arc64: gdb: Fix an order of registers for ENTER

ENTER in ARCv3 stores different registers and in a different
order rather than ARCv2's variant:

    1. R14-R27 instead of R13-R26.
    2. FP is stored last.

Stack unwinder relies on that information while handling ENTER.
Note that this patch does not add support of floating point
registers for ENTER.

Signed-off-by: Yuriy Kolerov <kolerov93@gmail.com>

Author: kolerov

gdb/arc64-tdep.c

@@ -1189,15 +1189,15 @@ arc_is_in_prologue (struct gdbarch *gdbarch, const struct arc_instruction &insn,
 	 registers according to given arguments thus greatly reducing code
 	 size.  Which registers will be actually saved depends on arguments.
 
-	 ENTER_S {R13-...,FP,BLINK} stores registers in following order:
+	 ENTER_S {R14-...,FP,BLINK} stores registers in following order:
 
 	 new SP ->
+		   FP
 		   BLINK
-		   R13
 		   R14
 		   R15
+		   R16
 		   ...
-		   FP
 	 old SP ->
 
 	 There are up to three arguments for this opcode, as presented by ARC
@@ -1239,14 +1239,8 @@ arc_is_in_prologue (struct gdbarch *gdbarch, const struct arc_instruction &insn,
       /* Current store address.  */
       pv_t addr = regs[ARC_SP_REGNUM];
 
-      if (is_fp_saved)
-	{
-	  addr = pv_add_constant (addr, -reg_size);
-	  stack->store (addr, reg_size, regs[ARC_FP_REGNUM]);
-	}
-
-      /* Registers are stored in backward order: from GP (R26) to R13.  */
-      for (int i = ARC_R13_REGNUM + regs_saved - 1; i >= ARC_R13_REGNUM; i--)
+      /* Registers are stored in backward order: from GP (R27) to R14.  */
+      for (int i = ARC_R14_REGNUM + regs_saved - 1; i >= ARC_R14_REGNUM; i--)
 	{
 	  addr = pv_add_constant (addr, -reg_size);
 	  stack->store (addr, reg_size, regs[i]);
@@ -1259,6 +1253,12 @@ arc_is_in_prologue (struct gdbarch *gdbarch, const struct arc_instruction &insn,
 			regs[ARC_BLINK_REGNUM]);
 	}
 
+      if (is_fp_saved)
+	{
+	  addr = pv_add_constant (addr, -reg_size);
+	  stack->store (addr, reg_size, regs[ARC_FP_REGNUM]);
+	}
+
       gdb_assert (pv_is_identical (addr, new_sp));
 
       regs[ARC_SP_REGNUM] = new_sp;

gdb/arc64-tdep.h

@@ -40,11 +40,10 @@ enum arc_regnum
   ARC_R4_REGNUM = 4,
   ARC_R7_REGNUM = 7,
   ARC_R9_REGNUM = 9,
-  ARC_R13_REGNUM = 13,
+  ARC_R14_REGNUM = 14,
   ARC_R16_REGNUM = 16,
-  ARC_R26_REGNUM = 26,
   /* Frame pointer.  */
-  ARC_FP_REGNUM,
+  ARC_FP_REGNUM = 27,
   /* Stack pointer.  */
   ARC_SP_REGNUM,
   /* Return address from interrupt.  */
@@ -92,8 +91,8 @@ enum arc_regnum
   /* Additional ABI constants.  */
   ARC_FIRST_ARG_REGNUM = ARC_R0_REGNUM,
   ARC_LAST_ARG_REGNUM = ARC_R7_REGNUM,
-  ARC_FIRST_CALLEE_SAVED_REGNUM = ARC_R13_REGNUM,
-  ARC_LAST_CALLEE_SAVED_REGNUM = ARC_R26_REGNUM
+  ARC_FIRST_CALLEE_SAVED_REGNUM = ARC_R14_REGNUM,
+  ARC_LAST_CALLEE_SAVED_REGNUM = ARC_FP_REGNUM
 };
 
 /* arc64 DWARF register numbers.  */