Fix non-determinism in DAGISel emitter.

 - This manifested as non-determinism in the .inc output in rare cases (when two
   distinct patterns ended up being equivalent, which is rather rare). That
   meant the pattern matching was non-deterministic, which could eventually mean
   the code generator selected different instructions based on the arch.

 - It's probably worth making the DAGISel ensure a total ordering (or force the
   user to), but the simple fix here is to totally order the Record* maps based
   on a unique ID.

 - PR4672, PR4711.

Yay:
--
ddunbar@giles:~$ cat ~/llvm.obj.64/lib/Target/*/*.inc | shasum
d1099ff34b21459a5a3e7021c225c080e6017ece  -
ddunbar@giles:~$ cat ~/llvm.obj.ppc/lib/Target/*/*.inc | shasum
d1099ff34b21459a5a3e7021c225c080e6017ece  -
--

llvm-svn: 79846

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
index 2f12a6c4cbe..f0a8c4d74ff 100644
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -100,6 +100,9 @@ bool isExtVectorInVTs(const std::vector<unsigned char> &EVTs) {
 } // end namespace EEVT.
 } // end namespace llvm.
 
+bool RecordPtrCmp::operator()(const Record *LHS, const Record *RHS) const {
+  return LHS->getID() < RHS->getID();
+}
 
 /// Dependent variable map for CodeGenDAGPattern variant generation
 typedef std::map<std::string, int> DepVarMap;