New testcase, check that dead code doesn't pessimize instcombine

llvm-svn: 28214

test/Regression/Transforms/InstCombine/deadcode.ll

@@ -0,0 +1,12 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep 'ret int %A'
+
+int %test(int %A) {
+  %X = or bool false, false
+  br bool %X, label %T, label %C
+T:
+  %B = add int %A, 1
+  br label %C
+C:
+  %C = phi int [%B, %T], [%A, %0]
+  ret int %C
+}