github.com/bgentry/go@v0.0.0-20150121062915-6cf5a733d54d/src/cmd/gc/align.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 <u.h>
#include <libc.h>
#include "go.h"

/*
 * machine size and rounding
 * alignment is dictated around
 * the size of a pointer, set in betypeinit
 * (see ../6g/galign.c).
 */

static int defercalc;

vlong
rnd(vlong o, vlong r)
{
	if(r < 1 || r > 8 || (r&(r-1)) != 0)
		fatal("rnd");
	return (o+r-1)&~(r-1);
}

static void
offmod(Type *t)
{
	Type *f;
	int32 o;

	o = 0;
	for(f=t->type; f!=T; f=f->down) {
		if(f->etype != TFIELD)
			fatal("offmod: not TFIELD: %lT", f);
		f->width = o;
		o += widthptr;
		if(o >= MAXWIDTH) {
			yyerror("interface too large");
			o = widthptr;
		}
	}
}

static vlong
widstruct(Type *errtype, Type *t, vlong o, int flag)
{
	Type *f;
	int64 w;
	int32 maxalign;
	vlong starto, lastzero;
	
	starto = o;
	maxalign = flag;
	if(maxalign < 1)
		maxalign = 1;
	lastzero = 0;
	for(f=t->type; f!=T; f=f->down) {
		if(f->etype != TFIELD)
			fatal("widstruct: not TFIELD: %lT", f);
		if(f->type == T) {
			// broken field, just skip it so that other valid fields
			// get a width.
			continue;
		}
		dowidth(f->type);
		if(f->type->align > maxalign)
			maxalign = f->type->align;
		if(f->type->width < 0)
			fatal("invalid width %lld", f->type->width);
		w = f->type->width;
		if(f->type->align > 0)
			o = rnd(o, f->type->align);
		f->width = o;	// really offset for TFIELD
		if(f->nname != N) {
			// this same stackparam logic is in addrescapes
			// in typecheck.c.  usually addrescapes runs after
			// widstruct, in which case we could drop this,
			// but function closure functions are the exception.
			if(f->nname->stackparam) {
				f->nname->stackparam->xoffset = o;
				f->nname->xoffset = 0;
			} else
				f->nname->xoffset = o;
		}
		if(w == 0)
			lastzero = o;
		o += w;
		if(o >= MAXWIDTH) {
			yyerror("type %lT too large", errtype);
			o = 8;  // small but nonzero
		}
	}
	// For nonzero-sized structs which end in a zero-sized thing, we add
	// an extra byte of padding to the type.  This padding ensures that
	// taking the address of the zero-sized thing can't manufacture a
	// pointer to the next object in the heap.  See issue 9401.
	if(flag == 1 && o > starto && o == lastzero)
		o++;

	// final width is rounded
	if(flag)
		o = rnd(o, maxalign);
	t->align = maxalign;

	// type width only includes back to first field's offset
	t->width = o - starto;
	return o;
}

void
dowidth(Type *t)
{
	int32 et;
	int64 w;
	int lno;
	Type *t1;

	if(widthptr == 0)
		fatal("dowidth without betypeinit");

	if(t == T)
		return;

	if(t->width > 0)
		return;

	if(t->width == -2) {
		lno = lineno;
		lineno = t->lineno;
		if(!t->broke) {
			t->broke = 1;
			yyerror("invalid recursive type %T", t);
		}
		t->width = 0;
		lineno = lno;
		return;
	}

	// break infinite recursion if the broken recursive type
	// is referenced again
	if(t->broke && t->width == 0)
		return;

	// defer checkwidth calls until after we're done
	defercalc++;

	lno = lineno;
	lineno = t->lineno;
	t->width = -2;
	t->align = 0;

	et = t->etype;
	switch(et) {
	case TFUNC:
	case TCHAN:
	case TMAP:
	case TSTRING:
		break;

	default:
		/* simtype == 0 during bootstrap */
		if(simtype[t->etype] != 0)
			et = simtype[t->etype];
		break;
	}

	w = 0;
	switch(et) {
	default:
		fatal("dowidth: unknown type: %T", t);
		break;

