[PATCH], PR target/82015, add PowerPC warning for unpack_vector_int128 with illegal 2nd argument

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

One of the local programmers tried to use the __builtin_unpack_vector_int128
function, but his second argument was not the constant 0 or 1.  The compiler
put the 2nd argument into a register, but there wasn't a valid insn for this,
and raised an insn not found message.  GCC should warn about this illegal
usage.

This patch adds such a warning.  While I was mucking about with this built-in
function, I fixed the constraints to allow the 64-bit integer for unpack result
and pack inputs to be in the traditional Altivec registers as well as the
traditional floating point registers.

I did a bootstrap of the compiler, and there were no regressions on a little
endian power8 system.  I verified that the new test is run.  Can I apply this
patch to the trunk?

Can I apply the part of the patch from rs6000.c to the existing GCC 6/7
branches as well after a shake down period?  The patch to rs6000.md is not
appropriate for GCC 6 (since DImode can't go into Altivec registers).  For GCC
7, it would need to be modified to use the 'wi' constraint instead of 'wa',
since GCC 7 still had support for the -mno-upper-regs-di option to control
access to the traditional Altivec register.

[gcc]
2017-08-28  Michael Meissner  <meissner@linux.vnet.ibm.com>

	PR target/82015
	* config/rs6000/rs6000.c (rs6000_expand_binop_builtin): Insure
	that the second argument of the built-in functions to unpack
	128-bit scalar types to 64-bit values is 0 or 1.  Change to use a
	switch statement instead a lot of if statements.
	* config/rs6000/rs6000.md (unpack<mode>, FMOVE128_VSX iterator):
	Allow 64-bit values to be in Altivec registers as well as
	traditional floating point registers.
	(pack<mode>, FMOVE128_VSX iterator): Likewise.

[gcc/testsuite]
2017-08-28  Michael Meissner  <meissner@linux.vnet.ibm.com>

	PR target/82015
	* gcc.target/powerpc/pr82015.c: New test.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797

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