Don't scan prologue past epilogue

This patch is to stop prologue analysis past epilogue in for arm mode,
while we've already had done the same to thumb mode (see
thumb_instruction_restores_sp).  This is useful to parse functions
with empty body (epilogue follows prologue).

gdb:

2014-12-12  Yao Qi  <yao@codesourcery.com>

	* arm-tdep.c (arm_instruction_restores_sp): New function.
	(arm_analyze_prologue): Call arm_instruction_restores_sp.
	(arm_in_function_epilogue_p): Move code to
	arm_instruction_restores_sp.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index bdbe56b10ac588437ed6492e6d22021e276b7323..c444ce77c07d21deb88a2291deff5668839b00b0 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2014-12-12  Yao Qi  <yao@codesourcery.com>
+
+       * arm-tdep.c (arm_instruction_restores_sp): New function.
+       (arm_analyze_prologue): Call arm_instruction_restores_sp.
+       (arm_in_function_epilogue_p): Move code to
+       arm_instruction_restores_sp.
+
 2014-12-11  Doug Evans  <xdje42@gmail.com>
 
        * cp-namespace.c (cp_lookup_nested_symbol): Fix comments.

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 7ec3bff50076d2c5a3f085de497085b0b52cb364..34070452e1731be227b4af81011933a3643fcb5a 100644 (file)
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -1664,6 +1664,30 @@ arm_instruction_changes_pc (uint32_t this_instr)
       }
 }
 
+/* Return 1 if the ARM instruction INSN restores SP in epilogue, 0
+   otherwise.  */
+
+static int
+arm_instruction_restores_sp (unsigned int insn)
+{
+  if (bits (insn, 28, 31) != INST_NV)
+    {
+      if ((insn & 0x0df0f000) == 0x0080d000
+         /* ADD SP (register or immediate).  */
+         || (insn & 0x0df0f000) == 0x0040d000
+         /* SUB SP (register or immediate).  */
+         || (insn & 0x0ffffff0) == 0x01a0d000
+         /* MOV SP.  */
+         || (insn & 0x0fff0000) == 0x08bd0000
+         /* POP (LDMIA).  */
+         || (insn & 0x0fff0000) == 0x049d0000)
+         /* POP of a single register.  */
+       return 1;
+    }
+
+  return 0;
+}
+
 /* Analyze an ARM mode prologue starting at PROLOGUE_START and
    continuing no further than PROLOGUE_END.  If CACHE is non-NULL,
    fill it in.  Return the first address not recognized as a prologue
@@ -1861,6 +1885,11 @@ arm_analyze_prologue (struct gdbarch *gdbarch,
       else if (arm_instruction_changes_pc (insn))
        /* Don't scan past anything that might change control flow.  */
        break;
+      else if (arm_instruction_restores_sp (insn))
+       {
+         /* Don't scan past the epilogue.  */
+         break;
+       }
       else if ((insn & 0xfe500000) == 0xe8100000       /* ldm */
               && pv_is_register (regs[bits (insn, 16, 19)], ARM_SP_REGNUM))
        /* Ignore block loads from the stack, potentially copying
@@ -3351,7 +3380,7 @@ arm_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
 {
   enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
   unsigned int insn;
-  int found_return, found_stack_adjust;
+  int found_return;
   CORE_ADDR func_start, func_end;
 
   if (arm_pc_is_thumb (gdbarch, pc))
@@ -3391,28 +3420,8 @@ arm_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
   if (pc < func_start + 4)
     return 0;
 
-  found_stack_adjust = 0;
   insn = read_memory_unsigned_integer (pc - 4, 4, byte_order_for_code);
-  if (bits (insn, 28, 31) != INST_NV)
-    {
-      if ((insn & 0x0df0f000) == 0x0080d000)
-       /* ADD SP (register or immediate).  */
-       found_stack_adjust = 1;
-      else if ((insn & 0x0df0f000) == 0x0040d000)
-       /* SUB SP (register or immediate).  */
-       found_stack_adjust = 1;
-      else if ((insn & 0x0ffffff0) == 0x01a0d000)
-       /* MOV SP.  */
-       found_stack_adjust = 1;
-      else if ((insn & 0x0fff0000) == 0x08bd0000)
-       /* POP (LDMIA).  */
-       found_stack_adjust = 1;
-      else if ((insn & 0x0fff0000) == 0x049d0000)
-       /* POP of a single register.  */
-       found_stack_adjust = 1;
-    }
-
-  if (found_stack_adjust)
+  if (arm_instruction_restores_sp (insn))
     return 1;
 
   return 0;