Fix a ValueTracking rule: RHS means operand 1, not 0. Add a simple

ashr instcombine to help expose this code. And apply the fix to
SelectionDAG's copy of this code too.

llvm-svn: 65364

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/ashr-nop.ll b/llvm/test/Transforms/InstCombine/ashr-nop.ll
new file mode 100644
index 00000000000..bb0da346b0c
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/ashr-nop.ll
@@ -0,0 +1,8 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep ashr
+
+define i32 @foo(i32 %x) {
+  %o = and i32 %x, 1
+  %n = add i32 %o, -1
+  %t = ashr i32 %n, 17
+  ret i32 %t
+}