Change the 'isStore' inferrer to look for 'SDNPMayStore' 
instead of "ISD::STORE".  This allows us to mark target-specific dag
nodes as storing (such as ppc byteswap stores).  This allows us to remove
more explicit isStore flags from the .td files.

Finally, add a warning for when a .td file contains an explicit 
isStore and tblgen is able to infer it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45654 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/TargetSelectionDAG.td b/lib/Target/TargetSelectionDAG.td
index 1bdbd20..4659ebd 100644
--- a/lib/Target/TargetSelectionDAG.td
+++ b/lib/Target/TargetSelectionDAG.td
@@ -189,6 +189,7 @@
 def SDNPOutFlag     : SDNodeProperty;   // Write a flag result
 def SDNPInFlag      : SDNodeProperty;   // Read a flag operand
 def SDNPOptInFlag   : SDNodeProperty;   // Optionally read a flag operand
+def SDNPMayStore    : SDNodeProperty;   // May write to memory, sets 'isStore'.
 
 //===----------------------------------------------------------------------===//
 // Selection DAG Node definitions.
@@ -313,8 +314,10 @@
 // Do not use ld, st directly. Use load, extload, sextload, zextload, store,
 // and truncst (see below).
 def ld         : SDNode<"ISD::LOAD"       , SDTLoad,  [SDNPHasChain]>;
-def st         : SDNode<"ISD::STORE"      , SDTStore, [SDNPHasChain]>;
-def ist        : SDNode<"ISD::STORE"      , SDTIStore, [SDNPHasChain]>;
+def st         : SDNode<"ISD::STORE"      , SDTStore,
+                        [SDNPHasChain, SDNPMayStore]>;
+def ist        : SDNode<"ISD::STORE"      , SDTIStore,
+                        [SDNPHasChain, SDNPMayStore]>;
 
 def vector_shuffle : SDNode<"ISD::VECTOR_SHUFFLE", SDTVecShuffle, []>;
 def build_vector : SDNode<"ISD::BUILD_VECTOR", SDTypeProfile<1, 0, []>, []>;