propagate IR-level fast-math-flags to DAG nodes, disabled by default

This is an updated version of the patch that was checked in at:
http://reviews.llvm.org/rL237046

but subsequently reverted because it exposed a bug in the DAG Combiner:
http://reviews.llvm.org/D9893

This time, there's an enablement flag ("EnableFMFInDAG") around the code in
SelectionDAGBuilder where we copy the set of FP optimization flags from IR
instructions to DAG nodes. So, in theory, there should be no functional change
from this patch as-is, but it will allow testing with the added functionality
to proceed via "-enable-fmf-dag" passed to llc.

This patch adds the minimum plumbing necessary to use IR-level
fast-math-flags (FMF) in the backend without actually using
them for anything yet. This is a follow-on to:
http://reviews.llvm.org/rL235997

Differential Revision: http://reviews.llvm.org/D10403

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239828 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/SelectionDAG.h b/include/llvm/CodeGen/SelectionDAG.h
index 78fdd040773e3f12bc4edc367fcf716c2cc30228..aa50dea25765228de708e815e805054641f4b168 100644 (file)
--- a/include/llvm/CodeGen/SelectionDAG.h
+++ b/include/llvm/CodeGen/SelectionDAG.h
@@ -669,7 +669,7 @@ public:
   SDValue getNode(unsigned Opcode, SDLoc DL, EVT VT);
   SDValue getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N);
   SDValue getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1, SDValue N2,
-                  bool nuw = false, bool nsw = false, bool exact = false);
+                  const SDNodeFlags *Flags = nullptr);
   SDValue getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1, SDValue N2,
                   SDValue N3);
   SDValue getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1, SDValue N2,
@@ -990,8 +990,7 @@ public:
 
   /// Get the specified node if it's already available, or else return NULL.
   SDNode *getNodeIfExists(unsigned Opcode, SDVTList VTs, ArrayRef<SDValue> Ops,
-                          bool nuw = false, bool nsw = false,
-                          bool exact = false);
+                          const SDNodeFlags *Flags = nullptr);
 
   /// Creates a SDDbgValue node.
   SDDbgValue *getDbgValue(MDNode *Var, MDNode *Expr, SDNode *N, unsigned R,
@@ -1253,8 +1252,8 @@ private:
   void allnodes_clear();
 
   BinarySDNode *GetBinarySDNode(unsigned Opcode, SDLoc DL, SDVTList VTs,
-                                SDValue N1, SDValue N2, bool nuw, bool nsw,
-                                bool exact);
+                                SDValue N1, SDValue N2,
+                                const SDNodeFlags *Flags = nullptr);
 
   /// Look up the node specified by ID in CSEMap.  If it exists, return it.  If
   /// not, return the insertion token that will make insertion faster.  This

diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index daa19430192a57ae9be54b45bda66b3167606876..69fe9ce1cc4785f310634698ff3fe63673f184ad 100644 (file)
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -1017,6 +1017,11 @@ static bool isBinOpWithFlags(unsigned Opcode) {
   case ISD::ADD:
   case ISD::SUB:
   case ISD::SHL:
+  case ISD::FADD:
+  case ISD::FDIV:
+  case ISD::FMUL:
+  case ISD::FREM:
+  case ISD::FSUB:
     return true;
   default:
     return false;
@@ -1029,8 +1034,8 @@ class BinaryWithFlagsSDNode : public BinarySDNode {
 public:
   SDNodeFlags Flags;
   BinaryWithFlagsSDNode(unsigned Opc, unsigned Order, DebugLoc dl, SDVTList VTs,
-                        SDValue X, SDValue Y)
-      : BinarySDNode(Opc, Order, dl, VTs, X, Y), Flags() {}
+                        SDValue X, SDValue Y, const SDNodeFlags &NodeFlags)
+      : BinarySDNode(Opc, Order, dl, VTs, X, Y), Flags(NodeFlags) {}
   static bool classof(const SDNode *N) {
     return isBinOpWithFlags(N->getOpcode());
   }

