Add IR support, ELF section and user documentation for partitioning feature.

The partitioning feature was proposed here:
http://lists.llvm.org/pipermail/llvm-dev/2019-February/130583.html

This is mostly just documentation. The feature itself will be contributed
in subsequent patches.

Differential Revision: https://reviews.llvm.org/D60242

llvm-svn: 361923

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index bf7776b1dc0..3317952d05d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1632,6 +1632,24 @@ bool AsmPrinter::doFinalization(Module &M) {
         OutStreamer->EmitAddrsigSym(getSymbol(&GV));
   }
 
+  // Emit symbol partition specifications (ELF only).
+  if (TM.getTargetTriple().isOSBinFormatELF()) {
+    unsigned UniqueID = 0;
+    for (const GlobalValue &GV : M.global_values()) {
+      if (!GV.hasPartition() || GV.isDeclarationForLinker() ||
+          GV.getVisibility() != GlobalValue::DefaultVisibility)
+        continue;
+
+      OutStreamer->SwitchSection(OutContext.getELFSection(
+          ".llvm_sympart", ELF::SHT_LLVM_SYMPART, 0, 0, "", ++UniqueID));
+      OutStreamer->EmitBytes(GV.getPartition());
+      OutStreamer->EmitZeros(1);
+      OutStreamer->EmitValue(
+          MCSymbolRefExpr::create(getSymbol(&GV), OutContext),
+          MAI->getCodePointerSize());
+    }
+  }
+
   // Allow the target to emit any magic that it wants at the end of the file,
   // after everything else has gone out.
   EmitEndOfAsmFile(M);