Pull in r175057 from upstream llvm trunk:

  X86: Disable generation of rep;movsl when %esi is used as a base pointer.

  This happens when there is both stack realignment and a dynamic alloca in the
  function. If we overwrite %esi (rep;movsl uses fixed registers) we'll lose the
  base pointer and the next register spill will write into oblivion.

  Fixes PR15249 and unbreaks firefox on i386/freebsd. Mozilla uses dynamic allocas
  and freebsd a 4 byte stack alignment.

MFC after:	1 week

1 files changed, 8 insertions, 0 deletions

diff --git a/contrib/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp b/contrib/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
index 723e50c..efc3490 100644
--- a/contrib/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
+++ b/contrib/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
@@ -202,6 +202,14 @@ X86SelectionDAGInfo::EmitTargetCodeForMemcpy(SelectionDAG &DAG, DebugLoc dl,
       SrcPtrInfo.getAddrSpace() >= 256)
     return SDValue();
 
+  // ESI might be used as a base pointer, in that case we can't simply overwrite
+  // the register.  Fall back to generic code.
+  const X86RegisterInfo *TRI =
+      static_cast<const X86RegisterInfo *>(DAG.getTarget().getRegisterInfo());
+  if (TRI->hasBasePointer(DAG.getMachineFunction()) &&
+      TRI->getBaseRegister() == X86::ESI)
+    return SDValue();
+
   MVT AVT;
   if (Align & 1)
     AVT = MVT::i8;