first stub for softfloats, intercepts float instructions and skips

        them in the stream.

R=rsc
https://golang.org/cl/174052

src/cmd/5l/Makefile

@@ -17,6 +17,7 @@ OFILES=\
 	optab.$O\
 	pass.$O\
 	thumb.$O\
+	softfloat.$O\
 	span.$O\
 	go.$O\
 

src/cmd/5l/l.h

@@ -451,6 +451,7 @@ void	putsymb(char*, int, int32, int);
 int32	regoff(Adr*);
 int	relinv(int);
 int32	rnd(int32, int32);
+void	softfloat(void);
 void	span(void);
 void	strnput(char*, int);
 void	undef(void);

src/cmd/5l/obj.c

@@ -71,6 +71,12 @@ isobjfile(char *f)
 	return v;
 }
 
+static char*
+linkername[] =
+{
+	"runtime·softfloat",
+};
+
 void
 usage(void)
 {
@@ -81,7 +87,7 @@ usage(void)
 void
 main(int argc, char *argv[])
 {
-	int c;
+	int c, i;
 
 	Binit(&bso, 1, OWRITE);
 	cout = -1;
@@ -257,6 +263,10 @@ main(int argc, char *argv[])
 	if(!debug['l'])
 		loadlib();
 
+	// mark some functions that are only referenced after linker code editing
+	// TODO(kaib): this doesn't work, the prog can't be found in runtime
+	for(i=0; i<nelem(linkername); i++)
+		mark(lookup(linkername[i], 0));
 	deadcode();
 
 	firstp = firstp->link;
@@ -294,6 +304,7 @@ main(int argc, char *argv[])
 	follow();
 	if(firstp == P)
 		goto out;
+	softfloat();
 	noops();
 	span();
 	asmb();

src/cmd/5l/softfloat.c

+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#define	EXTERN
+#include	"l.h"
+
+void
+softfloat()
+{
+	Prog *p, *prev, *psfloat;
+	Sym *symsfloat;
+	int wasfloat;
+	
+	symsfloat = lookup("_sfloat", 0);
+	psfloat = P;
+	if(symsfloat->type == STEXT)
+	for(p = firstp; p != P; p = p->link) {
+		if(p->as == ATEXT) {
+			if(p->from.sym == symsfloat) {
+				psfloat = p;
+				break;
+			}
+		}
+	}
+
+	wasfloat = 0;
+	p = firstp;
+	prev = P;
+	for(p = firstp; p != P; p = p->link) {
+		switch(p->as) {
+		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:
+			if (psfloat == P)
+				diag("floats used with _sfloat not defined");
+			if (!wasfloat) {
+				if (prev == P)
+					diag("float instruction without predecessor TEXT");
+				// BL		_sfloat(SB)
+				prev = appendp(prev);
+				prev->as = ABL;
+ 				prev->to.type = D_BRANCH;
+				prev->to.sym = symsfloat;
+				prev->cond = psfloat;
+				
+				wasfloat = 1;
+			}
+			break;
+		default:
+			wasfloat = 0;
+		}
+		prev = p;
+	}
+}

src/cmd/ld/go.c

@@ -364,7 +364,6 @@ err:
 	nerrors++;
 }
 
-static void mark(Sym*);
 static int markdepth;
 
 static void
@@ -408,7 +407,7 @@ marktext(Prog *p)
 	markdepth--;
 }
 
-static void
+void
 mark(Sym *s)
 {
 	if(s == S || s->reachable)

src/cmd/ld/lib.h

@@ -77,6 +77,8 @@ void	usage(void);
 void	ldobj1(Biobuf *f, int64 len, char *pn);
 void	ldobj(Biobuf*, int64, char*);
 void	ldpkg(Biobuf*, int64, char*);
+void	mark(Sym *s);
+
 
 int	pathchar(void);
 void*	mal(uint32);

src/pkg/runtime/Makefile

@@ -34,6 +34,7 @@ GOARM?=6
 OFILES_arm=\
 	cas$(GOARM).$O\
 	memset.$O\
+	softfloat.$O\
 	vlop.$O\
 	vlrt.$O\
 

src/pkg/runtime/arm/asm.s

@@ -73,7 +73,7 @@ TEXT mainstart(SB),7,$4
 	MOVW	R0, (R1)	// fail hard
 	RET
 
-// TODO(kaib): remove these once linker works properly
+// TODO(kaib): remove these once i actually understand how the linker removes symbols
 // pull in dummy dependencies
 TEXT _dep_dummy(SB),7,$0
 	BL	_div(SB)
@@ -81,6 +81,7 @@ TEXT _dep_dummy(SB),7,$0
 	BL	_mod(SB)
 	BL	_modu(SB)
 	BL	_modu(SB)
+	BL	_sfloat(SB)
 
 TEXT	breakpoint(SB),7,$0
 	BL	abort(SB)

src/pkg/runtime/arm/softfloat.c

+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "runtime.h"
+
+// returns number of bytes that the fp instruction is occupying
+static uint32
+isfltinstr(uint32 *pc)
+{
+	uint32 i;
+	uint32 c;
+	
+	i = *pc;
+	c = i >> 25 & 7;
+	
+	switch(c) {
+	case 6: // 110
+//printf(" %p coproc multi: %x\n", pc, i);
+		return 4;
+	case 7: // 111
+		if (i>>24 & 1) return 0; // ignore swi
+//printf(" %p coproc %x\n", pc, i);
+		return 4;
+	}
+
+	// lookahead for virtual instructions that span multiple arm instructions
+	c = ((*pc & 0x0f000000) >> 16) |
+		((*(pc + 1)  & 0x0f000000) >> 20) |
+		((*(pc + 2) & 0x0f000000) >> 24);
+	if(c == 0x50d) {
+//printf(" %p coproc const %x\n", pc, i);
+		return 12;
+	}
+
+//printf(" %p %x\n", pc, i);
+	return 0;
+}
+
+#pragma textflag 7
+uint32*
+_sfloat2(uint32 *lr, uint32 r0)
+{
+	uint32 skip;
+	
+//printf("softfloat: pre %p\n", lr);
+	while(skip = isfltinstr(lr))
+		lr += skip;
+//printf(" post: %p\n", lr);
+	return lr;
+}
+
+

src/pkg/runtime/arm/vlop.s

@@ -165,3 +165,20 @@ TEXT	_modu(SB), 7, $16
 out:
 	BL	rest<>(SB)
 	B	out
+
+// trampoline for _sfloat2. passes LR as arg0 and
+// saves registers R0-R11 on the stack for mutation
+// by _sfloat2
+TEXT	_sfloat(SB), 7, $52 // 4 arg + 12*4 saved regs
+	MOVW	R14, 4(R13)
+	MOVW	R0, 8(R13)
+	MOVW	$12(R13), R0
+	MOVM.IA.W	[R1-R11], (R0)
+	BL	_sfloat2(SB)
+	MOVW	R0, 0(R13)
+	MOVW	$12(R13), R0
+	MOVM.IA.W	(R0), [R1-R11]
+	MOVW	8(R13), R0
+	RET
+			
+