Index: lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- lib/CodeGen/CodeGenPrepare.cpp
+++ lib/CodeGen/CodeGenPrepare.cpp
@@ -1853,6 +1853,17 @@
   if (II) {
     switch (II->getIntrinsicID()) {
     default: break;
+    case Intrinsic::sideeffect: {
+      II->eraseFromParent();
+      return true;
+    }
+    case Intrinsic::assume:
+    case Intrinsic::var_annotation: {
+      Value *Arg = II->getOperand(0);
+      II->eraseFromParent();
+      RecursivelyDeleteTriviallyDeadInstructions(Arg);
+      return true;
+    }
     case Intrinsic::experimental_widenable_condition: {
       // Give up on future widening oppurtunties so that we can fold away dead
       // paths and merge blocks before going into block-local instruction
Index: test/Transforms/CodeGenPrepare/drop-intrinsics.ll
===================================================================
--- test/Transforms/CodeGenPrepare/drop-intrinsics.ll
+++ test/Transforms/CodeGenPrepare/drop-intrinsics.ll
@@ -0,0 +1,37 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -codegenprepare  -S %s | FileCheck %s
+
+declare i32 @foo()
+declare i8* @bar()
+declare void @llvm.assume(i1)
+declare void @llvm.sideeffect()
+declare void @llvm.var.annotation(i8*, i8*, i8*, i32)
+
+define void @drop_llvm_assume() {
+; CHECK-LABEL: @drop_llvm_assume(
+; CHECK-NEXT:    ret void
+;
+  %call = tail call i32 @foo() #0
+  %cmp = icmp eq i32 %call, 1
+  call void @llvm.assume(i1 %cmp)
+  ret void
+}
+
+define void @drop_llvm_sideeffect() {
+; CHECK-LABEL: @drop_llvm_sideeffect(
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.sideeffect()
+  ret void
+}
+
+define void @drop_llvm_var_annotation() {
+; CHECK-LABEL: @drop_llvm_var_annotation(
+; CHECK-NEXT:    ret void
+;
+  %s = call i8* @bar() #0
+  call void @llvm.var.annotation(i8* %s, i8* null, i8* null, i32 0)
+  ret void
+}
+
+attributes #0 = { nounwind readnone }