	/* compiler-specific stuff */
	case TINT8:
	case TUINT8:
	case TBOOL:		// bool is int8
		w = 1;
		break;
	case TINT16:
	case TUINT16:
		w = 2;
		break;
	case TINT32:
	case TUINT32:
	case TFLOAT32:
		w = 4;
		break;
	case TINT64:
	case TUINT64:
	case TFLOAT64:
	case TCOMPLEX64:
		w = 8;
		t->align = widthreg;
		break;
	case TCOMPLEX128:
		w = 16;
		t->align = widthreg;
		break;
	case TPTR32:
		w = 4;
		checkwidth(t->type);
		break;
	case TPTR64:
		w = 8;
		checkwidth(t->type);
		break;
	case TUNSAFEPTR:
		w = widthptr;
		break;
	case TINTER:		// implemented as 2 pointers
		w = 2*widthptr;
		t->align = widthptr;
		offmod(t);
		break;
	case TCHAN:		// implemented as pointer
		w = widthptr;
		checkwidth(t->type);

		// make fake type to check later to
		// trigger channel argument check.
		t1 = typ(TCHANARGS);
		t1->type = t;
		checkwidth(t1);
		break;
	case TCHANARGS:
		t1 = t->type;
		dowidth(t->type);	// just in case
		if(t1->type->width >= (1<<16))
			yyerror("channel element type too large (>64kB)");
		t->width = 1;
		break;
	case TMAP:		// implemented as pointer
		w = widthptr;
		checkwidth(t->type);
		checkwidth(t->down);
		break;
	case TFORW:		// should have been filled in
		if(!t->broke)
			yyerror("invalid recursive type %T", t);
		w = 1;	// anything will do
		break;
	case TANY:
		// dummy type; should be replaced before use.
		if(!debug['A'])
			fatal("dowidth any");
		w = 1;	// anything will do
		break;
	case TSTRING:
		if(sizeof_String == 0)
			fatal("early dowidth string");
		w = sizeof_String;
		t->align = widthptr;
		break;
	case TARRAY:
		if(t->type == T)
			break;
		if(t->bound >= 0) {
			uint64 cap;

			dowidth(t->type);
			if(t->type->width != 0) {
				cap = (MAXWIDTH-1) / t->type->width;
				if(t->bound > cap)
					yyerror("type %lT larger than address space", t);
			}
			w = t->bound * t->type->width;
			t->align = t->type->align;
		}
		else if(t->bound == -1) {
			w = sizeof_Array;
			checkwidth(t->type);
			t->align = widthptr;
		}
		else if(t->bound == -100) {
			if(!t->broke) {
				yyerror("use of [...] array outside of array literal");
				t->broke = 1;
			}
		}
		else
			fatal("dowidth %T", t);	// probably [...]T
		break;

	case TSTRUCT:
		if(t->funarg)
			fatal("dowidth fn struct %T", t);
		w = widstruct(t, t, 0, 1);
		break;

	case TFUNC:
		// make fake type to check later to
		// trigger function argument computation.
		t1 = typ(TFUNCARGS);
		t1->type = t;
		checkwidth(t1);

