This patch adds support for conditional multiplication and division.
It's mostly mechanical, but a few notes:

* The *_optab name and the .md names are the same as the unconditional
  forms, just with "cond_" added to the front.  This means we still
  have the awkward difference between sdiv and div, etc.

* It was easier to retain the difference between integer and FP
  division in the function names, given that they map to different
  tree codes (TRUNC_DIV_EXPR and RDIV_EXPR).

* SVE has no direct support for IFN_COND_MOD, but it seemed more
  consistent to add it anyway.

* Adding IFN_COND_MUL enables an extra fully-masked reduction
  in gcc.dg/vect/pr53773.c.

* In practice we don't actually use the integer division forms without
  if-conversion support (added by a later patch).

2018-05-25  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* doc/sourcebuild.texi (vect_double_cond_arith): Include
	multiplication and division.
	* doc/md.texi (cond_mul@var{m}, cond_div@var{m}, cond_mod@var{m})
	(cond_udiv@var{m}, cond_umod@var{m}): Document.
	* optabs.def (cond_smul_optab, cond_sdiv_optab, cond_smod_optab)
	(cond_udiv_optab, cond_umod_optab): New optabs.
	* internal-fn.def (IFN_COND_MUL, IFN_COND_DIV, IFN_COND_MOD)
	(IFN_COND_RDIV): New internal functions.
	* internal-fn.c (get_conditional_internal_fn): Handle TRUNC_DIV_EXPR,
	TRUNC_MOD_EXPR and RDIV_EXPR.
	* match.pd (UNCOND_BINARY, COND_BINARY): Handle them.
	* config/aarch64/iterators.md (UNSPEC_COND_MUL, UNSPEC_COND_DIV):
	New unspecs.
	(SVE_INT_BINARY): Include mult.
	(SVE_COND_FP_BINARY): Include UNSPEC_MUL and UNSPEC_DIV.
	(optab, sve_int_op): Handle mult.
	(optab, sve_fp_op, commutative): Handle UNSPEC_COND_MUL and
	UNSPEC_COND_DIV.
	* config/aarch64/aarch64-sve.md (cond_<optab><mode>): New pattern
	for SVE_INT_BINARY_SD.

gcc/testsuite/
	* lib/target-supports.exp
	(check_effective_target_vect_double_cond_arith): Include
	multiplication and division.
	* gcc.dg/vect/pr53773.c: Do not expect a scalar tail when using
	fully-masked loops with a fixed vector length.
	* gcc.dg/vect/vect-cond-arith-1.c: Add multiplication and division
	tests.
	* gcc.target/aarch64/sve/vcond_8.c: Likewise.
	* gcc.target/aarch64/sve/vcond_9.c: Likewise.
	* gcc.target/aarch64/sve/vcond_12.c: Add multiplication tests.

From-SVN: r260713