Index: lib/Transforms/Scalar/InstSimplifyPass.cpp
===================================================================
--- lib/Transforms/Scalar/InstSimplifyPass.cpp
+++ lib/Transforms/Scalar/InstSimplifyPass.cpp
@@ -17,6 +17,7 @@
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/PatternMatch.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Utils.h"
@@ -46,6 +47,15 @@
 
         // Don't waste time simplifying unused instructions.
         if (!I->use_empty()) {
+          using namespace PatternMatch;
+          if (match(I, m_Intrinsic<Intrinsic::is_constant>())) {
+            Constant *RetVal = ConstantInt::get(I->getType(), 0);
+            replaceAndRecursivelySimplify(I, RetVal, nullptr, nullptr);
+            BI = BB->begin();
+            BE = BB->end();
+            Changed = true;
+            continue;
+          }
           if (Value *V = SimplifyInstruction(I, SQ, ORE)) {
             // Mark all uses for resimplification next time round the loop.
             for (User *U : I->users())
Index: test/CodeGen/Generic/is-constant.ll
===================================================================
--- test/CodeGen/Generic/is-constant.ll
+++ test/CodeGen/Generic/is-constant.ll
@@ -1,7 +1,12 @@
-; RUN: opt -O2 -S < %s  | FileCheck %s
+; RUN: opt --early-cse --inline --simplifycfg -S < %s  | FileCheck %s
 ; RUN: llc -o /dev/null 2>&1 < %s
 ; RUN: llc -O0 -o /dev/null 2>&1 < %s
 
+;; Ensure that the Simplify Instructions pass removes all remaining
+;; llvm.is.constant intrinsics.
+; RUN: opt --early-cse --inline --instsimplify --simplifycfg -S < %s  | FileCheck --check-prefix=O2 %s
+; O2-NOT: call i1 @llvm.is.constant
+
 ;; The llc runs above are just to ensure it doesn't blow up upon
 ;; seeing an is_constant intrinsic.