From 331bb6cab54e6697e12cc9c5a4ca0ae618c37dd3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 23 May 2012 16:08:59 +0200
Subject: BEAM loader: Support preservation of extra operand in transforms

It was not possible to preserve extra arguments in transformations.
The following (hypothetical) example will now work:

some_op Lit=c SizeArg Rest=* => move Lit x | some_op x SizeArg Rest
---
 erts/emulator/beam/beam_load.c   | 18 ++++++++++++++++--
 erts/emulator/utils/beam_makeops | 23 ++++++++++++++++-------
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 938fd8f2c9..58207ec75b 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -4376,6 +4376,7 @@ transform_engine(LoaderState* st)
     Uint* restart;		/* Where to restart if current match fails. */
     GenOpArg def_vars[TE_MAX_VARS]; /* Default buffer for variables. */
     GenOpArg* var = def_vars;
+    int num_vars = 0;
     int i;			/* General index. */
     Uint mask;
     GenOp* instr;
@@ -4578,9 +4579,9 @@ transform_engine(LoaderState* st)
 	    {
 		int n = *pc++;
 		int formal_arity = gen_opc[instr->op].arity;
-		int num_vars = n + (instr->arity - formal_arity);
 		int j = formal_arity;
 
+		num_vars = n + (instr->arity - formal_arity);
 		var = erts_alloc(ERTS_ALC_T_LOADER_TMP,
 				 num_vars * sizeof(GenOpArg));
 		for (i = 0; i < n; i++) {
@@ -4592,7 +4593,6 @@ transform_engine(LoaderState* st)
 	    }
 	    break;
 #endif
-
 	case TOP_next_arg:
 	    ap++;
 	    break;
@@ -4680,6 +4680,20 @@ transform_engine(LoaderState* st)
 	    instr->a[ap].val = var[i].val;
 	    ap++;
 	    break;
+#if defined(TOP_store_rest_args)
+	case TOP_store_rest_args:
+	    {
+		int n = *pc++;
+		int num_extra = num_vars - n;
+
+		ASSERT(n <= num_vars);
+		GENOP_ARITY(instr, instr->arity+num_extra);
+		memcpy(instr->a, instr->def_args, ap*sizeof(GenOpArg));
+		memcpy(instr->a+ap, var+n, num_extra*sizeof(GenOpArg));
+		ap += num_extra;
+	    }
+	    break;
+#endif
 	case TOP_try_me_else:
 	    restart = pc + 1;
 	    restart += *pc++;
diff --git a/erts/emulator/utils/beam_makeops b/erts/emulator/utils/beam_makeops
index 16a949c2a6..0b7c16f606 100755
--- a/erts/emulator/utils/beam_makeops
+++ b/erts/emulator/utils/beam_makeops
@@ -1202,6 +1202,7 @@ sub parse_transformation {
 
     my($from, $to) = split(/\s*=>\s*/);
     my(@op);
+    my $rest_var;
 
     # The source instructions.
 
@@ -1212,7 +1213,7 @@ sub parse_transformation {
 	    $_ = (&compile_transform_function($name, split(/\s*,\s*/, $arglist)));
 	} else {
 	    (@op) = split;
-	    $_ = &compile_transform(1, @op);
+	    ($rest_var,$_) = compile_transform(1, $rest_var, @op);
 	}
     }
 
@@ -1230,7 +1231,7 @@ sub parse_transformation {
 	@to = split(/\s*\|\s*/, $to);
 	foreach (@to) {
 	    (@op) = split;
-	    $_ = &compile_transform(0, @op);
+	    (undef,$_) = compile_transform(0, $rest_var, @op);
 	}
     }
     push(@transformations, [$., $orig, [@from], [reverse @to]]);
@@ -1243,12 +1244,18 @@ sub compile_transform_function {
 }
 
 sub compile_transform {
-    my($src, $name, @ops) = @_;
+    my($src, $rest_var, $name, @ops) = @_;
     my $arity = 0;
-    
+
     foreach (@ops) {
 	my(@list) = &tr_parse_op($src, $_);
-	$arity++ unless $list[1] eq '*';
+	if ($list[1] eq '*') {
+	    $rest_var = $list[0];
+	} elsif (defined $rest_var and $list[0] eq $rest_var) {
+	    $list[1] = '*';
+	} else {
+	    $arity++;
+	}
 	$_ = [ @list ];
     }
     
@@ -1260,7 +1267,7 @@ sub compile_transform {
 	$is_transformed{$name,$arity} = 1;
     }
     
-    [$name,$arity,@ops];
+    ($rest_var,[$name,$arity,@ops]);
 }
 
 sub tr_parse_op {
@@ -1681,7 +1688,9 @@ sub tr_gen_to {
 	foreach $op (@ops) {
 	    my($var, $type, $type_val) = @$op;
 
-	    if ($var ne '') {
+	    if ($type eq '*') {
+		push(@code, make_op($var, 'store_rest_args', $var{$var}));
+	    } elsif ($var ne '') {
 		&error($where, "variable '$var' unbound")
 		    unless defined $var{$var};
 		push(@code, &make_op($var, 'store_var_next_arg', $var{$var}));
-- 
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