The expression icmp eq (select (icmp eq x, 0), 1, x), 0 folds to false.

Spotted by my super-optimizer in 186.crafty and 450.soplex.  We really
need a proper infrastructure for handling generalizations of this kind
of thing (which occur a lot), however this case is so simple that I decided
to go ahead and implement it directly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143214 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstSimplify/compare.ll

@@ -204,6 +204,15 @@ define i1 @select4(i1 %cond) {
 ; CHECK: ret i1 %cond
 }
 
+define i1 @select5(i32 %x) {
+; CHECK: @select5
+  %c = icmp eq i32 %x, 0
+  %s = select i1 %c, i32 1, i32 %x
+  %c2 = icmp eq i32 %s, 0
+  ret i1 %c2
+; CHECK: ret i1 false
+}
+
 define i1 @urem1(i32 %X, i32 %Y) {
 ; CHECK: @urem1
   %A = urem i32 %X, %Y