREG;
+			q1->from.reg = REGSP;
+			q1->from.offset = 0;
+			q1->reg = NREG;
+			q1->to.type = D_REG;
+			q1->to.reg = REGTMP;
+
+			/* SUB $8,SP */
+			q1 = appendp(ctxt, q1);
+			q1->as = AMOVW;
+			q1->from.type = D_REG;
+			q1->from.reg = REGTMP;
+			q1->reg = NREG;
+			q1->to.type = D_OREG;
+			q1->to.reg = REGSP;
+			q1->to.offset = -8;
+			q1->scond |= C_WBIT;
+			q1->spadj = 8;
+
+			break;
+		case AMOVW:
+			if((p->scond & C_WBIT) && p->to.type == D_OREG && p->to.reg == REGSP)
+				p->spadj = -p->to.offset;
+			if((p->scond & C_PBIT) && p->from.type == D_OREG && p->from.reg == REGSP && p->to.reg != REGPC)
+				p->spadj = -p->from.offset;
+			if(p->from.type == D_CONST && p->from.reg == REGSP && p->to.type == D_REG && p->to.reg == REGSP)
+				p->spadj = -p->from.offset;
+			break;
+		}
+	}
+}
+
+static void
+softfloat(Link *ctxt, LSym *cursym)
+{
+	Prog *p, *next, *psfloat;
+	LSym *symsfloat;
+	int wasfloat;
+
+	if(!ctxt->debugfloat)
+		return;
+
+	symsfloat = linklookup(ctxt, "_sfloat", 0);
+	psfloat = nil;
+	if(symsfloat->type == STEXT)
+		psfloat = symsfloat->text;
+
+	wasfloat = 0;
+	for(p = cursym->text; p != nil; p = p->link)
+		if(p->pcond != nil)
+			p->pcond->mark |= LABEL;
+	for(p = cursym->text; p != nil; p = p->link) {
+		switch(p->as) {
+		case AMOVW:
+			if(p->to.type == D_FREG || p->from.type == D_FREG)
+				goto soft;
+			goto notsoft;
+
+		case AMOVWD:
+		case AMOVWF:
+		case AMOVDW:
+		case AMOVFW:
+		case AMOVFD:
+		case AMOVDF:
+		case AMOVF:
+		case AMOVD:
+
+		case ACMPF:
+		case ACMPD:
+		case AADDF:
+		case AADDD:
+		case ASUBF:
+		case ASUBD:
+		case AMULF:
+		case AMULD:
+		case ADIVF:
+		case ADIVD:
+		case ASQRTF:
+		case ASQRTD:
+		case AABSF:
+		case AABSD:
+			goto soft;
+
+		default:
+			goto notsoft;
+
+		soft:
+			if (psfloat == nil)
+				ctxt->diag("floats used with _sfloat not defined");
+			if (!wasfloat || (p->mark&LABEL)) {
+				next = ctxt->arch->prg();
+				*next = *p;
+
+				// BL _sfloat(SB)
+				*p = zprg;
+				p->link = next;
+				p->as = ABL;
+ 				p->to.type = D_BRANCH;
+				p->to.sym = symsfloat;
+				p->pcond = psfloat;
+				p->lineno = next->lineno;
+
+				p = next;
+				wasfloat = 1;
+			}
+			break;
+
+		notsoft:
+			wasfloat = 0;
+		}
+	}
+}
+
+static Prog*
+stacksplit(Link *ctxt, Prog *p, int32 framesize)
+{
+	int32 arg;
+
+	// MOVW			g_stackguard(g), R1
+	p = appendp(ctxt, p);
+	p->as = AMOVW;
+	p->from.type = D_OREG;
+	p->from.reg = REGG;
+	p->to.type = D_REG;
+	p->to.reg = 1;
+	
+	if(framesize <= StackSmall) {
+		// small stack: SP < stackguard
+		//	CMP	stackguard, SP
+		p = appendp(ctxt, p);
+		p->as = ACMP;
+		p->from.type = D_REG;
+		p->from.reg = 1;
+		p->reg = REGSP;
+	} else if(framesize <= StackBig) {
+		// large stack: SP-framesize < stackguard-StackSmall
+		//	MOVW $-framesize(SP), R2
+		//	CMP stackguard, R2
+		p = appendp(ctxt, p);
+		p->as = AMOVW;
+		p->from.type = D_CONST;
+		p->from.reg = REGSP;
+		p->from.offset = -framesize;
+		p->to.type = D_REG;
+		p->to.reg = 2;
+		
+		p = appendp(ctxt, p);
+		p->as = ACMP;
+		p->from.type = D_REG;
+		p->from.reg = 1;
+		p->reg = 2;
+	} else {
+		// Such a large stack we need to protect against wraparound
+		// if SP is close to zero.
