Fixed mingw\cygwin linkonce linkage once again.
Added workaround for linker bug with linkonce sections.
Changed sections prefix to allow linker merge them
(PE loader doesn't like too much long-named sections :) )
All of this unbreaks libstdc++ on mingw32 allowing (small)
programs to be compiled, linked and run.

llvm-svn: 31033
diff --git a/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp b/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
index bb6bb3d..dc2ecca 100755
--- a/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
@@ -40,7 +40,7 @@
     if (Subtarget->isTargetDarwin()) {
       return ".section __TEXT,__textcoal_nt,coalesced,pure_instructions";
     } else if (Subtarget->isTargetCygwin()) {
-      return "\t.section\t.llvm.linkonce.t." + CurrentFnName + ",\"ax\"\n";
+      return "\t.section\t.text$linkonce." + CurrentFnName + ",\"ax\"\n";
     } else {
       return "\t.section\t.llvm.linkonce.t." + CurrentFnName +
              ",\"ax\",@progbits\n";
@@ -90,6 +90,7 @@
     O << "\t.globl\t" << CurrentFnName << "\n";    
     break;
   case Function::LinkOnceLinkage:
+  case Function::WeakLinkage:
     if (Subtarget->isTargetDarwin()) {
       O << "\t.globl\t" << CurrentFnName << "\n";
       O << "\t.weak_definition\t" << CurrentFnName << "\n";
@@ -102,20 +103,13 @@
       O << "\t.weak " << CurrentFnName << "\n";
     }
     break;
-  case Function::WeakLinkage:
-    if (Subtarget->isTargetDarwin()) {
-      O << "\t.globl\t" << CurrentFnName << "\n";
-      O << "\t.weak_definition\t" << CurrentFnName << "\n";
-    } else if (Subtarget->isTargetCygwin()) {
-      EmitAlignment(4, F);     // FIXME: This should be parameterized somewhere.
-      O << "\t.weak " << CurrentFnName << "\n";
-    } else {
-      EmitAlignment(4, F);     // FIXME: This should be parameterized somewhere.
-      O << "\t.weak " << CurrentFnName << "\n";
-    }
-    break;
   }
   O << CurrentFnName << ":\n";
+  // Add some workaround for linkonce linkage on Cygwin\MinGW
+  if (Subtarget->isTargetCygwin() &&
+      (F->getLinkage() == Function::LinkOnceLinkage ||
+       F->getLinkage() == Function::WeakLinkage))
+    O << "_llvm$workaround$fake$stub_" << CurrentFnName << ":\n";
 
   if (Subtarget->isTargetDarwin()) {
     // Emit pre-function debug information.