split dwarf2_fetch_cfa_info from dwarf2_compile_expr_to_ax

This removes dwarf2_compile_expr_to_ax, replacing it with a utility
function that fetches the CFA data and adding the code to actually
compile to an agent expression directly into
dwarf2_compile_expr_to_ax.  This refactoring lets a later patch reuse
the new dwarf2_fetch_cfa_info.

gdb/ChangeLog
2014-12-12  Tom Tromey  <tromey@redhat.com>

	* dwarf2loc.c (dwarf2_compile_expr_to_ax) <DW_OP_call_frame_cfa>:
	Update.
	* dwarf2-frame.c (dwarf2_fetch_cfa_info): New function, based on
	dwarf2_compile_cfa_to_ax.
	(dwarf2_compile_cfa_to_ax): Remove.
	* dwarf2-frame.h (dwarf2_fetch_cfa_info): Declare.
	(dwarf2_compile_cfa_to_ax): Remove.

4 files changed, 78 insertions, 33 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index df93995..ff001eb 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,13 @@
+2014-12-12  Tom Tromey  <tromey@redhat.com>
+
+	* dwarf2loc.c (dwarf2_compile_expr_to_ax) <DW_OP_call_frame_cfa>:
+	Update.
+	* dwarf2-frame.c (dwarf2_fetch_cfa_info): New function, based on
+	dwarf2_compile_cfa_to_ax.
+	(dwarf2_compile_cfa_to_ax): Remove.
+	* dwarf2-frame.h (dwarf2_fetch_cfa_info): Declare.
+	(dwarf2_compile_cfa_to_ax): Remove.
+
 2014-12-12  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* infcall.h (call_function_by_hand_dummy): Declare.
diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index 8747f4c..199ccea 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -882,11 +882,15 @@ dwarf2_frame_find_quirks (struct dwarf2_frame_state *fs,
 }
 
 
-void
-dwarf2_compile_cfa_to_ax (struct agent_expr *expr, struct axs_value *loc,
-			  struct gdbarch *gdbarch,
-			  CORE_ADDR pc,
-			  struct dwarf2_per_cu_data *data)
+/* See dwarf2-frame.h.  */
+
+int
+dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
+		       struct dwarf2_per_cu_data *data,
+		       int *regnum_out, LONGEST *offset_out,
+		       CORE_ADDR *text_offset_out,
+		       const gdb_byte **cfa_start_out,
+		       const gdb_byte **cfa_end_out)
 {
   struct dwarf2_fde *fde;
   CORE_ADDR text_offset;
@@ -932,26 +936,20 @@ dwarf2_compile_cfa_to_ax (struct agent_expr *expr, struct axs_value *loc,
 	if (regnum == -1)
 	  error (_("Unable to access DWARF register number %d"),
 		 (int) fs.regs.cfa_reg); /* FIXME */
-	ax_reg (expr, regnum);
 
-	if (fs.regs.cfa_offset != 0)
-	  {
-	    if (fs.armcc_cfa_offsets_reversed)
-	      ax_const_l (expr, -fs.regs.cfa_offset);
-	    else
-	      ax_const_l (expr, fs.regs.cfa_offset);
-	    ax_simple (expr, aop_add);
-	  }
+	*regnum_out = regnum;
+	if (fs.armcc_cfa_offsets_reversed)
+	  *offset_out = -fs.regs.cfa_offset;
+	else
+	  *offset_out = fs.regs.cfa_offset;
+	return 1;
       }
-      break;
 
     case CFA_EXP:
-      ax_const_l (expr, text_offset);
-      dwarf2_compile_expr_to_ax (expr, loc, gdbarch, addr_size,
-				 fs.regs.cfa_exp,
-				 fs.regs.cfa_exp + fs.regs.cfa_exp_len,
-				 data);
-      break;
+      *text_offset_out = text_offset;
+      *cfa_start_out = fs.regs.cfa_exp;
+      *cfa_end_out = fs.regs.cfa_exp + fs.regs.cfa_exp_len;
+      return 0;
 
     default:
       internal_error (__FILE__, __LINE__, _("Unknown CFA rule."));
diff --git a/gdb/dwarf2-frame.h b/gdb/dwarf2-frame.h
index 0470cac..5ccf0c8 100644
--- a/gdb/dwarf2-frame.h
+++ b/gdb/dwarf2-frame.h
@@ -120,15 +120,26 @@ extern const struct frame_base *
 
 CORE_ADDR dwarf2_frame_cfa (struct frame_info *this_frame);
 
-/* Update the agent expression EXPR with code to compute the CFA for a
-   frame at PC.  GDBARCH is the architecture of the function at PC.
-   This function may call dwarf2_compile_expr_to_ax; DATA is passed
-   through to that function if needed.  */
-
-extern void dwarf2_compile_cfa_to_ax (struct agent_expr *expr,
-				      struct axs_value *loc,
-				      struct gdbarch *gdbarch,
-				      CORE_ADDR pc,
-				      struct dwarf2_per_cu_data *data);
+/* Find the CFA information for PC.
+
+   Return 1 if a register is used for the CFA, or 0 if another
+   expression is used.  Throw an exception on error.
+
+   GDBARCH is the architecture to use.
+   DATA is the per-CU data.
+
+   REGNUM_OUT is an out parameter that is set to the register number.
+   OFFSET_OUT is the offset to use from this register.
+   These are only filled in when 1 is returned.
+
+   TEXT_OFFSET_OUT, CFA_START_OUT, and CFA_END_OUT describe the CFA
+   in other cases.  These are only used when 0 is returned.  */
+
+extern int dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
+				  struct dwarf2_per_cu_data *data,
+				  int *regnum_out, LONGEST *offset_out,
+				  CORE_ADDR *text_offset_out,
+				  const gdb_byte **cfa_start_out,
+				  const gdb_byte **cfa_end_out);
 
 #endif /* dwarf2-frame.h */
diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index fbaa7d3..bbe4568 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -3282,8 +3282,34 @@ dwarf2_compile_expr_to_ax (struct agent_expr *expr, struct axs_value *loc,
 	  break;
 
 	case DW_OP_call_frame_cfa:
-	  dwarf2_compile_cfa_to_ax (expr, loc, arch, expr->scope, per_cu);
-	  loc->kind = axs_lvalue_memory;
+	  {
+	    int regnum;
+	    CORE_ADDR text_offset;
+	    LONGEST off;
+	    const gdb_byte *cfa_start, *cfa_end;
+
+	    if (dwarf2_fetch_cfa_info (arch, expr->scope, per_cu,
+				       &regnum, &off,
+				       &text_offset, &cfa_start, &cfa_end))
+	      {
+		/* Register.  */
+		ax_reg (expr, regnum);
+		if (off != 0)
+		  {
+		    ax_const_l (expr, off);
+		    ax_simple (expr, aop_add);
+		  }
+	      }
+	    else
+	      {
+		/* Another expression.  */
+		ax_const_l (expr, text_offset);
+		dwarf2_compile_expr_to_ax (expr, loc, arch, addr_size,
+					   cfa_start, cfa_end, per_cu);
+	      }
+
+	    loc->kind = axs_lvalue_memory;
+	  }
 	  break;
 
 	case DW_OP_GNU_push_tls_address: