Function Layout, Global Variable Layout and Pooled Constants Layout Reordering

src/IceELFObjectWriter.cpp

Index: src/IceELFObjectWriter.cpp
diff --git a/src/IceELFObjectWriter.cpp b/src/IceELFObjectWriter.cpp
index 05497548c99fdcb080ccdd7b47420defa8ff7de1..21bd77795aeff931669289e2e3554eec8a72ff84 100644
--- a/src/IceELFObjectWriter.cpp
+++ b/src/IceELFObjectWriter.cpp
@@ -390,8 +390,9 @@ void ELFObjectWriter::writeDataOfType(SectionType ST,
            Var->getInitializers()) {
         switch (Init->getKind()) {
         case VariableDeclaration::Initializer::DataInitializerKind: {
-          const auto Data = llvm::cast<VariableDeclaration::DataInitializer>(
-                                Init.get())->getContents();
+          const auto Data =

[John, 2015/06/24 00:24:00]

please change this to

const auto& Data,

or this will copy contents.

[qining, 2015/06/24 01:20:40]

Done.

+              llvm::cast<VariableDeclaration::DataInitializer>(Init.get())
+                  ->getContents();
           Section->appendData(Str, llvm::StringRef(Data.data(), Data.size()));
           break;
         }
@@ -507,6 +508,13 @@ template <typename ConstType> void ELFObjectWriter::writeConstantPool(Type Ty) {
   const SizeT SymbolSize = 0;
   Section->setFileOffset(alignFileOffset(Align));
 
+  // If the -reorder-pooled-constant option is set to true, we should shuffle
+  // the constants before we emit them.
+  if (Ctx.getFlags().shouldReorderPooledConstants())
+    RandomShuffle(Pool.begin(), Pool.end(), [this](uint64_t N) {

[John, 2015/06/24 00:24:00]

Can you capture [Ctx] instead of [this]?

[qining, 2015/06/24 01:20:40]

Done. But it seems I can't capture Ctx or its reference directly as it is a
member of this class. My workaround is declaring a pointer to Ctx and capture
the pointer instead. But actually I'm not sure this is better than capturing
this.

[John, 2015/06/24 08:15:54]

Oh, I was genuinely asking whether capturing [Ctx] would work. I wasn't sure. My
hint that this should not work in C++11 is that capturing [Ctx] actually mean
capturing [this->Ctx], which is not valid.

+      return (uint32_t)Ctx.getRNG().next(N);
+    });
+
   // Write the data.
   for (Constant *C : Pool) {
     if (!C->getShouldBePooled())