diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -107,6 +107,10 @@
     MaxFixpointIterations("attributor-max-iterations", cl::Hidden,
                           cl::desc("Maximal number of fixpoint iterations."),
                           cl::init(32));
+static cl::opt<bool> VerifyMaxFixpointIterations(
+    "attributor-max-iterations-verify", cl::Hidden,
+    cl::desc("Verify that max-iterations is a tight bound for a fixpoint"),
+    cl::init(false));
 
 static cl::opt<bool> DisableAttributor(
     "attributor-disable", cl::Hidden,
@@ -2509,6 +2513,10 @@
       Worklist.insert(QuerriedAAs.begin(), QuerriedAAs.end());
     }
 
+    LLVM_DEBUG(dbgs() << "[Attributor] #Iteration: " << IterationCounter
+                      << ", Worklist+Dependent size: " << Worklist.size()
+                      << "\n");
+
     // Reset the changed set.
     ChangedAAs.clear();
 
@@ -2529,7 +2537,7 @@
     Worklist.clear();
     Worklist.insert(ChangedAAs.begin(), ChangedAAs.end());
 
-  } while (!Worklist.empty() && ++IterationCounter < MaxFixpointIterations);
+  } while (!Worklist.empty() && IterationCounter++ < MaxFixpointIterations);
 
   size_t NumFinalAAs = AllAbstractAttributes.size();
 
@@ -2537,6 +2545,10 @@
                     << IterationCounter << "/" << MaxFixpointIterations
                     << " iterations\n");
 
+  if (VerifyMaxFixpointIterations && IterationCounter != MaxFixpointIterations)
+    llvm_unreachable("The fixpoint was not reached with exactly the number of "
+                     "specified iterations!");
+
   bool FinishedAtFixpoint = Worklist.empty();
 
   // Reset abstract arguments not settled in a sound fixpoint by now. This
diff --git a/llvm/test/Transforms/FunctionAttrs/align.ll b/llvm/test/Transforms/FunctionAttrs/align.ll
--- a/llvm/test/Transforms/FunctionAttrs/align.ll
+++ b/llvm/test/Transforms/FunctionAttrs/align.ll
@@ -1,4 +1,4 @@
-; RUN: opt -attributor -attributor-disable=false -attributor-max-iterations=32 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=17 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
diff --git a/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll b/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
--- a/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
+++ b/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations=19 -S < %s | FileCheck %s
+; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=18 -S < %s | FileCheck %s
 ;
 ; Test cases specifically designed for the "no-capture" argument attribute.
 ; We use FIXME's to indicate problems and missing attributes.
diff --git a/llvm/test/Transforms/FunctionAttrs/arg_returned.ll b/llvm/test/Transforms/FunctionAttrs/arg_returned.ll
--- a/llvm/test/Transforms/FunctionAttrs/arg_returned.ll
+++ b/llvm/test/Transforms/FunctionAttrs/arg_returned.ll
@@ -1,5 +1,5 @@
 ; RUN: opt -functionattrs -S < %s | FileCheck %s --check-prefix=FNATTR
-; RUN: opt -attributor -attributor-disable=false -attributor-max-iterations=27 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=26 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 ; RUN: opt -attributor -attributor-disable=false -functionattrs -S < %s | FileCheck %s --check-prefix=BOTH
 ;
 ; Test cases specifically designed for the "returned" argument attribute.
diff --git a/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll b/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll
--- a/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll
+++ b/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll
@@ -1,4 +1,4 @@
-; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations=4 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR
+; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR
 
 
 declare void @deref_phi_user(i32* %a);
diff --git a/llvm/test/Transforms/FunctionAttrs/fn_noreturn.ll b/llvm/test/Transforms/FunctionAttrs/fn_noreturn.ll
--- a/llvm/test/Transforms/FunctionAttrs/fn_noreturn.ll
+++ b/llvm/test/Transforms/FunctionAttrs/fn_noreturn.ll
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations=3 -S < %s | FileCheck %s
+; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=4 -S < %s | FileCheck %s
 ;
 ; Test cases specifically designed for the "no-return" function attribute.
 ; We use FIXME's to indicate problems and missing attributes.
diff --git a/llvm/test/Transforms/FunctionAttrs/liveness.ll b/llvm/test/Transforms/FunctionAttrs/liveness.ll
--- a/llvm/test/Transforms/FunctionAttrs/liveness.ll
+++ b/llvm/test/Transforms/FunctionAttrs/liveness.ll
@@ -1,4 +1,4 @@
-; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations=6 -S < %s | FileCheck %s
+; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=6 -S < %s | FileCheck %s
 
 declare void @no_return_call() nofree noreturn nounwind readnone
 
diff --git a/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll b/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
--- a/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
+++ b/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -attributor -attributor-disable=false -attributor-max-iterations=8 < %s | FileCheck %s
+; RUN: opt -S -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=8 < %s | FileCheck %s
 
