1 files changed, 28 insertions, 1 deletions
diff --git a/lib/Target/PowerPC/PPCTargetMachine.cpp b/lib/Target/PowerPC/PPCTargetMachine.cpp
index 8079c6e..c7f7882 100644
--- a/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -194,4 +194,31 @@ bool PPCTargetMachine::addSimpleCodeEmitter(PassManagerBase &PM,
   return false;
 }
 
-
+/// getLSDAEncoding - Returns the LSDA pointer encoding. The choices are 4-byte,
+/// 8-byte, and target default. The CIE is hard-coded to indicate that the LSDA
+/// pointer in the FDE section is an "sdata4", and should be encoded as a 4-byte
+/// pointer by default. However, some systems may require a different size due
+/// to bugs or other conditions. We will default to a 4-byte encoding unless the
+/// system tells us otherwise.
+///
+/// The issue is when the CIE says their is an LSDA. That mandates that every
+/// FDE have an LSDA slot. But if the function does not need an LSDA. There
+/// needs to be some way to signify there is none. The LSDA is encoded as
+/// pc-rel. But you don't look for some magic value after adding the pc. You
+/// have to look for a zero before adding the pc. The problem is that the size
+/// of the zero to look for depends on the encoding. The unwinder bug in SL is
+/// that it always checks for a pointer-size zero. So on x86_64 it looks for 8
+/// bytes of zero. If you have an LSDA, it works fine since the 8-bytes are
+/// non-zero so it goes ahead and then reads the value based on the encoding.
+/// But if you use sdata4 and there is no LSDA, then the test for zero gives a
+/// false negative and the unwinder thinks there is an LSDA.
+///
+/// FIXME: This call-back isn't good! We should be using the correct encoding
+/// regardless of the system. However, there are some systems which have bugs
+/// that prevent this from occuring.
+DwarfLSDAEncoding::Encoding PPCTargetMachine::getLSDAEncoding() const {
+  if (Subtarget.isDarwin() && Subtarget.getDarwinVers() != 10)
+    return DwarfLSDAEncoding::Default;
+
+  return DwarfLSDAEncoding::EightByte;
+}