[llvm] r347210 - [SelectionDAG] add simplifySelect() to reduce code duplication; NFC
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 19 06:35:22 PST 2018
Author: spatel
Date: Mon Nov 19 06:35:22 2018
New Revision: 347210
URL: http://llvm.org/viewvc/llvm-project?rev=347210&view=rev
Log:
[SelectionDAG] add simplifySelect() to reduce code duplication; NFC
This should be extended to handle FP and vectors in follow-up patches.
Modified:
llvm/trunk/include/llvm/CodeGen/SelectionDAG.h
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
Modified: llvm/trunk/include/llvm/CodeGen/SelectionDAG.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SelectionDAG.h?rev=347210&r1=347209&r2=347210&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/SelectionDAG.h (original)
+++ llvm/trunk/include/llvm/CodeGen/SelectionDAG.h Mon Nov 19 06:35:22 2018
@@ -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,
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=347210&r1=347209&r2=347210&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Nov 19 06:35:22 2018
@@ -7236,24 +7236,8 @@ SDValue DAGCombiner::visitSELECT(SDNode
EVT VT0 = N0.getValueType();
SDLoc DL(N);
- // select undef, N1, N2 --> N1 (if it's a constant), otherwise N2
- if (N0.isUndef())
- return isa<ConstantSDNode>(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<const ConstantSDNode>(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)
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=347210&r1=347209&r2=347210&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Mon Nov 19 06:35:22 2018
@@ -5078,24 +5078,8 @@ SDValue SelectionDAG::getNode(unsigned O
break;
}
case ISD::SELECT:
- // select undef, N2, N3 --> N2 (if it's a constant), otherwise N3
- if (N1.isUndef())
- return isa<ConstantSDNode>(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<ConstantSDNode>(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(S
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<ConstantSDNode>(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<ConstantSDNode>(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) };
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