diff --git a/mach/proto/mcg/hop.c b/mach/proto/mcg/hop.c
index a11b99792..352ad9b2b 100644
--- a/mach/proto/mcg/hop.c
+++ b/mach/proto/mcg/hop.c
@@ -50,7 +50,7 @@ void hop_add_eoi_insel(struct hop* hop)
 
 void hop_print(char k, struct hop* hop)
 {
-	int i;
+	int i, j;
 	bool soi = true;
 
 	i = 0;
@@ -60,7 +60,14 @@ void hop_print(char k, struct hop* hop)
 
 		if (soi)
 		{
-			tracef(k, "%c: %d from $%d: ", k, hop->id, hop->ir->id);
+			tracef(k, "%c: %d from $%d:", k, hop->id, hop->ir->id);
+
+			for (j=0; j<hop->ins.count; j++)
+				tracef(k, " <%%%d", hop->ins.item[j]->id);
+			for (j=0; j<hop->outs.count; j++)
+				tracef(k, " >%%%d", hop->outs.item[j]->id);
+			tracef(k, " ");
+
 			soi = false;
 		}
 
diff --git a/mach/proto/mcg/hop.h b/mach/proto/mcg/hop.h
index d802ed01a..66903cbfe 100644
--- a/mach/proto/mcg/hop.h
+++ b/mach/proto/mcg/hop.h
@@ -28,6 +28,9 @@ struct hop
 	struct ir* ir;
 	ARRAYOF(struct insel) insels;
 	struct vreg* output;
+
+	ARRAYOF(struct vreg) ins;
+	ARRAYOF(struct vreg) outs;
 	PMAPOF(struct vreg, struct hreg) registers;
 };
 
diff --git a/mach/proto/mcg/mcg.h b/mach/proto/mcg/mcg.h
index 07da36467..601249f07 100644
--- a/mach/proto/mcg/mcg.h
+++ b/mach/proto/mcg/mcg.h
@@ -109,6 +109,8 @@ extern void pass_promote_float_ops(struct procedure* proc);
 extern void pass_remove_dead_blocks(struct procedure* proc);
 extern void pass_split_critical_edges(struct procedure* proc);
 
+extern void register_allocator(struct procedure* proc);
+
 #endif
 
 /* vim: set sw=4 ts=4 expandtab : */
diff --git a/mach/proto/mcg/pass_instructionselection.c b/mach/proto/mcg/pass_instructionselection.c
index 5f965c9bc..ca7589e86 100644
--- a/mach/proto/mcg/pass_instructionselection.c
+++ b/mach/proto/mcg/pass_instructionselection.c
@@ -37,15 +37,19 @@ static void emit_return_reg(void)
     hop_add_vreg_insel(current_hop, current_hop->output);
 }
 
-static void emit_reg(int child)
+static struct vreg* find_vreg_of_child(int child)
 {
     struct insn* insn = current_insn->children[child];
-    struct vreg* vreg;
 
     if (insn->hop)
-        vreg = insn->hop->output;
+        return insn->hop->output;
     else
-        vreg = insn->ir->result;
+        return insn->ir->result;
+}
+
+static void emit_reg(int child)
+{
+    struct vreg* vreg = find_vreg_of_child(child);
 
     if (vreg)
         hop_add_vreg_insel(current_hop, vreg);
@@ -71,6 +75,18 @@ static void emit_eoi(void)
 	hop_add_eoi_insel(current_hop);
 }
 
