gc: inlining (disabled without -l)

Cross- and intra package inlining of single assignments or return <expression>.
Minus some hairy cases, currently including other calls, expressions with closures and ... arguments.

R=rsc, rogpeppe, adg, gri
CC=golang-dev
https://golang.org/cl/5400043

src/cmd/gc/Makefile

@@ -27,6 +27,7 @@ OFILES=\
 	fmt.$O\
 	gen.$O\
 	init.$O\
+	inl.$O\
 	lex.$O\
 	md5.$O\
 	mparith1.$O\

src/cmd/gc/export.c

@@ -7,7 +7,7 @@
 #include	"go.h"
 #include	"y.tab.h"
 
-static void	dumpexporttype(Type*);
+static void	dumpexporttype(Type *t);
 
 // Mark n's symbol as exported
 void
@@ -78,7 +78,7 @@ dumppkg(Pkg *p)
 {
 	char *suffix;
 
-	if(p == nil || p == localpkg || p->exported)
+	if(p == nil || p == localpkg || p->exported || p == builtinpkg)
 		return;
 	p->exported = 1;
 	suffix = "";
@@ -87,6 +87,68 @@ dumppkg(Pkg *p)
 	Bprint(bout, "\timport %s \"%Z\"%s\n", p->name, p->path, suffix);
 }
 
+// Look for anything we need for the inline body
+static void reexportdep(Node *n);
+static void
+reexportdeplist(NodeList *ll)
+{
+	for(; ll ;ll=ll->next)
+		reexportdep(ll->n);
+}
+
+static void
+reexportdep(Node *n)
+{
+	Type *t;
+
+	if(!n)
+		return;
+
+	switch(n->op) {
+	case ONAME:
+		switch(n->class&~PHEAP) {
+		case PFUNC:
+		case PEXTERN:
+			if (n->sym && n->sym->pkg != localpkg && n->sym->pkg != builtinpkg)
+				exportlist = list(exportlist, n);
+		}
+		break;
+
+	case OTYPE:
+	case OLITERAL:
+		if (n->sym && n->sym->pkg != localpkg && n->sym->pkg != builtinpkg)
+			exportlist = list(exportlist, n);
+		break;
+
+	// for operations that need a type when rendered, put the type on the export list.
+	case OCONV:
+	case OCONVIFACE:
+	case OCONVNOP:
+	case ODOTTYPE:
+	case OSTRUCTLIT:
+	case OPTRLIT:
+		t = n->type;
+		if(!t->sym && t->type)
+			t = t->type;
+		if (t && t->sym && t->sym->def && t->sym->pkg != localpkg  && t->sym->pkg != builtinpkg) {
+//			print("reexport convnop %+hN\n", t->sym->def);
+			exportlist = list(exportlist, t->sym->def);
+		}
+		break;
+	}
+
+	reexportdep(n->left);
+	reexportdep(n->right);
+	reexportdeplist(n->list);
+	reexportdeplist(n->rlist);
+	reexportdeplist(n->ninit);
+	reexportdep(n->ntest);
+	reexportdep(n->nincr);
+	reexportdeplist(n->nbody);
+	reexportdeplist(n->nelse);
+}
+
+
 static void
 dumpexportconst(Sym *s)
 {
@@ -123,9 +185,13 @@ dumpexportvar(Sym *s)
 	t = n->type;
 	dumpexporttype(t);
 
-	if(t->etype == TFUNC && n->class == PFUNC)
+	if(t->etype == TFUNC && n->class == PFUNC) {
+		if (n->inl) {
+			Bprint(bout, "\tfunc %#S%#hT { %#H }\n", s, t, n->inl);
+			reexportdeplist(n->inl);
+		} else
 			Bprint(bout, "\tfunc %#S%#hT\n", s, t);
-	else
+	} else
 		Bprint(bout, "\tvar %#S %#T\n", s, t);
 }
 
