diff --git a/bolt/lib/Core/HashUtilities.cpp b/bolt/lib/Core/HashUtilities.cpp
--- a/bolt/lib/Core/HashUtilities.cpp
+++ b/bolt/lib/Core/HashUtilities.cpp
@@ -106,8 +106,6 @@
 
 std::string hashBlock(BinaryContext &BC, const BinaryBasicBlock &BB,
                       OperandHashFuncTy OperandHashFunc) {
-  assert(BB.size() > 0 && "computing hash over an empty basic block");
-
   const bool IsX86 = BC.isX86();
 
   // The hash is computed by creating a string of all instruction opcodes and
diff --git a/bolt/lib/Passes/BinaryPasses.cpp b/bolt/lib/Passes/BinaryPasses.cpp
--- a/bolt/lib/Passes/BinaryPasses.cpp
+++ b/bolt/lib/Passes/BinaryPasses.cpp
@@ -1317,6 +1317,7 @@
 void PrintProgramStats::runOnFunctions(BinaryContext &BC) {
   uint64_t NumRegularFunctions = 0;
   uint64_t NumStaleProfileFunctions = 0;
+  uint64_t NumAllStaleFunctions = 0;
   uint64_t NumInferredFunctions = 0;
   uint64_t NumNonSimpleProfiledFunctions = 0;
   uint64_t NumUnknownControlFlowFunctions = 0;
@@ -1360,6 +1361,7 @@
       if (Function.hasInferredProfile()) {
         ++NumInferredFunctions;
         InferredSampleCount += SampleCount;
+        ++NumAllStaleFunctions;
       }
     } else {
       if (opts::ReportStaleFuncs) {
@@ -1369,6 +1371,7 @@
       }
       ++NumStaleProfileFunctions;
       StaleSampleCount += SampleCount;
+      ++NumAllStaleFunctions;
     }
   }
   BC.NumProfiledFuncs = ProfiledFunctions.size();
@@ -1416,6 +1419,13 @@
     }
   }
   if (NumInferredFunctions) {
+    const float PctAllStale =
+        NumAllStaleFunctions / (float)NumAllProfiledFunctions * 100.0f;
+    outs() << "BOLT-INFO: " << NumAllStaleFunctions
+           << format(" (%.1f%% of all profiled)", PctAllStale) << " function"
+           << (NumAllStaleFunctions == 1 ? "" : "s")
+           << " have invalid (possibly stale) profile."
+              " Use -report-stale to see the list.\n";
     outs() << format("BOLT-INFO: inferred profile for %d (%.2f%% of all "
                      "profiled) functions responsible for %.2f%% samples\n",
                      NumInferredFunctions,
diff --git a/bolt/test/X86/Inputs/blarge_profile_stale.yaml b/bolt/test/X86/Inputs/blarge_profile_stale.yaml
new file mode 100644
--- /dev/null
+++ b/bolt/test/X86/Inputs/blarge_profile_stale.yaml
@@ -0,0 +1,51 @@
+---
+header:
+  profile-version: 1
+  binary-name:     '/data/users/spupyrev/llvm-upstream/build/tools/bolt/test/X86/Output/reader-yaml.test.tmp.exe'
+  binary-build-id: '<unknown>'
+  profile-flags:   [ lbr ]
+  profile-origin:  branch profile reader
+  profile-events:  ''
+functions:
+  - name:            SolveCubic
+    fid:             6
+    hash:            0xC6E9098E973BBE19
+    exec:            151
+    nblocks:         18
+    blocks:
+      - bid:             0
+        insns:           43
+        hash:            0x8A41C5F60CF1B879
+        exec:            151
+        succ:            [ { bid: 1, cnt: 4, mis: 2 }, { bid: 11, cnt: 0 } ]
+      - bid:             1
+        insns:           7
+        hash:            0x6D641B0E41067EE6
+        succ:            [ { bid: 10, cnt: 0 }, { bid: 2, cnt: 0 } ]
+      - bid:             13
+        insns:           26
+        hash:            0x2C528DB7C11E0C22
+        succ:            [ { bid: 15, cnt: 89 }, { bid: 14, cnt: 0 } ]
+      - bid:             15
+        insns:           9
+        hash:            0x7A5F8FF268495B78
+  - name:            usqrt
+    fid:             7
+    hash:            0x8B62B1F9AD81EA35
+    exec:            20
+    nblocks:         6
+    blocks:
+      - bid:             0
+        insns:           4
+        hash:            0xF5818B6ACA0B4B1A
+        exec:            20
+        succ:            [ { bid: 1, cnt: 0 } ]
+      - bid:             1
+        insns:           9
+        hash:            0x388CD0AB1361C40C
+        succ:            [ { bid: 3, cnt: 320, mis: 171 }, { bid: 2, cnt: 0 } ]
+      - bid:             3
+        insns:           2
+        hash:            0xB096EE55E872A023
+        succ:            [ { bid: 1, cnt: 300, mis: 33 }, { bid: 4, cnt: 20 } ]
+...
