[PATCH], Tweak PowerPC movdi constraints

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

This patch tweaks the movdi constraints for the PowerPC to use "^" or "$"
constraints instead of "?*".  This allows the register allocator to more often
allocate DImode to a floating point/vector register when it is desirable to do
so.

I did a full Spec 2006 run with this patch installed, and most of the
benchmarks were neutral in terms of performance.  The 482.sphinx3 benchmark had
a 2.5% performance boost with these patches.  There were no benchmarks that
regressed with this patch.

I built bootstrap compilers and did make check with no regressions on:
    1)	Little endian power8, --with-cpu=power8
    2)	Big endian power8, --with-cpu=power8 (no 32-bit support)
    3)	Big endian power7, --with-cpu=power7 (both 32/64-bit support)

Can I check this patch into the trunk?

[gcc]
2016-11-18  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config/rs6000/rs6000.md (movdi_internal32): Change FPR/VSX "?*"
	load/store constraints to "^" if the instruction allows d-form
	addressing or "$" if it only allows x-form addressing.  Change
	FPR/VSX move constraints to "^".
	(movdi_internal64): Likewise.

[gcc/testsuite]
2016-11-18  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* gcc.target/powerpc/ppc-round2.c: Allow XSCVDPSXWS and XSCVDPUXWS
	to be generated instead of FCTIWUZ or FCTIWZ.

-- 
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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