@@ -148,7 +214,6 @@ dumpexporttype(Type *t)
 
 	if(t == T)
 		return;
-
 	if(t->printed || t == types[t->etype] || t == bytetype || t == runetype || t == errortype)
 		return;
 	t->printed = 1;
@@ -177,6 +242,10 @@ dumpexporttype(Type *t)
 	Bprint(bout, "\ttype %#S %#lT\n", t->sym, t);
 	for(i=0; i<n; i++) {
 		f = m[i];
+		if (f->type->nname && f->type->nname->inl) { // nname was set by caninl
+			Bprint(bout, "\tfunc (%#T) %#hhS%#hT { %#H }\n", getthisx(f->type)->type, f->sym, f->type, f->type->nname->inl);
+			reexportdeplist(f->type->nname->inl);
+		} else
 			Bprint(bout, "\tfunc (%#T) %#hhS%#hT\n", getthisx(f->type)->type, f->sym, f->type);
 	}
 }

src/cmd/gc/go.h

@@ -260,6 +260,7 @@ struct	Node
 	NodeList*	exit;
 	NodeList*	cvars;	// closure params
 	NodeList*	dcl;	// autodcl for this func/closure
+	NodeList*	inl;	// copy of the body for use in inlining
 
 	// OLITERAL/OREGISTER
 	Val	val;
@@ -280,6 +281,9 @@ struct	Node
 	Node*	outer;	// outer PPARAMREF in nested closure
 	Node*	closure;	// ONAME/PHEAP <-> ONAME/PPARAMREF
 
+	// ONAME substitute while inlining
+	Node* inlvar;
+
 	// OPACK
 	Pkg*	pkg;
 	
@@ -473,6 +477,7 @@ enum
 	// misc
 	ODDD,
 	ODDDARG,
+	OINLCALL,	// intermediary representation of an inlined call
 
 	// for back ends
 	OCMP, ODEC, OEXTEND, OINC, OREGISTER, OINDREG,
@@ -986,6 +991,12 @@ Node*	temp(Type*);
 void	fninit(NodeList *n);
 Sym*	renameinit(void);
 
+/*
+ *	inl.c
+ */
+void	caninl(Node *fn);
+void	inlcalls(Node *fn);
+
 /*
  *	lex.c
  */

src/cmd/gc/go.y

@@ -1295,6 +1295,12 @@ hidden_fndcl:
 		checkwidth($$->type);
 		addmethod($4, $$->type, 0);
 		funchdr($$);
+		
+		// inl.c's inlnode in on a dotmeth node expects to find the inlineable body as
+		// (dotmeth's type)->nname->inl, and dotmeth's type has been pulled
+		// out by typecheck's lookdot as this $$->ttype.  So by providing
+		// this back link here we avoid special casing there.
+		$$->type->nname = $$;
 	}
 
 fntype:
@@ -1790,11 +1796,15 @@ hidden_import:
 		if($2 == N)
 			break;
 
+		$2->inl = $3;
+
 		funcbody($2);
 		importlist = list(importlist, $2);
 
 		if(debug['E']) {
-			print("import [%Z] func %lN \n", $2->sym->pkg->path, $2);
+			print("import [%Z] func %lN \n", importpkg->path, $2);
+			if(debug['l'] > 2 && $2->inl)
+				print("inl body:%+H\n", $2->inl);
 		}
 	}
 

