It was getting 32-bit ABI register sizes wrong.  This fixes it, and some 
related ABI problems.  One note:

-         /* Irix 6.2 N32 ABI uses sd instructions for saving $gp and $ra,
-            but the register size used is only 32 bits. Make the address
-            for the saved register point to the lower 32 bits.  */
+         /* Irix 6.2 N32 ABI uses sd instructions for saving $gp and
+            $ra.  */
           PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
-         set_reg_offset (temp_saved_regs, reg,
-                         sp + low_word + 8 - mips_isa_regsize 
(current_gdbarch)
);
+         set_reg_offset (temp_saved_regs, reg, sp + low_word);

the computation ``8 - mips_isa_regsize'' is always ``0'' for the case in 
question so I eliminated the expression.  The original reason for the 
hack has gone.

committed,
Andrew