+static void constrain_input_reg(int child, int attr)
+{
+    struct vreg* vreg = find_vreg_of_child(child);
+
+    if (vreg)
+        array_appendu(&current_hop->ins, vreg);
+}
+
+static void constrain_output_reg(int attr)
+{
+}
+
 static const struct burm_emitter_data emitter_data =
 {
     &emit_string,
@@ -79,6 +95,8 @@ static const struct burm_emitter_data emitter_data =
     &emit_reg,
     &emit_value,
     &emit_eoi,
+    &constrain_input_reg,
+    &constrain_output_reg
 };
 
 static void emit(struct insn* insn)
@@ -142,11 +160,16 @@ static struct insn* walk_instructions(struct burm_node* node, int goal)
                     break;
 
                 default:
+                    /* FIXME: some instructions don't emit anything, so
+                     * allocating a register for them is a waste of time. */
                     vreg = new_vreg();
             }
 
             insn->hop = current_hop = new_hop(0, insn->ir);
             insn->hop->output = vreg;
+            if (vreg)
+                array_appendu(&current_hop->outs, vreg);
+
             emit(insn);
             hop_print('I', current_hop);
 
diff --git a/mach/proto/mcg/procedure.c b/mach/proto/mcg/procedure.c
index 8fbccd5d6..8d0f83953 100644
--- a/mach/proto/mcg/procedure.c
+++ b/mach/proto/mcg/procedure.c
@@ -61,8 +61,9 @@ void procedure_compile(struct procedure* proc)
     pass_promote_float_ops(proc);
     print_blocks('6', proc);
 
-
     pass_instruction_selector(proc);
+
+    register_allocator(proc);
 }
 
 static bool collect_outputs_cb(struct ir* ir, void* user)
diff --git a/mach/proto/mcg/registerallocator.c b/mach/proto/mcg/registerallocator.c
index 84db0ea7d..eae72fac6 100644
--- a/mach/proto/mcg/registerallocator.c
+++ b/mach/proto/mcg/registerallocator.c
@@ -1,2 +1,34 @@
+#include "mcg.h"
+
+static ARRAYOF(struct basicblock) blocks;
+
+static void recursively_walk_blocks(struct basicblock* bb)
+{
+	int i;
+
+	if (array_appendu(&blocks, bb))
+		return;
+	tracef('R', "R: considering block %s\n", bb->name);
+
+	for (i=0; i<bb->nexts.count; i++)
+		recursively_walk_blocks(bb->nexts.item[i]);
+}
+
+static void order_blocks(struct procedure* proc)
+{
+	/* Put them into preorder; this ensures that when we do the allocation,
+	 * we do all of a block's predecessors before the block (except for
+	 * backward edges). */
+	
+	blocks.count = 0;
+	recursively_walk_blocks(proc->blocks.item[0]);
+	assert(blocks.count == proc->blocks.count);
+}
+
+void register_allocator(struct procedure* proc)
+{
+	order_blocks(proc);
+}
+
 /* vim: set sw=4 ts=4 expandtab : */
 
diff --git a/mach/proto/mcg/table b/mach/proto/mcg/table
index 8ab4a4d51..f3f359f4b 100644
--- a/mach/proto/mcg/table
+++ b/mach/proto/mcg/table
@@ -29,7 +29,6 @@ REGISTERS
 
 DECLARATIONS
 
-	reg;
 	cc;
 
 	address   fragment;
@@ -40,28 +39,24 @@ PATTERNS
 
 /* Special */
 
-	reg;
-
 	PAIR(BLOCK4, BLOCK4);
 
 
 /* Miscellaneous special things */
 
-	PUSH4(in:reg)
+	PUSH4(in:(int)reg)
 		emit "push %in"
 		cost 4;
 
-	reg = POP4
-		with int reg
-		emit "pop %reg"
+	out:(int)reg = POP4
+		emit "pop %out"
 		cost 4;
 
 	RET
 		emit "ret"
 		cost 4;
 
-	SETRET4(in:reg)
-		with ret reg
+	SETRET4(in:(ret)reg)
 		emit "mov r0, %in"
 		cost 4;
 
@@ -69,51 +64,38 @@ PATTERNS
 		emit "add sp, sp, %delta"
 		cost 4;
 
