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bswap: Fix up a thinko with empty CONSTRUCTORs [PR98378]

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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.
This commit is contained in:
Jakub Jelinek 2020-12-19 12:46:40 +01:00
parent b1a2242e24
commit 9032d2b241
1 changed files with 2 additions and 0 deletions
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gcc/gimple-ssa-store-merging.c
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@ -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;