teach tblgen to allow patterns like (add (i32 (bitconvert (i32 GPR))), 4),

transforming it into (add (i32 GPR), 4).  This allows us to write type
generic multi patterns and have tblgen automatically drop the bitconvert
in the case when the types align.  This allows us to fold an extra load
in the changed testcase.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99756 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 37 insertions, 1 deletions

diff --git a/utils/TableGen/CodeGenDAGPatterns.cpp b/utils/TableGen/CodeGenDAGPatterns.cpp
index 6bb239ac69..a29c5539fc 100644
--- a/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -1591,6 +1591,40 @@ TreePatternNode *TreePattern::ParseTreePattern(Init *TheInit, StringRef OpName){
   return Result;
 }
 
+/// SimplifyTree - See if we can simplify this tree to eliminate something that
+/// will never match in favor of something obvious that will.  This is here
+/// strictly as a convenience to target authors because it allows them to write
+/// more type generic things and have useless type casts fold away.
+///
+/// This returns true if any change is made.
+static bool SimplifyTree(TreePatternNode *&N) {
+  if (N->isLeaf())
+    return false;
+
+  // If we have a bitconvert with a resolved type and if the source and
+  // destination types are the same, then the bitconvert is useless, remove it.
+  if (N->getOperator()->getName() == "bitconvert" &&
+      N->getNumChildren() > 0 && // FIXME
+      N->getExtType(0).isConcrete() &&
+      N->getExtType(0) == N->getChild(0)->getExtType(0) &&
+      N->getName().empty()) {
+    N = N->getChild(0);
+    SimplifyTree(N);
+    return true;
+  }
+
+  // Walk all children.
+  bool MadeChange = false;
+  for (unsigned i = 0, e = N->getNumChildren(); i != e; ++i) {
+    TreePatternNode *Child = N->getChild(i);
+    MadeChange |= SimplifyTree(Child);
+    N->setChild(i, Child);
+  }
+  return MadeChange;
+}
+
+
+
 /// InferAllTypes - Infer/propagate as many types throughout the expression
 /// patterns as possible.  Return true if all types are inferred, false
 /// otherwise.  Throw an exception if a type contradiction is found.
@@ -1602,8 +1636,10 @@ InferAllTypes(const StringMap<SmallVector<TreePatternNode*,1> > *InNamedTypes) {
   bool MadeChange = true;
   while (MadeChange) {
     MadeChange = false;
-    for (unsigned i = 0, e = Trees.size(); i != e; ++i)
+    for (unsigned i = 0, e = Trees.size(); i != e; ++i) {
       MadeChange |= Trees[i]->ApplyTypeConstraints(*this, false);
+      MadeChange |= SimplifyTree(Trees[i]);
+    }
 
     // If there are constraints on our named nodes, apply them.
     for (StringMap<SmallVector<TreePatternNode*,1> >::iterator