+		//	SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
+		// The +StackGuard on both sides is required to keep the left side positive:
+		// SP is allowed to be slightly below stackguard. See stack.h.
+		//	CMP $StackPreempt, R1
+		//	MOVW.NE $StackGuard(SP), R2
+		//	SUB.NE R1, R2
+		//	MOVW.NE $(framesize+(StackGuard-StackSmall)), R3
+		//	CMP.NE R3, R2
+		p = appendp(ctxt, p);
+		p->as = ACMP;
+		p->from.type = D_CONST;
+		p->from.offset = (uint32)StackPreempt;
+		p->reg = 1;
+
+		p = appendp(ctxt, p);
+		p->as = AMOVW;
+		p->from.type = D_CONST;
+		p->from.reg = REGSP;
+		p->from.offset = StackGuard;
+		p->to.type = D_REG;
+		p->to.reg = 2;
+		p->scond = C_SCOND_NE;
+		
+		p = appendp(ctxt, p);
+		p->as = ASUB;
+		p->from.type = D_REG;
+		p->from.reg = 1;
+		p->to.type = D_REG;
+		p->to.reg = 2;
+		p->scond = C_SCOND_NE;
+		
+		p = appendp(ctxt, p);
+		p->as = AMOVW;
+		p->from.type = D_CONST;
+		p->from.offset = framesize + (StackGuard - StackSmall);
+		p->to.type = D_REG;
+		p->to.reg = 3;
+		p->scond = C_SCOND_NE;
+		
+		p = appendp(ctxt, p);
+		p->as = ACMP;
+		p->from.type = D_REG;
+		p->from.reg = 3;
+		p->reg = 2;
+		p->scond = C_SCOND_NE;
+	}
+	
+	// MOVW.LS		$framesize, R1
+	p = appendp(ctxt, p);
+	p->as = AMOVW;
+	p->scond = C_SCOND_LS;
+	p->from.type = D_CONST;
+	p->from.offset = framesize;
+	p->to.type = D_REG;
+	p->to.reg = 1;
+
+	// MOVW.LS		$args, R2
+	p = appendp(ctxt, p);
+	p->as = AMOVW;
+	p->scond = C_SCOND_LS;
+	p->from.type = D_CONST;
+	arg = ctxt->cursym->text->to.offset2;
+	if(arg == 1) // special marker for known 0
+		arg = 0;
+	if(arg&3)
+		ctxt->diag("misaligned argument size in stack split");
+	p->from.offset = arg;
+	p->to.type = D_REG;
+	p->to.reg = 2;
+
+	// MOVW.LS	R14, R3
+	p = appendp(ctxt, p);
+	p->as = AMOVW;
+	p->scond = C_SCOND_LS;
+	p->from.type = D_REG;
+	p->from.reg = REGLINK;
+	p->to.type = D_REG;
+	p->to.reg = 3;
+
+	// BL.LS		runtime.morestack(SB) // modifies LR, returns with LO still asserted
+	p = appendp(ctxt, p);
+	p->as = ABL;
+	p->scond = C_SCOND_LS;
+	p->to.type = D_BRANCH;
+	p->to.sym = ctxt->symmorestack[0];
+	
+	// BLS	start
+	p = appendp(ctxt, p);
+	p->as = ABLS;
+	p->to.type = D_BRANCH;
+	p->pcond = ctxt->cursym->text->link;
+	
+	return p;
+}
+
+static void
+initdiv(Link *ctxt)
+{
+	if(ctxt->sym_div != nil)
+		return;
+	ctxt->sym_div = linklookup(ctxt, "_div", 0);
+	ctxt->sym_divu = linklookup(ctxt, "_divu", 0);
+	ctxt->sym_mod = linklookup(ctxt, "_mod", 0);
+	ctxt->sym_modu = linklookup(ctxt, "_modu", 0);
+}
+
+static void xfol(Link*, Prog*, Prog**);
+
+static void
+follow(Link *ctxt, LSym *s)
+{
+	Prog *firstp, *lastp;
+
+	ctxt->cursym = s;
+
+	firstp = ctxt->arch->prg();
+	lastp = firstp;
+	xfol(ctxt, s->text, &lastp);
+	lastp->link = nil;
+	s->text = firstp->link;
+}
+
+static int
+relinv(int a)
+{
+	switch(a) {
+	case ABEQ:	return ABNE;
+	case ABNE:	return ABEQ;
+	case ABCS:	return ABCC;
+	case ABHS:	return ABLO;
+	case ABCC:	return ABCS;
+	case ABLO:	return ABHS;
+	case ABMI:	return ABPL;
+	case ABPL:	return ABMI;
+	case ABVS:	return ABVC;
