Fix reassociate to use a worklist instead of recursing when new

reassociation opportunities are exposed. This fixes a bug where
the nested reassociation expects to be the IR to be consistent,
but it isn't, because the outer reassociation has disconnected
some of the operands.  rdar://9167457


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129324 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/Reassociate/secondary.ll

@@ -0,0 +1,24 @@
+; RUN: opt -S -reassociate < %s | FileCheck %s
+; rdar://9167457
+
+; Reassociate shouldn't break this testcase involving a secondary
+; reassociation.
+
+; CHECK:     define
+; CHECK-NOT: undef
+; CHECK:     %factor = mul i32 %tmp3, -2
+; CHECK-NOT: undef
+; CHECK:     }
+
+define void @x0f2f640ab6718391b59ce96d9fdeda54(i32 %arg, i32 %arg1, i32 %arg2, i32* %.out) nounwind {
+_:
+  %tmp = sub i32 %arg, %arg1
+  %tmp3 = mul i32 %tmp, -1268345047
+  %tmp4 = add i32 %tmp3, 2014710503
+  %tmp5 = add i32 %tmp3, -1048397418
+  %tmp6 = sub i32 %tmp4, %tmp5
+  %tmp7 = sub i32 -2014710503, %tmp3
+  %tmp8 = add i32 %tmp6, %tmp7
+  store i32 %tmp8, i32* %.out
+  ret void
+}