Looking at PR77308, one of the issues is that the bswap optimization 
phase doesn't work on ARM.  This is due to an odd check that uses
SLOW_UNALIGNED_ACCESS (which is always true on ARM).  Since the testcase
in PR77308 generates much better code with this patch (~13% fewer
instructions), it seems best to remove this check.

    gcc/
	* tree-ssa-math-opts.c (bswap_replace): Remove test
	of SLOW_UNALIGNED_ACCESS.

    testsuite/
	* gcc.dg/optimize-bswapdi-3.c: Remove xfail.
	* gcc.dg/optimize-bswaphi-1.c: Likewise. 	
	* gcc.dg/optimize-bswapsi-2.c: Likewise.

From-SVN: r242506