ARM EH: Extend DWARF_FRAME_REGISTERS count to 48 and map reg# 256 -> 16.

gcc/unwind-dw2.c

 /* DWARF2 exception handling and frame unwind runtime interface routines.
    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
    2008, 2009, 2010  Free Software Foundation, Inc.
 
    This file is part of GCC.
 
    GCC is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3, or (at your option)
    any later version.
@@ skipping 33 matching lines @@
 #else
 #undef STACK_GROWS_DOWNWARD
 #define STACK_GROWS_DOWNWARD 1
 #endif
 
 /* Dwarf frame registers used for pre gcc 3.0 compiled glibc.  */
 #ifndef PRE_GCC3_DWARF_FRAME_REGISTERS
 #define PRE_GCC3_DWARF_FRAME_REGISTERS DWARF_FRAME_REGISTERS
 #endif
 
+/* @LOCALMOD-BEGIN */
+#if defined(__arm__)
+/*
+ * Override DWARF_REG_TO_UNWIND_COLUMN to map high ARM register numbers
+ * into lower and obsolete register numbers. See unwind-pnacl.h.
+ */
+int DWARF_REG_TO_UNWIND_COLUMN(int REGNO) {
+  if (REGNO >= 0 && REGNO < 16)
+    return REGNO;
+  if (REGNO >= 256 && REGNO < 287)
+    return (REGNO - 256 + 16);
+  /*
+   * Otherwise, assume REGNO is already mapped down from 256-287 -> 16-48.
+   * The normal 16-48 ARM dwarf registers are obsolete
+   * so this is sort of okay.
+   */
+  if (REGNO < DWARF_FRAME_REGISTERS)
+    return REGNO;
+  abort();
+}
+
+#else
 #ifndef DWARF_REG_TO_UNWIND_COLUMN
 #define DWARF_REG_TO_UNWIND_COLUMN(REGNO) (REGNO)
 #endif
+#endif  // __arm__
+/* @LOCALMOD-END
+
 
 /* This is the register and unwind state for a particular frame.  This
    provides the information necessary to unwind up past a frame and return
    to its caller.  */
 struct _Unwind_Context
 {
   void *reg[DWARF_FRAME_REGISTERS+1];
   void *cfa;
   void *ra;
   void *lsda;
@@ skipping 1574 matching lines @@
 alias (_Unwind_Resume_or_Rethrow);
 alias (_Unwind_SetGR);
 // @LOCALMOD-BEGIN
 alias (_Unwind_PNaClSetResult0);
 alias (_Unwind_PNaClSetResult1);
 // @LOCALMOD-END
 alias (_Unwind_SetIP);
 #endif
 
 #endif /* !USING_SJLJ_EXCEPTIONS */