diff --git a/util/ego/cs/cs_profit.c b/util/ego/cs/cs_profit.c
index 50cb708fd..8845aaa29 100644
--- a/util/ego/cs/cs_profit.c
+++ b/util/ego/cs/cs_profit.c
@@ -111,6 +111,21 @@ void cs_machinit(void *vp)
 	choose_cset(f, &forbidden, sp_lmnem);
 }
 
+bool may_become_aar(avail_p avp)
+{
+	/* Check whether it is desirable to treat a LAR or SAR as an
+	 * AAR LOI/STI. This depends on the size of the array-elements.
+	 */
+	offset sz;
+
+	sz = array_elemsize(avp->av_othird);
+	if (sz == UNKNOWN_SIZE)
+		return FALSE;
+	if (time_space_ratio < 50)
+		return sz <= AR_limit;
+	return TRUE;
+}
+
 STATIC bool sli_no_eliminate(line_p lnp)
 {
 	/* Return whether the SLI-instruction in lnp is part of
@@ -157,8 +172,10 @@ STATIC bool gains(avail_p avp)
 
 STATIC bool okay_lines(avail_p avp, occur_p ocp)
 {
+	/* Check whether all lines in this occurrence can in
+	 * principle be eliminated; no stores, messages, calls etc.
+	 */
 	register line_p lnp, next;
-	offset sz;
 
 	for (lnp = ocp->oc_lfirst; lnp != (line_p) 0; lnp = next) {
 		next = lnp != ocp->oc_llast ? lnp->l_next : (line_p) 0;
@@ -171,18 +188,6 @@ STATIC bool okay_lines(avail_p avp, occur_p ocp)
 				return FALSE;
 		}
 	}
-	/* All lines in this occurrence can in principle be eliminated;
-	 * no stores, messages, calls etc.
-	 * We now check whether it is desirable to treat a LAR or a SAR
-	 * as an AAR LOI/STI. This depends on the size of the array-elements.
-	 */
-	if (INSTR(ocp->oc_llast) == op_lar || INSTR(ocp->oc_llast) == op_sar) {
-		sz = array_elemsize(avp->av_othird);
-		if (sz == UNKNOWN_SIZE) return FALSE;
-		if (avp->av_instr == (byte) op_aar && time_space_ratio < 50) {
-			return sz <= AR_limit;
-		}
-	}
 	return TRUE;
 }
 
diff --git a/util/ego/cs/cs_profit.h b/util/ego/cs/cs_profit.h
index 7ec5e3c17..43f2bade9 100644
--- a/util/ego/cs/cs_profit.h
+++ b/util/ego/cs/cs_profit.h
@@ -7,6 +7,12 @@ void cs_machinit(void *vp);	/* (FILE *f)
 				 * Read phase-specific information from f.
 				 */
 
+bool may_become_aar(avail_p avp);
+				/*
+				 * Return whether a LAR/SAR may become
+				 * an AAR LOI/STI.
+				 */
+
 bool desirable(avail_p avp);	/*
 				 * Return whether it is desirable to eliminate
 				 * the recurrences of the expression in avp.
diff --git a/util/ego/cs/cs_vnm.c b/util/ego/cs/cs_vnm.c
index 4dbeb3df2..67507f805 100644
--- a/util/ego/cs/cs_vnm.c
+++ b/util/ego/cs/cs_vnm.c
@@ -50,11 +50,13 @@ STATIC void put_expensive_load(bblock_p bp, line_p lnp, line_p lfirst,
 
 STATIC void put_aar(bblock_p bp, line_p lnp, line_p lfirst, entity_p enp)
 {
-	/* Enp points to an ENARRELEM. We do as if its address was computed. */
-
+	/* Enter the implicit AAR in a LAR or SAR, where enp points to
+	 * the ENARRELEM, and AAR computes its address.
+	 */
 	struct avail av;
 	occur_p	ocp;
 
+	assert(INSTR(lnp) == op_lar || INSTR(lnp) == op_sar);
 	assert(enp->en_kind == ENARRELEM);
 	av.av_instr = op_aar;
 	av.av_size = ps;
@@ -62,9 +64,14 @@ STATIC void put_aar(bblock_p bp, line_p lnp, line_p lfirst, entity_p enp)
 	av.av_osecond = enp->en_index;
 	av.av_othird = enp->en_adesc;
 
-	ocp = newoccur(lfirst, lnp, bp);
-
-	av_enter(&av, ocp, TERNAIR_OP);
+	/* Before we enter an available AAR, we must check whether we
+	 * may convert this LAR/SAR to AAR LOI/STI.  This is so we
+	 * don't LOI/STI a large or unknown size.
+	 */
+	if (may_become_aar(&av)) {
+		ocp = newoccur(lfirst, lnp, bp);
+		av_enter(&av, ocp, TERNAIR_OP);
+	}
 }
 
 STATIC void push_avail(avail_p avp, line_p lfirst)