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@intel.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160229 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1e87d51..0e5ecd5 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -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();
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index a8dce21..3947648 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -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 &&