commit 36de0173c17efcc30c56ef10304377e71313e8bc
Author: Jiong Wang <jiong.wang@arm.com>
Date:   Wed Oct 19 15:42:04 2016 +0100

    dwarf val expression

diff --git a/gcc/dwarf2cfi.c b/gcc/dwarf2cfi.c
index 6491d5a..b8c88fb 100644
--- a/gcc/dwarf2cfi.c
+++ b/gcc/dwarf2cfi.c
@@ -1235,7 +1235,7 @@ dwarf2out_frame_debug_cfa_register (rtx set)
   reg_save (sregno, dregno, 0);
 }
 
-/* A subroutine of dwarf2out_frame_debug, process a REG_CFA_EXPRESSION note. */
+/* A subroutine of dwarf2out_frame_debug, process a REG_CFA_EXPRESSION note.  */
 
 static void
 dwarf2out_frame_debug_cfa_expression (rtx set)
@@ -1267,6 +1267,29 @@ dwarf2out_frame_debug_cfa_expression (rtx set)
   update_row_reg_save (cur_row, regno, cfi);
 }
 
+/* A subroutine of dwarf2out_frame_debug, process a REG_CFA_VAL_EXPRESSION
+   note.  */
+
+static void
+dwarf2out_frame_debug_cfa_val_expression (rtx set)
+{
+  rtx dest = SET_DEST (set);
+  gcc_assert (REG_P (dest));
+
+  rtx span = targetm.dwarf_register_span (dest);
+  gcc_assert (!span);
+
+  rtx src = SET_SRC (set);
+  dw_cfi_ref cfi = new_cfi ();
+  cfi->dw_cfi_opc = DW_CFA_val_expression;
+  cfi->dw_cfi_oprnd1.dw_cfi_reg_num = dwf_regno (dest);
+  cfi->dw_cfi_oprnd2.dw_cfi_loc
+    = mem_loc_descriptor (src, GET_MODE (src),
+			  GET_MODE (dest), VAR_INIT_STATUS_INITIALIZED);
+  add_cfi (cfi);
+  update_row_reg_save (cur_row, dwf_regno (dest), cfi);
+}
+
 /* A subroutine of dwarf2out_frame_debug, process a REG_CFA_RESTORE note.  */
 
 static void
@@ -2033,10 +2056,16 @@ dwarf2out_frame_debug (rtx_insn *insn)
 	break;
 
       case REG_CFA_EXPRESSION:
+      case REG_CFA_VAL_EXPRESSION:
 	n = XEXP (note, 0);
 	if (n == NULL)
 	  n = single_set (insn);
-	dwarf2out_frame_debug_cfa_expression (n);
+
+	if (REG_NOTE_KIND (note) == REG_CFA_EXPRESSION)
+	  dwarf2out_frame_debug_cfa_expression (n);
+	else
+	  dwarf2out_frame_debug_cfa_val_expression (n);
+
 	handled_one = true;
 	break;
 
@@ -3015,7 +3044,8 @@ output_cfa_loc (dw_cfi_ref cfi, int for_eh)
   dw_loc_descr_ref loc;
   unsigned long size;
 
-  if (cfi->dw_cfi_opc == DW_CFA_expression)
+  if (cfi->dw_cfi_opc == DW_CFA_expression
+      || cfi->dw_cfi_opc == DW_CFA_val_expression)
     {
       unsigned r =
 	DWARF2_FRAME_REG_OUT (cfi->dw_cfi_oprnd1.dw_cfi_reg_num, for_eh);
@@ -3041,7 +3071,8 @@ output_cfa_loc_raw (dw_cfi_ref cfi)
   dw_loc_descr_ref loc;
   unsigned long size;
 
-  if (cfi->dw_cfi_opc == DW_CFA_expression)
+  if (cfi->dw_cfi_opc == DW_CFA_expression
+      || cfi->dw_cfi_opc == DW_CFA_val_expression)
     {
       unsigned r =
 	DWARF2_FRAME_REG_OUT (cfi->dw_cfi_oprnd1.dw_cfi_reg_num, 1);
@@ -3188,6 +3219,7 @@ output_cfi (dw_cfi_ref cfi, dw_fde_ref fde, int for_eh)
 
 	case DW_CFA_def_cfa_expression:
 	case DW_CFA_expression:
+	case DW_CFA_val_expression:
 	  output_cfa_loc (cfi, for_eh);
 	  break;
 
