add a note

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27227 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/README_ALTIVEC.txt b/lib/Target/PowerPC/README_ALTIVEC.txt
index 7754f4c13c85f464b8cfc5dd2c047e0d0b73e476..d4c944b6de7b594a2eccc0483d6a02fe7073c2f2 100644 (file)
--- a/lib/Target/PowerPC/README_ALTIVEC.txt
+++ b/lib/Target/PowerPC/README_ALTIVEC.txt
@@ -134,4 +134,14 @@ This would fix two problems:
 2. Identical operations in different types are not getting CSE'd (e.g. 
    { 0U, 0U, 0U, 0U } and {0.0, 0.0, 0.0, 0.0}.
 
+//===----------------------------------------------------------------------===//
+
+Two identical comparisons in predicate and nonpredicate form like this:
+
+a = vec_cmpb(x, y);
+b = vec_any_out(x, y);
+
+Should turn into one "." compare instruction, not a dot and "nondot" form.
+
+//===----------------------------------------------------------------------===//