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Re: [Patch] catch builtin_bswap16 construct
On Mon, 2012-09-24 at 09:15 +0200, Eric Botcazou wrote:
> > A while ago I've tried doing that for SH (implementing bswap16 with RTL
> > combine). It was like an explosion of patterns, because combine would
> > try out a lot of things depending on the surrounding code around the
> > actual bswap16. In the end I decided to drop that stuff for the most
> > part.
>
> OK, thanks for your feedback. Note that you won't get the benefit of the
> optimization for SH if you don't define a bswaphi2 pattern.
Sure sure. I'll resume my efforts after Christophe's patch is in.
>
> > BTW, the built-in documentation says:
> >
> > Built-in Function: int16_t __builtin_bswap16 (int16_t x)
> > Built-in Function: int32_t __builtin_bswap32 (int32_t x)
> >
> > However, it seems the result is always unsigned for those.
>
> Yes, builtins.def contains:
>
> DEF_GCC_BUILTIN (BUILT_IN_BSWAP16, "bswap16", BT_FN_UINT16_UINT16,
> ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_GCC_BUILTIN (BUILT_IN_BSWAP32, "bswap32", BT_FN_UINT32_UINT32,
> ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_GCC_BUILTIN (BUILT_IN_BSWAP64, "bswap64", BT_FN_UINT64_UINT64,
> ATTR_CONST_NOTHROW_LEAF_LIST)
>
> The documentation indeed needs to be fixed.
>
OK, I'll check it out.
Cheers,
Oleg