diff --git a/clang/CMakeLists.txt b/clang/CMakeLists.txt
--- a/clang/CMakeLists.txt
+++ b/clang/CMakeLists.txt
@@ -335,6 +335,17 @@
                       "LLVM_LINK_LLVM_DYLIB=OFF")
 endif()
 
+set(CLANG_DEFAULT_FFP_CONTRACT "on" CACHE STRING
+  "Default fused FP contract (\"fast\", \"on\", \"off\", \"fast-honor-pragmas\")")
+if (NOT(CLANG_DEFAULT_FFP_CONTRACT STREQUAL "fast" OR
+        CLANG_DEFAULT_FFP_CONTRACT STREQUAL "on" OR
+        CLANG_DEFAULT_FFP_CONTRACT STREQUAL "off" OR
+        CLANG_DEFAULT_FFP_CONTRACT STREQUAL "fast-honor-pragmas"))
+  message(WARNING "Resetting default fused FP contract")
+  set(CLANG_DEFAULT_RTLIB "on" CACHE STRING
+    "Default fused FP contract (\"fast\", \"on\", \"off\", \"fast-honor-pragmas\", empty for platform default)" FORCE)
+endif()
+
 # The libdir suffix must exactly match whatever LLVM's configuration used.
 set(CLANG_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}")
 
diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -37,6 +37,7 @@
   set(CLANG_DEFAULT_OBJCOPY llvm-objcopy CACHE STRING "")
 endif()
 set(CLANG_DEFAULT_RTLIB compiler-rt CACHE STRING "")
+set(CLANG_DEFAULT_FFP_CONTRACT off CACHE STRING "")
 set(CLANG_ENABLE_ARCMT OFF CACHE BOOL "")
 set(CLANG_ENABLE_STATIC_ANALYZER ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
diff --git a/clang/cmake/caches/Fuchsia.cmake b/clang/cmake/caches/Fuchsia.cmake
--- a/clang/cmake/caches/Fuchsia.cmake
+++ b/clang/cmake/caches/Fuchsia.cmake
@@ -28,6 +28,7 @@
   set(CLANG_DEFAULT_OBJCOPY llvm-objcopy CACHE STRING "")
 endif()
 set(CLANG_DEFAULT_RTLIB compiler-rt CACHE STRING "")
+set(CLANG_DEFAULT_FFP_CONTRACT off CACHE STRING "")
 set(CLANG_ENABLE_ARCMT OFF CACHE BOOL "")
 set(CLANG_ENABLE_STATIC_ANALYZER ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
diff --git a/clang/include/clang/Config/config.h.cmake b/clang/include/clang/Config/config.h.cmake
--- a/clang/include/clang/Config/config.h.cmake
+++ b/clang/include/clang/Config/config.h.cmake
@@ -32,6 +32,9 @@
 /* Default OpenMP runtime used by -fopenmp. */
 #define CLANG_DEFAULT_OPENMP_RUNTIME "${CLANG_DEFAULT_OPENMP_RUNTIME}"
 
+/* Default fused FP contract */
+#define CLANG_DEFAULT_FFP_CONTRACT "${CLANG_DEFAULT_FFP_CONTRACT}"
+
 /* Default architecture for OpenMP offloading to Nvidia GPUs. */
 #define CLANG_OPENMP_NVPTX_DEFAULT_ARCH "${CLANG_OPENMP_NVPTX_DEFAULT_ARCH}"
 
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -27,6 +27,7 @@
 #include "clang/Basic/LangOptions.h"
 #include "clang/Basic/ObjCRuntime.h"
 #include "clang/Basic/Version.h"
+#include "clang/Config/config.h"
 #include "clang/Driver/Distro.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/InputInfo.h"
@@ -2641,7 +2642,7 @@
 
   llvm::DenormalMode DenormalFPMath = DefaultDenormalFPMath;
   llvm::DenormalMode DenormalFP32Math = DefaultDenormalFP32Math;
-  StringRef FPContract = "on";
+  StringRef FPContract = CLANG_DEFAULT_FFP_CONTRACT;
   bool StrictFPModel = false;