Fix correctness check for test_vec_fpextend_double

Summary:
Remove the CHECK-DAG calls introduced in r235341, and add a comment that
this test may break due to scheduling variations.

This patch completes the fix discussed in http://reviews.llvm.org/D8804

Reviewers: dsanders, srhines

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9178

llvm-svn: 235530

llvm/test/CodeGen/Mips/fp16-promote.ll

@@ -57,14 +57,16 @@ define <4 x float> @test_vec_fpext_float(<4 x half>* %p) #0 {
   ret <4 x float> %b
 }
 
+; This test is not robust against variations in instruction scheduling.
+; See the discussion in http://reviews.llvm.org/D8804
 ; CHECK-LIBCALL-LABEL: test_vec_fpext_double:
-; CHECK-LIBCALL-DAG: %call16(__gnu_h2f_ieee)
-; CHECK-LIBCALL-DAG: %call16(__gnu_h2f_ieee)
-; CHECK-LIBCALL-DAG: %call16(__gnu_h2f_ieee)
-; CHECK-LIBCALL-DAG: %call16(__gnu_h2f_ieee)
-; CHECK-LIBCALL-DAG: cvt.d.s
-; CHECK-LIBCALL-DAG: cvt.d.s
-; CHECK-LIBCALL-DAG: cvt.d.s
+; CHECK-LIBCALL: %call16(__gnu_h2f_ieee)
+; CHECK-LIBCALL: %call16(__gnu_h2f_ieee)
+; CHECK-LIBCALL: %call16(__gnu_h2f_ieee)
+; CHECK-LIBCALL: cvt.d.s
+; CHECK-LIBCALL: cvt.d.s
+; CHECK-LIBCALL: cvt.d.s
+; CHECK-LIBCALL: %call16(__gnu_h2f_ieee)
 ; CHECK-LIBCALL: cvt.d.s
 define <4 x double> @test_vec_fpext_double(<4 x half>* %p) #0 {
   %a = load <4 x half>, <4 x half>* %p, align 8