i386: Use const reference of struct ix86_frame to avoid copy

We can use const reference of struct ix86_frame to avoid making a local
copy of ix86_frame.  ix86_expand_epilogue makes a local copy of struct
ix86_frame and uses the reg_save_offset field as a local variable.  This
patch uses a separate local variable for reg_save_offset.

Tested on x86-64 with ada.

	PR target/83905
	* config/i386/i386.c (ix86_expand_prologue): Use cost reference
	of struct ix86_frame.
	(ix86_expand_epilogue): Likewise.  Add a local variable for
	the reg_save_offset field in struct ix86_frame.

From-SVN: r256996

gcc/ChangeLog

+2018-01-23  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/83905
+	* config/i386/i386.c (ix86_expand_prologue): Use cost reference
+	of struct ix86_frame.
+	(ix86_expand_epilogue): Likewise.  Add a local variable for
+	the reg_save_offset field in struct ix86_frame.
+
 2018-01-23  Bin Cheng  <bin.cheng@arm.com>
 
 	PR tree-optimization/82604

gcc/config/i386/i386.c

@@ -13376,7 +13376,6 @@ ix86_expand_prologue (void)
 {
   struct machine_function *m = cfun->machine;
   rtx insn, t;
-  struct ix86_frame frame;
   HOST_WIDE_INT allocate;
   bool int_registers_saved;
   bool sse_registers_saved;
@@ -13404,7 +13403,7 @@ ix86_expand_prologue (void)
   m->fs.sp_valid = true;
   m->fs.sp_realigned = false;
 
-  frame = m->frame;
+  const struct ix86_frame &frame = cfun->machine->frame;
 
   if (!TARGET_64BIT && ix86_function_ms_hook_prologue (current_function_decl))
     {
@@ -14282,7 +14281,6 @@ ix86_expand_epilogue (int style)
 {
   struct machine_function *m = cfun->machine;
   struct machine_frame_state frame_state_save = m->fs;
-  struct ix86_frame frame;
   bool restore_regs_via_mov;
   bool using_drap;
   bool restore_stub_is_tail = false;
@@ -14295,7 +14293,7 @@ ix86_expand_epilogue (int style)
     }
 
   ix86_finalize_stack_frame_flags ();
-  frame = m->frame;
+  const struct ix86_frame &frame = cfun->machine->frame;
 
   m->fs.sp_realigned = stack_realign_fp;
   m->fs.sp_valid = stack_realign_fp
@@ -14339,11 +14337,13 @@ ix86_expand_epilogue (int style)
 				  + UNITS_PER_WORD);
     }
 
+  HOST_WIDE_INT reg_save_offset = frame.reg_save_offset;
+
   /* Special care must be taken for the normal return case of a function
      using eh_return: the eax and edx registers are marked as saved, but
      not restored along this path.  Adjust the save location to match.  */
   if (crtl->calls_eh_return && style != 2)
-    frame.reg_save_offset -= 2 * UNITS_PER_WORD;
+    reg_save_offset -= 2 * UNITS_PER_WORD;
 
   /* EH_RETURN requires the use of moves to function properly.  */
   if (crtl->calls_eh_return)
@@ -14359,11 +14359,11 @@ ix86_expand_epilogue (int style)
   else if (TARGET_EPILOGUE_USING_MOVE
 	   && cfun->machine->use_fast_prologue_epilogue
 	   && (frame.nregs > 1
-	       || m->fs.sp_offset != frame.reg_save_offset))
+	       || m->fs.sp_offset != reg_save_offset))
     restore_regs_via_mov = true;
   else if (frame_pointer_needed
 	   && !frame.nregs
-	   && m->fs.sp_offset != frame.reg_save_offset)
+	   && m->fs.sp_offset != reg_save_offset)
     restore_regs_via_mov = true;
   else if (frame_pointer_needed
 	   && TARGET_USE_LEAVE
@@ -14431,7 +14431,7 @@ ix86_expand_epilogue (int style)
       rtx t;
 
       if (frame.nregs)
-	ix86_emit_restore_regs_using_mov (frame.reg_save_offset, style == 2);
+	ix86_emit_restore_regs_using_mov (reg_save_offset, style == 2);
 
       /* eh_return epilogues need %ecx added to the stack pointer.  */
       if (style == 2)
@@ -14526,19 +14526,19 @@ ix86_expand_epilogue (int style)
 	 in epilogues.  */
       if (!m->fs.sp_valid || m->fs.sp_realigned
  	  || (TARGET_SEH
-	      && (m->fs.sp_offset - frame.reg_save_offset
+	      && (m->fs.sp_offset - reg_save_offset
 		  >= SEH_MAX_FRAME_SIZE)))
 	{
 	  pro_epilogue_adjust_stack (stack_pointer_rtx, hard_frame_pointer_rtx,
 				     GEN_INT (m->fs.fp_offset
-					      - frame.reg_save_offset),
+					      - reg_save_offset),
 				     style, false);
 	}
-      else if (m->fs.sp_offset != frame.reg_save_offset)
+      else if (m->fs.sp_offset != reg_save_offset)
 	{
 	  pro_epilogue_adjust_stack (stack_pointer_rtx, stack_pointer_rtx,
 				     GEN_INT (m->fs.sp_offset
-					      - frame.reg_save_offset),
+					      - reg_save_offset),
 				     style,
 				     m->fs.cfa_reg == stack_pointer_rtx);
 	}