src/cmd/gc/inl.c

@@ -0,0 +1,688 @@
+// Copyright 2011 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.
+//
+// The inlining facility makes 2 passes: first caninl determines which
+// functions are suitable for inlining, and for those that are it
+// saves a copy of the body. Then inlcalls walks each function body to
+// expand calls to inlinable functions.
+//
+
+#include <u.h>
+#include <libc.h>
+#include "go.h"
+
+// Used by caninl.
+static Node*	inlcopy(Node *n);
+static NodeList* inlcopylist(NodeList *ll);
+static int	ishairy(Node *n);
+static int	ishairylist(NodeList *ll); 
+
+// Used by inlcalls
+static void	inlnodelist(NodeList *l);
+static void	inlnode(Node **np);
+static void	mkinlcall(Node **np, Node *fn);
+static Node*	inlvar(Node *n);
+static Node*	retvar(Type *n, int i);
+static Node*	newlabel(void);
+static Node*	inlsubst(Node *n);
+static NodeList* inlsubstlist(NodeList *ll);
+
+// Used during inlsubst[list]
+static Node *inlfn;		// function currently being inlined
+static Node *inlretlabel;	// target of the goto substituted in place of a return
+static NodeList *inlretvars;	// temp out variables
+
+
+// Caninl determines whether fn is inlineable. Currently that means:
+// fn is exactly 1 statement, either a return or an assignment, and
+// some temporary constraints marked TODO.  If fn is inlineable, saves
+// fn->nbody in fn->inl and substitutes it with a copy.
+void
+caninl(Node *fn)
+{
+	Node *savefn;
+	Type *t;
+
+	if(fn->op != ODCLFUNC)
+		fatal("caninl %N", fn);
+	if(!fn->nname)
+		fatal("caninl no nname %+N", fn);
+
+	// exactly 1 statement
+	if(fn->nbody == nil || fn->nbody->next != nil)
+		return;
+
+	// the single statement should be a return or an assignment.
+	switch(fn->nbody->n->op) {
+	default:
+		return;
+	case ORETURN:
+	case OAS:
+	case OAS2:
+	  // case OEMPTY:  // TODO
+		break;
+	}
+
+	// can't handle ... args yet
+	for(t=fn->type->type->down->down->type; t; t=t->down)
+		if(t->isddd)
+			return;
+
+	// TODO Anything non-trivial
+	if(ishairy(fn))
+		return;
+
+	savefn = curfn;
+	curfn = fn;
+
+	fn->nname->inl = fn->nbody;
+	fn->nbody = inlcopylist(fn->nname->inl);
+
+	// hack, TODO, check for better way to link method nodes back to the thing with the ->inl
+	// this is so export can find the body of a method
+	fn->type->nname = fn->nname;
+
+	if(debug['l']>1)
+		print("%L: can inline %#N as: %#T { %#H }\n", fn->lineno, fn->nname, fn->type, fn->nname->inl);
+
+	curfn = savefn;
+}
+
+// Look for anything we want to punt on.
+static int
+ishairylist(NodeList *ll)
+{
+	for(;ll;ll=ll->next)
+		if(ishairy(ll->n))
+			return 1;
+	return 0;
+}
+
+static int
+ishairy(Node *n)
+{
+	if(!n)
+		return 0;
+
+	switch(n->op) {
+	case OPROC:
+	case ODEFER:
+	case OCALL:
+	case OCALLFUNC:
+	case OCALLINTER:
+	case OCALLMETH:
+	case OCLOSURE:
+		return 1;
+	}
+
+	return  ishairy(n->left) ||
+		ishairy(n->right) ||
+		ishairylist(n->list) ||
+		ishairylist(n->rlist) ||
+		ishairylist(n->ninit) ||
+		ishairy(n->ntest) ||
+		ishairy(n->nincr) ||
+		ishairylist(n->nbody) ||
+		ishairylist(n->nelse);
+}
+
+// Inlcopy and inlcopylist recursively copy the body of a function.
+// Any name-like node of non-local class is marked for re-export by adding it to
+// the exportlist.
+static NodeList*
+inlcopylist(NodeList *ll)
