[llvm] 6c2ad4c - [SDAG] Extract helper to determine neutral element (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-10-29T22:05:06+01:00
New Revision: 6c2ad4cf8758335e0896ba0540b21bbf6d239fbd

URL: https://github.com/llvm/llvm-project/commit/6c2ad4cf8758335e0896ba0540b21bbf6d239fbd
DIFF: https://github.com/llvm/llvm-project/commit/6c2ad4cf8758335e0896ba0540b21bbf6d239fbd.diff

LOG: [SDAG] Extract helper to determine neutral element (NFC)

Make the existing VECREDUCE based code more generic, but expressing
it in terms of the neutral value of the base opcode instead.

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/SelectionDAG.h
    llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
    llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
index 4c0412315c19..efbb8bdb5f9b 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -2000,6 +2000,10 @@ class SelectionDAG {
 
   bool shouldOptForSize() const;
 
+  /// Get the (commutative) neutral element for the given opcode, if it exists.
+  SDValue getNeutralElement(unsigned Opcode, const SDLoc &DL, EVT VT,
+                            SDNodeFlags Flags);
+
 private:
   void InsertNode(SDNode *N);
   bool RemoveNodeFromCSEMaps(SDNode *N);

diff  --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 333c604690ab..b46ea1be7a30 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -4757,48 +4757,9 @@ SDValue DAGTypeLegalizer::WidenVecOp_VECREDUCE(SDNode *N) {
   EVT ElemVT = OrigVT.getVectorElementType();
   SDNodeFlags Flags = N->getFlags();
 
-  SDValue NeutralElem;
-  switch (N->getOpcode()) {
-  case ISD::VECREDUCE_ADD:
-  case ISD::VECREDUCE_OR:
-  case ISD::VECREDUCE_XOR:
-  case ISD::VECREDUCE_UMAX:
-    NeutralElem = DAG.getConstant(0, dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_MUL:
-    NeutralElem = DAG.getConstant(1, dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_AND:
-  case ISD::VECREDUCE_UMIN:
-    NeutralElem = DAG.getAllOnesConstant(dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_SMAX:
-    NeutralElem = DAG.getConstant(
-        APInt::getSignedMinValue(ElemVT.getSizeInBits()), dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_SMIN:
-    NeutralElem = DAG.getConstant(
-        APInt::getSignedMaxValue(ElemVT.getSizeInBits()), dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_FADD:
-    NeutralElem = DAG.getConstantFP(-0.0, dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_FMUL:
-    NeutralElem = DAG.getConstantFP(1.0, dl, ElemVT);
-    break;
-  case ISD::VECREDUCE_FMIN:
-  case ISD::VECREDUCE_FMAX: {
-    // Neutral element for fminnum is NaN, Inf or FLT_MAX, depending on FMF.
-    const fltSemantics &Semantics = DAG.EVTToAPFloatSemantics(ElemVT);
-    APFloat NeutralAF = !Flags.hasNoNaNs() ? APFloat::getQNaN(Semantics) :
-                        !Flags.hasNoInfs() ? APFloat::getInf(Semantics) :
-                        APFloat::getLargest(Semantics);
-    if (N->getOpcode() == ISD::VECREDUCE_FMAX)
-      NeutralAF.changeSign();
-
-    NeutralElem = DAG.getConstantFP(NeutralAF, dl, ElemVT);
-  }
-  }
+  SDValue NeutralElem = DAG.getNeutralElement(
+      ISD::getVecReduceBaseOpcode(N->getOpcode()), dl, ElemVT, Flags);
+  assert(NeutralElem && "Neutral element must exist");
 
   // Pad the vector with the neutral element.
   unsigned OrigElts = OrigVT.getVectorNumElements();

diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 8939392708a2..709b0f44f0a5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -10090,6 +10090,44 @@ SDValue SelectionDAG::getTokenFactor(const SDLoc &DL,
   return getNode(ISD::TokenFactor, DL, MVT::Other, Vals);
 }
 
+SDValue SelectionDAG::getNeutralElement(unsigned Opcode, const SDLoc &DL,
+                                        EVT VT, SDNodeFlags Flags) {
+  switch (Opcode) {
+  default:
+    return SDValue();
+  case ISD::ADD:
+  case ISD::OR:
+  case ISD::XOR:
+  case ISD::UMAX:
+    return getConstant(0, DL, VT);
+  case ISD::MUL:
+    return getConstant(1, DL, VT);
+  case ISD::AND:
+  case ISD::UMIN:
+    return getAllOnesConstant(DL, VT);
+  case ISD::SMAX:
+    return getConstant(APInt::getSignedMinValue(VT.getSizeInBits()), DL, VT);
+  case ISD::SMIN:
+    return getConstant(APInt::getSignedMaxValue(VT.getSizeInBits()), DL, VT);
+  case ISD::FADD:
+    return getConstantFP(-0.0, DL, VT);
+  case ISD::FMUL:
+    return getConstantFP(1.0, DL, VT);
+  case ISD::FMINNUM:
+  case ISD::FMAXNUM: {
+    // Neutral element for fminnum is NaN, Inf or FLT_MAX, depending on FMF.
+    const fltSemantics &Semantics = EVTToAPFloatSemantics(VT);
+    APFloat NeutralAF = !Flags.hasNoNaNs() ? APFloat::getQNaN(Semantics) :
+                        !Flags.hasNoInfs() ? APFloat::getInf(Semantics) :
+                        APFloat::getLargest(Semantics);
+    if (Opcode == ISD::FMAXNUM)
+      NeutralAF.changeSign();
+
+    return getConstantFP(NeutralAF, DL, VT);
+  }
+  }
+}
+
 #ifndef NDEBUG
 static void checkForCyclesHelper(const SDNode *N,
                                  SmallPtrSetImpl<const SDNode*> &Visited,