Index: tools/CMakeLists.txt
===================================================================
--- tools/CMakeLists.txt
+++ tools/CMakeLists.txt
@@ -27,3 +27,5 @@
   add_executable(timeit-target ${CMAKE_CURRENT_SOURCE_DIR}/timeit.c)
   llvm_add_host_executable(timeit-host timeit timeit.c)
 endif()
+
+add_executable(FP-contraction_detection___-target ${CMAKE_CURRENT_SOURCE_DIR}/FP-contraction_detection.c)
Index: tools/FP-contraction_detection.c
===================================================================
--- /dev/null
+++ tools/FP-contraction_detection.c
@@ -0,0 +1,66 @@
+#include <memory.h>
+#include <stdio.h>
+#include <stdint.h>
+
+// for ease of future change
+#define FP_type double
+
+__attribute__((noinline))
+FP_type FMA_test_using_default_compiler_setting( FP_type a, FP_type b, FP_type c) {
+  return a+b*c;
+}
+
+__attribute__((noinline))
+FP_type FMA_test_with_pragma_for_NO_contraction( FP_type a, FP_type b, FP_type c) {
+  #pragma STDC FP_CONTRACT OFF
+  return a+b*c;
+}
+
+__attribute__((noinline))
+FP_type FMA_test_with_pragma_for_YES_contraction(FP_type a, FP_type b, FP_type c) {
+  #pragma STDC FP_CONTRACT ON
+  return a+b*c;
+}
+
+#pragma clang optimize off
+__attribute__((optnone))         // for Clang
+__attribute__((optimize("-O0"))) // for GCC
+__attribute__((noinline))
+FP_type FMA_test_trying_to_disable_optimization( FP_type a, FP_type b, FP_type c) {
+  return a+b*c;
+}
+
+
+// the following routine: with thanks to Matthias Braun
+static double u64_to_double(uint64_t x) {
+  double d;
+  memcpy(&d, &x, sizeof(x));
+  return d;
+}
+
+
+int main() {
+
+  double A, B, C;
+  // the next 3 lines: thanks to the author of <https://www.pgroup.com/lit/articles/insider/v3n3a4.htm>
+  A = u64_to_double(0x3c54c9b71a0e6500);
+  B = u64_to_double(0xbf43a04556d864ae);
+  C = u64_to_double(0xbfc55364b6b08299);
+
+  FP_type result_1 = FMA_test_using_default_compiler_setting( A, B, C);
+  FP_type result_2 = FMA_test_with_pragma_for_NO_contraction( A, B, C);
+  FP_type result_3 = FMA_test_with_pragma_for_YES_contraction(A, B, C);
+  FP_type result_4 = FMA_test_trying_to_disable_optimization( A, B, C);
+
+  printf("(%d "  , result_1 == result_2);
+  printf( "%d "  , result_1 ==             result_3);
+  printf( "%d) " , result_1 ==                         result_4);
+  printf("(%d "  ,             result_2 == result_3);
+  printf( "%d) " ,             result_2 ==             result_4);
+  printf("(%d)\n",                         result_3 == result_4);
+
+  return ! ( (result_1 == result_2) && (result_1 == result_3) && (result_1 == result_4) &&
+             (result_2 == result_3) && (result_2 == result_4) &&
+             (result_3 == result_4)
+           );
+}
Index: tools/Makefile
===================================================================
--- tools/Makefile
+++ tools/Makefile
@@ -24,6 +24,9 @@
 	chmod u+x $@
 endif
 
+FP-contraction_detection___-target: FP-contraction_detection.c
+	$(LD_ENV_OVERRIDES) $(LCC) -o $@ $< $(LDFLAGS) $(CFLAGS) $(TARGET_FLAGS) -O3
+
 fpcmp: fpcmp.c
 	$(ORIGINAL_CC) $(CFLAGS) -O3 -o $@ $<