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cfgrtl: Fix MEM_EXPR update in duplicate_insn_chain [PR114924]

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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.

(cherry picked from commit fe40d525619eee9c2821126390df75068df4773a)
This commit is contained in:
Alex Coplan 2024-05-03 09:23:59 +01:00
parent fa7e05d90b
commit 242fbc0df6
1 changed files with 2 additions and 1 deletions
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3
gcc/cfgrtl.cc
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@ -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);
}
}
}