PR middle-end/18293
	* expmed.c (EXACT_POWER_OF_2_OR_ZERO_P): Move definition earlier.
	(expand_mult): Special case powers of two to avoid synth_mult.
	* loop.c (product_cheap_p): Handle case where expand_mult does
	require/generate any instructions (i.e. multiplication by zero).

From-SVN: r91851