diff --git a/bolt/test/X86/reader-stale-yaml.test b/bolt/test/X86/reader-stale-yaml.test
new file mode 100644
--- /dev/null
+++ b/bolt/test/X86/reader-stale-yaml.test
@@ -0,0 +1,39 @@
+# This script checks that YamlProfileReader in llvm-bolt is reading data
+# correctly and stale data is corrected.
+
+RUN: yaml2obj %p/Inputs/blarge.yaml &> %t.exe
+RUN: llvm-bolt %t.exe -o /dev/null --b %p/Inputs/blarge_profile_stale.yaml --print-cfg --print-only=usqrt --infer-stale-profile=1 \
+RUN:   2>&1 | FileCheck %s -check-prefix=CHECK
+
+# Verify that yaml reader works as expected.
+CHECK:  pre-processing profile using YAML profile reader
+
+# Verify the inferred counts of "usqrt" that has stale profile:
+#   - the function has nblocks=6 in the profile, which makes it stale
+#   - block with bid=0 has an incorrect (missing) count, which is inferred
+CHECK:    Binary Function "usqrt" after building cfg {
+CHECK:      State       : CFG constructed
+CHECK:      Address     : 0x401170
+CHECK:      Size        : 0x43
+CHECK:      Section     : .text
+CHECK:      IsSimple    : 1
+CHECK:      BB Count    : 5
+CHECK:      Exec Count  : 20
+CHECK:      RawBranchCount : 640
+CHECK:    }
+
+# Verify block counts.
+CHECK:    .LBB01 (4 instructions, align : 1)
+CHECK:      Successors: .Ltmp[[#BB13:]] (mispreds: 0, count: 20)
+CHECK:    .Ltmp[[#BB13:]] (9 instructions, align : 1)
+CHECK:      Successors: .Ltmp[[#BB12:]] (mispreds: 0, count: 320), .LFT[[#BB0:]] (mispreds: 0, count: 0)
+CHECK:    .LFT[[#BB0:]] (2 instructions, align : 1)
+CHECK:      Successors: .Ltmp[[#BB12:]] (mispreds: 0, count: 0)
+CHECK:    .Ltmp[[#BB12:]] (2 instructions, align : 1)
+CHECK:      Successors: .Ltmp[[#BB13:]] (mispreds: 0, count: 300), .LFT[[#BB1:]] (mispreds: 0, count: 20)
+CHECK:    .LFT[[#BB1:]] (2 instructions, align : 1)
+
+# Check the overal inference stats.
+CHECK:  2 out of 7 functions in the binary (28.6%) have non-empty execution profile
+CHECK:  1 (50.0% of all profiled) function have invalid (possibly stale) profile
+CHECK:  inferred profile for 1 (50.00% of all profiled) functions responsible for 87.31% samples