Index: lib/Transforms/Scalar/EarlyCSE.cpp
===================================================================
--- lib/Transforms/Scalar/EarlyCSE.cpp
+++ lib/Transforms/Scalar/EarlyCSE.cpp
@@ -578,6 +578,28 @@
       continue;
     }
 
+    if (CmpInst *CI = dyn_cast<CmpInst>(Inst)) {
+      Value *X, *Y;
+      ConstantInt *C;
+      bool IdempotentUser = false;
+      for (auto *U : CI->users()) {
+        if (match(U, m_Select(m_Value(X), m_ConstantInt(C), m_Value(Y))) ||
+            match(U, m_Select(m_Value(X), m_Value(Y), m_ConstantInt(C)))) {
+          if (C->isOne() || C->isZero()) {
+            if (!AvailableValues.lookup(Inst))
+              AvailableValues.insert(Inst, Inst);
+            IdempotentUser = true;
+            break;
+          }
+        }
+      }
+      if (IdempotentUser) {
+        DEBUG(dbgs() << "EarlyCSE skipping compare inst: " << *Inst
+                     << " in " << BB->getName() << "\n");
+        continue;
+      }
+    }
+
     // If this is a simple instruction that we can value number, process it.
     if (SimpleValue::canHandle(Inst)) {
       // See if the instruction has an available value.  If so, use it.
Index: test/Transforms/EarlyCSE/basic.ll
===================================================================
--- test/Transforms/EarlyCSE/basic.ll
+++ test/Transforms/EarlyCSE/basic.ll
@@ -277,3 +277,23 @@
   ret void
 }
 
+define void @cond_idem(i32 %A, i32 %B, i32 %C) #0 {
+; CHECK-LABEL: @cond_idem(
+entry:
+  %cmp = icmp sgt i32 %A, 0
+; CHECK: %cmp = icmp sgt i32 %A, 0
+  %cmp1 = icmp sgt i32 %B, 0
+  %cmp1. = select i1 %cmp, i1 %cmp1, i1 false
+  %lnot = xor i1 %cmp1., true
+  %conv = zext i1 %lnot to i32
+  %cmp2 = icmp sgt i32 %A, 0
+; CHECK: %cmp2 = icmp sgt i32 %A, 0
+  %cmp4 = icmp sgt i32 %C, 0
+  %0 = select i1 %cmp2, i1 %cmp4, i1 false
+  %lnot6 = xor i1 %0, true
+  %conv7 = zext i1 %lnot6 to i32
+  call void @foo(i32 %conv, i32 %conv7)
+  ret void
+}
+
+declare void @foo(i32, i32) #0