Implemented support for "pragma clang optimize on/off", based on attribute 'optnone'.

This patch implements support for selectively disabling optimizations on a
range of function definitions through a pragma. The implementation is that
all function definitions in the range are decorated with attribute
'optnone'.

    #pragma clang optimize off
    // All function definitions in here are decorated with 'optnone'.
    #pragma clang optimize on
    // Compilation resumes as normal.

llvm-svn: 209510
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a3dd2e7..a522ef4 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7373,6 +7373,11 @@
   // marking the function.
   AddCFAuditedAttribute(NewFD);
 
+  // If this is a function definition, check if we have to apply optnone due to
+  // a pragma.
+  if(D.isFunctionDefinition())
+    AddRangeBasedOptnone(NewFD);
+
   // If this is the first declaration of an extern C variable, update
   // the map of such variables.
   if (NewFD->isFirstDecl() && !NewFD->isInvalidDecl() &&