Index: MicroBenchmarks/MemFunctions/main.cpp
===================================================================
--- MicroBenchmarks/MemFunctions/main.cpp
+++ MicroBenchmarks/MemFunctions/main.cpp
@@ -18,10 +18,17 @@
 //===----------------------------------------------------------------------===//
 
 #include <cstring>
+#include <cstdlib>
+#include <iostream>
 #include <vector>
 
 #include "benchmark/benchmark.h"
 
+// This calls the real memcmp to check the reuslts.
+int RealMemCmp(const char* p, const char* q, size_t s) __attribute__((no_builtin("memcmp"))) {
+  return memcmp(p, q, s);
+}
+
 // Benchmarks `memcmp(p, q, size) OP 0` where n is known at compile time and OP
 // is defined by `Pred`. The compiler typically inlines the memcmp + comparion
 // to loads and compares.
@@ -44,6 +51,13 @@
   for (int i = 0; i < kNumElements; ++i)
     Mod().template Change<kSize>(p + i * kSize);
 
+  // First check the validity of the results.
+  if (Pred()(RealMemCmp(p, q, kSize)) != Pred()(memcmp(p, q, kSize))) {
+    std::cerr << "invalid results for Pred=" << Pred::kDisplay << " Mod=" << Mod::kDisplay << " kSize=" << kSize << std::endl;
+    std::exit(1);
+  }
+
+
   benchmark::DoNotOptimize(p);
   benchmark::DoNotOptimize(q);
 
@@ -52,7 +66,7 @@
     benchmark::ClobberMemory();
 
     for (int i = 0; i < kNumElements; ++i) {
-      int res = Pred()(memcmp(p + i * kSize, q + i * kSize, kSize));
+      bool res = Pred()(memcmp(p + i * kSize, q + i * kSize, kSize));
       benchmark::DoNotOptimize(res);
     }
   }
@@ -62,36 +76,43 @@
 // Predicates.
 struct EqZero {
   bool operator()(int v) const { return v == 0; }
+  inline static constexpr const char kDisplay[] = "EqZero";
 };
 struct LessThanZero {
   bool operator()(int v) const { return v < 0; }
+  inline static constexpr const char kDisplay[] = "LessThanZero";
 };
 struct GreaterThanZero {
   bool operator()(int v) const { return v > 0; }
+  inline static constexpr const char kDisplay[] = "GreaterThanZero";
 };
 
 // Functors to change the first/mid/last or no value.
 struct None {
   template <int kSize>
   void Change(char* const p) const {}
+  inline static constexpr const char kDisplay[] = "None";
 };
 struct First {
   template <int kSize>
   void Change(char* const p) const {
-    p[0] = 128;
+    p[0] = 0xff;
   }
+  inline static constexpr const char kDisplay[] = "First";
 };
 struct Mid {
   template <int kSize>
   void Change(char* const p) const {
-    p[kSize / 2] = 128;
+    p[kSize / 2] = 0xff;
   }
+  inline static constexpr const char kDisplay[] = "Mid";
 };
 struct Last {
   template <int kSize>
   void Change(char* const p) const {
-    p[kSize - 1] = 128;
+    p[kSize - 1] = 0xff;
   }
+  inline static constexpr const char kDisplay[] = "Last";
 };
 
 #define MEMCMP_BENCHMARK_PRED_CHANGE(size, pred, change) \