Hi,

When translating conditional reductions based on integer induction, the
compiler uses the value zero to indicate the absence of any matches: if
the index of the last match is still zero at the end of the loop, the
default value is returned. The problem with this approach is that this
default value is returned not only when there were no matches at all,
but also when the last match occurred at index 0. This causes the test
gcc.dg/vect/pr65947-14.c to fail.

This patch corrects this by reusing the vector of indices used for
COND_REDUCTION, which starts at 1. If the 1-based index of the last
match is non-zero, 1 is subtracted from it, otherwise the initial value
is returned.

I tested this patch on x86_64-pc-linux-gnu (both with SSE and AVX2,
causing both paths through the reduc_code != ERROR_MARK branch being
taken).

2017-11-21  Kilian Verhetsel <kilian.verhetsel@uclouvain.be>

	* tree-vect-loop.c
        (vect_create_epilog_for_reduction): Fix the returned value for
	INTEGER_INDUC_COND_REDUCTION whose last match occurred at
	index 0.	
	(vectorizable_reduction): For INTEGER_INDUC_COND_REDUCTION,
	pass the PHI statement that sets the induction variable to the
	code generating the epilogue.