Implement global merge optimization for global variables.

This commit implements two command line switches -global-merge-on-external
and -global-merge-aligned, and both of them are false by default, so this
optimization is disabled by default for all targets.

For ARM64, some back-end behaviors need to be tuned to get this optimization
further enabled.

llvm-svn: 208934

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 37a2c3220cb..0c4865f2f27 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -946,8 +946,11 @@ bool AsmPrinter::doFinalization(Module &M) {
       EmitVisibility(Name, Alias.getVisibility());
 
       // Emit the directives as assignments aka .set:
-      OutStreamer.EmitAssignment(Name,
-                                 MCSymbolRefExpr::Create(Target, OutContext));
+      const MCExpr *Expr = MCSymbolRefExpr::Create(Target, OutContext);
+      if (uint64_t Offset = Alias.calculateOffset(*TM.getDataLayout()))
+        Expr = MCBinaryExpr::CreateAdd(Expr,
+                 MCConstantExpr::Create(Offset, OutContext), OutContext);
+      OutStreamer.EmitAssignment(Name, Expr);
     }
   }