fix minsize detection: minsize attribute implies optimizing for size

Also, add a test for optsize because this was not part of any existing regression test.

llvm-svn: 244651
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 3768807..9e0ac96 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -214,8 +214,7 @@
     TLI = TM->getSubtargetImpl(F)->getTargetLowering();
   TLInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
   TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
-  // FIXME: Use Function::optForSize().
-  OptSize = F.hasFnAttribute(Attribute::OptimizeForSize);
+  OptSize = F.optForSize();
 
   /// This optimization identifies DIV instructions that can be
   /// profitably bypassed and carried out with a shorter, faster divide.