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ab72941310d4353e718657bd6056133b9e2ee0a7..95828fe374ba721d52c5058b31b157b70f0a34cc 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1463,12 +1463,9 @@ SDValue DAGCombiner::combine(SDNode *N) {
     if (isa<ConstantSDNode>(N0) || !isa<ConstantSDNode>(N1)) {
       SDValue Ops[] = {N1, N0};
       SDNode *CSENode;
-      if (const BinaryWithFlagsSDNode *BinNode =
-              dyn_cast<BinaryWithFlagsSDNode>(N)) {
+      if (const auto *BinNode = dyn_cast<BinaryWithFlagsSDNode>(N)) {
         CSENode = DAG.getNodeIfExists(N->getOpcode(), N->getVTList(), Ops,
-                                      BinNode->Flags.hasNoUnsignedWrap(),
-                                      BinNode->Flags.hasNoSignedWrap(),
-                                      BinNode->Flags.hasExact());
+                                      &BinNode->Flags);
       } else {
         CSENode = DAG.getNodeIfExists(N->getOpcode(), N->getVTList(), Ops);
       }

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 20cec6ebad1ad1498ba6f36ebf02a081554a4d80..98eb8bf487f2af921f1438ba9f943f1d1b56a5c2 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -400,19 +400,24 @@ static void AddNodeIDOperands(FoldingSetNodeID &ID,
     ID.AddInteger(Op.getResNo());
   }
 }
+/// Add logical or fast math flag values to FoldingSetNodeID value.
+static void AddNodeIDFlags(FoldingSetNodeID &ID, unsigned Opcode,
+                           const SDNodeFlags *Flags) {
+  if (!Flags || !isBinOpWithFlags(Opcode))
+    return;
 
-static void AddBinaryNodeIDCustom(FoldingSetNodeID &ID, bool nuw, bool nsw,
-                                  bool exact) {
-  ID.AddBoolean(nuw);
-  ID.AddBoolean(nsw);
-  ID.AddBoolean(exact);
+  unsigned RawFlags = Flags->getRawFlags();
+  // If no flags are set, do not alter the ID. We must match the ID of nodes
+  // that were created without explicitly specifying flags. This also saves time
+  // and allows a gradual increase in API usage of the optional optimization
+  // flags.
+  if (RawFlags != 0)
+    ID.AddInteger(RawFlags);
 }
 
-/// AddBinaryNodeIDCustom - Add BinarySDNodes special infos
-static void AddBinaryNodeIDCustom(FoldingSetNodeID &ID, unsigned Opcode,
-                                  bool nuw, bool nsw, bool exact) {
-  if (isBinOpWithFlags(Opcode))
-    AddBinaryNodeIDCustom(ID, nuw, nsw, exact);
+static void AddNodeIDFlags(FoldingSetNodeID &ID, const SDNode *N) {
+  if (auto *Node = dyn_cast<BinaryWithFlagsSDNode>(N))
+    AddNodeIDFlags(ID, Node->getOpcode(), &Node->Flags);
 }
 
 static void AddNodeIDNode(FoldingSetNodeID &ID, unsigned short OpC,
@@ -507,20 +512,6 @@ static void AddNodeIDCustom(FoldingSetNodeID &ID, const SDNode *N) {
     ID.AddInteger(ST->getPointerInfo().getAddrSpace());
     break;
   }
-  case ISD::SDIV:
-  case ISD::UDIV:
-  case ISD::SRA:
-  case ISD::SRL:
-  case ISD::MUL:
-  case ISD::ADD:
-  case ISD::SUB:
-  case ISD::SHL: {
-    const BinaryWithFlagsSDNode *BinNode = cast<BinaryWithFlagsSDNode>(N);
-    AddBinaryNodeIDCustom(
-        ID, N->getOpcode(), BinNode->Flags.hasNoUnsignedWrap(),
-        BinNode->Flags.hasNoSignedWrap(), BinNode->Flags.hasExact());
-    break;
-  }
   case ISD::ATOMIC_CMP_SWAP:
   case ISD::ATOMIC_CMP_SWAP_WITH_SUCCESS:
   case ISD::ATOMIC_SWAP:
@@ -564,6 +555,8 @@ static void AddNodeIDCustom(FoldingSetNodeID &ID, const SDNode *N) {
   }
   } // end switch (N->getOpcode())
 
