Use .set expression for x86 pic jump table reference to reduce assembly relocation. rdar://7738756

llvm-svn: 101085

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp b/llvm/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
index 2056e9506d7..9e6cf50b6a9 100644
--- a/llvm/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
@@ -169,6 +169,15 @@ MCOperand X86MCInstLower::LowerSymbolOperand(const MachineOperand &MO,
     Expr = MCBinaryExpr::CreateSub(Expr, 
                                MCSymbolRefExpr::Create(GetPICBaseSymbol(), Ctx),
                                    Ctx);
+    if (MO.isJTI() && AsmPrinter.MAI->hasSetDirective()) {
+      // If .set directive is supported, use it to reduce the number of
+      // relocations the assembler will generate for differences between
+      // local labels. This is only safe when the symbols are in the same
+      // section so we are restricting it to jumptable references.
+      MCSymbol *Label = Ctx.CreateTempSymbol();
+      AsmPrinter.OutStreamer.EmitAssignment(Label, Expr);
+      Expr = MCSymbolRefExpr::Create(Label, Ctx);
+    }
     break;
   }