BitcodeWriter: Remove redundant (and incorrect) check for whether to emit module summary.

[pcc]

Summary

The function name Module::empty() is slightly misleading in that it
only tests for the presence of functions in the module. However we
still want to emit the module summary if the module contains only
global variables or aliases. The presence of such entities can be
determined simply by checking the summary directly, as we are doing
below.

[mehdi_amini]

LGTM

Thanks, that's indeed misleading. But probably coherent with Module::begin /end...

llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp

 // Current version for the summary.
 // This is bumped whenever we introduce changes in the way some record are
 // interpreted, like flags for instance.
 static const uint64_t INDEX_VERSION = 1;
 
 /// Emit the per-module summary section alongside the rest of
 /// the module's bitcode.
 void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
-  if (M.empty())
-    return;
-
   if (Index->begin() == Index->end())
     return;
 
   Stream.EnterSubblock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID, 4);
 
   Stream.EmitRecord(bitc::FS_VERSION, ArrayRef<uint64_t>{INDEX_VERSION});
 
   // Abbrev for FS_PERMODULE.

llvm/trunk/test/Bitcode/thinlto-summary-globalvar.ll

+; RUN: opt -module-summary %s -o - | llvm-bcanalyzer -dump | FileCheck %s
+
+; CHECK: <GLOBALVAL_SUMMARY_BLOCK
+
+@a = global i32 0