Explain FIXME.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131952 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index ff88b6f..e9cfe43 100644
--- a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -225,10 +225,11 @@
 
 static SectionKind
 getELFKindForNamedSection(StringRef Name, SectionKind K) {
-  // FIXME: Why is this here? Codegen is should not be in the business
-  // of figuring section flags. If the user wrote section(".eh_frame"),
-  // we should just pass that to MC which will defer to the assembly
-  // or use its default if producing an object file.
+  // N.B.: The defaults used in here are no the same ones used in MC.
+  // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
+  // both gas and MC will produce a section with no flags. Given
+  // section(".eh_frame") gcc will produce
+  // .section	.eh_frame,"a",@progbits
   if (Name.empty() || Name[0] != '.') return K;
 
   // Some lame default implementation based on some magic section names.