diff --git a/flang/lib/Evaluate/host.cpp b/flang/lib/Evaluate/host.cpp
--- a/flang/lib/Evaluate/host.cpp
+++ b/flang/lib/Evaluate/host.cpp
@@ -11,6 +11,9 @@
 #include "flang/Common/idioms.h"
 #include "llvm/Support/Errno.h"
 #include <cfenv>
+#if __x86_64__
+#include <xmmintrin.h>
+#endif
 
 namespace Fortran::evaluate::host {
 using namespace Fortran::parser::literals;
@@ -30,12 +33,13 @@
   }
 #if __x86_64__
   hasSubnormalFlushingHardwareControl_ = true;
+  unsigned int new_mxcsr{_mm_getcsr()};
   if (context.flushSubnormalsToZero()) {
-    currentFenv_.__mxcsr |= 0x8000; // result
-    currentFenv_.__mxcsr |= 0x0040; // operands
+    new_mxcsr |= 0x8000;
+    new_mxcsr |= 0x0040;
   } else {
-    currentFenv_.__mxcsr &= ~0x8000; // result
-    currentFenv_.__mxcsr &= ~0x0040; // operands
+    new_mxcsr &= ~0x8000;
+    new_mxcsr &= ~0x0040;
   }
 #elif defined(__aarch64__)
 #if defined(__GNU_LIBRARY__)
@@ -69,12 +73,17 @@
   // registers. Therefore, fetestexcept should not be used.
   hardwareFlagsAreReliable_ = false;
 #endif
+#if __x86_64__
+  _mm_setcsr(new_mxcsr);
+#else
   errno = 0;
   if (fesetenv(&currentFenv_) != 0) {
     common::die("Folding with host runtime: fesetenv() failed: %s",
         llvm::sys::StrError(errno).c_str());
     return;
   }
+#endif
+
   switch (context.rounding().mode) {
   case common::RoundingMode::TiesToEven:
     fesetround(FE_TONEAREST);
diff --git a/flang/unittests/Evaluate/fp-testing.cpp b/flang/unittests/Evaluate/fp-testing.cpp
--- a/flang/unittests/Evaluate/fp-testing.cpp
+++ b/flang/unittests/Evaluate/fp-testing.cpp
@@ -3,6 +3,9 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#if __x86_64__ && defined(_MSC_VER)
+#include <xmmintrin.h>
+#endif
 
 using Fortran::common::RoundingMode;
 using Fortran::evaluate::RealFlag;
@@ -20,31 +23,34 @@
         llvm::sys::StrError(errno).c_str());
     std::abort();
   }
-  if (fegetenv(&currentFenv_) != 0) {
-    std::fprintf(
-        stderr, "fegetenv() failed: %s\n", llvm::sys::StrError(errno).c_str());
-    std::abort();
-  }
+
 #if __x86_64__
+  unsigned int new_mxcsr{_mm_getcsr()};
   if (treatSubnormalOperandsAsZero) {
-    currentFenv_.__mxcsr |= 0x0040;
+    new_mxcsr |= 0x0040;
   } else {
-    currentFenv_.__mxcsr &= ~0x0040;
+    new_mxcsr &= ~0x0040;
   }
   if (flushSubnormalResultsToZero) {
-    currentFenv_.__mxcsr |= 0x8000;
+    new_mxcsr |= 0x8000;
   } else {
-    currentFenv_.__mxcsr &= ~0x8000;
+    new_mxcsr &= ~0x8000;
   }
+  _mm_setcsr(new_mxcsr);
 #else
+  if (fegetenv(&currentFenv_) != 0) {
+    std::fprintf(
+        stderr, "fegetenv() failed: %s\n", llvm::sys::StrError(errno).c_str());
+    std::abort();
+  }
   // TODO others
-#endif
   errno = 0;
   if (fesetenv(&currentFenv_) != 0) {
     std::fprintf(
         stderr, "fesetenv() failed: %s\n", llvm::sys::StrError(errno).c_str());
     std::abort();
   }
+#endif
 }
 
 ScopedHostFloatingPointEnvironment::~ScopedHostFloatingPointEnvironment() {