Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1433,6 +1433,10 @@
     if (match(Next, m_Intrinsic<Intrinsic::assume>(m_Specific(IIOperand))))
       return eraseInstFromFunction(CI);
 
+    // If this assume is in an unreachable block, it can't be useful.
+    if (isa<UnreachableInst>(II->getParent()->getTerminator()))
+      return eraseInstFromFunction(*II);
+
     // Canonicalize assume(a && b) -> assume(a); assume(b);
     // Note: New assumption intrinsics created here are registered by
     // the InstCombineIRInserter object.
Index: llvm/test/Transforms/InstCombine/assume.ll
===================================================================
--- llvm/test/Transforms/InstCombine/assume.ll
+++ llvm/test/Transforms/InstCombine/assume.ll
@@ -543,7 +543,6 @@
 
 define void @PR36270(i32 %b) {
 ; CHECK-LABEL: @PR36270(
-; CHECK-NEXT:    tail call void @llvm.assume(i1 false)
 ; CHECK-NEXT:    unreachable
 ;
   %B7 = xor i32 -1, 2147483647
@@ -573,8 +572,6 @@
 ; CHECK-NEXT:    tail call void @llvm.assume(i1 [[CMP3]])
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
-; CHECK-NEXT:    [[CMP4:%.*]] = icmp eq i32 [[X]], 2
-; CHECK-NEXT:    tail call void @llvm.assume(i1 [[CMP4]])
 ; CHECK-NEXT:    unreachable
 ;
 entry: