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Re: [PATCH 2/3] Simplify and inline get_uleb128 and get_sleb128
- From: Richard Henderson <rth at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Wed, 23 Apr 2014 08:27:11 -0700
- Subject: Re: [PATCH 2/3] Simplify and inline get_uleb128 and get_sleb128
On 04/23/2014 03:17 AM, Petr Machata wrote:
> Wouldn't something like this get us off the hook as well?
> - (var) |= (typeof (var)) __s.i << ((nth) * 7); \
> + (var) |= (typeof (var)) \
> + (((uint64_t) (typeof (var)) __s.i) << ((nth) * 7)); \
> We are really only using the bitfield trick to avoid having to
> sign-extend by hand, but we can shift unsigned without losing anything.
It gets us off the hook, but might introduce a 64-bit shift where
only a 32-bit shift was required.
Sadly, (unsigned typeof(var)) doesn't work. ;-)
But I gave the multiplication change a look, and the compiler is in fact
optimizing the multiplication by a power of 2 back into a shift.