On 20 September 2012 09:12, Eric Botcazou <ebotca...@adacore.com> wrote: >> The attached patch catches C constructs: >> (A << 8) | (A >> 8) >> where A is unsigned 16 bits >> and maps them to builtin_bswap16(A) which can provide more efficient >> implementations on some targets. > > This belongs in tree-ssa-math-opts.c:execute_optimize_bswap instead. > OK I'll have a look at that. Actually I modified fold-const.c because it's here that the similar 32 bits pattern is turned into a rotate.
> When I implemented __builtin_bswap16, I didn't add this because I thought this > would be overkill since the RTL combiner should be able to catch the pattern. > Have you investigated on this front? But I don't have a strong opinion. > No I didn't. As I said above, I looked at where the 32 bits pattern was handled and added the 16 bits one. Christophe.
