ARM: permit tail calls to weak externals on COFF

Weak externals are resolved statically, so we can actually generate the tail
call on PE/COFF targets without breaking the requirements.  It is questionable
whether we want to propagate the current behaviour for MachO as the requirements
are part of the ARM ELF specifications, and it seems that prior to the SVN
r215890, we would have tail'ed the call.  For now, be conservative and only
permit it on PE/COFF where the call will always be fully resolved.

llvm-svn: 225119

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 7c4ebc03d8b..85a6617bbf6 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -2026,7 +2026,9 @@ ARMTargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
   // cannot rely on the linker replacing the tail call with a return.
   if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
     const GlobalValue *GV = G->getGlobal();
-    if (GV->hasExternalWeakLinkage())
+    const Triple TT(getTargetMachine().getTargetTriple());
+    if (GV->hasExternalWeakLinkage() &&
+        (!TT.isOSWindows() || TT.isOSBinFormatELF() || TT.isOSBinFormatMachO()))
       return false;
   }