[binutils-gdb/gdb-7.8-branch] Support gdbarch_convert_register_p targets in address_from_register

[Michael Eager <eager at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d99093fd0a66da4667938224d1cdb54714f93b25

commit d99093fd0a66da4667938224d1cdb54714f93b25
Author: Michael Eager <eager@eagercon.com>
Date:   Mon Mar 2 09:57:14 2015 -0800

    Support gdbarch_convert_register_p targets in address_from_register
    
    Since the last change to address_from_register, it no longer supports
    targets that require a special conversion (gdbarch_convert_register_p)
    for plain pointer type; I had assumed no target does so.
    
    This turned out to be incorrect: MIPS64 n32 big-endian needs such a
    conversion in order to properly sign-extend pointer values.
    
    This patch fixes this regression by handling targets that need a
    special conversion in address_from_register as well.
    
    gdb/ChangeLog:
    
    	* findvar.c (address_from_register): Handle targets requiring
    	a special conversion routine even for plain pointer types

Diff:
---
 gdb/ChangeLog |  5 +++++
 gdb/findvar.c | 25 +++++++++++++++++++++----
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 7527a53..2ad0da9 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-03-02  Ulrich Weigand  <uweigand@de.ibm.com>
+
+	* findvar.c (address_from_register): Handle targets requiring
+	a special conversion routine even for plain pointer types.
+
 2015-01-15  Joel Brobecker  <brobecker@adacore.com>
 
 	* version.in: Set GDB version number to 7.8.2.DATE-cvs.
diff --git a/gdb/findvar.c b/gdb/findvar.c
index 9390c8a..1a542d8 100644
--- a/gdb/findvar.c
+++ b/gdb/findvar.c
@@ -766,11 +766,28 @@ address_from_register (int regnum, struct frame_info *frame)
      would therefore abort in get_frame_id.  However, since we only need
      a temporary value that is never used as lvalue, we actually do not
      really need to set its VALUE_FRAME_ID.  Therefore, we re-implement
-     the core of value_from_register, but use the null_frame_id.
+     the core of value_from_register, but use the null_frame_id.  */
 
-     This works only if we do not require a special conversion routine,
-     which is true for plain pointer types for all current targets.  */
-  gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
+  /* Some targets require a special conversion routine even for plain
+     pointer types.  Avoid constructing a value object in those cases.  */
+  if (gdbarch_convert_register_p (gdbarch, regnum, type))
+    {
+      gdb_byte *buf = alloca (TYPE_LENGTH (type));
+      int optim, unavail, ok;
+
+      ok = gdbarch_register_to_value (gdbarch, frame, regnum, type,
+				      buf, &optim, &unavail);
+      if (!ok)
+	{
+	  /* This function is used while computing a location expression.
+	     Complain about the value being optimized out, rather than
+	     letting value_as_address complain about some random register
+	     the expression depends on not being saved.  */
+	  error_value_optimized_out ();
+	}
+
+      return unpack_long (type, buf);
+    }
 
   value = gdbarch_value_from_register (gdbarch, type, regnum, null_frame_id);
   read_frame_register_value (value, frame);