+{
+	NodeList *l;
+
+	l = nil;
+	for(; ll; ll=ll->next)
+		l = list(l, inlcopy(ll->n));
+	return l;
+}
+
+static Node*
+inlcopy(Node *n)
+{
+	Node *m;
+
+	if(n == N)
+		return N;
+
+	switch(n->op) {
+	case ONAME:
+	case OTYPE:
+	case OLITERAL:
+		return n;
+	}
+
+	m = nod(OXXX, N, N);
+	*m = *n;
+	m->inl = nil;
+	m->left	  = inlcopy(n->left);
+	m->right  = inlcopy(n->right);
+	m->list   = inlcopylist(n->list);
+	m->rlist  = inlcopylist(n->rlist);
+	m->ninit  = inlcopylist(n->ninit);
+	m->ntest  = inlcopy(n->ntest);
+	m->nincr  = inlcopy(n->nincr);
+	m->nbody  = inlcopylist(n->nbody);
+	m->nelse  = inlcopylist(n->nelse);
+
+	return m;
+}
+
+
+// Inlcalls/nodelist/node walks fn's statements and expressions and substitutes any
+// calls made to inlineable functions.  This is the external entry point.
+void
+inlcalls(Node *fn)
+{
+	Node *savefn;
+
+	savefn = curfn;
+	curfn = fn;
+	inlnode(&fn);
+	if(fn != curfn)
+		fatal("inlnode replaced curfn");
+	curfn = savefn;
+}
+
+// Turn an OINLCALL into a statement.
+static void
+inlconv2stmt(Node *n)
+{
+	n->op = OBLOCK;
+	n->list = n->nbody;
+	n->nbody = nil;
+	n->rlist = nil;
+}
+
+// Turn an OINLCALL into a single valued expression.
+static void
+inlconv2expr(Node *n)
+{
+	n->op = OCONVNOP;
+	n->left = n->rlist->n;
+	n->rlist = nil;
+	n->ninit = concat(n->ninit, n->nbody);
+	n->nbody = nil;
+}
+
+// Turn the OINLCALL in n->list into an expression list on n.
+// Used in return and call statements.
+static void
+inlgluelist(Node *n)
+{
+	Node *c;
+
+	c = n->list->n;
+	n->ninit = concat(n->ninit, c->ninit);
+	n->ninit = concat(n->ninit, c->nbody);
+	n->list  = c->rlist;
+} 
+
+// Turn the OINLCALL in n->rlist->n into an expression list on n.
+// Used in OAS2FUNC.
+static void
+inlgluerlist(Node *n)
+{
+	Node *c;
+
+	c = n->rlist->n;
+	n->ninit = concat(n->ninit, c->ninit);
+	n->ninit = concat(n->ninit, c->nbody);
+	n->rlist = c->rlist;
+} 
+
+static void
+inlnodelist(NodeList *l)
+{
+	for(; l; l=l->next)
+		inlnode(&l->n);
+}
+
+// inlnode recurses over the tree to find inlineable calls, which will
+// be turned into OINLCALLs by mkinlcall.  When the recursion comes
+// back up will examine left, right, list, rlist, ninit, ntest, nincr,
+// nbody and nelse and use one of the 4 inlconv/glue functions above
+// to turn the OINLCALL into an expression, a statement, or patch it
+// in to this nodes list or rlist as appropriate.
+// NOTE it makes no sense to pass the glue functions down the recursion to the level where the OINLCALL gets created because they have to edit /this/ n,
+// so you'd have to push that one down as well, but then you may as well do it here.  so this is cleaner and shorter and less complicated.
+static void
+inlnode(Node **np)
+{
+	Node *n;
+	NodeList *l;
+
+	if(*np == nil)
+		return;
+
+	n = *np;
+
+	switch(n->op) {
+	case ODEFER:
+	case OPROC:
+		// inhibit inlining of their argument
+		switch(n->left->op) {
+		case OCALLFUNC:
+		case OCALLMETH:
+			n->left->etype = n->op;
+		}
+
+	case OCLOSURE:
+		// TODO.  do them here rather than in lex.c phase 6b
+		return;
+	}
+
+	inlnodelist(n->ninit);
+	for(l=n->ninit; l; l=l->next)
+		if(l->n->op == OINLCALL)
+			inlconv2stmt(l->n);
+
+	inlnode(&n->left);
+	if(n->left && n->left->op == OINLCALL)
+		inlconv2expr(n->left);
+
