rs6000: Add testcase for PR88233

This testcase tests that with -mcpu=power8 we do not generate any
mtvsr* instructions, and we do the copy with {l,st}xvd2x.


gcc/testsuite/
	PR rtl-optimization/88233
	* gcc.target/powerpc/pr88233.c: New testcase.

From-SVN: r273245

gcc/testsuite/ChangeLog

+2019-07-08  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/88233
+	* gcc.target/powerpc/pr88233.c: New testcase.
+
 2019-07-08  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	PR testsuite/91059

gcc/testsuite/gcc.target/powerpc/pr88233.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -mcpu=power8" } */
+
+typedef struct { double a[2]; } A;
+A
+foo (const A *a)
+{
+  return *a;
+}
+
+/* { dg-final { scan-assembler-not {\mmtvsr} } } */
+/* { dg-final { scan-assembler-times {\mlxvd2x\M} 1 } } */
+/* { dg-final { scan-assembler-times {\mstxvd2x\M} 1 } } */