ThinLTO : Import always_inline functions irrespective of the threshold

Summary: A user can force a function to be inlined by specifying the always_inline attribute. Currently, thinlto implementation is not aware of always_inline functions and does not guarantee import of such functions, which in turn can prevent inlining of such functions.

Patch by Bharathi Seshadri <bseshadr@cisco.com>

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70014

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -960,6 +960,7 @@ static FunctionSummary::FFlags getDecodedFFlags(uint64_t RawFlags) {
   Flags.NoRecurse = (RawFlags >> 2) & 0x1;
   Flags.ReturnDoesNotAlias = (RawFlags >> 3) & 0x1;
   Flags.NoInline = (RawFlags >> 4) & 0x1;
+  Flags.AlwaysInline = (RawFlags >> 5) & 0x1;
   return Flags;
 }