-	reg = in:REG
-		cost 1;
-
-	reg = NOP(in:reg)
-		cost 1;
-
 
 /* Memory operations */
 
-	STORE4(addr:address, value:reg)
-		with int value
+	STORE4(addr:address, value:(int)reg)
 		emit "str %value, %addr"
 		cost 4;
 
-	STORE1(addr:address, value:reg)
-		with int value
+	STORE1(addr:address, value:(int)reg)
 		emit "strb %value, %addr"
 		cost 4;
 
-	reg = LOAD4(addr:address)
-		with int reg
-		emit "ldr %reg, %addr"
+	out:(int)reg = LOAD4(addr:address)
+		emit "ldr %out, %addr"
 		cost 4;
 
-	reg = LOAD1(addr:address)
-		with int reg
-		emit "ldrb %reg, %addr"
+	out:(int)reg = LOAD1(addr:address)
+		emit "ldrb %out, %addr"
 		cost 4;
 
-	reg = CIU14(LOAD1(addr:address))
-		with int reg
-		emit "ldrb %reg, %addr"
+	out:(int)reg = CIU14(LOAD1(addr:address))
+		emit "ldrb %out, %addr"
 		cost 4;
 	
-	reg = CII14(CIU41(CIU14(LOAD1(addr:address))))
-		with int reg
-		emit "ldrsb %reg, %addr"
+	out:(int)reg = CII14(CIU41(CIU14(LOAD1(addr:address))))
+		emit "ldrsb %out, %addr"
 		cost 4;
 
 
 /* Locals */
 
-	reg = in:LOCAL4
-		with int reg
-		emit "add %reg, fp, #$in"
+	out:(int)reg = in:LOCAL4
+		emit "add %out, fp, #$in"
 		cost 4;
 
 	address = in:LOCAL4
@@ -122,16 +104,13 @@ PATTERNS
 
 /* Memory addressing modes */
 
-	address = ADD4(addr:reg, offset:CONST4)
-		with int addr
+	address = ADD4(addr:(int)reg, offset:CONST4)
 		emit "[%addr, #$offset]";
 
-	address = ADD4(addr1:reg, addr2:reg)
-		with int addr1, int addr2
+	address = ADD4(addr1:(int)reg, addr2:(int)reg)
 		emit "[%addr1, %addr2]";
 
-	address = addr:reg
-		with int addr
+	address = addr:(int)reg
 		emit "[%addr]";
 
 
@@ -142,17 +121,17 @@ PATTERNS
 		emit "b $addr"
 		cost 4;
 
-	CJUMPEQ(value:cc, PAIR(true:BLOCK4, false:BLOCK4))
+	CJUMPEQ(value:(cc)cc, PAIR(true:BLOCK4, false:BLOCK4))
 		emit "beq $true"
 		emit "b $false"
 		cost 8;
 
-	CJUMPLE(value:cc, PAIR(true:BLOCK4, false:BLOCK4))
+	CJUMPLE(value:(cc)cc, PAIR(true:BLOCK4, false:BLOCK4))
 		emit "ble $true"
 		emit "b $false"
 		cost 8;
 
-	CJUMPLT(value:cc, PAIR(true:BLOCK4, false:BLOCK4))
+	CJUMPLT(value:(cc)cc, PAIR(true:BLOCK4, false:BLOCK4))
 		emit "blt $true"
 		emit "b $false"
 		cost 8;
@@ -164,96 +143,81 @@ PATTERNS
 
 /* Comparisons */
 
-	cc = COMPARES4(left:reg, right:aluparam)
-		with cc cc
+	(cc)cc = COMPARES4(left:(int)reg, right:aluparam)
 		emit "cmp %left, %right"
 		cost 4;
 
-	cc = COMPARES4(COMPARES4(left:reg, right:aluparam), CONST4)
-		with cc cc
+	(cc)cc = COMPARES4(COMPARES4(left:(int)reg, right:aluparam), CONST4)
 		emit "cmp %left, %right"
 		cost 4;
 
