* mn10300-tdep.c (mn10300_analyze_prologue): Check for an

	instruction pattern that appears frequently in position
	independent code.  Fix bug in code which looks for "fmov" and
	backtracks if no "fmov" is found.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 23ce666..2e594f2 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2008-01-28  Kevin Buettner  <kevinb@redhat.com>
+
+       * mn10300-tdep.c (mn10300_analyze_prologue): Check for an
+       instruction pattern that appears frequently in position
+       independent code.  Fix bug in code which looks for "fmov" and
+       backtracks if no "fmov" is found.
+
 2008-01-28  Doug Evans  <dje@google.com>
 
        * dbxread.c (read_dbx_symtab): Fix indentation.

diff --git a/gdb/mn10300-tdep.c b/gdb/mn10300-tdep.c
index e0fc6a7..8cf9bb3 100644 (file)
--- a/gdb/mn10300-tdep.c
+++ b/gdb/mn10300-tdep.c
@@ -608,6 +608,22 @@ mn10300_analyze_prologue (struct gdbarch *gdbarch, struct frame_info *fi,
        goto finish_prologue;
     }
 
+  /* Check for "mov pc, a2", an instruction found in optimized, position
+     independent code.  Skip it if found.  */
+  if (buf[0] == 0xf0 && buf[1] == 0x2e)
+    {
+      addr += 2;
+
+      /* Quit now if we're beyond the stop point.  */
+      if (addr >= stop)
+       goto finish_prologue;
+
+      /* Get the next two bytes so the prologue scan can continue.  */
+      status = read_memory_nobpt (addr, buf, 2);
+      if (status != 0)
+       goto finish_prologue;
+    }
+
   if (AM33_MODE (gdbarch) == 2)
     {
       /* Determine if any floating point registers are to be saved.
@@ -635,6 +651,7 @@ mn10300_analyze_prologue (struct gdbarch *gdbarch, struct frame_info *fi,
         was actually encountered.  As a consequence, ``addr'' would
         sometimes be advanced even when no fmov instructions were found.  */
       CORE_ADDR restore_addr = addr;
+      int fmov_found = 0;
 
       /* First, look for add -SIZE,sp (i.e. add imm8,sp  (0xf8feXX)
                                          or add imm16,sp (0xfafeXXXX)
@@ -715,12 +732,9 @@ mn10300_analyze_prologue (struct gdbarch *gdbarch, struct frame_info *fi,
                        break;
 
                      /* An fmov instruction has just been seen.  We can
-                        now really commit to the pattern match.  Set the
-                        address to restore at the end of this speculative
-                        bit of code to the actually address that we've
-                        been incrementing (or not) throughout the
-                        speculation.  */
-                     restore_addr = addr;
+                        now really commit to the pattern match.  */
+
+                     fmov_found = 1;
 
                      /* Get the floating point register number from the 
                         2nd and 3rd bytes of the "fmov" instruction:
@@ -739,29 +753,18 @@ mn10300_analyze_prologue (struct gdbarch *gdbarch, struct frame_info *fi,
                      imm_size = (buf[0] == 0xf9) ? 3 : 4;
                    }
                }
-             else
-               {
-                 /* No "fmov" was found. Reread the two bytes at the original
-                    "addr" to reset the state. */
-                 addr = restore_addr;
-                 if (!safe_frame_unwind_memory (fi, addr, buf, 2))
-                   goto finish_prologue;
-               }
            }
-         /* else the prologue consists entirely of an "add -SIZE,sp"
-            instruction. Handle this below. */
        }
-      /* else no "add -SIZE,sp" was found indicating no floating point
-        registers are saved in this prologue.  */
-
-      /* In the pattern match code contained within this block, `restore_addr'
-        is set to the starting address at the very beginning and then
-        iteratively to the next address to start scanning at once the
-        pattern match has succeeded.  Thus `restore_addr' will contain
-        the address to rewind to if the pattern match failed.  If the
-        match succeeded, `restore_addr' and `addr' will already have the
-        same value.  */
-      addr = restore_addr;
+      /* If no fmov instructions were found by the above sequence, reset
+         the state and pretend that the above bit of code never happened.  */
+      if (!fmov_found)
+       {
+         addr = restore_addr;
+         status = read_memory_nobpt (addr, buf, 2);
+         if (status != 0)
+           goto finish_prologue;
+         stack_extra_size = 0;
+       }
     }
 
   /* Now see if we set up a frame pointer via "mov sp,a3" */