[PATCH] add gdbarch_in_function_epilogue_p hook for sparc64

[jose.marchesi@oracle.com (Jose E. Marchesi)]

Hi.

watchpoint_update and watchpoint_cond avoid checking for watchpoints
when we are located at a function epilogue in the current frame.  This
is done in order to avoid using corrupted local registers and unwinding
a corrupted/destroyed stack.

The code determining whether we are in a function epilogue is provided
by the backends via the gdbarch_in_function_epilogue_p hook.  The patch
below adds such a hook for sparc.

Note that despite sparc_in_function_epilogue_p must work on both sparc32
and sparc64 the patch only installs the hook on sparc64 targets.  This
is because I can't test it in sparc32.

This patch makes all the tests on watch-cond.exp to pass on
sparc64-unknown-linux-gnu.

2013-10-16  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* sparc-tdep.c (sparc_in_function_epilogue_p): New function.
	(X_RETTURN): New macro.
	* sparc-tdep.h: sparc_in_function_epilogue_p prototype.

	* sparc64-tdep.c (sparc64_init_abi): Hook
	sparc_in_function_epilogue_p.


Index: sparc-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/sparc-tdep.c,v
retrieving revision 1.233
diff -u -r1.233 sparc-tdep.c
--- sparc-tdep.c	24 Jun 2013 22:18:32 -0000	1.233
+++ sparc-tdep.c	16 Oct 2013 14:00:49 -0000
@@ -88,6 +88,8 @@
 #define X_DISP19(i) ((((i) & 0x7ffff) ^ 0x40000) - 0x40000)
 #define X_DISP10(i) ((((((i) >> 11) && 0x300) | (((i) >> 5) & 0xff)) ^ 0x200) - 0x200)
 #define X_SIMM13(i) ((((i) & 0x1fff) ^ 0x1000) - 0x1000)
+/* Macros to identify some instructions.  */
+#define X_RETTURN(i) ((X_OP (i) == 0x2) && (X_OP3 (i) == 0x39))
 
 /* Fetch the instruction at PC.  Instructions are always big-endian
    even if the processor operates in little-endian mode.  */
@@ -421,6 +434,29 @@
   regcache_raw_write (regcache, regnum + 1, buf + 4);
 }
 \f
+/* Return true if we are in a function's epilogue, i.e. after an
+   instruction that destroyed a function's stack frame.  */
+
+int
+sparc_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
+{
+  /* This function must return true if we are one instruction after an
+     instruction that destroyed the stack frame of the current
+     function.  The SPARC instructions used to restore the callers
+     stack frame are RESTORE and RETURN/RETT.
+
+     Of these RETURN/RETT is a branch instruction and thus we return
+     true if we are in its delay slot.
+
+     RESTORE is almost always found in the delay slot of a branch
+     instruction that transfer control to the caller, such as JMPL.
+     Thus the next instruction is in the caller frame and we don't
+     need to do anything about it.  */
+
+  unsigned int insn = sparc_fetch_instruction (pc - 4);  
+  return X_RETTURN (insn);
+}
+\f
 
 static CORE_ADDR
 sparc32_frame_align (struct gdbarch *gdbarch, CORE_ADDR address)
Index: sparc-tdep.h
===================================================================
RCS file: /cvs/src/src/gdb/sparc-tdep.h,v
retrieving revision 1.33
diff -u -r1.33 sparc-tdep.h
--- sparc-tdep.h	1 Jan 2013 06:32:51 -0000	1.33
+++ sparc-tdep.h	16 Oct 2013 14:00:49 -0000
@@ -193,6 +193,9 @@
 extern struct sparc_frame_cache *
   sparc32_frame_cache (struct frame_info *this_frame, void **this_cache);
 
+extern int
+sparc_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc);
+
 \f
 
 extern int sparc_software_single_step (struct frame_info *frame);
Index: sparc64-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/sparc64-tdep.c,v
retrieving revision 1.62
diff -u -r1.62 sparc64-tdep.c
--- sparc64-tdep.c	1 Jan 2013 06:32:51 -0000	1.62
+++ sparc64-tdep.c	16 Oct 2013 14:00:49 -0000
@@ -1197,6 +1198,9 @@
 
   set_gdbarch_skip_prologue (gdbarch, sparc64_skip_prologue);
 
+  /* Detect whether PC is in function epilogue.  */
+  set_gdbarch_in_function_epilogue_p (gdbarch, sparc_in_function_epilogue_p);
+
   /* Hook in the DWARF CFI frame unwinder.  */
   dwarf2_frame_set_init_reg (gdbarch, sparc64_dwarf2_frame_init_reg);
   /* FIXME: kettenis/20050423: Don't enable the unwinder until the