Re: [RFA] Improve Sparc epilogue analysis

David S. Miller
2002-04-24T07:09:15Z

From: Michael Snyder <msnyder@redhat.com>
Date: Tue, 23 Apr 2002 12:19:57 -0700

No. Examine prologue serves two roles. One is simply
to skip to the end of the prologue, but the other is to
actually determine where the registers are saved by the
prologue. You've short-circuited the second usage.

Your idea is sound, though -- you've just implemented
it in the wrong place. Instead of modifying examine_prologue,
how about if you modify sparc_gdbarch_skip_prologue?

Right. There is even extra confusion arising from the
fact that we have two functions for the same thing.

These are sparc_skip_prologue and sparc_gdbarch_skip_prologue.

I killed the latter, and we can "static" the former
when all the sparc targets are multi-arch'd.

How does this revised patch look?

2002-04-23 David S. Miller <davem@redhat.com>

* sparc-tdep.c (sparc_gdbarch_skip_prologue): Kill, duplicates
sparc_skip_prologue.
(sparc_skip_prologue): Kill frameless_p arg, and use line number
information to find prologue when possible.
(sparc_prologue_frameless_p): Use line number information.
(sparc_gdbarch_init): Update set_gdbarch_skip_prologue call.
(sparc_init_extra_frame_info): Use sparc_skip_prologue to find
prologue bounds instead of looking at line number info by hand.
* config/sparc/tm-sparc.h (sparc_skip_prologue): Update for killed
second argument.
(SKIP_PROLOGUE): Likewise.

--- ./config/sparc/tm-sparc.h.~1~ Sun Apr 21 19:18:59 2002
+++ ./config/sparc/tm-sparc.h Tue Apr 23 22:38:43 2002
@@ -250,8 +250,8 @@ extern int sparc_intreg_size (void);
/* Advance PC across any function entry prologue instructions
to reach some "real" code. */

-extern CORE_ADDR sparc_skip_prologue (CORE_ADDR, int);
-#define SKIP_PROLOGUE(PC) sparc_skip_prologue (PC, 0)
+extern CORE_ADDR sparc_skip_prologue (CORE_ADDR);
+#define SKIP_PROLOGUE(PC) sparc_skip_prologue (PC)

/* Immediately after a function call, return the saved pc.
Can't go through the frames for this because on some machines
--- ./sparc-tdep.c.~1~ Sun Apr 21 20:51:34 2002
+++ ./sparc-tdep.c Tue Apr 23 23:00:46 2002
@@ -279,6 +279,8 @@ struct frame_extra_info
int sp_offset;
};

+CORE_ADDR sparc_skip_prologue (CORE_ADDR);
+
/* Call this for each newly created frame. For SPARC, we need to
calculate the bottom of the frame, and do some extra work if the
prologue has been generated via the -mflat option to GCC. In
@@ -393,25 +395,20 @@ sparc_init_extra_frame_info (int fromlea
to the current value of the stack pointer and set
the in_prologue flag. */
CORE_ADDR addr;
- struct symtab_and_line sal;

- sal = find_pc_line (prologue_start, 0);
- if (sal.line == 0) /* no line info, use PC */
- prologue_end = fi->pc;
- else if (sal.end < prologue_end)
- prologue_end = sal.end;
+ prologue_end = sparc_skip_prologue (prologue_start);
if (fi->pc < prologue_end)
{
- for (addr = prologue_start; addr < fi->pc; addr += 4)
+ for (addr = fi->pc; addr < prologue_end; addr += 4)
{
insn = read_memory_integer (addr, 4);
if (X_OP (insn) == 2 && X_OP3 (insn) == 0x3c)
break; /* SAVE seen, stop searching */
}
- if (addr >= fi->pc)
+ if (addr < prologue_end)
{
fi->extra_info->in_prologue = 1;
- fi->frame = read_register (SP_REGNUM);
+ fi->frame = read_sp ();
}
}
}
@@ -685,18 +682,50 @@ examine_prologue (CORE_ADDR start_pc, in
return pc;
}

+/* Advance PC across any function entry prologue instructions to reach
+ some "real" code. */
+
CORE_ADDR
-sparc_skip_prologue (CORE_ADDR start_pc, int frameless_p)
+sparc_skip_prologue (CORE_ADDR start_pc)
{
- return examine_prologue (start_pc, frameless_p, NULL, NULL);
+ struct symtab_and_line sal;
+ CORE_ADDR func_start, func_end;
+
+ /* This is the preferred method, find the end of the prologue by
+ using the debugging information. */
+ if (find_pc_partial_function (start_pc, NULL, &func_start, &func_end))
+ {
+ sal = find_pc_line (func_start, 0);
+
+ if (sal.end < func_end
+ && start_pc <= sal.end)
+ return sal.end
+ }
+
+ /* Oh well, examine the code by hand. */
+ return examine_prologue (start_pc, 0, NULL, NULL);
}

/* Is the prologue at IP frameless? */

int
-sparc_prologue_frameless_p (CORE_ADDR ip)
+sparc_prologue_frameless_p (CORE_ADDR start_pc)
{
- return ip == sparc_skip_prologue (ip, 1);
+ struct symtab_and_line sal;
+ CORE_ADDR func_start, func_end;
+
+ /* This is the preferred method, find the end of the prologue by
+ using the debugging information. */
+ if (find_pc_partial_function (start_pc, NULL, &func_start, &func_end))
+ {
+ sal = find_pc_line (func_start, 0);
+
+ if (sal.end < func_end
+ && start_pc <= sal.end)
+ return start_pc == sal.end;
+ }
+
+ return start_pc == examine_prologue (start_pc, 1, NULL, NULL);
}

/* Check instruction at ADDR to see if it is a branch.
@@ -2784,15 +2813,6 @@ sparc64_register_byte (int regno)
return 64 * 8 + (regno - 80) * 8;
}

-/* Advance PC across any function entry prologue instructions to reach
- some "real" code. */
-
-static CORE_ADDR
-sparc_gdbarch_skip_prologue (CORE_ADDR ip)
-{
- return examine_prologue (ip, 0, NULL, NULL);
-}
-
/* Immediately after a function call, return the saved pc.
Can't go through the frames for this because on some machines
the new frame is not set up until the new function executes
@@ -2993,7 +3013,7 @@ sparc_gdbarch_init (struct gdbarch_info
set_gdbarch_saved_pc_after_call (gdbarch, sparc_saved_pc_after_call);
set_gdbarch_prologue_frameless_p (gdbarch, sparc_prologue_frameless_p);
set_gdbarch_short_bit (gdbarch, 2 * TARGET_CHAR_BIT);
- set_gdbarch_skip_prologue (gdbarch, sparc_gdbarch_skip_prologue);
+ set_gdbarch_skip_prologue (gdbarch, sparc_skip_prologue);
set_gdbarch_sp_regnum (gdbarch, SPARC_SP_REGNUM);
set_gdbarch_use_generic_dummy_frames (gdbarch, 0);
set_gdbarch_write_pc (gdbarch, generic_target_write_pc);