diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 0f2f570615bd..cc16e03c01c6 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2799,6 +2799,20 @@ Instruction *InstCombinerImpl::visitFree(CallInst &FI) {
   if (isa<ConstantPointerNull>(Op))
     return eraseInstFromFunction(FI);
 
+  // If we free a pointer we've been explicitly told won't be freed, this
+  // would be full UB and thus we can conclude this is unreachable. Cases:
+  // 1) freeing a pointer which is explicitly nofree
+  // 2) calling free from a call site marked nofree
+  // 3) calling free in a function scope marked nofree
+  if (auto *A = dyn_cast<Argument>(Op->stripPointerCasts()))
+    if (A->hasAttribute(Attribute::NoFree) ||
+        FI.hasFnAttr(Attribute::NoFree) ||
+        FI.getFunction()->hasFnAttribute(Attribute::NoFree)) {
+      // Leave a marker since we can't modify the CFG here.
+      CreateNonTerminatorUnreachable(&FI);
+      return eraseInstFromFunction(FI);
+    }
+
   // If we optimize for code size, try to move the call to free before the null
   // test so that simplify cfg can remove the empty block and dead code
   // elimination the branch. I.e., helps to turn something like:
diff --git a/llvm/test/Transforms/InstCombine/malloc-free-delete.ll b/llvm/test/Transforms/InstCombine/malloc-free-delete.ll
index fad542893c91..c2f35cfe0ad6 100644
--- a/llvm/test/Transforms/InstCombine/malloc-free-delete.ll
+++ b/llvm/test/Transforms/InstCombine/malloc-free-delete.ll
@@ -351,7 +351,7 @@ define void @test10()  {
 
 define void @test11() {
 ; CHECK-LABEL: @test11(
-; CHECK-NEXT:    [[CALL:%.*]] = call dereferenceable(8) i8* @_Znwm(i64 8) #7
+; CHECK-NEXT:    [[CALL:%.*]] = call dereferenceable(8) i8* @_Znwm(i64 8) #8
 ; CHECK-NEXT:    call void @_ZdlPv(i8* nonnull [[CALL]])
 ; CHECK-NEXT:    ret void
 ;
@@ -390,3 +390,32 @@ if.end:                                           ; preds = %entry, %if.then
   ret void
 }
 
+; Freeing a no-free pointer -> full UB
+define void @test13(i8* nofree %foo) {
+; CHECK-LABEL: @test13(
+; CHECK-NEXT:    store i1 true, i1* undef, align 1
+; CHECK-NEXT:    ret void
+;
+  call void @free(i8* %foo)
+  ret void
+}
+
+; Freeing a no-free pointer -> full UB
+define void @test14(i8* %foo) nofree {
+; CHECK-LABEL: @test14(
+; CHECK-NEXT:    store i1 true, i1* undef, align 1
+; CHECK-NEXT:    ret void
+;
+  call void @free(i8* %foo)
+  ret void
+}
+
+; free call marked no-free -> full UB
+define void @test15(i8* %foo) {
+; CHECK-LABEL: @test15(
+; CHECK-NEXT:    store i1 true, i1* undef, align 1
+; CHECK-NEXT:    ret void
+;
+  call void @free(i8* %foo) nofree
+  ret void
+}