PATCH: S/390: document fp state machine

[Jim Blandy <jimb at zwingli dot cygnus dot com>]

2001-12-04  Jim Blandy  <jimb@redhat.com>

	* s390-tdep.c (s390_get_frame_info): More doc fixes.

Index: gdb/s390-tdep.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gdb/s390-tdep.c,v
retrieving revision 2.25
diff -c -r2.25 s390-tdep.c
*** gdb/s390-tdep.c	2001/12/04 23:52:34	2.25
--- gdb/s390-tdep.c	2001/12/05 00:06:00
***************
*** 209,221 ****
    int fprs_saved[S390_NUM_FPRS];
    int regidx, instrlen;
    int const_pool_state;
!   int frame_pointer_found, varargs_state;
    int loop_cnt, gdb_gpr_store, gdb_fpr_store;
-   int frame_pointer_regidx = 0xf;
    int offset, expected_offset;
    int err = 0;
    disassemble_info info;
  
    /* What we've seen so far regarding saving the back chain link:
       0 -- nothing yet; sp still has the same value it had at the entry
            point.  Since not all functions allocate frames, this is a
--- 209,229 ----
    int fprs_saved[S390_NUM_FPRS];
    int regidx, instrlen;
    int const_pool_state;
!   int varargs_state;
    int loop_cnt, gdb_gpr_store, gdb_fpr_store;
    int offset, expected_offset;
    int err = 0;
    disassemble_info info;
  
+   /* Have we seen an instruction initializing the frame pointer yet?
+      If we've seen an `lr %r11, %r15', then frame_pointer_found is
+      non-zero, and frame_pointer_regidx == 11.  Otherwise,
+      frame_pointer_found is zero and frame_pointer_regidx is 15,
+      indicating that we're using the stack pointer as our frame
+      pointer.  */
+   int frame_pointer_found = 0;
+   int frame_pointer_regidx = 0xf;
+ 
    /* What we've seen so far regarding saving the back chain link:
       0 -- nothing yet; sp still has the same value it had at the entry
            point.  Since not all functions allocate frames, this is a
***************
*** 236,242 ****
       4 -- The frame and link are now fully initialized.  We've
            reserved space for the new stack frame, and stored the old
            stack pointer captured in the back chain pointer field.  */
!   int save_link_state;
    int save_link_regidx, subtract_sp_regidx;
  
    /* What we've seen so far regarding r12 --- the GOT (Global Offset
--- 244,250 ----
       4 -- The frame and link are now fully initialized.  We've
            reserved space for the new stack frame, and stored the old
            stack pointer captured in the back chain pointer field.  */
!   int save_link_state = 0;
    int save_link_regidx, subtract_sp_regidx;
  
    /* What we've seen so far regarding r12 --- the GOT (Global Offset
***************
*** 250,260 ****
       When got_state is 1, then got_load_addr is the address of the
       load instruction, and got_load_len is the length of that
       instruction.  */
!   int got_state;
    CORE_ADDR got_load_addr = 0, got_load_len = 0;
  
-   const_pool_state = save_link_state = got_state = varargs_state = 0;
-   frame_pointer_found = 0;
    memset (gprs_saved, 0, sizeof (gprs_saved));
    memset (fprs_saved, 0, sizeof (fprs_saved));
    info.read_memory_func = dis_asm_read_memory;
--- 258,268 ----
       When got_state is 1, then got_load_addr is the address of the
       load instruction, and got_load_len is the length of that
       instruction.  */
!   int got_state= 0;
    CORE_ADDR got_load_addr = 0, got_load_len = 0;
+ 
+   const_pool_state = varargs_state = 0;
  
    memset (gprs_saved, 0, sizeof (gprs_saved));
    memset (fprs_saved, 0, sizeof (fprs_saved));
    info.read_memory_func = dis_asm_read_memory;