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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28572 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 807768002b..650eabf2d4 100644
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -251,3 +251,22 @@ void %test(uint* %P) {
         ret void
 }
 
+//===---------------------------------------------------------------------===//
+
+dag/inst combine "clz(x)>>5 -> x==0" for 32-bit x.
+
+Compile:
+
+int bar(int x)
+{
+  int t = __builtin_clz(x);
+  return -(t>>5);
+}
+
+to:
+
+_bar:   addic r3,r3,-1
+        subfe r3,r3,r3
+        blr
+
+