+  AddNodeIDFlags(ID, N);
+
   // Target specific memory nodes could also have address spaces to check.
   if (N->isTargetMemoryOpcode())
     ID.AddInteger(cast<MemSDNode>(N)->getPointerInfo().getAddrSpace());
@@ -960,14 +953,16 @@ void SelectionDAG::allnodes_clear() {
 
 BinarySDNode *SelectionDAG::GetBinarySDNode(unsigned Opcode, SDLoc DL,
                                             SDVTList VTs, SDValue N1,
-                                            SDValue N2, bool nuw, bool nsw,
-                                            bool exact) {
+                                            SDValue N2,
+                                            const SDNodeFlags *Flags) {
   if (isBinOpWithFlags(Opcode)) {
+    // If no flags were passed in, use a default flags object.
+    SDNodeFlags F;
+    if (Flags == nullptr)
+      Flags = &F;
+
     BinaryWithFlagsSDNode *FN = new (NodeAllocator) BinaryWithFlagsSDNode(
-        Opcode, DL.getIROrder(), DL.getDebugLoc(), VTs, N1, N2);
-    FN->Flags.setNoUnsignedWrap(nuw);
-    FN->Flags.setNoSignedWrap(nsw);
-    FN->Flags.setExact(exact);
+        Opcode, DL.getIROrder(), DL.getDebugLoc(), VTs, N1, N2, *Flags);
 
     return FN;
   }
@@ -3269,7 +3264,7 @@ SDValue SelectionDAG::FoldConstantArithmetic(unsigned Opcode, SDLoc DL, EVT VT,
 }
 
 SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1,
-                              SDValue N2, bool nuw, bool nsw, bool exact) {
+                              SDValue N2, const SDNodeFlags *Flags) {
   ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.getNode());
   ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.getNode());
   switch (Opcode) {
@@ -3756,22 +3751,20 @@ SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL, EVT VT, SDValue N1,
   // Memoize this node if possible.
   BinarySDNode *N;
   SDVTList VTs = getVTList(VT);
-  const bool BinOpHasFlags = isBinOpWithFlags(Opcode);
   if (VT != MVT::Glue) {
     SDValue Ops[] = {N1, N2};
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTs, Ops);
-    if (BinOpHasFlags)
-      AddBinaryNodeIDCustom(ID, Opcode, nuw, nsw, exact);
+    AddNodeIDFlags(ID, Opcode, Flags);
     void *IP = nullptr;
     if (SDNode *E = FindNodeOrInsertPos(ID, DL.getDebugLoc(), IP))
       return SDValue(E, 0);
 
-    N = GetBinarySDNode(Opcode, DL, VTs, N1, N2, nuw, nsw, exact);
+    N = GetBinarySDNode(Opcode, DL, VTs, N1, N2, Flags);
 
     CSEMap.InsertNode(N, IP);
   } else {
-    N = GetBinarySDNode(Opcode, DL, VTs, N1, N2, nuw, nsw, exact);
+    N = GetBinarySDNode(Opcode, DL, VTs, N1, N2, Flags);
   }
 
   InsertNode(N);
@@ -6075,13 +6068,12 @@ SelectionDAG::getTargetInsertSubreg(int SRIdx, SDLoc DL, EVT VT,
 /// getNodeIfExists - Get the specified node if it's already available, or
 /// else return NULL.
 SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
-                                      ArrayRef<SDValue> Ops, bool nuw, bool nsw,
-                                      bool exact) {
+                                      ArrayRef<SDValue> Ops,
+                                      const SDNodeFlags *Flags) {
   if (VTList.VTs[VTList.NumVTs - 1] != MVT::Glue) {
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTList, Ops);
-    if (isBinOpWithFlags(Opcode))
-      AddBinaryNodeIDCustom(ID, nuw, nsw, exact);
+    AddNodeIDFlags(ID, Opcode, Flags);
     void *IP = nullptr;
     if (SDNode *E = FindNodeOrInsertPos(ID, DebugLoc(), IP))
       return E;

