Restrict matching add/sub sp, #imm

Currently, GDB matches both add/sub sp, #imm in prologue and epilogue,
which is not very precise.  On the instruction level, the immediate
number in both instruction can't be negative, so 'sub sp, #imm' only
appears in prologue while 'add sp, #imm' only appears in epilogue.
Note that on assembly level, we can write 'add sp, -8', but gas will
translate to 'sub sp, 8' instruction.

This patch is to only match 'sub sp, #imm' in prologue and match
'add sp, #immm' in epilogue.  It paves the way for the following
patch.

gdb:

2014-07-11  Yao Qi  <yao@codesourcery.com>

	* arm-tdep.c (thumb_analyze_prologue): Don't match instruction
	'add sp, #imm'.
	(thumb_in_function_epilogue_p): Don't match 'sub sp, #imm'.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index afad8f31ff98ab0d36440602b896cb01ba411ac6..112a8698e946f8f505bbdd4308b588bb680905c2 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2014-07-11  Yao Qi  <yao@codesourcery.com>
+
+       * arm-tdep.c (thumb_analyze_prologue): Don't match instruction
+       'add sp, #imm'.
+       (thumb_in_function_epilogue_p): Don't match 'sub sp, #imm'.
+
 2014-07-11  Gary Benson  <gbenson@redhat.com>
 
        * amd64-linux-nat.c (gdbcore.h): Remove include.

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 8cc60a4bb1322115c2fea803689fe3cc7f9e1286..6b1cf3c1f04f320ad253505f353d14acd7136f9d 100644 (file)
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -737,16 +737,11 @@ thumb_analyze_prologue (struct gdbarch *gdbarch,
                pv_area_store (stack, regs[ARM_SP_REGNUM], 4, regs[regno]);
              }
        }
-      else if ((insn & 0xff00) == 0xb000)      /* add sp, #simm  OR  
-                                                  sub sp, #simm */
+      else if ((insn & 0xff80) == 0xb080)      /* sub sp, #imm */
        {
          offset = (insn & 0x7f) << 2;          /* get scaled offset */
-         if (insn & 0x80)                      /* Check for SUB.  */
-           regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
-                                                  -offset);
-         else
-           regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
-                                                  offset);
+         regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
+                                                -offset);
        }
       else if ((insn & 0xf800) == 0xa800)      /* add Rd, sp, #imm */
        regs[bits (insn, 8, 10)] = pv_add_constant (regs[ARM_SP_REGNUM],
@@ -3264,7 +3259,7 @@ thumb_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
        found_return = 1;
       else if (insn == 0x46bd)  /* mov sp, r7 */
        found_stack_adjust = 1;
-      else if ((insn & 0xff00) == 0xb000)  /* add sp, imm or sub sp, imm  */
+      else if ((insn & 0xff80) == 0xb000)  /* add sp, imm */
        found_stack_adjust = 1;
       else if ((insn & 0xfe00) == 0xbc00)  /* pop <registers> */
        {
@@ -3324,7 +3319,7 @@ thumb_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
 
       if (insn2 == 0x46bd)  /* mov sp, r7 */
        found_stack_adjust = 1;
-      else if ((insn2 & 0xff00) == 0xb000)  /* add sp, imm or sub sp, imm  */
+      else if ((insn2 & 0xff80) == 0xb000)  /* add sp, imm */
        found_stack_adjust = 1;
       else if ((insn2 & 0xff00) == 0xbc00)  /* pop <registers> without PC */
        found_stack_adjust = 1;