we have a shuffle instr, add an example.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27592 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/README_ALTIVEC.txt b/lib/Target/PowerPC/README_ALTIVEC.txt
index 0cf7a194093bed08efc4db7b63c9ce91e9216fca..7e92f0b78886a58eaa390a257d6ba5b1bff55dea 100644 (file)
--- a/lib/Target/PowerPC/README_ALTIVEC.txt
+++ b/lib/Target/PowerPC/README_ALTIVEC.txt
@@ -96,11 +96,6 @@ instructions.
  
 //===----------------------------------------------------------------------===//
 
-We need an LLVM 'shuffle' instruction, that corresponds to the VECTOR_SHUFFLE
-node.
-
-//===----------------------------------------------------------------------===//
-
 We need a way to teach tblgen that some operands of an intrinsic are required to
 be constants.  The verifier should enforce this constraint.
 
@@ -133,4 +128,10 @@ There are a wide variety of vector_shuffle operations that we can do with a pair
 of instructions (e.g. a vsldoi + vpkuhum).  We should pattern match these, but
 there are a huge number of these.
 
+Specific examples:
+
+C = vector_shuffle A, B, <0, 1, 2, 4>
+->  t = vsldoi A, A, 12
+->  C = vsldoi A, B, 4
+
 //===----------------------------------------------------------------------===//