rs6000: MMA builtin usage ICEs when used in a #pragma omp parallel and using -fopenmp...

rs6000: MMA builtin usage ICEs when used in a #pragma omp parallel and using -fopenmp [PR100777]

Using an MMA builtin within an openmp parallel code block, leads to an SSA
verification ICE on the temporaries we create while expanding the MMA builtins
at gimple time.  The solution is to use create_tmp_reg_or_ssa_name(), which
knows when to create either an SSA or register temporary.

2021-06-14  Peter Bergner  <bergner@linux.ibm.com>

gcc/
	PR target/100777
	* config/rs6000/rs6000-call.c (rs6000_gimple_fold_mma_builtin): Use
	create_tmp_reg_or_ssa_name().

gcc/testsuite/
	PR target/100777
	* gcc.target/powerpc/pr100777.c: New test.

(cherry picked from commit 20073534c0ccca0a4e079c053ee0874af10b2ea0)