From: Vladimir N. Makarov <vmakarov@redhat.com>
Date: Thu, 20 Jul 2023 18:34:26 +0000 (-0400)
Subject: [LRA]: Exclude reloading of frame pointer in subreg for some cases
X-Git-Tag: basepoints/gcc-15~7456
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4b8878fbf7b74ea5c3405c9f558df0517036f131;p=thirdparty%2Fgcc.git

[LRA]: Exclude reloading of frame pointer in subreg for some cases

LRA for avr port reloads frame pointer in subreg although we can just
simplify the subreg.  It results in generation of bad performance code.  The following
patch fixes this.

gcc/ChangeLog:

	* lra-constraints.cc (simplify_operand_subreg): Check frame pointer
	simplification.
---

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 76a155e99c24..f3784cf5a5be 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -1797,6 +1797,16 @@ simplify_operand_subreg (int nop, machine_mode reg_mode)
       alter_subreg (curr_id->operand_loc[nop], false);
       return true;
     }
+  auto fp_subreg_can_be_simplified_after_reload_p = [] (machine_mode innermode,
+							poly_uint64 offset,
+							machine_mode mode) {
+    reload_completed = 1;
+    bool res = simplify_subreg_regno (FRAME_POINTER_REGNUM,
+				      innermode,
+				      offset, mode) >= 0;
+    reload_completed = 0;
+    return res;
+  };
   /* Force a reload of the SUBREG_REG if this is a constant or PLUS or
      if there may be a problem accessing OPERAND in the outer
      mode.  */
@@ -1809,6 +1819,12 @@ simplify_operand_subreg (int nop, machine_mode reg_mode)
 	   >= hard_regno_nregs (hard_regno, mode))
        && simplify_subreg_regno (hard_regno, innermode,
 				 SUBREG_BYTE (operand), mode) < 0
+       /* Exclude reloading of frame pointer in subreg if frame pointer can not
+	  be simplified here only because the reload is not finished yet.  */
+       && (hard_regno != FRAME_POINTER_REGNUM
+	   || !fp_subreg_can_be_simplified_after_reload_p (innermode,
+							   SUBREG_BYTE (operand),
+							   mode))
        /* Don't reload subreg for matching reload.  It is actually
 	  valid subreg in LRA.  */
        && ! LRA_SUBREG_P (operand))