From c036d844be3aaf95a1479ccfd07607777ec86522 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Mon, 19 Nov 2018 14:35:22 +0000 Subject: [PATCH] [SelectionDAG] add simplifySelect() to reduce code duplication; NFC This should be extended to handle FP and vectors in follow-up patches. llvm-svn: 347210 --- llvm/include/llvm/CodeGen/SelectionDAG.h | 3 ++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 20 ++---------- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 43 +++++++++++++++----------- 3 files changed, 30 insertions(+), 36 deletions(-) diff --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h index 2a9763f..541abf0 100644 --- a/llvm/include/llvm/CodeGen/SelectionDAG.h +++ b/llvm/include/llvm/CodeGen/SelectionDAG.h @@ -962,6 +962,9 @@ public: False, getCondCode(Cond)); } + /// Try to simplify a select/vselect into 1 of its operands or a constant. + SDValue simplifySelect(SDValue Cond, SDValue TVal, SDValue FVal); + /// VAArg produces a result and token chain, and takes a pointer /// and a source value as input. SDValue getVAArg(EVT VT, const SDLoc &dl, SDValue Chain, SDValue Ptr, diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 0f428b7..31589fe 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -7236,24 +7236,8 @@ SDValue DAGCombiner::visitSELECT(SDNode *N) { EVT VT0 = N0.getValueType(); SDLoc DL(N); - // select undef, N1, N2 --> N1 (if it's a constant), otherwise N2 - if (N0.isUndef()) - return isa(N1) ? N1 : N2; - // select, ?, undef, N2 --> N2 - if (N1.isUndef()) - return N2; - // select, ?, N1, undef --> N1 - if (N2.isUndef()) - return N1; - - // fold (select true, X, Y) -> X - // fold (select false, X, Y) -> Y - if (auto *N0C = dyn_cast(N0)) - return N0C->isNullValue() ? N2 : N1; - - // select ?, N1, N1 --> N1 - if (N1 == N2) - return N1; + if (SDValue V = DAG.simplifySelect(N0, N1, N2)) + return V; // fold (select X, X, Y) -> (or X, Y) // fold (select X, 1, Y) -> (or C, Y) diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 45c435a3..7be9459 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -5078,24 +5078,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT, break; } case ISD::SELECT: - // select undef, N2, N3 --> N2 (if it's a constant), otherwise N3 - if (N1.isUndef()) - return isa(N2) ? N2 : N3; - // select, ?, undef, N3 --> N3 - if (N2.isUndef()) - return N3; - // select, ?, N2, undef --> N2 - if (N3.isUndef()) - return N2; - - // select true, N2, N3 --> N2 - // select false, N2, N3 --> N3 - if (auto *N1C = dyn_cast(N1)) - return N1C->isNullValue() ? N3 : N2; - - // select ?, N2, N2 --> N2 - if (N2 == N3) - return N2; + if (SDValue V = simplifySelect(N1, N2, N3)) + return V; break; case ISD::VECTOR_SHUFFLE: llvm_unreachable("should use getVectorShuffle constructor!"); @@ -6795,6 +6779,29 @@ SDValue SelectionDAG::getMaskedScatter(SDVTList VTs, EVT VT, const SDLoc &dl, return V; } +SDValue SelectionDAG::simplifySelect(SDValue Cond, SDValue T, SDValue F) { + // select undef, T, F --> T (if T is a constant), otherwise F + // select, ?, undef, F --> F + // select, ?, T, undef --> T + if (Cond.isUndef()) + return isa(T) ? T : F; + if (T.isUndef()) + return F; + if (F.isUndef()) + return T; + + // fold (select true, T, F) -> T + // fold (select false, T, F) -> F + if (auto *CondC = dyn_cast(Cond)) + return CondC->isNullValue() ? F : T; + + // select ?, T, T --> T + if (T == F) + return T; + + return SDValue(); +} + SDValue SelectionDAG::getVAArg(EVT VT, const SDLoc &dl, SDValue Chain, SDValue Ptr, SDValue SV, unsigned Align) { SDValue Ops[] = { Chain, Ptr, SV, getTargetConstant(Align, dl, MVT::i32) }; -- 2.7.4