		// width of func type is pointer
		w = widthptr;
		break;

	case TFUNCARGS:
		// function is 3 cated structures;
		// compute their widths as side-effect.
		t1 = t->type;
		w = widstruct(t->type, *getthis(t1), 0, 0);
		w = widstruct(t->type, *getinarg(t1), w, widthreg);
		w = widstruct(t->type, *getoutarg(t1), w, widthreg);
		t1->argwid = w;
		if(w%widthreg)
			warn("bad type %T %d\n", t1, w);
		t->align = 1;
		break;
	}

	if(widthptr == 4 && w != (int32)w)
		yyerror("type %T too large", t);

	t->width = w;
	if(t->align == 0) {
		if(w > 8 || (w&(w-1)) != 0)
			fatal("invalid alignment for %T", t);
		t->align = w;
	}
	lineno = lno;

	if(defercalc == 1)
		resumecheckwidth();
	else
		--defercalc;
}

/*
 * when a type's width should be known, we call checkwidth
 * to compute it.  during a declaration like
 *
 *	type T *struct { next T }
 *
 * it is necessary to defer the calculation of the struct width
 * until after T has been initialized to be a pointer to that struct.
 * similarly, during import processing structs may be used
 * before their definition.  in those situations, calling
 * defercheckwidth() stops width calculations until
 * resumecheckwidth() is called, at which point all the
 * checkwidths that were deferred are executed.
 * dowidth should only be called when the type's size
 * is needed immediately.  checkwidth makes sure the
 * size is evaluated eventually.
 */
typedef struct TypeList TypeList;
struct TypeList {
	Type *t;
	TypeList *next;
};

static TypeList *tlfree;
static TypeList *tlq;

void
checkwidth(Type *t)
{
	TypeList *l;

	if(t == T)
		return;

	// function arg structs should not be checked
	// outside of the enclosing function.
	if(t->funarg)
		fatal("checkwidth %T", t);

	if(!defercalc) {
		dowidth(t);
		return;
	}
	if(t->deferwidth)
		return;
	t->deferwidth = 1;

	l = tlfree;
	if(l != nil)
		tlfree = l->next;
	else
		l = mal(sizeof *l);

	l->t = t;
	l->next = tlq;
	tlq = l;
}

void
defercheckwidth(void)
{
	// we get out of sync on syntax errors, so don't be pedantic.
	if(defercalc && nerrors == 0)
		fatal("defercheckwidth");
	defercalc = 1;
}

void
resumecheckwidth(void)
{
	TypeList *l;

	if(!defercalc)
		fatal("resumecheckwidth");
	for(l = tlq; l != nil; l = tlq) {
		l->t->deferwidth = 0;
		tlq = l->next;
		dowidth(l->t);
		l->next = tlfree;
		tlfree = l;
	}
	defercalc = 0;
}

void
typeinit(void)
{
	int i, etype, sameas;
	Type *t;
	Sym *s, *s1;

	if(widthptr == 0)
		fatal("typeinit before betypeinit");

	for(i=0; i<NTYPE; i++)
		simtype[i] = i;

	types[TPTR32] = typ(TPTR32);
	dowidth(types[TPTR32]);

	types[TPTR64] = typ(TPTR64);
	dowidth(types[TPTR64]);
	
	t = typ(TUNSAFEPTR);
	types[TUNSAFEPTR] = t;
	t->sym = pkglookup("Pointer", unsafepkg);
	t->sym->def = typenod(t);
	
	dowidth(types[TUNSAFEPTR]);

	tptr = TPTR32;
	if(widthptr == 8)
		tptr = TPTR64;

	for(i=TINT8; i<=TUINT64; i++)
		isint[i] = 1;
	isint[TINT] = 1;
	isint[TUINT] = 1;
	isint[TUINTPTR] = 1;

	isfloat[TFLOAT32] = 1;
	isfloat[TFLOAT64] = 1;

	iscomplex[TCOMPLEX64] = 1;
	iscomplex[TCOMPLEX128] = 1;

	isptr[TPTR32] = 1;
	isptr[TPTR64] = 1;

	isforw[TFORW] = 1;

	issigned[TINT] = 1;
	issigned[TINT8] = 1;
	issigned[TINT16] = 1;
	issigned[TINT32] = 1;
	issigned[TINT64] = 1;

