The result of a POPCOUNT operation in RTL should have the same mode
as its operand.  This corrects the specification of popcount in
the nvptx backend, splitting the current generic define_insn into
two, one for popcountsi2 and the other for popcountdi2 (the latter
with an explicit truncate).

This patch has been tested on nvptx-none (hosted on x86_64-pc-linux-gnu)
with make and make -k check with no new failures.  This functionality is
already tested by gcc.target/nvptx/popc-[123].c.  Ok for mainline?


2023-01-09  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/nvptx/nvptx.md (popcount<mode>2): Split into...
	(popcountsi2): define_insn handling SImode popcount.
	(popcountdi2): define_insn handling DImode popcount, with an
	explicit truncate:SI to produce an SImode result.

Thanks in advance,
Roger
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