From: Alex Coplan <alex.coplan@arm.com>
Date: Fri, 3 May 2024 08:23:59 +0000 (+0100)
Subject: cfgrtl: Fix MEM_EXPR update in duplicate_insn_chain [PR114924]
X-Git-Tag: basepoints/gcc-16~9427
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe40d525619eee9c2821126390df75068df4773a;p=thirdparty%2Fgcc.git

cfgrtl: Fix MEM_EXPR update in duplicate_insn_chain [PR114924]

The PR shows that when cfgrtl.cc:duplicate_insn_chain attempts to
update the MR_DEPENDENCE_CLIQUE information for a MEM_EXPR we can end up
accidentally dropping (e.g.) an ARRAY_REF from the MEM_EXPR and end up
replacing it with the underlying MEM_REF.  This leads to an
inconsistency in the MEM_EXPR information, and could lead to wrong code.

While the walk down to the MEM_REF is necessary to update
MR_DEPENDENCE_CLIQUE, we should use the outer tree expression for the
MEM_EXPR.  This patch does that.

gcc/ChangeLog:

	PR rtl-optimization/114924
	* cfgrtl.cc (duplicate_insn_chain): When updating MEM_EXPRs,
	don't strip (e.g.) ARRAY_REFs from the final MEM_EXPR.
---

diff --git a/gcc/cfgrtl.cc b/gcc/cfgrtl.cc
index 304c429c99b..a5dc3512159 100644
--- a/gcc/cfgrtl.cc
+++ b/gcc/cfgrtl.cc
@@ -4432,12 +4432,13 @@ duplicate_insn_chain (rtx_insn *from, rtx_insn *to,
 			   since MEM_EXPR is shared so make a copy and
 			   walk to the subtree again.  */
 			tree new_expr = unshare_expr (MEM_EXPR (*iter));
+			tree orig_new_expr = new_expr;
 			if (TREE_CODE (new_expr) == WITH_SIZE_EXPR)
 			  new_expr = TREE_OPERAND (new_expr, 0);
 			while (handled_component_p (new_expr))
 			  new_expr = TREE_OPERAND (new_expr, 0);
 			MR_DEPENDENCE_CLIQUE (new_expr) = newc;
-			set_mem_expr (const_cast <rtx> (*iter), new_expr);
+			set_mem_expr (const_cast <rtx> (*iter), orig_new_expr);
 		      }
 		  }
 	    }