	/*
	 * initialize okfor
	 */
	for(i=0; i<NTYPE; i++) {
		if(isint[i] || i == TIDEAL) {
			okforeq[i] = 1;
			okforcmp[i] = 1;
			okforarith[i] = 1;
			okforadd[i] = 1;
			okforand[i] = 1;
			okforconst[i] = 1;
			issimple[i] = 1;
			minintval[i] = mal(sizeof(*minintval[i]));
			maxintval[i] = mal(sizeof(*maxintval[i]));
		}
		if(isfloat[i]) {
			okforeq[i] = 1;
			okforcmp[i] = 1;
			okforadd[i] = 1;
			okforarith[i] = 1;
			okforconst[i] = 1;
			issimple[i] = 1;
			minfltval[i] = mal(sizeof(*minfltval[i]));
			maxfltval[i] = mal(sizeof(*maxfltval[i]));
		}
		if(iscomplex[i]) {
			okforeq[i] = 1;
			okforadd[i] = 1;
			okforarith[i] = 1;
			okforconst[i] = 1;
			issimple[i] = 1;
		}
	}

	issimple[TBOOL] = 1;

	okforadd[TSTRING] = 1;

	okforbool[TBOOL] = 1;

	okforcap[TARRAY] = 1;
	okforcap[TCHAN] = 1;

	okforconst[TBOOL] = 1;
	okforconst[TSTRING] = 1;

	okforlen[TARRAY] = 1;
	okforlen[TCHAN] = 1;
	okforlen[TMAP] = 1;
	okforlen[TSTRING] = 1;

	okforeq[TPTR32] = 1;
	okforeq[TPTR64] = 1;
	okforeq[TUNSAFEPTR] = 1;
	okforeq[TINTER] = 1;
	okforeq[TCHAN] = 1;
	okforeq[TSTRING] = 1;
	okforeq[TBOOL] = 1;
	okforeq[TMAP] = 1;	// nil only; refined in typecheck
	okforeq[TFUNC] = 1;	// nil only; refined in typecheck
	okforeq[TARRAY] = 1;	// nil slice only; refined in typecheck
	okforeq[TSTRUCT] = 1;	// it's complicated; refined in typecheck

	okforcmp[TSTRING] = 1;

	for(i=0; i<nelem(okfor); i++)
		okfor[i] = okfornone;

	// binary
	okfor[OADD] = okforadd;
	okfor[OAND] = okforand;
	okfor[OANDAND] = okforbool;
	okfor[OANDNOT] = okforand;
	okfor[ODIV] = okforarith;
	okfor[OEQ] = okforeq;
	okfor[OGE] = okforcmp;
	okfor[OGT] = okforcmp;
	okfor[OLE] = okforcmp;
	okfor[OLT] = okforcmp;
	okfor[OMOD] = okforand;
	okfor[OMUL] = okforarith;
	okfor[ONE] = okforeq;
	okfor[OOR] = okforand;
	okfor[OOROR] = okforbool;
	okfor[OSUB] = okforarith;
	okfor[OXOR] = okforand;
	okfor[OLSH] = okforand;
	okfor[ORSH] = okforand;

	// unary
	okfor[OCOM] = okforand;
	okfor[OMINUS] = okforarith;
	okfor[ONOT] = okforbool;
	okfor[OPLUS] = okforarith;

	// special
	okfor[OCAP] = okforcap;
	okfor[OLEN] = okforlen;

	// comparison
	iscmp[OLT] = 1;
	iscmp[OGT] = 1;
	iscmp[OGE] = 1;
	iscmp[OLE] = 1;
	iscmp[OEQ] = 1;
	iscmp[ONE] = 1;

	mpatofix(maxintval[TINT8], "0x7f");
	mpatofix(minintval[TINT8], "-0x80");
	mpatofix(maxintval[TINT16], "0x7fff");
	mpatofix(minintval[TINT16], "-0x8000");
	mpatofix(maxintval[TINT32], "0x7fffffff");
	mpatofix(minintval[TINT32], "-0x80000000");
	mpatofix(maxintval[TINT64], "0x7fffffffffffffff");
	mpatofix(minintval[TINT64], "-0x8000000000000000");

	mpatofix(maxintval[TUINT8], "0xff");
	mpatofix(maxintval[TUINT16], "0xffff");
	mpatofix(maxintval[TUINT32], "0xffffffff");
	mpatofix(maxintval[TUINT64], "0xffffffffffffffff");

