From 9032d2b2414ed22e53a9980a51b835d3caf83c48 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Sat, 19 Dec 2020 12:46:40 +0100
Subject: [PATCH] bswap: Fix up a thinko with empty CONSTRUCTORs [PR98378]
The code I've added recently in find_bswap_or_nop for VECTOR CONSTRUCTORs
is missing punt on an important case - namely empty CONSTRUCTORs, because in that
case the loop will not initialize *n and the code after the loop will then
use the uninitialized structure.
2020-12-19 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/98378
* gimple-ssa-store-merging.c (find_bswap_or_nop): Punt if CONSTRUCTOR
has no elements.
---
gcc/gimple-ssa-store-merging.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c
index 2894205fa3c3..2ab51e23c077 100644
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -873,6 +873,8 @@ find_bswap_or_nop (gimple *stmt, struct symbolic_number *n, bool *bswap)
if (sz != 16 && sz != 32 && sz != 64)
return NULL;
tree rhs = gimple_assign_rhs1 (stmt);
+ if (CONSTRUCTOR_NELTS (rhs) == 0)
+ return NULL;
tree eltype = TREE_TYPE (TREE_TYPE (rhs));
unsigned HOST_WIDE_INT eltsz
= int_size_in_bytes (eltype) * BITS_PER_UNIT;
--
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