File gcc7-lra-elim.patch of Package cross-avr-gcc7-bootstrap.30294

From 9cd11fd48509234e18122036bf504981f5a91b9a Mon Sep 17 00:00:00 2001
From: Richard Sandiford <richard.sandiford@arm.com>
Date: Thu, 31 Aug 2023 11:59:56 +0100
Subject: [PATCH] lra: Avoid unfolded plus-0
To: gcc-patches@gcc.gnu.org

While backporting another patch to an earlier release, I hit a
situation in which lra_eliminate_regs_1 would eliminate an address to:

    (plus (reg:P R) (const_int 0))

This address compared not-equal to plain:

    (reg:P R)

which caused an ICE in a later peephole2.  (The ICE showed up in
gfortran.fortran-torture/compile/pr80464.f90 on the branch but seems
to be latent on trunk.)

These unfolded PLUSes shouldn't occur in the insn stream, and later code
in the same function tried to avoid them.

gcc/
	* lra-eliminations.cc (lra_eliminate_regs_1): Use simplify_gen_binary
	rather than gen_rtx_PLUS.
---
 gcc/lra-eliminations.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/lra-eliminations.c b/gcc/lra-eliminations.c
index 993da861cf9..a3daf443caf 100644
--- a/gcc/lra-eliminations.c
+++ b/gcc/lra-eliminations.c
@@ -391,8 +391,8 @@ lra_eliminate_regs_1 (rtx_insn *insn, rtx x, machine_mode mem_mode,
 	      rtx to = subst_p ? ep->to_rtx : ep->from_rtx;
 
 	      if (! update_p && ! full_p)
-		return gen_rtx_PLUS (Pmode, to, XEXP (x, 1));
-	      
+		return simplify_gen_binary (PLUS, Pmode, to, XEXP (x, 1));
+
 	      if (update_sp_offset != 0)
 		offset = ep->to_rtx == stack_pointer_rtx ? update_sp_offset : 0;
 	      else
-- 
2.35.3