+	inlnode(&n->right);
+	if(n->right && n->right->op == OINLCALL)
+		inlconv2expr(n->right);
+
+	inlnodelist(n->list);
+	switch(n->op) {
+	case OBLOCK:
+		for(l=n->list; l; l=l->next)
+			if(l->n->op == OINLCALL)
+				inlconv2stmt(l->n);
+		break;
+
+	case ORETURN:
+		if(count(n->list) == 1 && curfn->type->outtuple > 1 && n->list->n->op == OINLCALL) {
+			inlgluelist(n);
+			break;
+		}
+		
+		goto list_dflt;
+
+	case OCALLMETH:
+	case OCALLINTER:
+	case OCALLFUNC:
+		// if we just replaced arg in f(arg()) with an inlined call
+		// and arg returns multiple values, glue as list
+		if(count(n->list) == 1 && n->list->n->op == OINLCALL && count(n->list->n->rlist) > 1) {
+			inlgluelist(n);
+			break;
+		}
+
+		// fallthrough
+	default:
+	list_dflt:
+		for(l=n->list; l; l=l->next)
+			if(l->n->op == OINLCALL)
+				inlconv2expr(l->n);
+	}
+
+	inlnodelist(n->rlist);
+	switch(n->op) {
+	case OAS2FUNC:
+		if(n->rlist->n->op == OINLCALL) {
+			inlgluerlist(n);
+			n->op = OAS2;
+			n->typecheck = 0;
+			typecheck(np, Etop);
+			break;
+		}
+
+		// fallthrough
+	default:
+		for(l=n->rlist; l; l=l->next)
+			if(l->n->op == OINLCALL)
+				inlconv2expr(l->n);
+
+	}
+
+	inlnode(&n->ntest);
+	if(n->ntest && n->ntest->op == OINLCALL)
+		inlconv2expr(n->ntest);
+
+	inlnode(&n->nincr);
+	if(n->nincr && n->nincr->op == OINLCALL)
+		inlconv2stmt(n->nincr);
+
+	inlnodelist(n->nbody);
+	for(l=n->nbody; l; l=l->next)
+		if(l->n->op == OINLCALL)
+			inlconv2stmt(l->n);
+
+	inlnodelist(n->nelse);
+	for(l=n->nelse; l; l=l->next)
+		if(l->n->op == OINLCALL)
+			inlconv2stmt(l->n);
+
+	// with all the branches out of the way, it is now time to
+	// transmogrify this node itself unless inhibited by the
+	// switch at the top of this function.
+	switch(n->op) {
+	case OCALLFUNC:
+	case OCALLMETH:
+		if (n->etype == OPROC || n->etype == ODEFER)
+			return;
+	}
+
+	switch(n->op) {
+	case OCALLFUNC:
+		if(debug['l']>3)
+			print("%L:call to func %lN\n", n->lineno, n->left);
+		mkinlcall(np, n->left);
+		break;
+
+	case OCALLMETH:
+		if(debug['l']>3)
+			print("%L:call to meth %lN\n", n->lineno, n->left->right);
+		// typecheck resolved ODOTMETH->type, whose nname points to the actual function.
+		if(n->left->type->nname) 
+			mkinlcall(np, n->left->type->nname);
+		else
+			fatal("no function definition for [%p] %+T\n", n->left->type, n->left->type);
+		break;
+	}
+}
+
+// if *np is a call, and fn is a function with an inlinable body, substitute *np with an OINLCALL.
+// On return ninit has the parameter assignments, the nbody is the
+// inlined function body and list, rlist contain the input, output
+// parameters.
+static void
+mkinlcall(Node **np, Node *fn)
+{
+	int i;
+	Node *n, *call, *saveinlfn, *as;
+	NodeList *dcl, *ll, *ninit, *body;
+	Type *t;
+
+	if (fn->inl == nil)
+		return;
+
+	n = *np;
+
+	// Bingo, we have a function node, and it has an inlineable body
+	if(debug['l']>1)
+		print("%L: inlining call to %S %#T { %#H }\n", n->lineno, fn->sym, fn->type, fn->inl);
+
+	if(debug['l']>2)
+		print("%L: Before inlining: %+N\n", n->lineno, n);
+
+	saveinlfn = inlfn;
+	inlfn = fn;
+
+	ninit = n->ninit;
+
+	if (fn->defn) // local function
+		dcl = fn->defn->dcl;
+	else // imported function
+		dcl = fn->dcl;
+
+	// Make temp names to use instead of the originals for anything but the outparams
