From fe1486e118d72d660284af43cb739e20d094b585 Mon Sep 17 00:00:00 2001
From: Denis Chertykov <chertykov@gmail.com>
Date: Fri, 15 Nov 2024 00:50:36 +0400
Subject: [PATCH] The fix for PR117191

Wrong code appears after dse2 pass because it removes necessary insns.
(ie insn 554 - store to frame spill slot)
This happened because LRA pass doesn't cleanup the code exactly like reload does.
The reload1.c has a special pass for such cleanup.
The reload removes CLOBBER insns with spill slots like this:
(insn 202 184 186 7 (clobber (mem/c:TI (plus:HI (reg/f:HI 28 r28)
                (const_int 1 [0x1])) [3 %sfp+1 S16 A8])) -1
     (nil))

Fragment from reload1.c:
--------------------------------------------------------------------------------
  reload_completed = 1;

  /* Make a pass over all the insns and delete all USEs which we inserted
     only to tag a REG_EQUAL note on them.  Remove all REG_DEAD and REG_UNUSED
     notes.  Delete all CLOBBER insns, except those that refer to the return
     value and the special mem:BLK CLOBBERs added to prevent the scheduler
     from misarranging variable-array code, and simplify (subreg (reg))
     operands.  Strip and regenerate REG_INC notes that may have been moved
     around.  */

  for (insn = first; insn; insn = NEXT_INSN (insn))
    if (INSN_P (insn))
      {
	rtx *pnote;

	if (CALL_P (insn))
	  replace_pseudos_in (& CALL_INSN_FUNCTION_USAGE (insn),
			      VOIDmode, CALL_INSN_FUNCTION_USAGE (insn));

	if ((GET_CODE (PATTERN (insn)) == USE
	     /* We mark with QImode USEs introduced by reload itself.  */
	     && (GET_MODE (insn) == QImode
		 || find_reg_note (insn, REG_EQUAL, NULL_RTX)))
	    || (GET_CODE (PATTERN (insn)) == CLOBBER
		&& (!MEM_P (XEXP (PATTERN (insn), 0))
		    || GET_MODE (XEXP (PATTERN (insn), 0)) != BLKmode
		    || (GET_CODE (XEXP (XEXP (PATTERN (insn), 0), 0)) != SCRATCH
			&& XEXP (XEXP (PATTERN (insn), 0), 0)
				!= stack_pointer_rtx))
		&& (!REG_P (XEXP (PATTERN (insn), 0))
		    || ! REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0)))))
	  {
	    delete_insn (insn);
	    continue;
	  }
--------------------------------------------------------------------------------

LRA have a similar place where it removes unnecessary insns, but not CLOBBER insns with
memory spill slots. It's `lra_final_code_change' function.

I just mark a CLOBBER insn with pseudo spilled to memory for removing it later together
with LRA temporary CLOBBER insns.

	PR rtl-optimization/117191
gcc/
	* lra-spills.cc (spill_pseudos): Mark a CLOBBER insn with pseudo
	spilled to memory for removing it later together with LRA temporary
	CLOBBER insns.
---
 gcc/lra-spills.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/lra-spills.cc b/gcc/lra-spills.cc
index c149c3388cd..3f5c8d2bcb0 100644
--- a/gcc/lra-spills.cc
+++ b/gcc/lra-spills.cc
@@ -537,6 +537,11 @@ spill_pseudos (void)
 		      break;
 		    }
 		}
+	      if (GET_CODE (PATTERN (insn)) == CLOBBER)
+		/* This is a CLOBBER insn with pseudo spilled to memory.
+		   Mark it for removing it later together with LRA temporary
+		   CLOBBER insns.  */
+		LRA_TEMP_CLOBBER_P (PATTERN (insn)) = 1;
 	      if (lra_dump_file != NULL)
 		fprintf (lra_dump_file,
 			 "Changing spilled pseudos to memory in insn #%u\n",