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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27758 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/Target/PowerPC/README_ALTIVEC.txt b/lib/Target/PowerPC/README_ALTIVEC.txt
index 5d7ecd5691..2887b798b0 100644
--- a/lib/Target/PowerPC/README_ALTIVEC.txt
+++ b/lib/Target/PowerPC/README_ALTIVEC.txt
@@ -110,3 +110,13 @@ vec_ste(&destloc,0,vTemp);
 We can do an arbitrary non-constant value by using lvsr/perm/ste.
 
 //===----------------------------------------------------------------------===//
+
+If we want to tie instruction selection into the scheduler, we can do some
+constant formation with different instructions.  For example, we can generate
+"vsplti -1" with "vcmpequw R,R" and 1,1,1,1 with "vsubcuw R,R", both of which
+use different execution units, thus could help scheduling.
+
+This is probably only reasonable for a post-pass scheduler.
+
+//===----------------------------------------------------------------------===//
+