Re: Conditional negation elimination in tree-ssa-phiopt.c

[Marc Glisse]

On Mon, 11 Aug 2014, Kyrill Tkachov wrote:

The aarch64 target has a conditional negation instruction
CSNEG Rd, Rs1, Rs2, cond
with semantics Rd = if cond then Rs1 else -Rs2.

This, however doesn't get end up getting matched for code such as:
int
foo2 (unsigned a, unsigned b)
{
 int r = 0;
 r = a & b;
 if (a & b)
   return -r;
 return r;
}

Note that in this particular case, we should just return -(a&b) like llvm 
does.

--
Marc Glisse