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4035820244a9749abc25ac4f0b3f33daeef6860f..d1f881412f27bf0211be6e3d9b22bd29027a1965 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -78,6 +78,10 @@ LimitFPPrecision("limit-float-precision",
                  cl::location(LimitFloatPrecision),
                  cl::init(0));
 
+static cl::opt<bool>
+EnableFMFInDAG("enable-fmf-dag", cl::init(false), cl::Hidden,
+                cl::desc("Enable fast-math-flags for DAG nodes"));
+
 // Limit the width of DAG chains. This is important in general to prevent
 // prevent DAG-based analysis from blowing up. For example, alias analysis and
 // load clustering may not complete in reasonable time. It is difficult to
@@ -2148,6 +2152,8 @@ void SelectionDAGBuilder::visitBinary(const User &I, unsigned OpCode) {
   bool nuw = false;
   bool nsw = false;
   bool exact = false;
+  FastMathFlags FMF;
+
   if (const OverflowingBinaryOperator *OFBinOp =
           dyn_cast<const OverflowingBinaryOperator>(&I)) {
     nuw = OFBinOp->hasNoUnsignedWrap();
@@ -2156,9 +2162,22 @@ void SelectionDAGBuilder::visitBinary(const User &I, unsigned OpCode) {
   if (const PossiblyExactOperator *ExactOp =
           dyn_cast<const PossiblyExactOperator>(&I))
     exact = ExactOp->isExact();
-
+  if (const FPMathOperator *FPOp = dyn_cast<const FPMathOperator>(&I))
+    FMF = FPOp->getFastMathFlags();
+
+  SDNodeFlags Flags;
+  Flags.setExact(exact);
+  Flags.setNoSignedWrap(nsw);
+  Flags.setNoUnsignedWrap(nuw);
+  if (EnableFMFInDAG) {
+    Flags.setAllowReciprocal(FMF.allowReciprocal());
+    Flags.setNoInfs(FMF.noInfs());
+    Flags.setNoNaNs(FMF.noNaNs());
+    Flags.setNoSignedZeros(FMF.noSignedZeros());
+    Flags.setUnsafeAlgebra(FMF.unsafeAlgebra());
+  }
   SDValue BinNodeValue = DAG.getNode(OpCode, getCurSDLoc(), Op1.getValueType(),
-                                     Op1, Op2, nuw, nsw, exact);
+                                     Op1, Op2, &Flags);
   setValue(&I, BinNodeValue);
 }
 
@@ -2206,9 +2225,12 @@ void SelectionDAGBuilder::visitShift(const User &I, unsigned Opcode) {
             dyn_cast<const PossiblyExactOperator>(&I))
       exact = ExactOp->isExact();
   }
-
+  SDNodeFlags Flags;
+  Flags.setExact(exact);
+  Flags.setNoSignedWrap(nsw);
+  Flags.setNoUnsignedWrap(nuw);
   SDValue Res = DAG.getNode(Opcode, getCurSDLoc(), Op1.getValueType(), Op1, Op2,
-                            nuw, nsw, exact);
+                            &Flags);
   setValue(&I, Res);
 }
 

diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 9daf2a50ad8fbe3e2e9b3a3898ef3c6a7623103b..c70c3a270403c78d08afe8a5f5d9f705da1de992 100644 (file)
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -2671,8 +2671,9 @@ SDValue TargetLowering::BuildExactSDIV(SDValue Op1, SDValue Op2, SDLoc dl,
     // TODO: For UDIV use SRL instead of SRA.
     SDValue Amt =
         DAG.getConstant(ShAmt, dl, getShiftAmountTy(Op1.getValueType()));
-    Op1 = DAG.getNode(ISD::SRA, dl, Op1.getValueType(), Op1, Amt, false, false,
-                      true);
+    SDNodeFlags Flags;
+    Flags.setExact(true);
+    Op1 = DAG.getNode(ISD::SRA, dl, Op1.getValueType(), Op1, Amt, &Flags);
     d = d.ashr(ShAmt);
   }