 ; TEST 1 - negative.
 
diff --git a/llvm/test/Transforms/FunctionAttrs/nofree-attributor.ll b/llvm/test/Transforms/FunctionAttrs/nofree-attributor.ll
--- a/llvm/test/Transforms/FunctionAttrs/nofree-attributor.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nofree-attributor.ll
@@ -1,5 +1,5 @@
 ; RUN: opt -functionattrs --disable-nofree-inference=false -S < %s | FileCheck %s --check-prefix=FNATTR
-; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations=4 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=8 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
diff --git a/llvm/test/Transforms/FunctionAttrs/nonnull.ll b/llvm/test/Transforms/FunctionAttrs/nonnull.ll
--- a/llvm/test/Transforms/FunctionAttrs/nonnull.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nonnull.ll
@@ -1,6 +1,6 @@
 ; RUN: opt -S -functionattrs -enable-nonnull-arg-prop %s | FileCheck %s --check-prefixes=BOTH,FNATTR
 ; RUN: opt -S -passes=function-attrs -enable-nonnull-arg-prop %s | FileCheck %s --check-prefixes=BOTH,FNATTR
-; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations=32 -S < %s | FileCheck %s --check-prefixes=BOTH,ATTRIBUTOR
+; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=12 -S < %s | FileCheck %s --check-prefixes=BOTH,ATTRIBUTOR
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
diff --git a/llvm/test/Transforms/FunctionAttrs/noreturn_async.ll b/llvm/test/Transforms/FunctionAttrs/noreturn_async.ll
--- a/llvm/test/Transforms/FunctionAttrs/noreturn_async.ll
+++ b/llvm/test/Transforms/FunctionAttrs/noreturn_async.ll
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations=5 -S < %s | FileCheck %s
+; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=4 -S < %s | FileCheck %s
 ;
 ; This file is the same as noreturn_sync.ll but with a personality which
 ; indicates that the exception handler *can* catch asynchronous exceptions. As
diff --git a/llvm/test/Transforms/FunctionAttrs/noreturn_sync.ll b/llvm/test/Transforms/FunctionAttrs/noreturn_sync.ll
--- a/llvm/test/Transforms/FunctionAttrs/noreturn_sync.ll
+++ b/llvm/test/Transforms/FunctionAttrs/noreturn_sync.ll
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations=32 -S < %s | FileCheck %s
+; RUN: opt -functionattrs -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=7 -S < %s | FileCheck %s
 ;
 ; This file is the same as noreturn_async.ll but with a personality which
 ; indicates that the exception handler *cannot* catch asynchronous exceptions.
diff --git a/llvm/test/Transforms/FunctionAttrs/nosync.ll b/llvm/test/Transforms/FunctionAttrs/nosync.ll
--- a/llvm/test/Transforms/FunctionAttrs/nosync.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nosync.ll
@@ -1,5 +1,5 @@
 ; RUN: opt -functionattrs -S < %s | FileCheck %s --check-prefix=FNATTR
-; RUN: opt -attributor -attributor-disable=false -attributor-max-iterations=4 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=4 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; Test cases designed for the nosync function attribute.
diff --git a/llvm/test/Transforms/FunctionAttrs/nounwind.ll b/llvm/test/Transforms/FunctionAttrs/nounwind.ll
--- a/llvm/test/Transforms/FunctionAttrs/nounwind.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nounwind.ll
@@ -1,5 +1,5 @@
 ; RUN: opt < %s -functionattrs -S | FileCheck %s
-; RUN: opt < %s -attributor -attributor-disable=false -attributor-max-iterations=9 -S | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt < %s -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=12 -S | FileCheck %s --check-prefix=ATTRIBUTOR
 
 ; TEST 1
 ; CHECK: Function Attrs: norecurse nounwind readnone
diff --git a/llvm/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll b/llvm/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
--- a/llvm/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
+++ b/llvm/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -enable-nonnull-arg-prop -attributor -attributor-disable=false -attributor-max-iterations=33 -S < %s | FileCheck %s
+; RUN: opt -functionattrs -enable-nonnull-arg-prop -attributor -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=28 -S < %s | FileCheck %s
 ;
 ; This is an evolved example to stress test SCC parameter attribute propagation.
 ; The SCC in this test is made up of the following six function, three of which
diff --git a/llvm/test/Transforms/FunctionAttrs/willreturn.ll b/llvm/test/Transforms/FunctionAttrs/willreturn.ll
--- a/llvm/test/Transforms/FunctionAttrs/willreturn.ll
+++ b/llvm/test/Transforms/FunctionAttrs/willreturn.ll
@@ -1,5 +1,5 @@
 ; RUN: opt -functionattrs -S < %s | FileCheck %s --check-prefix=FNATTR
-; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor --attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"