[gcc r13-5333] xtensa: Revise complex hard register clobber elimination

[gcc r13-5333] xtensa: Revise complex hard register clobber elimination

[Max Filippov]

https://gcc.gnu.org/g:1c407dc088231ba5f2cc63d9278f4b797db48de1

commit r13-5333-g1c407dc088231ba5f2cc63d9278f4b797db48de1
Author: Takayuki 'January June' Suwa <jjsuwa_sys3175@yahoo.co.jp>
Date:   Fri Jan 20 12:33:37 2023 +0900

    xtensa: Revise complex hard register clobber elimination
    
    In the previously posted patch
    "xtensa: Make complex hard register clobber elimination more robust and accurate",
    the check code for insns that refer to the [DS]Cmode hard register before
    it is overwritten after it is clobbered is incomplete.  Fortunately such
    insns are seldom emitted, so it didn't matter.
    
    This patch fixes that for the sake of completeness.
    
    gcc/ChangeLog:
    
            * config/xtensa/xtensa.md:
            Fix exit from loops detecting references before overwriting in the
            split pattern.

Diff:
---
 gcc/config/xtensa/xtensa.md | 72 +++++++++++++++++++++++----------------------
 1 file changed, 37 insertions(+), 35 deletions(-)

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index dd3fc37353b..d3996b26cb5 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -2973,45 +2973,47 @@
 {
   auto_sbitmap bmp (FIRST_PSEUDO_REGISTER);
   rtx_insn *insn;
-  rtx reg = gen_rtx_REG (SImode, 0);
+  rtx reg = gen_rtx_REG (SImode, 0), dest;
+  unsigned int regno;
+  sbitmap_iterator iter;
   bitmap_set_range (bmp, REGNO (operands[0]), REG_NREGS (operands[0]));
   for (insn = next_nonnote_nondebug_insn_bb (curr_insn);
        insn; insn = next_nonnote_nondebug_insn_bb (insn))
-    {
-      sbitmap_iterator iter;
-      unsigned int regno;
-      if (NONJUMP_INSN_P (insn))
-	{
-	  EXECUTE_IF_SET_IN_BITMAP (bmp, 2, regno, iter)
-	    {
-	      set_regno_raw (reg, regno, REG_NREGS (reg));
-	      if (reg_overlap_mentioned_p (reg, PATTERN (insn)))
-		break;
-	    }
-	  if (GET_CODE (PATTERN (insn)) == SET)
-	    {
-	      rtx x = SET_DEST (PATTERN (insn));
-	      if (REG_P (x) && HARD_REGISTER_P (x))
-		bitmap_clear_range (bmp, REGNO (x), REG_NREGS (x));
-	      else if (SUBREG_P (x) && HARD_REGISTER_P (SUBREG_REG (x)))
-		{
-		  struct subreg_info info;
-		  subreg_get_info (regno = REGNO (SUBREG_REG (x)),
-				   GET_MODE (SUBREG_REG (x)),
-				   SUBREG_BYTE (x), GET_MODE (x), &info);
-		  if (!info.representable_p)
-		    break;
-		  bitmap_clear_range (bmp, regno + info.offset, info.nregs);
-		}
-	    }
-	  if (bitmap_empty_p (bmp))
-	    goto FALLTHRU;
-	}
-      else if (CALL_P (insn))
+    if (NONJUMP_INSN_P (insn))
+      {
 	EXECUTE_IF_SET_IN_BITMAP (bmp, 2, regno, iter)
-	 if (call_used_or_fixed_reg_p (regno))
-	   break;
-    }
+	  {
+	    set_regno_raw (reg, regno, REG_NREGS (reg));
+	    if (reg_referenced_p (reg, PATTERN (insn)))
+	      goto ABORT;
+	  }
+	if (GET_CODE (PATTERN (insn)) == SET
+	    || GET_CODE (PATTERN (insn)) == CLOBBER)
+	  {
+	    dest = SET_DEST (PATTERN (insn));
+	    if (REG_P (dest) && HARD_REGISTER_P (dest))
+	      bitmap_clear_range (bmp, REGNO (dest), REG_NREGS (dest));
+	    else if (SUBREG_P (dest)
+		     && HARD_REGISTER_P (SUBREG_REG (dest)))
+	      {
+		struct subreg_info info;
+		subreg_get_info (regno = REGNO (SUBREG_REG (dest)),
+				 GET_MODE (SUBREG_REG (dest)),
+				 SUBREG_BYTE (dest), GET_MODE (dest),
+				 &info);
+		if (!info.representable_p)
+		  break;
+		bitmap_clear_range (bmp, regno + info.offset, info.nregs);
+	      }
+	  }
+	if (bitmap_empty_p (bmp))
+	  goto FALLTHRU;
+      }
+    else if (CALL_P (insn))
+      EXECUTE_IF_SET_IN_BITMAP (bmp, 2, regno, iter)
+	if (call_used_or_fixed_reg_p (regno))
+	  goto ABORT;
+ABORT:
   FAIL;
 FALLTHRU:;
 })