diff --git a/SingleSource/UnitTests/Vectorizer/common.h b/SingleSource/UnitTests/Vectorizer/common.h
index 35107b15b1..ac779d5447 100644
--- a/SingleSource/UnitTests/Vectorizer/common.h
+++ b/SingleSource/UnitTests/Vectorizer/common.h
@@ -1,6 +1,14 @@
 #include <memory>
 #include <random>
 
+#define DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(Init, Loop, Type)                    \
+  auto ScalarFn = [](auto *A, Type TC) -> Type {                               \
+    Init _Pragma("clang loop vectorize(disable) interleave_count(1)") Loop     \
+  };                                                                           \
+  auto VectorFn = [](auto *A, Type TC) -> Type {                               \
+    Init _Pragma("clang loop vectorize(enable)") Loop                          \
+  };
+
 #define DEFINE_SCALAR_AND_VECTOR_FN2(Init, Loop)                               \
   auto ScalarFn = [](auto *A, auto *B, unsigned TC) {                          \
     Init _Pragma("clang loop vectorize(disable) interleave_count(1)") Loop     \
diff --git a/SingleSource/UnitTests/Vectorizer/fmax-reduction.cpp b/SingleSource/UnitTests/Vectorizer/fmax-reduction.cpp
new file mode 100644
index 0000000000..dcae59295d
--- /dev/null
+++ b/SingleSource/UnitTests/Vectorizer/fmax-reduction.cpp
@@ -0,0 +1,274 @@
+#include <algorithm>
+#include <functional>
+#include <iostream>
+#include <limits>
+#include <memory>
+#include <stdint.h>
+
+#include "common.h"
+
+static bool isEqual(float A, float B) {
+  if (std::isnan(A) || std::isnan(B))
+    return std::isnan(A) && std::isnan(B);
+
+  if (A == 0.0f)
+    return B == 0.0f && std::signbit(A) == std::signbit(B);
+
+  return A == B;
+}
+
+template <typename Ty> using Fn1Ty = std::function<Ty(Ty *, unsigned)>;
+
+template <typename Ty>
+static void check(Fn1Ty<Ty> ScalarFn, Fn1Ty<Ty> VectorFn, float *Src,
+                  unsigned N, const char *Type) {
+  auto Reference = ScalarFn(Src, N);
+  auto ToCheck = VectorFn(Src, N);
+  if (!isEqual(Reference, ToCheck)) {
+    std::cerr << "Miscompare " << Type << ": " << Reference << " != " << ToCheck
+              << "\n";
+    exit(1);
+  }
+}
+
+template <typename Ty>
+static void checkVectorFunction(Fn1Ty<Ty> ScalarFn, Fn1Ty<Ty> VectorFn,
+                                const char *Name) {
+  std::cout << "Checking " << Name << "\n";
+
+  unsigned N = 1024;
+  std::unique_ptr<Ty[]> Src1(new Ty[N]);
+  init_data(Src1, N);
+
+  // Check with random inputs.
+
+  // Check with sorted inputs.
+  std::sort(&Src1[0], &Src1[N]);
+  check(ScalarFn, VectorFn, &Src1[0], N, "sorted");
+
+  // Check with reverse sorted inputs.
+  std::reverse(&Src1[0], &Src1[N]);
+  check(ScalarFn, VectorFn, &Src1[0], N, "reverse-sorted");
+
+  // Check with all max values.
+  for (unsigned I = 0; I != N; ++I)
+    Src1[I] = std::numeric_limits<Ty>::max();
+  check(ScalarFn, VectorFn, &Src1[0], N, "all-max");
+
+  // Check with all min values.
+  for (unsigned I = 0; I != N; ++I)
+    Src1[I] = std::numeric_limits<Ty>::min();
+  check(ScalarFn, VectorFn, &Src1[0], N, "all-min");
+
+  // Check with various denormals.
+  Src1[0] = std::numeric_limits<Ty>::denorm_min();
+  for (unsigned I = 1; I != N; ++I)
+    Src1[I] = std::numeric_limits<Ty>::denorm_min() / I;
+  check(ScalarFn, VectorFn, &Src1[0], N, "denormals");
+
+  // Check with inputs all zero.
+  for (unsigned I = 0; I != N; ++I)
+    Src1[I] = 0.0;
+  check(ScalarFn, VectorFn, &Src1[0], N, "all-zeros");
+
+  // Check with NaN at different indices.
+  for (unsigned NaNIdx = 3; NaNIdx != 32; NaNIdx++) {
+    for (unsigned I = 0; I != N; ++I)
+      Src1[I] = 100;
+    Src1[NaNIdx] = std::numeric_limits<Ty>::quiet_NaN();
+
+    check(ScalarFn, VectorFn, &Src1[0], N, "NaN");
+  }
+
+  // Check with multiple signed-zeros at different positions.
+  for (unsigned Idx = 0; Idx != 64; ++Idx) {
+    for (unsigned I = 0; I != N; ++I)
+      Src1[I] = -1.0;
+
+    for (unsigned Offset = 1; Offset != 32; ++Offset) {
+      Src1[Idx] = -0.0;
+      Src1[Idx + Offset] = +0.0;
+
+      check(ScalarFn, VectorFn, &Src1[0], N, "signed-zeros");
+    }
+  }
+
+  for (unsigned Idx = 0; Idx != 64; ++Idx) {
+    for (unsigned I = 0; I != N; ++I)
+      Src1[I] = -1.0;
+
+    for (unsigned Offset = 1; Offset != 32; ++Offset) {
+      Src1[Idx] = +0.0;
+      Src1[Idx + Offset] = -0.0;
+
+      check(ScalarFn, VectorFn, &Src1[0], N, "signed-zeros");
+    }
+  }
+
+  // Check with max value at all possible indices.