+	for(ll = dcl; ll; ll=ll->next)
+		if(ll->n->op == ONAME && ll->n->class != PPARAMOUT) {
+			ll->n->inlvar = inlvar(ll->n);
+			ninit = list(ninit, nod(ODCL, ll->n->inlvar, N));  // otherwise gen won't emit the allocations for heapallocs
+		}
+
+	// assign arguments to the parameters' temp names
+	if(fn->type->thistuple) {
+		if (!n->left->op == ODOTMETH || !n->left->left)
+			fatal("method call without receiver: %+N", n);
+		t = getthisx(fn->type)->type;
+		if(t != T && t->nname) {
+			if(!t->nname->inlvar)
+				fatal("missing inlvar for %N\n", t->nname);
+			as = nod(OAS, t->nname->inlvar, n->left->left);
+			typecheck(&as, Etop);
+			ninit = list(ninit, as);
+		} // else if !ONAME add to init anyway?
+	}
+
+	as = nod(OAS2, N, N);
+	if(fn->type->intuple > 1 && n->list && !n->list->next) {
+		// TODO check that n->list->n is a call?
+		as->rlist = n->list;
+		for(t = getinargx(fn->type)->type; t; t=t->down) {
+			if(t->nname) {
+				if(!t->nname->inlvar)
+					fatal("missing inlvar for %N\n", t->nname);
+				as->list = list(as->list, t->nname->inlvar);
+			} else {
+				as->list = list(as->list, temp(t->type));
+			}
+		}		
+	} else {
+		ll = n->list;
+		for(t = getinargx(fn->type)->type; t && ll; t=t->down) {
+			if(t->nname) {
+				if(!t->nname->inlvar)
+					fatal("missing inlvar for %N\n", t->nname);
+				as->list = list(as->list, t->nname->inlvar);
+				as->rlist = list(as->rlist, ll->n);
+			}
+			ll=ll->next;
+		}
+		if(ll || t)
+			fatal("arg count mismatch: %#T  vs %,H\n",  getinargx(fn->type), n->list);
+	}
+
+	if (as->rlist) {
+		typecheck(&as, Etop);
+		ninit = list(ninit, as);
+	}
+
+	// make the outparams.  No need to declare because currently they'll only be used in the assignment that replaces returns.
+	inlretvars = nil;
+	i = 0;
+	for(t = getoutargx(fn->type)->type; t; t = t->down)
+		inlretvars = list(inlretvars, retvar(t, i++));
+	
+	inlretlabel = newlabel();
+	body = inlsubstlist(fn->inl);
+
+	body = list(body, nod(OGOTO, inlretlabel, N));	// avoid 'not used' when function doesnt have return
+	body = list(body, nod(OLABEL, inlretlabel, N));
+
+	typechecklist(body, Etop);
+
+	call = nod(OINLCALL, N, N);
+	call->ninit = ninit;
+	call->nbody = body;
+	call->rlist = inlretvars;
+	call->type = n->type;
+	call->lineno = n->lineno;
+	call->typecheck = 1;
+
+	*np = call;
+
+	inlfn =	saveinlfn;
+	if(debug['l']>2)
+		print("%L: After inlining %+N\n\n", n->lineno, *np);
+
+}
+
+// Every time we expand a function we generate a new set of tmpnames,
+// PAUTO's in the calling functions, and link them off of the
+// PPARAM's, PAUTOS and PPARAMOUTs of the called function. 
+static Node*
+inlvar(Node *var)
+{
+	Node *n;
+
+	if(debug['l']>3)
+		print("inlvar %+N\n", var);
+
+	n = newname(var->sym);
+	n->type = var->type;
+	n->class = PAUTO;
+	n->used = 1;
+	n->curfn = curfn;   // the calling function, not the called one
+	curfn->dcl = list(curfn->dcl, n);
+	return n;
+}
+
+// Make a new pparamref
+static Node*
+inlref(Node *var)
+{
+	Node *n;
+
+	if (!var->closure)
+		fatal("No ->closure: %N", var);
+
+	if (!var->closure->inlvar)
+		fatal("No ->closure->inlref: %N", var);
+
+	n = nod(OXXX, N, N);
+	*n = *var;
+
+//	if(debug['l']>1)
+//		print("inlref: %N -> %N\n", var, var->closure->inlvar);
+