-	reg = cc
-		with int reg
-		emit "mov %reg, #0"
-		emit "movlt %reg, #-1"
-		emit "movgt %reg, #1"
+	out:(int)reg = (cc)cc
+		emit "mov %out, #0"
+		emit "movlt %out, #-1"
+		emit "movgt %out, #1"
 		cost 12;
 
 
 /* Conversions */
 
-	reg = CII14(CIU41(value:reg))
-		with int reg
-		emit "sxtb %reg, %value"
+	out:(int)reg = CII14(CIU41(value:(int)reg))
+		emit "sxtb %out, %value"
 		cost 4;
 
-	reg = CIU41(in:reg)
-		with int reg
-		emit "and %reg, %in, #0xff"
+	out:(int)reg = CIU41(in:(int)reg)
+		emit "and %out, %in, #0xff"
 		cost 4;
 
 
 /* ALU operations */
 
-	reg = ADD4(left:reg, right:aluparam)
-		with int reg
-		emit "add %reg, %left, %right"
+	out:(int)reg = ADD4(left:(int)reg, right:aluparam)
+		emit "add %out, %left, %right"
 		cost 4;
 
-	reg = ADD4(left:aluparam, right:reg)
-		with int reg
-		emit "add %reg, %right, %left"
+	out:(int)reg = ADD4(left:aluparam, right:(int)reg)
+		emit "add %out, %right, %left"
 		cost 4;
 
-	reg = MOD4(left:reg, right:reg)
-		with int reg
-		emit "udiv %reg, %left, %right"
-		emit "mls %reg, %reg, %right, %left"
+	out:(int)reg = MOD4(left:(int)reg, right:(int)reg)
+		emit "udiv %out, %left, %right"
+		emit "mls %out, %out, %right, %left"
 		cost 8;
 
-	reg = DIV4(left:reg, right:aluparam)
-		with int reg
-		emit "div %reg, %left, %right"
+	out:(int)reg = DIV4(left:(int)reg, right:aluparam)
+		emit "div %out, %left, %right"
 		cost 4;
 
 	aluparam = value:CONST4
 		emit "#$value";
 
-	aluparam = value:reg
+	aluparam = value:(int)reg
 		emit "%value";
 
-	reg = value:aluparam
-		with int reg
-		emit "mov %reg, %value"
+	out:(int)reg = value:aluparam
+		emit "mov %out, %value"
 		cost 4;
 
-	reg = value:LABEL4
-		with int reg
-		emit "adr %reg, $value"
+	out:(int)reg = value:LABEL4
+		emit "adr %out, $value"
 		cost 4;
 
-	reg = value:BLOCK4
-		with int reg
-		emit "adr %reg, $value"
+	out:(int)reg = value:BLOCK4
+		emit "adr %out, $value"
 		cost 4;
 
-	reg = value:CONST4
-		with int reg
-		emit "ldr %reg, address-containing-$value"
+	out:(int)reg = value:CONST4
+		emit "ldr %out, address-containing-$value"
 		cost 8;
 
-	reg = value:CONSTF4
-		with int reg
-		emit "vldr %reg, address-containing-$value"
+	out:(int)reg = value:CONSTF4
+		emit "vldr %out, address-containing-$value"
 		cost 8;
 
 /* FPU operations */
 
-	reg = ADDF4(left:reg, right:reg)
-		with int reg
-		emit "fadds %reg, %left, %right"
+	out:(float)reg = ADDF4(left:(float)reg, right:(float)reg)
+		emit "fadds %out, %left, %right"
 		cost 4;
 
 /* vim: set sw=4 ts=4 expandtab : */
diff --git a/util/mcgg/gram.y b/util/mcgg/gram.y
index a7ba08d70..fbd191052 100644
--- a/util/mcgg/gram.y
+++ b/util/mcgg/gram.y
@@ -11,8 +11,6 @@
 
 extern int yylex(void);
 
