Index: clang/lib/Frontend/InitPreprocessor.cpp
===================================================================
--- clang/lib/Frontend/InitPreprocessor.cpp
+++ clang/lib/Frontend/InitPreprocessor.cpp
@@ -1039,6 +1039,9 @@
 
   Builder.defineMacro("__USER_LABEL_PREFIX__", TI.getUserLabelPrefix());
 
+  if (!LangOpts.MathErrno)
+    Builder.defineMacro("__NO_MATH_ERRNO__");
+
   if (LangOpts.FastMath || LangOpts.FiniteMathOnly)
     Builder.defineMacro("__FINITE_MATH_ONLY__", "1");
   else
Index: clang/test/Preprocessor/init-aarch64.c
===================================================================
--- clang/test/Preprocessor/init-aarch64.c
+++ clang/test/Preprocessor/init-aarch64.c
@@ -192,6 +192,7 @@
 // AARCH64-NEXT: #define __LONG_MAX__ 9223372036854775807L
 // AARCH64-NEXT: #define __LP64__ 1
 // AARCH64-NEXT: #define __NO_INLINE__ 1
+// AARCH64-NEXT: #define __NO_MATH_ERRNO__ 1
 // AARCH64-NEXT: #define __OBJC_BOOL_IS_BOOL 0
 // AARCH64-NEXT: #define __OPENCL_MEMORY_SCOPE_ALL_SVM_DEVICES 3
 // AARCH64-NEXT: #define __OPENCL_MEMORY_SCOPE_DEVICE 2
Index: clang/test/Preprocessor/init.c
===================================================================
--- clang/test/Preprocessor/init.c
+++ clang/test/Preprocessor/init.c
@@ -1691,6 +1691,7 @@
 // WEBASSEMBLY64-NEXT:#define __LONG_MAX__ 9223372036854775807L
 // WEBASSEMBLY64-NEXT:#define __LP64__ 1
 // WEBASSEMBLY-NEXT:#define __NO_INLINE__ 1
+// WEBASSEMBLY-NEXT:#define __NO_MATH_ERRNO__ 1
 // WEBASSEMBLY-NEXT:#define __OBJC_BOOL_IS_BOOL 0
 // WEBASSEMBLY-NEXT:#define __OPENCL_MEMORY_SCOPE_ALL_SVM_DEVICES 3
 // WEBASSEMBLY-NEXT:#define __OPENCL_MEMORY_SCOPE_DEVICE 2
Index: clang/test/Preprocessor/predefined-macros.c
===================================================================
--- clang/test/Preprocessor/predefined-macros.c
+++ clang/test/Preprocessor/predefined-macros.c
@@ -60,6 +60,15 @@
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-FAST-MATH
 // CHECK-FAST-MATH: #define __FAST_MATH__ 1
 // CHECK-FAST-MATH: #define __FINITE_MATH_ONLY__ 1
+// CHECK-FAST-MATH: #define __NO_MATH_ERRNO__ 1
+//
+// RUN: %clang_cc1 %s -E -dM -fmath-errno -o - \
+// RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-MATH-ERRNO
+// CHECK-MATH-ERRNO-NOT: __NO_MATH_ERRNO__
+//
+// RUN: %clang %s -E -dM -fno-math-errno -o - \
+// RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-NO-MATH-ERRNO
+// CHECK-NO-MATH-ERRNO: #define __NO_MATH_ERRNO__ 1
 //
 // RUN: %clang_cc1 %s -E -dM -ffinite-math-only -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-FINITE-MATH-ONLY