Modify emission of jump tables on darwin to emit an extra "l" label that

delimits the boundaries of jump tables.  This lets the linker's dead code
stripping optimization do a better job.

llvm-svn: 33315

2 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCTargetAsmInfo.cpp b/llvm/lib/Target/PowerPC/PPCTargetAsmInfo.cpp
index b9f5849bdf6..b54c9e9eb65 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetAsmInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetAsmInfo.cpp
@@ -57,6 +57,13 @@ DarwinTargetAsmInfo::DarwinTargetAsmInfo(const PPCTargetMachine &TM)
   UsedDirective = "\t.no_dead_strip\t";
   WeakRefDirective = "\t.weak_reference\t";
   HiddenDirective = "\t.private_extern\t";
+  
+  // In non-PIC modes, emit a special label before jump tables so that the
+  // linker can perform more accurate dead code stripping.
+  if (TM.getRelocationModel() != Reloc::PIC_) {
+    // Emit a local label that is preserved until the linker runs.
+    JumpTableSpecialLabelPrefix = "l";
+  }
 }
 
 LinuxTargetAsmInfo::LinuxTargetAsmInfo(const PPCTargetMachine &TM)
diff --git a/llvm/lib/Target/X86/X86TargetAsmInfo.cpp b/llvm/lib/Target/X86/X86TargetAsmInfo.cpp
index 1735220ae2c..2bb4a6c2272 100644
--- a/llvm/lib/Target/X86/X86TargetAsmInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetAsmInfo.cpp
@@ -68,6 +68,13 @@ X86TargetAsmInfo::X86TargetAsmInfo(const X86TargetMachine &TM) {
     WeakRefDirective = "\t.weak_reference\t";
     HiddenDirective = "\t.private_extern\t";
     
+    // In non-PIC modes, emit a special label before jump tables so that the
+    // linker can perform more accurate dead code stripping.
+    if (TM.getRelocationModel() != Reloc::PIC_) {
+      // Emit a local label that is preserved until the linker runs.
+      JumpTableSpecialLabelPrefix = "l";
+    }
+    
     NeedsSet = true;
     DwarfAbbrevSection = ".section __DWARF,__debug_abbrev,regular,debug";
     DwarfInfoSection = ".section __DWARF,__debug_info,regular,debug";