[llvm-commits] [llvm] r134729 - /llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp

[Jim Grosbach]

Author: grosbach
Date: Fri Jul  8 15:18:11 2011
New Revision: 134729

URL: http://llvm.org/viewvc/llvm-project?rev=134729&view=rev
Log:
Add more info to FIXME.

Modified:
    llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp

Modified: llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp?rev=134729&r1=134728&r2=134729&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp Fri Jul  8 15:18:11 2011
@@ -1637,7 +1637,11 @@
     return false;
 
   // FIXME: Completely disable sibcall for Thumb1 since Thumb1RegisterInfo::
-  // emitEpilogue is not ready for them.
+  // emitEpilogue is not ready for them. Thumb tail calls also use t2B, as
+  // the Thumb1 16-bit unconditional branch doesn't have sufficient relocation
+  // support in the assembler and linker to be used. This would need to be
+  // fixed to fully support tail calls in Thumb1.
+  //
   // Doing this is tricky, since the LDM/POP instruction on Thumb doesn't take
   // LR.  This means if we need to reload LR, it takes an extra instructions,
   // which outweighs the value of the tail call; but here we don't know yet