+  for (unsigned Idx = 0; Idx != N; ++Idx) {
+    for (unsigned I = 0; I != N; ++I)
+      Src1[I] = I;
+
+    Src1[Idx] = N + 1;
+
+    check(ScalarFn, VectorFn, &Src1[0], N, "full");
+
+    for (unsigned Offset = 1; Offset != 16; ++Offset) {
+      if (Idx + Offset < N)
+        Src1[Idx + Offset] = N + 1;
+
+      check(ScalarFn, VectorFn, &Src1[0], N, "full");
+    }
+  }
+
+  // Check with NaN value at all possible indices.
+  for (unsigned Idx = 0; Idx != N; ++Idx) {
+    for (unsigned I = 0; I != N; ++I)
+      Src1[I] = I;
+
+    Src1[Idx] = std::numeric_limits<float>::quiet_NaN();
+    check(ScalarFn, VectorFn, &Src1[0], N, "full-with-nan");
+
+    // Check with multiple NaNs at different offsets.
+    for (unsigned Offset = 1; Offset != 16; ++Offset) {
+      if (Idx + Offset < N)
+        Src1[Idx + Offset] = std::numeric_limits<float>::quiet_NaN();
+
+      check(ScalarFn, VectorFn, &Src1[0], N, "full-with-multiple-nan");
+    }
+  }
+
+  // Check with multiple infinity values at different positions.
+  for (unsigned Idx = 0; Idx != 64; ++Idx) {
+    for (unsigned I = 0; I != N; ++I)
+      Src1[I] = -1.0;
+
+    for (unsigned Offset = 1; Offset != 16; ++Offset) {
+      Src1[Idx] = -std::numeric_limits<float>::infinity();
+      Src1[Idx + Offset] = std::numeric_limits<float>::infinity();
+
+      check(ScalarFn, VectorFn, &Src1[0], N, "infinity");
+    }
+  }
+}
+
+int main(void) {
+  rng = std::mt19937(15);
+
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = -2.0;, for (unsigned I = 0; I < 1024;
+                                I++) { Max = std::fmax(Max, A[I]); } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmaxnum_start_neg_2");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::min();
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = std::fmax(Max, A[I]); } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmaxnum_start_min");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::denorm_min();
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = std::fmax(Max, A[I]); } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmaxnum_start_denorm_min");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::quiet_NaN();
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = std::fmax(Max, A[I]); } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmaxnum_start_is_nan");
+  }
+
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = -2.0;
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = A[I] > Max ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmax_strict_start_neg_2");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::min();
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = A[I] > Max ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmax_strict_start_min");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::denorm_min();
+        , for (unsigned I = 0; I < 1025;
+               I++) { Max = A[I] > Max ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn,
+                               "fmax_strict_start_denorm_min");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::quiet_NaN();
+        , for (unsigned I = 0; I < 1025;
+               I++) { Max = A[I] > Max ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn, "fmax_strict_start_nan");
+  }
+
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = -2.0;
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = Max >= A[I] ? Max : A[I]; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn,
+                               "fmax_non_strict_start_neg_2");
+  }
+
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = -2.0;
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = Max > A[I] ? Max : A[I]; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn,
+                               "fmax_cmp_max_gt_start_neg_2");
+  }
+
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = -2.0;
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = Max < A[I] ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn,
+                               "fmax_cmp_max_lt_start_neg_2");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::denorm_min();
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = Max < A[I] ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn,
+                               "fmax_cmp_max_lt_start_denorm_min");
+  }
+  {
+    DEFINE_SCALAR_AND_VECTOR_FN1_TYPE(
+        float Max = std::numeric_limits<float>::quiet_NaN();
+        , for (unsigned I = 0; I < 1024;
+               I++) { Max = Max < A[I] ? A[I] : Max; } return Max;
+        , float);
+    checkVectorFunction<float>(ScalarFn, VectorFn,
+                               "fmax_cmp_max_lt_start_neg_nan");
+  }
+
+  return 0;
+}
diff --git a/SingleSource/UnitTests/Vectorizer/fmax-reduction.cpp.reference_output b/SingleSource/UnitTests/Vectorizer/fmax-reduction.cpp.reference_output
new file mode 100644
index 0000000000..e58266f902
--- /dev/null
+++ b/SingleSource/UnitTests/Vectorizer/fmax-reduction.cpp.reference_output
@@ -0,0 +1,14 @@
+Checking fmaxnum_start_neg_2
+Checking fmaxnum_start_min
+Checking fmaxnum_start_denorm_min
+Checking fmaxnum_start_is_nan
+Checking fmax_strict_start_neg_2
+Checking fmax_strict_start_min
+Checking fmax_strict_start_denorm_min
+Checking fmax_strict_start_nan
+Checking fmax_non_strict_start_neg_2
+Checking fmax_cmp_max_gt_start_neg_2
+Checking fmax_cmp_max_lt_start_neg_2
+Checking fmax_cmp_max_lt_start_denorm_min
+Checking fmax_cmp_max_lt_start_neg_nan
+exit 0