[PATCH] [ARC] Restore blink first when optimizing for speed.

[Claudiu Zissulescu]

Hi,

When not optimizing for size, we can restore first blink, hence the return
instruction will be executed faster.

OK to apply?
Claudiu

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claz...@synopsys.com>

        * config/arc/arc.c (GMASK_LEN): Define.
        (arc_restore_callee_saves): Restore first blink when
        !optimize_size.
---
 gcc/config/arc/arc.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
index de2c8d5df9c..9a6920a709f 100644
--- a/gcc/config/arc/arc.c
+++ b/gcc/config/arc/arc.c
@@ -2545,6 +2545,9 @@ struct GTY (()) arc_frame_info
   bool save_return_addr;
 };
 
+/* GMASK bit length -1.  */
+#define GMASK_LEN 31
+
 /* Defining data structures for per-function information.  */
 
 typedef struct GTY (()) machine_function
@@ -3087,6 +3090,8 @@ arc_restore_callee_saves (unsigned int gmask,
 {
   rtx reg;
   int frame_deallocated = 0;
+  HOST_WIDE_INT offs = cfun->machine->frame_info.reg_size;
+  bool early_blink_restore;
 
   /* Emit mov fp,sp.  */
   if (arc_frame_pointer_needed () && offset)
@@ -3112,9 +3117,21 @@ arc_restore_callee_saves (unsigned int gmask,
       offset = 0;
     }
 
+  /* When we do not optimize for size, restore first blink.  */
+  early_blink_restore = restore_blink && !optimize_size && offs;
+  if (early_blink_restore)
+    {
+      rtx addr = plus_constant (Pmode, stack_pointer_rtx, offs);
+      reg = gen_rtx_REG (Pmode, RETURN_ADDR_REGNUM);
+      rtx insn = frame_move_inc (reg, gen_frame_mem (Pmode, addr),
+                                stack_pointer_rtx, NULL_RTX);
+      add_reg_note (insn, REG_CFA_RESTORE, reg);
+      restore_blink = false;
+    }
+
   /* N.B. FRAME_POINTER_MASK and RETURN_ADDR_MASK are cleared in gmask.  */
   if (gmask)
-    for (int i = 0; i <= 31; i++)
+    for (int i = 0; i <= GMASK_LEN; i++)
       {
        machine_mode restore_mode = SImode;
 
@@ -3127,7 +3144,23 @@ arc_restore_callee_saves (unsigned int gmask,
          continue;
 
        reg = gen_rtx_REG (restore_mode, i);
-       frame_deallocated += frame_restore_reg (reg, 0);
+       offs = 0;
+       switch (restore_mode)
+         {
+         case E_DImode:
+           if ((GMASK_LEN - __builtin_clz (gmask)) == (i + 1)
+               && early_blink_restore)
+             offs = 4;
+           break;
+         case E_SImode:
+           if ((GMASK_LEN - __builtin_clz (gmask)) == i
+               && early_blink_restore)
+             offs = 4;
+           break;
+         default:
+           offs = 0;
+         }
+       frame_deallocated += frame_restore_reg (reg, offs);
        offset = 0;
 
        if (restore_mode == DImode)
-- 
2.20.1