perlasm/ppc-xlate.pl: comply with ABIs that specify vrsave as reserved.

RT#4162

Reviewed-by: Richard Levitte <levitte@openssl.org>

crypto/perlasm/ppc-xlate.pl

@@ -151,6 +151,26 @@
     "	vor	$vx,$vy,$vy";
 };
 
+# Some ABIs specify vrsave, special-purpose register #256, as reserved
+# for system use.
+my $no_vrsave = ($flavour =~ /aix|linux64le/);
+my $mtspr = sub {
+    my ($f,$idx,$ra) = @_;
+    if ($idx == 256 && $no_vrsave) {
+	"	or	$ra,$ra,$ra";
+    } else {
+	"	mtspr	$idx,$ra";
+    }
+};
+my $mfspr = sub {
+    my ($f,$rd,$idx) = @_;
+    if ($idx == 256 && $no_vrsave) {
+	"	li	$rd,-1";
+    } else {
+	"	mfspr	$rd,$idx";
+    }
+};
+
 # PowerISA 2.06 stuff
 sub vsxmem_op {
     my ($f, $vrt, $ra, $rb, $op) = @_;