+	var = var->closure->inlvar;
+
+	return n;
+}
+
+// Synthesize a variable to store the inlined function's results in.
+static Node*
+retvar(Type *t, int i)
+{
+	Node *n;
+
+	snprint(namebuf, sizeof(namebuf), ".r%d", i);
+	n = newname(lookup(namebuf));
+	n->type = t->type;
+	n->class = PAUTO;
+	n->used = 1;
+	n->curfn = curfn;   // the calling function, not the called one
+	curfn->dcl = list(curfn->dcl, n);
+	return n;
+}
+
+static Node*
+newlabel(void)
+{
+	Node *n;
+	static int label;
+	
+	label++;
+	snprint(namebuf, sizeof(namebuf), ".inlret%.6d", label);
+	n = newname(lookup(namebuf));
+	n->etype = 1;  // flag 'safe' for escape analysis (no backjumps)
+	return n;
+}
+
+// inlsubst and inlsubstlist recursively copy the body of the saved
+// pristine ->inl body of the function while substituting references
+// to input/output parameters with ones to the tmpnames, and
+// substituting returns with assignments to the output.
+static NodeList*
+inlsubstlist(NodeList *ll)
+{
+	NodeList *l;
+
+	l = nil;
+	for(; ll; ll=ll->next)
+		l = list(l, inlsubst(ll->n));
+	return l;
+}
+
+static int closuredepth;
+
+static Node*
+inlsubst(Node *n)
+{
+	Node *m, *as;
+	NodeList *ll;
+
+	if(n == N)
+		return N;
+
+	switch(n->op) {
+	case ONAME:
+		if(n->inlvar) { // These will be set during inlnode
+			if (debug['l']>2)
+				print ("substituting name %N  ->  %N\n", n, n->inlvar);
+			return n->inlvar;
+		}
+		if (debug['l']>2)
+			print ("not substituting name %N\n", n);
+		return n;
+
+	case OLITERAL:
+	case OTYPE:
+		return n;
+
+	case ORETURN:
+		// only rewrite returns belonging to this function, not nested ones.
+		if (closuredepth > 0)
+			break;
+		
+//		dump("Return before substitution", n);
+		m = nod(OGOTO, inlretlabel, N);
+		m->ninit  = inlsubstlist(n->ninit);
+
+		// rewrite naked return for function with return values to return PPARAMOUTs
+		if(count(n->list) == 0 && inlfn->type->outtuple > 0) {
+			for(ll = inlfn->dcl; ll; ll=ll->next)
+				if(ll->n->op == ONAME && ll->n->class == PPARAMOUT)
+					n->list = list(n->list, ll->n);
+
+//			dump("Return naked -> dressed ", n);
+		}
+
+		if(inlretvars && n->list) {
+			as = nod(OAS2, N, N);
+			as->list = inlretvars;
+			as->rlist = inlsubstlist(n->list);
+			typecheck(&as, Etop);
+			m->ninit = list(m->ninit, as);
+		}
+
+		typechecklist(m->ninit, Etop);
+		typecheck(&m, Etop);
+//		dump("Return after substitution", m);
+		return m;
+	}
+
+
+	m = nod(OXXX, N, N);
+	*m = *n;
+	m->ninit = nil;
+	
+	if(n->op == OCLOSURE) {
+		closuredepth++;
+
+		for(ll = m->dcl; ll; ll=ll->next)
+			if(ll->n->op == ONAME) {
+				ll->n->inlvar = inlvar(ll->n);
+				m->ninit = list(m->ninit, nod(ODCL, ll->n->inlvar, N));  // otherwise gen won't emit the allocations for heapallocs
+			}
+		
+		for (ll=m->cvars; ll; ll=ll->next)
+			if (ll->n->op == ONAME)
+				ll->n->cvars = list(ll->n->cvars, inlref(ll->n));
+	}
+	
+	m->left	  = inlsubst(n->left);
+	m->right  = inlsubst(n->right);
+	m->list	  = inlsubstlist(n->list);
+	m->rlist  = inlsubstlist(n->rlist);
+	m->ninit  = concat(m->ninit, inlsubstlist(n->ninit));
+	m->ntest  = inlsubst(n->ntest);
+	m->nincr  = inlsubst(n->nincr);
+	m->nbody  = inlsubstlist(n->nbody);
+	m->nelse  = inlsubstlist(n->nelse);
+
+	if(n->op == OCLOSURE)
+		closuredepth--;
+
+	return m;
+}