-static int nextern = 1;
-
 %}
 %union {
 	int n;
@@ -86,17 +84,6 @@ declarations
 declaration
     : ID                              { $$ = nonterm($1, true); }
     | declaration FRAGMENT            { $$ = $1; $$->is_fragment = true; }
-    | allocates                       { $$ = $1; }
-    ;
-
-allocates
-    : declaration ALLOCATES '(' ID ')'
-        {
-            $$ = $1;
-            if ($$->allocate)
-                yyerror("pattern type is defined to already allocate a register");
-            $$->allocate = getregattr($4);
-        }
     ;
 
 patterns
@@ -106,8 +93,8 @@ patterns
 	;
 
 pattern
-    : ID '=' rhs                        { nonterm($1, false); $$ = rule($1,     $3, nextern++); }
-    | rhs                               {                     $$ = rule("stmt", $1, nextern++); }
+    : terminfo '=' rhs                  { nonterm($1.name, false); $$ = rule(&$1,  $3); }
+    | rhs                               {                          $$ = rule(NULL, $1); }
     | pattern PREFERS predicate         { $$ = $1; array_append(&$$->prefers, $3); }
     | pattern WHEN predicate            { $$ = $1; array_append(&$$->requires, $3); }
     | pattern COST INT                  { $$ = $1; $$->cost = $3; }
@@ -123,7 +110,9 @@ rhs
 
 terminfo
     : ID                                { $$.name = $1; }
+    | '(' ID ')' ID                     { $$.attr = $2; $$.name = $4; }
     | ID ':' ID                         { $$.label = $1; $$.name = $3; }
+    | ID ':' '(' ID ')' ID              { $$.label = $1; $$.attr = $4; $$.name = $6; }
     ;
 
 pattern_emit
diff --git a/util/mcgg/iburg.c b/util/mcgg/iburg.c
index b9ecd2cd2..5683b6cc4 100644
--- a/util/mcgg/iburg.c
+++ b/util/mcgg/iburg.c
@@ -14,6 +14,7 @@
 #include "ircodes.h"
 #include "astring.h"
 #include "smap.h"
+#include "mcgg.h"
 
 static char rcsid[] = "$Id$";
 
@@ -131,6 +132,20 @@ int main(int argc, char* argv[])
 	makeregattr("bytes4");
 	makeregattr("bytes8");
 
+	/* Define some standard terms. */
+
+	{
+		const static struct terminfo reg = { "reg", NULL, "" };
+		const static struct terminfo REG = { "REG", NULL, NULL };
+		const static struct terminfo NOP = { "NOP", NULL, NULL };
+
+		nonterm("reg", true);
+
+		rule(NULL, tree(&reg, NULL, NULL))->cost = 1;
+		rule(&reg, tree(&REG, NULL, NULL))->cost = 1;
+		rule(&reg, tree(&NOP, tree(&reg, NULL, NULL), NULL))->cost = 1;
+	}
+
 	yyin = infp;
 	yyparse();
 
@@ -336,7 +351,7 @@ Term term(const char* id, int esn)
 }
 
 /* tree - create & initialize a tree node with the given fields */
-Tree tree(struct terminfo* ti, Tree left, Tree right)
+Tree tree(const struct terminfo* ti, Tree left, Tree right)
 {
 	Tree t = calloc(1, sizeof *t);
 	Term p = lookup(ti->name);
@@ -363,31 +378,57 @@ Tree tree(struct terminfo* ti, Tree left, Tree right)
 	if (p->kind == TERM && arity != p->arity)
 		yyerror("inconsistent arity for terminal `%s'\n", ti->name);
 	t->op = p;
-	t->label = ti->label;
 	t->nterms = p->kind == TERM;
 	if (t->left = left)
 		t->nterms += left->nterms;
 	if (t->right = right)
 		t->nterms += right->nterms;
+
+	/* Special rules that have no output register attribute use "" as the
+	 * attribute name; these can't be made by the grammar. */
+
+	t->label = ti->label;
+	if ((p->kind == TERM) && (ti->attr))
+		yyerror("can't specify an input register attribute for terminal '%s'", ti->name);
+	if (p->kind == NONTERM)
+	{
+		Nonterm nt = (Nonterm)p;
+		if (nt->is_fragment && ti->attr)
+			yyerror("can't specify an input register attribute for fragment '%s'", ti->name);
+		if (!nt->is_fragment && !ti->attr)
+			yyerror("must specify an input register attribute for non-fragment '%s'", ti->name);
+
+		if (ti->attr && ti->attr[0])
+		{
+			nt->attr = smap_get(&registerattrs, ti->attr);
+			if (!nt->attr)
+				yyerror("'%s' doesn't seem to be a known register attribute", ti->attr);
+		}
+	}
 	return t;
 }
 
