* alpha-tdep.c (heuristic_proc_desc): Add heuristic to

	determine the return address register, needed for OSF/1-3.2C.
	* config/alpha/tm-alpha.h (T7_REGNUM, T9_REGNUM):  Define.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 23d6a7b67a34e6a805f246a14a5599b90ebbb43c..d7f1b98ac60ff82b4ff0347d98c34cca370b2f21 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+Sat Dec  2 03:02:21 1995  Peter Schauer  (pes@regent.e-technik.tu-muenchen.de)
+
+       * alpha-tdep.c (heuristic_proc_desc):  Add heuristic to
+       determine the return address register, needed for OSF/1-3.2C.
+       * config/alpha/tm-alpha.h (T7_REGNUM, T9_REGNUM):  Define.
+
 Fri Dec  1 07:23:57 1995  Michael Meissner  <meissner@tiktok.cygnus.com>
 
        * ppcbug-rom.c (ppcbug_cmds): Turn on MO_GETMEM_READ_SINGLE

diff --git a/gdb/alpha-tdep.c b/gdb/alpha-tdep.c
index 622ee44de4c5b5243e04ae56ef1d8b609f2293be..7fbf6422e7003d29ba806f6ad7299c87e45241c0 100644 (file)
--- a/gdb/alpha-tdep.c
+++ b/gdb/alpha-tdep.c
@@ -359,6 +359,7 @@ heuristic_proc_desc(start_pc, limit_pc, next_frame)
     int frame_size;
     int has_frame_reg = 0;
     unsigned long reg_mask = 0;
+    int pcreg = -1;
 
     if (start_pc == 0)
       return NULL;
@@ -388,17 +389,68 @@ heuristic_proc_desc(start_pc, limit_pc, next_frame)
            int reg = (word & 0x03e00000) >> 21;
            reg_mask |= 1 << reg;
            temp_saved_regs.regs[reg] = sp + (short)word;
+
+           /* Starting with OSF/1-3.2C, the system libraries are shipped
+              without local symbols, but they still contain procedure
+              descriptors without a symbol reference. GDB is currently
+              unable to find these procedure descriptors and uses
+              heuristic_proc_desc instead.
+              As some low level compiler support routines (__div*, __add*)
+              use a non-standard return address register, we have to
+              add some heuristics to determine the return address register,
+              or stepping over these routines will fail.
+              Usually the return address register is the first register
+              saved on the stack, but assembler optimization might
+              rearrange the register saves.
+              So we recognize only a few registers (t7, t9, ra) within
+              the procedure prologue as valid return address registers.
+
+              FIXME: Rewriting GDB to access the procedure descriptors,
+              e.g. via the minimal symbol table, might obviate this hack.  */
+           if (pcreg == -1
+               && cur_pc < (start_pc + 20)
+               && (reg == T7_REGNUM || reg == T9_REGNUM || reg == RA_REGNUM))
+             pcreg = reg;
          }
        else if (word == 0x47de040f)                    /* bis sp,sp fp */
          has_frame_reg = 1;
       }
+    if (pcreg == -1)
+      {
+       /* If we haven't found a valid return address register yet,
+          keep searching in the procedure prologue.  */
+       while (cur_pc < (limit_pc + 20) && cur_pc < (start_pc + 20))
+         {
+           char buf[4];
+           unsigned long word;
+           int status;
+
+           status = read_memory_nobpt (cur_pc, buf, 4); 
+           if (status)
+             memory_error (status, cur_pc);
+           cur_pc += 4;
+           word = extract_unsigned_integer (buf, 4);
+
+           if ((word & 0xfc1f0000) == 0xb41e0000       /* stq reg,n($sp) */
+               && (word & 0xffff0000) != 0xb7fe0000)   /* reg != $zero */
+             {
+               int reg = (word & 0x03e00000) >> 21;
+               if (reg == T7_REGNUM || reg == T9_REGNUM || reg == RA_REGNUM)
+                 {
+                   pcreg = reg;
+                   break;
+                 }
+             }
+         }
+      }
+
     if (has_frame_reg)
       PROC_FRAME_REG(&temp_proc_desc) = GCC_FP_REGNUM;
     else
       PROC_FRAME_REG(&temp_proc_desc) = SP_REGNUM;
     PROC_FRAME_OFFSET(&temp_proc_desc) = frame_size;
     PROC_REG_MASK(&temp_proc_desc) = reg_mask;
-    PROC_PC_REG(&temp_proc_desc) = RA_REGNUM;
+    PROC_PC_REG(&temp_proc_desc) = (pcreg == -1) ? RA_REGNUM : pcreg;
     PROC_LOCALOFF(&temp_proc_desc) = 0;        /* XXX - bogus */
     return &temp_proc_desc;
 }