src/cmd/gc/lex.c

@@ -336,11 +336,43 @@ main(int argc, char *argv[])
 	if(nsavederrors+nerrors)
 		errorexit();
 
-	// Phase 4: escape analysis.
+	// Phase 4: Inlining
+	if (debug['l']) {  		// TODO only if debug['l'] > 1, otherwise lazily when used.
+		// Typecheck imported function bodies
+		for(l=importlist; l; l=l->next) {
+			if (l->n->inl == nil)
+				continue;
+			curfn = l->n;
+			saveerrors();
+			importpkg = l->n->sym->pkg;
+			if (debug['l']>2)
+				print("typecheck import [%S] %lN { %#H }\n", l->n->sym, l->n, l->n->inl);
+			typechecklist(l->n->inl, Etop);
+			importpkg = nil;
+ 		}
+		curfn = nil;
+		
+		if(nsavederrors+nerrors)
+			errorexit();
+	}
+
+	if (debug['l']) {
+		// Find functions that can be inlined and clone them before walk expands them.
+		for(l=xtop; l; l=l->next)
+			if(l->n->op == ODCLFUNC)
+				caninl(l->n);
+		
+		// Expand inlineable calls in all functions
+		for(l=xtop; l; l=l->next)
+			if(l->n->op == ODCLFUNC)
+				inlcalls(l->n);
+	}
+
+	// Phase 5: escape analysis.
 	if(!debug['N'])
 		escapes();
 
-	// Phase 5: Compile top level functions.
+	// Phase 6: Compile top level functions.
 	for(l=xtop; l; l=l->next)
 		if(l->n->op == ODCLFUNC)
 			funccompile(l->n, 0);
@@ -348,7 +380,7 @@ main(int argc, char *argv[])
 	if(nsavederrors+nerrors == 0)
 		fninit(xtop);
 
-	// Phase 5b: Compile all closures.
+	// Phase 6b: Compile all closures.
 	while(closures) {
 		l = closures;
 		closures = nil;
@@ -356,7 +388,7 @@ main(int argc, char *argv[])
 			funccompile(l->n, 1);
 	}
 
-	// Phase 6: check external declarations.
+	// Phase 7: check external declarations.
 	for(l=externdcl; l; l=l->next)
 		if(l->n->op == ONAME)
 			typecheck(&l->n, Erv);