 /* rule - create & initialize a rule with the given fields */
-Rule rule(char* id, Tree pattern, int ern)
+Rule rule(const struct terminfo* ti, Tree pattern)
 {
+	static int number = 1;
+	static const struct terminfo stmt = { "stmt", NULL, NULL };
 	Rule r = calloc(1, sizeof *r);
 	Rule *q;
 	Term p = pattern->op;
 
+	if (!ti)
+		ti = &stmt;
+
 	nrules++;
 	r->lineno = yylineno;
-	r->lhs = nonterm(id, false);
+	r->lhs = nonterm(ti->name, false);
 	r->packed = ++r->lhs->lhscount;
 	for (q = &r->lhs->rules; *q; q = &(*q)->decode)
 		;
 	*q = r;
 	r->pattern = pattern;
-	r->ern = ern;
+	r->ern = number++;
 	if (p->kind == TERM)
 	{
 		r->next = p->rules;
@@ -405,6 +446,23 @@ Rule rule(char* id, Tree pattern, int ern)
 		yyerror("duplicate external rule number `%d'\n", r->ern);
 	r->link = *q;
 	*q = r;
+
+	r->label = ti->label;
+	if (r->lhs->is_fragment && ti->attr)
+		yyerror("can't specify an output register attribute for a fragment");
+	if (!r->lhs->is_fragment && !ti->attr && (r->lhs->number != NONTERM_STMT))
+		yyerror("must specify an output register attribute for non-fragments");
+
+	/* Special rules that have no output register attribute use "" as the
+	 * attribute name; these can't be made by the grammar. */
+
+	if (ti->attr && ti->attr[0])
+	{
+		r->attr = smap_get(&registerattrs, ti->attr);
+		if (!r->attr)
+			yyerror("'%s' doesn't seem to be a known register attribute", ti->attr);
+	}
+
 	return r;
 }
 
@@ -986,6 +1044,28 @@ static void emitpredicatedefinitions(Rule r)
 	}
 }
 
+static void emit_input_regs(Tree node, int* index)
+{
+	/* This must return the same ordering as the burm_kids() function uses. */
+
+	Nonterm nt = node->op;
+	if ((nt->kind == NONTERM) && !nt->is_fragment && !node->left && !node->right)
+	{
+		uint32_t attr = 0;
+		if (nt->attr->number)
+			attr = 1<<nt->attr->number;
+		print("%1data->constrain_input_reg(%d, 0x%x);\n", *index, attr);
+	}
+
+	if (!node->left && !node->right)
+		(*index)++;
+
+	if (node->left)
+		emit_input_regs(node->left, index);
+	if (node->right)
+		emit_input_regs(node->right, index);
+}
+
 /* emitinsndata - emit the code generation data */
 static void emitinsndata(Rule rules)
 {
@@ -1011,6 +1091,14 @@ static void emitinsndata(Rule rules)
 		print("/* %R */\n", r);
 		print("static void %Pemitter_%d(const struct %Pemitter_data* data) {\n", r->ern);
 