+	case ABVC:	return ABVS;
+	case ABHI:	return ABLS;
+	case ABLS:	return ABHI;
+	case ABGE:	return ABLT;
+	case ABLT:	return ABGE;
+	case ABGT:	return ABLE;
+	case ABLE:	return ABGT;
+	}
+	sysfatal("unknown relation: %s", anames5[a]);
+	return 0;
+}
+
+static void
+xfol(Link *ctxt, Prog *p, Prog **last)
+{
+	Prog *q, *r;
+	int a, i;
+
+loop:
+	if(p == nil)
+		return;
+	a = p->as;
+	if(a == AB) {
+		q = p->pcond;
+		if(q != nil && q->as != ATEXT) {
+			p->mark |= FOLL;
+			p = q;
+			if(!(p->mark & FOLL))
+				goto loop;
+		}
+	}
+	if(p->mark & FOLL) {
+		for(i=0,q=p; i<4; i++,q=q->link) {
+			if(q == *last || q == nil)
+				break;
+			a = q->as;
+			if(a == ANOP) {
+				i--;
+				continue;
+			}
+			if(a == AB || (a == ARET && q->scond == 14) || a == ARFE || a == AUNDEF)
+				goto copy;
+			if(q->pcond == nil || (q->pcond->mark&FOLL))
+				continue;
+			if(a != ABEQ && a != ABNE)
+				continue;
+		copy:
+			for(;;) {
+				r = ctxt->arch->prg();
+				*r = *p;
+				if(!(r->mark&FOLL))
+					print("can't happen 1\n");
+				r->mark |= FOLL;
+				if(p != q) {
+					p = p->link;
+					(*last)->link = r;
+					*last = r;
+					continue;
+				}
+				(*last)->link = r;
+				*last = r;
+				if(a == AB || (a == ARET && q->scond == 14) || a == ARFE || a == AUNDEF)
+					return;
+				r->as = ABNE;
+				if(a == ABNE)
+					r->as = ABEQ;
+				r->pcond = p->link;
+				r->link = p->pcond;
+				if(!(r->link->mark&FOLL))
+					xfol(ctxt, r->link, last);
+				if(!(r->pcond->mark&FOLL))
+					print("can't happen 2\n");
+				return;
+			}
+		}
+		a = AB;
+		q = ctxt->arch->prg();
+		q->as = a;
+		q->lineno = p->lineno;
+		q->to.type = D_BRANCH;
+		q->to.offset = p->pc;
+		q->pcond = p;
+		p = q;
+	}
+	p->mark |= FOLL;
+	(*last)->link = p;
+	*last = p;
+	if(a == AB || (a == ARET && p->scond == 14) || a == ARFE || a == AUNDEF){
+		return;
+	}
+	if(p->pcond != nil)
+	if(a != ABL && a != ABX && p->link != nil) {
+		q = brchain(ctxt, p->link);
+		if(a != ATEXT && a != ABCASE)
+		if(q != nil && (q->mark&FOLL)) {
+			p->as = relinv(a);
+			p->link = p->pcond;
+			p->pcond = q;
+		}
+		xfol(ctxt, p->link, last);
+		q = brchain(ctxt, p->pcond);
+		if(q == nil)
+			q = p->pcond;
+		if(q->mark&FOLL) {
+			p->pcond = q;
+			return;
+		}
+		p = q;
+		goto loop;
+	}
+	p = p->link;
+	goto loop;
+}
+
+LinkArch linkarm = {
+	.name = "arm",
+
+	.addstacksplit = addstacksplit,
+	.assemble = span5,
+	.datasize = datasize,
+	.follow = follow,
+	.iscall = iscall,
+	.isdata = isdata,
+	.ldobj = ldobj5,
+	.nopout = nopout5,
+	.prg = prg,
+	.settextflag = settextflag,
+	.symtype = symtype,
+	.textflag = textflag,
+	.zfile = zfile,
+	.zhist = zhist,
+	.zname = zname,
+	.zprog = zprog,
+
+	.minlc = 4,
+	.ptrsize = 4,
+
+	.D_ADDR = D_ADDR,
+	.D_BRANCH = D_BRANCH,
+	.D_CONST = D_CONST,
+	.D_EXTERN = D_EXTERN,
+	.D_FCONST = D_FCONST,
+	.D_NONE = D_NONE,
+	.D_PCREL = D_PCREL,
+	.D_SCONST = D_SCONST,
+	.D_SIZE = D_SIZE,
+
+	.ACALL = ABL,
+	.AFUNCDATA = AFUNCDATA,
+	.AJMP = AB,
+	.ANOP = ANOP,
+	.APCDATA = APCDATA,
+	.ARET = ARET,
+	.ATEXT = ATEXT,
+	.AUSEFIELD = AUSEFIELD,
+};