	/* f is valid float if min < f < max.  (min and max are not themselves valid.) */
	mpatoflt(maxfltval[TFLOAT32], "33554431p103");	/* 2^24-1 p (127-23) + 1/2 ulp*/
	mpatoflt(minfltval[TFLOAT32], "-33554431p103");
	mpatoflt(maxfltval[TFLOAT64], "18014398509481983p970");	/* 2^53-1 p (1023-52) + 1/2 ulp */
	mpatoflt(minfltval[TFLOAT64], "-18014398509481983p970");

	maxfltval[TCOMPLEX64] = maxfltval[TFLOAT32];
	minfltval[TCOMPLEX64] = minfltval[TFLOAT32];
	maxfltval[TCOMPLEX128] = maxfltval[TFLOAT64];
	minfltval[TCOMPLEX128] = minfltval[TFLOAT64];

	/* for walk to use in error messages */
	types[TFUNC] = functype(N, nil, nil);

	/* types used in front end */
	// types[TNIL] got set early in lexinit
	types[TIDEAL] = typ(TIDEAL);
	types[TINTER] = typ(TINTER);

	/* simple aliases */
	simtype[TMAP] = tptr;
	simtype[TCHAN] = tptr;
	simtype[TFUNC] = tptr;
	simtype[TUNSAFEPTR] = tptr;

	/* pick up the backend typedefs */
	for(i=0; typedefs[i].name; i++) {
		s = lookup(typedefs[i].name);
		s1 = pkglookup(typedefs[i].name, builtinpkg);

		etype = typedefs[i].etype;
		if(etype < 0 || etype >= nelem(types))
			fatal("typeinit: %s bad etype", s->name);
		sameas = typedefs[i].sameas;
		if(sameas < 0 || sameas >= nelem(types))
			fatal("typeinit: %s bad sameas", s->name);
		simtype[etype] = sameas;
		minfltval[etype] = minfltval[sameas];
		maxfltval[etype] = maxfltval[sameas];
		minintval[etype] = minintval[sameas];
		maxintval[etype] = maxintval[sameas];

		t = types[etype];
		if(t != T)
			fatal("typeinit: %s already defined", s->name);

		t = typ(etype);
		t->sym = s1;

		dowidth(t);
		types[etype] = t;
		s1->def = typenod(t);
	}

	Array_array = rnd(0, widthptr);
	Array_nel = rnd(Array_array+widthptr, widthint);
	Array_cap = rnd(Array_nel+widthint, widthint);
	sizeof_Array = rnd(Array_cap+widthint, widthptr);

	// string is same as slice wo the cap
	sizeof_String = rnd(Array_nel+widthint, widthptr);

	dowidth(types[TSTRING]);
	dowidth(idealstring);
}

/*
 * compute total size of f's in/out arguments.
 */
int
argsize(Type *t)
{
	Iter save;
	Type *fp;
	int64 w, x;

	w = 0;

	fp = structfirst(&save, getoutarg(t));
	while(fp != T) {
		x = fp->width + fp->type->width;
		if(x > w)
			w = x;
		fp = structnext(&save);
	}

	fp = funcfirst(&save, t);
	while(fp != T) {
		x = fp->width + fp->type->width;
		if(x > w)
			w = x;
		fp = funcnext(&save);
	}

	w = (w+widthptr-1) & ~(widthptr-1);
	if((int)w != w)
		fatal("argsize too big");
	return w;
}