Revert the earlier change that removed the M_REMATERIALIZABLE machine
instruction flag, and use the flag along with a virtual member function
hook for targets to override if there are instructions that are only
trivially rematerializable with specific operands (i.e. constant pool
loads).

llvm-svn: 37728
diff --git a/llvm/utils/TableGen/CodeGenInstruction.h b/llvm/utils/TableGen/CodeGenInstruction.h
index 4f76de8..54d9b3f 100644
--- a/llvm/utils/TableGen/CodeGenInstruction.h
+++ b/llvm/utils/TableGen/CodeGenInstruction.h
@@ -91,6 +91,7 @@
     bool isConvertibleToThreeAddress;
     bool isCommutable;
     bool isTerminator;
+    bool isReMaterializable;
     bool hasDelaySlot;
     bool usesCustomDAGSchedInserter;
     bool hasVariableNumberOfOperands;