Define __FINITE_MATH_ONLY__ based on -ffast-math and -ffinite-math-only.

This macro was being unconditionally set to zero, preceded by a FIXME comment.
This fixes <rdar://problem/11845441>.  Patch by Michael Gottesman!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160491 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/InitPreprocessor.cpp b/lib/Frontend/InitPreprocessor.cpp
index 6120d11..3979731 100644
--- a/lib/Frontend/InitPreprocessor.cpp
+++ b/lib/Frontend/InitPreprocessor.cpp
@@ -527,9 +527,10 @@
   if (const char *Prefix = TI.getUserLabelPrefix())
     Builder.defineMacro("__USER_LABEL_PREFIX__", Prefix);
 
-  // Build configuration options.  FIXME: these should be controlled by
-  // command line options or something.
-  Builder.defineMacro("__FINITE_MATH_ONLY__", "0");
+  if (LangOpts.FastMath || LangOpts.FiniteMathOnly)
+    Builder.defineMacro("__FINITE_MATH_ONLY__", "1");
+  else
+    Builder.defineMacro("__FINITE_MATH_ONLY__", "0");
 
   if (LangOpts.GNUInline)
     Builder.defineMacro("__GNUC_GNU_INLINE__");