+		if (r->attr)
+			print("%1data->constrain_output_reg(0x%x);\n", 1<<r->attr->number);
+
+		{
+			int index = 0;
+			emit_input_regs(r->pattern, &index);
+		}
+
 		while (f)
 		{
 			switch (f->data[0])
@@ -1019,7 +1107,7 @@ static void emitinsndata(Rule rules)
 				{
 					const char* label = f->data + 1;
 
-					if (strcmp(label, r->lhs->name) == 0)
+					if (r->label && (strcmp(label, r->label) == 0))
 						print("%1data->emit_return_reg();\n", label);
 					else
 					{
@@ -1086,11 +1174,6 @@ static void emitinsndata(Rule rules)
 
 		print("%2&%Pemitter_%d,\n", r->ern);
 
-		if (r->lhs->allocate)
-			print("%2%d,\n", r->lhs->allocate->number);
-		else
-			print("%20,\n");
-
 		print("%2%s,\n", r->lhs->is_fragment ? "true" : "false");
 
 		print("%1},\n");
diff --git a/util/mcgg/iburg.h b/util/mcgg/iburg.h
index 60e51d7b4..48981722b 100644
--- a/util/mcgg/iburg.h
+++ b/util/mcgg/iburg.h
@@ -41,6 +41,7 @@ struct terminfo
 {
 	const char* name;
 	const char* label;
+	const char* attr;
 };
 
 struct reg
@@ -82,7 +83,7 @@ struct nonterm
 	Rule chain;       /* chain rules w/non-terminal on rhs */
 	Nonterm link;     /* next terminal in number order */
 	bool is_fragment; /* these instructions are all fragments */
-	struct regattr* allocate; /* allocate this kind of register */
+	struct regattr* attr; /* input register attribute */
 };
 extern void* lookup(const char* name);
 extern Nonterm nonterm(const char* id, bool allocate);
@@ -96,7 +97,7 @@ struct tree
 	Tree left, right;   /* operands */
 	int nterms;         /* number of terminal nodes in this tree */
 };
-extern Tree tree(struct terminfo* ti, Tree left, Tree right);
+extern Tree tree(const struct terminfo* ti, Tree left, Tree right);
 
 struct rule
 { /* rules: */
@@ -106,6 +107,8 @@ struct rule
 	int ern;                 /* external rule number */
 	int packed;              /* packed external rule number */
 	int cost;                /* associated cost */
+	const char* label;       /* label for LHS */
+	struct regattr* attr;    /* register attribute of result */
 	Rule link;               /* next rule in ern order */
 	Rule next;               /* next rule with same pattern root */
 	Rule chain;              /* next chain rule with same rhs */
@@ -116,7 +119,7 @@ struct rule
 	ARRAYOF(struct constraint) constraints; /* register constraints */
 	struct stringlist code;  /* compiler output code strings */
 };
-extern Rule rule(char* id, Tree pattern, int ern);
+extern Rule rule(const struct terminfo* ti, Tree pattern);
 extern int maxcost; /* maximum cost */
 
 /* gram.y: */
diff --git a/util/mcgg/mcgg.h b/util/mcgg/mcgg.h
index 65dc26f54..14353c0e3 100644
--- a/util/mcgg/mcgg.h
+++ b/util/mcgg/mcgg.h
@@ -44,6 +44,8 @@ struct burm_emitter_data
     void (*emit_reg)(int child);
     void (*emit_value)(int child);
     void (*emit_eoi)(void);
+    void (*constrain_input_reg)(int child, int attr);
+    void (*constrain_output_reg)(int attr);
 };
 
 typedef void burm_emitter_t(const struct burm_emitter_data* data);
@@ -52,7 +54,6 @@ struct burm_instruction_data
 {
     const char* name;
     burm_emitter_t* emitter;
-    int allocate;
     bool is_fragment;
 };
 
@@ -75,6 +76,11 @@ enum
     REGATTR_BYTES8
 };
 
+enum
+{
+    NONTERM_STMT = 1
+};
+
 #endif
 
 /* vim: set sw=4 ts=4 expandtab : */