@@ -3302,16 +3334,13 @@ output_cfi_directive (FILE *f, dw_cfi_ref cfi)
       break;
 
     case DW_CFA_def_cfa_expression:
-      if (f != asm_out_file)
-	{
-	  fprintf (f, "\t.cfi_def_cfa_expression ...\n");
-	  break;
-	}
-      /* FALLTHRU */
     case DW_CFA_expression:
+    case DW_CFA_val_expression:
       if (f != asm_out_file)
 	{
-	  fprintf (f, "\t.cfi_cfa_expression ...\n");
+	  fprintf (f, "\t.cfi_%scfa_%sexpression ...\n",
+		   cfi->dw_cfi_opc == DW_CFA_def_cfa_expression ? "def_" : "",
+		   cfi->dw_cfi_opc == DW_CFA_val_expression ? "val_" : "");
 	  break;
 	}
       fprintf (f, "\t.cfi_escape %#x,", cfi->dw_cfi_opc);
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 4a3df33..4a5c602 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -518,6 +518,7 @@ dw_cfi_oprnd1_desc (enum dwarf_call_frame_info cfi)
     case DW_CFA_def_cfa_register:
     case DW_CFA_register:
     case DW_CFA_expression:
+    case DW_CFA_val_expression:
       return dw_cfi_oprnd_reg_num;
 
     case DW_CFA_def_cfa_offset:
@@ -551,6 +552,7 @@ dw_cfi_oprnd2_desc (enum dwarf_call_frame_info cfi)
       return dw_cfi_oprnd_reg_num;
 
     case DW_CFA_expression:
+    case DW_CFA_val_expression:
       return dw_cfi_oprnd_loc;
 
     default:
@@ -14236,6 +14238,46 @@ mem_loc_descriptor (rtx rtl, machine_mode mode,
       resolve_one_addr (&rtl);
       goto symref;
 
+    /* RTL sequences inside PARALLEL record a series of DWARF operations for
+       the expression.  An UNSPEC rtx represents a raw DWARF operation,
+       new_loc_descr is called for it to build the operation directly.
+       Otherwise mem_loc_descriptor is called recursively.  */
+    case PARALLEL:
+      {
+	int index = 0;
+	dw_loc_descr_ref exp_result = NULL;
+
+	for (; index < XVECLEN (rtl, 0); index++)
+	  {
+	    rtx elem = XVECEXP (rtl, 0, index);
+	    if (GET_CODE (elem) == UNSPEC)
+	      {
+		/* Each DWARF operation UNSPEC contain two operands, if
+		   one operand is not used for the operation, const0_rtx is
+		   passed.  */
+		gcc_assert (XVECLEN (elem, 0) == 2);
+
+		HOST_WIDE_INT dw_op = XINT (elem, 1);
+		HOST_WIDE_INT oprnd1 = INTVAL (XVECEXP (elem, 0, 0));
+		HOST_WIDE_INT oprnd2 = INTVAL (XVECEXP (elem, 0, 1));
+		exp_result
+		  = new_loc_descr ((enum dwarf_location_atom) dw_op, oprnd1,
+				   oprnd2);
+	      }
+	    else
+	      exp_result
+		= mem_loc_descriptor (elem, mode, mem_mode,
+				      VAR_INIT_STATUS_INITIALIZED);
+
+	    if (!mem_loc_result)
+	      mem_loc_result = exp_result;
+	    else
+	      add_loc_descr (&mem_loc_result, exp_result);
+	  }
+
+	break;
+      }
+
     default:
       if (flag_checking)
 	{
diff --git a/gcc/reg-notes.def b/gcc/reg-notes.def
index 5374169..962dbb8 100644
--- a/gcc/reg-notes.def
+++ b/gcc/reg-notes.def
@@ -149,6 +149,11 @@ REG_NOTE (CFA_REGISTER)
    store of a register to an arbitrary (non-validated) memory address.  */
 REG_NOTE (CFA_EXPRESSION)
 
+/* Attached to insns that are RTX_FRAME_RELATED_P, but are too complex
+   for FRAME_RELATED_EXPR intuition.  The DWARF expression computes the value of
+   the given register.  */
+REG_NOTE (CFA_VAL_EXPRESSION)
+
 /* Attached to insns that are RTX_FRAME_RELATED_P, with the information
    that this is a restore operation, i.e. will result in DW_CFA_restore
    or the like.  Either the attached rtx, or the destination of the insn's
