implement a simple proof-of-concept optimization for

the new isel: fold movechild+record+moveparent into a
single recordchild N node.  This shrinks the X86 table
from 125443 to 117502 bytes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97031 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 2 deletions

diff --git a/utils/TableGen/DAGISelMatcherOpt.cpp b/utils/TableGen/DAGISelMatcherOpt.cpp
index 7859f36..d365820 100644
--- a/utils/TableGen/DAGISelMatcherOpt.cpp
+++ b/utils/TableGen/DAGISelMatcherOpt.cpp
@@ -14,6 +14,35 @@
 #include "DAGISelMatcher.h"
 using namespace llvm;
 
-void llvm::OptimizeMatcher(const MatcherNode *Matcher) {
-  // Nothing yet.
+
+static void FormRecordChildNodes(OwningPtr<MatcherNode> &Matcher) {
+  // If we reached the end of the chain, we're done.
+  MatcherNode *N = Matcher.get();
+  if (N == 0) return;
+  
+  // If we have a push node, walk down both edges.
+  if (PushMatcherNode *Push = dyn_cast<PushMatcherNode>(N))
+    FormRecordChildNodes(Push->getFailurePtr());
+  
+  // If we found a movechild node, check to see if our pattern matches.
+  if (MoveChildMatcherNode *MC = dyn_cast<MoveChildMatcherNode>(N)) {
+    if (RecordMatcherNode *RM = dyn_cast<RecordMatcherNode>(MC->getNext()))
+      if (MoveParentMatcherNode *MP = 
+                 dyn_cast<MoveParentMatcherNode>(RM->getNext())) {
+        MatcherNode *New
+          = new RecordChildMatcherNode(MC->getChildNo(), RM->getWhatFor());
+        New->setNext(MP->takeNext());
+        Matcher.reset(New);
+        return FormRecordChildNodes(Matcher);
+      }
+  }
+
+  FormRecordChildNodes(N->getNextPtr());
+}
+
+
+MatcherNode *llvm::OptimizeMatcher(MatcherNode *Matcher) {
+  OwningPtr<MatcherNode> MatcherPtr(Matcher);
+  FormRecordChildNodes(MatcherPtr);
+  return MatcherPtr.take();
 }