tree 6cf63e620d1db0638a9acbf6238492d530356882
parent fb32372651882adee2d41052f1e59012e8bb32a7
author Peter Bergner <bergner@linux.ibm.com> 1631634438 -0500
committer Peter Bergner <bergner@linux.ibm.com> 1631642648 -0500

rs6000: Disable optimizing multiple xxsetaccz instructions into one xxsetaccz

Fwprop will happily optimize two xxsetaccz instructions into one xxsetaccz
by propagating the results of the first to the uses of the second.
We really don't want that to happen given the late priming/depriming of
accumulators.  I fixed this by making the xxsetaccz source operand an
unspec volatile.  I also removed the mma_xxsetaccz define_expand and
define_insn_and_split and replaced it with a simple define_insn.
The expand and splitter patterns were leftovers from the pre opaque mode
code when the xxsetaccz code was part of the movpxi pattern, and we don't
need them now.

Rather than a new test case, I was able to just modify the current test case
to add another __builtin_mma_xxsetaccz call which shows the bad code gen
with unpatched compilers.

2021-09-14  Peter Bergner  <bergner@linux.ibm.com>

gcc/
	* config/rs6000/mma.md (unspec): Delete UNSPEC_MMA_XXSETACCZ.
	(unspecv): Add UNSPECV_MMA_XXSETACCZ.
	(*mma_xxsetaccz): Delete.
	(mma_xxsetaccz): Change to define_insn.  Remove operand 1.
	Use UNSPECV_MMA_XXSETACCZ.  Update comment.
	* config/rs6000/rs6000.c (rs6000_rtx_costs): Use UNSPECV_MMA_XXSETACCZ.

gcc/testsuite/
	* gcc.target/powerpc/mma-builtin-6.c: Add second call to xxsetacc
	built-in.  Update instruction counts.