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Refactor the code that checks that all operands of a node are UNDEFs.

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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
This commit is contained in:
Nadav Rotem 2012-07-15 08:38:23 +00:00
parent 7d532c8d07
commit b87bdac6a3
3 changed files with 32 additions and 13 deletions
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4
include/llvm/CodeGen/SelectionDAGNodes.h
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@ -74,6 +74,10 @@ namespace ISD {
/// 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
//===----------------------------------------------------------------------===//

20
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -7598,6 +7598,11 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
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 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
// 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 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
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 @@ SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
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();

21
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -219,6 +219,22 @@ bool ISD::isScalarToVector(const SDNode *N) {
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 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
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 &&