[llvm-commits] [llvm] r160229 - in /llvm/trunk: include/llvm/CodeGen/SelectionDAGNodes.h lib/CodeGen/SelectionDAG/DAGCombiner.cpp lib/CodeGen/SelectionDAG/SelectionDAG.cpp

[Nadav Rotem]

Author: nadav
Date: Sun Jul 15 03:38:23 2012
New Revision: 160229

URL: http://llvm.org/viewvc/llvm-project?rev=160229&view=rev
Log:
Refactor the code that checks that all operands of a node are UNDEFs.
Add a micro-optimization to getNode of CONCAT_VECTORS when both operands are undefs.
Can't find a testcase for this because VECTOR_SHUFFLE already handles undef operands, but Duncan suggested that we add this.

Together with Michael Kuperstein <michael.m.kuperstein at intel.com>


Modified:
    llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Modified: llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h?rev=160229&r1=160228&r2=160229&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h (original)
+++ llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h Sun Jul 15 03:38:23 2012
@@ -74,6 +74,10 @@
   /// ISD::SCALAR_TO_VECTOR node or a BUILD_VECTOR node where only the low
   /// element is not an undef.
   bool isScalarToVector(const SDNode *N);
+
+  /// allOperandsUndef - Return true if the node has at least one operand
+  /// and all operands of the specified node are ISD::UNDEF.
+  bool allOperandsUndef(const SDNode *N);
 }  // end llvm:ISD namespace
 
 //===----------------------------------------------------------------------===//

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=160229&r1=160228&r2=160229&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Sun Jul 15 03:38:23 2012
@@ -7598,6 +7598,11 @@
   unsigned NumInScalars = N->getNumOperands();
   DebugLoc dl = N->getDebugLoc();
   EVT VT = N->getValueType(0);
+
+  // A vector built entirely of undefs is undef.
+  if (ISD::allOperandsUndef(N))
+    return DAG.getUNDEF(VT);
+
   // Check to see if this is a BUILD_VECTOR of a bunch of values
   // which come from any_extend or zero_extend nodes. If so, we can create
   // a new BUILD_VECTOR using bit-casts which may enable other BUILD_VECTOR
@@ -7605,12 +7610,11 @@
   // using shuffles.
   EVT SourceType = MVT::Other;
   bool AllAnyExt = true;
-  bool AllUndef = true;
+
   for (unsigned i = 0; i != NumInScalars; ++i) {
     SDValue In = N->getOperand(i);
     // Ignore undef inputs.
     if (In.getOpcode() == ISD::UNDEF) continue;
-    AllUndef = false;
 
     bool AnyExt  = In.getOpcode() == ISD::ANY_EXTEND;
     bool ZeroExt = In.getOpcode() == ISD::ZERO_EXTEND;
@@ -7638,9 +7642,6 @@
     AllAnyExt &= AnyExt;
   }
 
-  if (AllUndef)
-    return DAG.getUNDEF(VT);
-
   // In order to have valid types, all of the inputs must be extended from the
   // same source type and all of the inputs must be any or zero extend.
   // Scalar sizes must be a power of two.
@@ -7817,14 +7818,7 @@
     return N->getOperand(0);
 
   // Check if all of the operands are undefs.
-  bool AllUndef = true;
-  for (unsigned i = 0; i < N->getNumOperands(); ++i)
-    if (N->getOperand(i).getOpcode() != ISD::UNDEF) {
-      AllUndef = false;
-      break;
-    }
-
-  if (AllUndef)
+  if (ISD::allOperandsUndef(N))
     return DAG.getUNDEF(N->getValueType(0));
 
   return SDValue();

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=160229&r1=160228&r2=160229&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Sun Jul 15 03:38:23 2012
@@ -219,6 +219,22 @@
   return true;
 }
 
+/// allOperandsUndef - Return true if the node has at least one operand
+/// and all operands of the specified node are ISD::UNDEF.
+bool ISD::allOperandsUndef(const SDNode *N) {
+  // Return false if the node has no operands.
+  // This is "logically inconsistent" with the definition of "all" but
+  // is probably the desired behavior.
+  if (N->getNumOperands() == 0)
+    return false;
+
+  for (unsigned i = 0, e = N->getNumOperands(); i != e ; ++i)
+    if (N->getOperand(i).getOpcode() != ISD::UNDEF)
+      return false;
+
+  return true;
+}
+
 /// getSetCCSwappedOperands - Return the operation corresponding to (Y op X)
 /// when given the operation for (X op Y).
 ISD::CondCode ISD::getSetCCSwappedOperands(ISD::CondCode Operation) {
@@ -2674,6 +2690,11 @@
     if (N1 == N2) return N1;
     break;
   case ISD::CONCAT_VECTORS:
+    // Concat of UNDEFs is UNDEF.
+    if (N1.getOpcode() == ISD::UNDEF &&
+        N2.getOpcode() == ISD::UNDEF)
+      return getUNDEF(VT);
+
     // A CONCAT_VECTOR with all operands BUILD_VECTOR can be simplified to
     // one big BUILD_VECTOR.
     if (N1.getOpcode() == ISD::BUILD_VECTOR &&