MIPS: Make the extracted stack offset signed in the prologue scanner

Make the extracted stack offset signed in the standard MIPS prologue
scanner, to simplify handling and make sure register offsets are correct
in all cases, especially where $fp equals the virtual frame pointer (old
GCC frames) and therefore offsets to save slots are negative.

	* mips-tdep.c (mips32_scan_prologue): Make the extracted stack
	offset signed.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 8b016dc4fac7a44a5035dd53e4fa205661c972ad..1d1e32c65ae4da1ffe0cc3d2f614aae59883074d 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-01-02  Maciej W. Rozycki  <macro@codesourcery.com>
+
+       * mips-tdep.c (mips32_scan_prologue): Keep the extracted stack
+       offset signed.
+
 2015-01-02  Doug Evans  <dje@google.com>
 
        * dwarf2read.c (setup_type_unit_groups): Remove outdated comment.

diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index 5cd66a1c2f580f8123337c49fb4476d50036f3d2..bd8faef26bd3f0f0e6a537fd66e96d96a74f3ab4 100644 (file)
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -3438,7 +3438,8 @@ restart:
   frame_offset = 0;
   for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += MIPS_INSN32_SIZE)
     {
-      unsigned long inst, high_word, low_word;
+      unsigned long inst, high_word;
+      long offset;
       int reg;
 
       this_non_prologue_insn = 0;
@@ -3450,15 +3451,15 @@ restart:
 
       /* Save some code by pre-extracting some useful fields.  */
       high_word = (inst >> 16) & 0xffff;
-      low_word = inst & 0xffff;
+      offset = ((inst & 0xffff) ^ 0x8000) - 0x8000;
       reg = high_word & 0x1f;
 
       if (high_word == 0x27bd          /* addiu $sp,$sp,-i */
          || high_word == 0x23bd        /* addi $sp,$sp,-i */
          || high_word == 0x67bd)       /* daddiu $sp,$sp,-i */
        {
-         if (low_word & 0x8000)        /* Negative stack adjustment?  */
-            frame_offset += 0x10000 - low_word;
+         if (offset < 0)               /* Negative stack adjustment?  */
+            frame_offset -= offset;
          else
            /* Exit loop if a positive stack adjustment is found, which
               usually means that the stack cleanup code in the function
@@ -3469,19 +3470,19 @@ restart:
       else if (((high_word & 0xFFE0) == 0xafa0) /* sw reg,offset($sp) */
                && !regsize_is_64_bits)
        {
-         set_reg_offset (gdbarch, this_cache, reg, sp + low_word);
+         set_reg_offset (gdbarch, this_cache, reg, sp + offset);
        }
       else if (((high_word & 0xFFE0) == 0xffa0)        /* sd reg,offset($sp) */
                && regsize_is_64_bits)
        {
          /* Irix 6.2 N32 ABI uses sd instructions for saving $gp and $ra.  */
-         set_reg_offset (gdbarch, this_cache, reg, sp + low_word);
+         set_reg_offset (gdbarch, this_cache, reg, sp + offset);
        }
       else if (high_word == 0x27be)    /* addiu $30,$sp,size */
        {
          /* Old gcc frame, r30 is virtual frame pointer.  */
-         if ((long) low_word != frame_offset)
-           frame_addr = sp + low_word;
+         if (offset != frame_offset)
+           frame_addr = sp + offset;
          else if (this_frame && frame_reg == MIPS_SP_REGNUM)
            {
              unsigned alloca_adjust;
@@ -3491,7 +3492,7 @@ restart:
                (this_frame, gdbarch_num_regs (gdbarch) + 30);
              frame_offset = 0;
 
-             alloca_adjust = (unsigned) (frame_addr - (sp + low_word));
+             alloca_adjust = (unsigned) (frame_addr - (sp + offset));
              if (alloca_adjust > 0)
                {
                   /* FP > SP + frame_size.  This may be because of
@@ -3540,7 +3541,7 @@ restart:
       else if ((high_word & 0xFFE0) == 0xafc0  /* sw reg,offset($30) */
                && !regsize_is_64_bits)
        {
-         set_reg_offset (gdbarch, this_cache, reg, frame_addr + low_word);
+         set_reg_offset (gdbarch, this_cache, reg, frame_addr + offset);
        }
       else if ((high_word & 0xFFE0) == 0xE7A0 /* swc1 freg,n($sp) */
                || (high_word & 0xF3E0) == 0xA3C0 /* sx reg,n($s8) */