[x86] Add a comment clarifying that this test should span all manners of
generic DAG combining of shuffles relevant to x86.
My plan is to fold a bunch of the other DAG combining test cases into
this one, while converting them to use the nice new FileCheck assertion
syntax.
llvm-svn: 218855
diff --git a/llvm/test/CodeGen/X86/vector-shuffle-combining.ll b/llvm/test/CodeGen/X86/vector-shuffle-combining.ll
index e60ecb7..5a52403 100644
--- a/llvm/test/CodeGen/X86/vector-shuffle-combining.ll
+++ b/llvm/test/CodeGen/X86/vector-shuffle-combining.ll
@@ -1,4 +1,9 @@
; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -x86-experimental-vector-shuffle-lowering | FileCheck %s --check-prefix=CHECK-SSE2
+;
+; Verify that the DAG combiner correctly folds bitwise operations across
+; shuffles, nested shuffles with undef, pairs of nested shuffles, and other
+; basic and always-safe patterns. Also test that the DAG combiner will combine
+; target-specific shuffle instructions where reasonable.
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-unknown"