Make the arm2gnu.pl converter handle apple specific details

This allows building the arm assembly for iOS.

This checks for the __APPLE__ preprocessor built-in define to
determine whether this extra handling should be enabled.

Signed-off-by: Timothy B. Terriberry <tterribe@xiph.org>

Makefile.am

@@ -225,7 +225,7 @@ $(CELT_SOURCES_ARM_ASM:%.s=%-gnu.S): $(top_srcdir)/celt/arm/arm2gnu.pl
 
 # convert ARM asm to GNU as format
 %-gnu.S: $(top_srcdir)/%.s
-	$(top_srcdir)/celt/arm/arm2gnu.pl < $< > $@
+	$(top_srcdir)/celt/arm/arm2gnu.pl @ARM2GNU_PARAMS@ < $< > $@
 # For autoconf-modified sources (e.g., armopts.s)
 %-gnu.S: %.s
 	$(top_srcdir)/celt/arm/arm2gnu.pl < $< > $@

celt/arm/arm2gnu.pl

@@ -26,6 +26,8 @@
 
 my $bigend;  # little/big endian
 my $nxstack;
+my $apple = 0;
+my $symprefix = "";
 
 $nxstack = 0;
 
@@ -39,6 +41,11 @@ while ($ARGV[0] =~ /^-/) {
     $nflag++;
     next;
     }
+    if (/^--apple/) {
+        $apple = 1;
+        $symprefix = "_";
+        next;
+    }
     die "I don't recognize this switch: $_\\n";
 }
 $printit++ unless $nflag;
@@ -79,7 +86,7 @@ while (<>) {
     s/\bINCLUDE[ \t]*([^ \t\n]+)/.include \"$1\"/;
     s/\bGET[ \t]*([^ \t\n]+)/.include \"${ my $x=$1; $x =~ s|\.s|-gnu.S|; \$x }\"/;
     s/\bIMPORT\b/.extern/;
-    s/\bEXPORT\b/.global/;
+    s/\bEXPORT\b\s*/.global $symprefix/;
     s/^(\s+)\[/$1IF/;
     s/^(\s+)\|/$1ELSE/;
     s/^(\s+)\]/$1ENDIF/;
@@ -135,7 +142,7 @@ while (<>) {
             # won't match the original source file (we could use the .line
             # directive, which is documented to be obsolete, but then gdb will
             # show the wrong line in the translated source file).
-            s/$/;   .arch armv7-a\n   .fpu neon\n   .object_arch armv4t/;
+            s/$/;   .arch armv7-a\n   .fpu neon\n   .object_arch armv4t/ unless ($apple);
         }
     }
 
@@ -157,9 +164,13 @@ while (<>) {
         $prefix = "";
         if ($proc)
         {
-            $prefix = $prefix.sprintf("\t.type\t%s, %%function; ",$proc);
+            $prefix = $prefix.sprintf("\t.type\t%s, %%function; ",$proc) unless ($apple);
+            # Make sure we $prefix isn't empty here (for the $apple case).
+            # We handle mangling the label here, make sure it doesn't match
+            # the label handling below (if $prefix would be empty).
+            $prefix = "; ";
             push(@proc_stack, $proc);
-            s/^[A-Za-z_\.]\w+/$&:/;
+            s/^[A-Za-z_\.]\w+/$symprefix$&:/;
         }
         $prefix = $prefix."\t.thumb_func; " if ($thumb);
         s/\bPROC\b/@ $&/;
@@ -172,7 +183,7 @@ while (<>) {
         my $proc;
         s/\bENDP\b/@ $&/;
         $proc = pop(@proc_stack);
-        $_ = "\t.size $proc, .-$proc".$_ if ($proc);
+        $_ = "\t.size $proc, .-$proc".$_ if ($proc && !$apple);
     }
     s/\bSUBT\b/@ $&/;
     s/\bDATA\b/@ $&/;   # DATA directive is deprecated -- Asm guide, p.7-25
@@ -337,6 +348,6 @@ while (<>) {
 }
 #If we had a code section, mark that this object doesn't need an executable
 # stack.
-if ($nxstack) {
+if ($nxstack && !$apple) {
     printf ("    .section\t.note.GNU-stack,\"\",\%\%progbits\n");
 }

configure.ac

@@ -317,6 +317,14 @@ AS_IF([test x"${enable_asm}" = x"yes"],[
                     [rtcd_support=ARM"$rtcd_support"],
                     [rtcd_support="no"]
                 )
+                AC_MSG_CHECKING([for apple style tools])
+                AC_PREPROC_IFELSE([AC_LANG_PROGRAM([
+#ifndef __APPLE__
+#error 1
+#endif],[])],
+                    [AC_MSG_RESULT([yes]); ARM2GNU_PARAMS="--apple"],
+                    [AC_MSG_RESULT([no]); ARM2GNU_PARAMS=""])
+                AC_SUBST(ARM2GNU_PARAMS)
             ],
             [
                 AC_MSG_WARN(