Detect bswap + rotate for byte permutation in pass_bswap.
The patch doesn't handle:
1. cast64_to_32,
2. memory source with rsize < range.
gcc/ChangeLog:
PR middle-end/108938
* gimple-ssa-store-merging.cc (is_bswap_or_nop_p): New
function, cut from original find_bswap_or_nop function.
(find_bswap_or_nop): Add a new parameter, detect bswap +
rotate and save rotate result in the new parameter.
(bswap_replace): Add a new parameter to indicate rotate and
generate rotate stmt if needed.
(maybe_optimize_vector_constructor): Adjust for new rotate
parameter in the upper 2 functions.
(pass_optimize_bswap::execute): Ditto.
(imm_store_chain_info::output_merged_store): Ditto.
gcc/testsuite/ChangeLog:
* gcc.target/i386/pr108938-1.c: New test.
* gcc.target/i386/pr108938-2.c: New test.
* gcc.target/i386/pr108938-3.c: New test.
* gcc.target/i386/pr108938-load-1.c: New test.
* gcc.target/i386/pr108938-load-2.c: New test.