[SelectionDAG] Add initial plumbing for the disjoint flag.

[topperc]

This copies the flag from IR to the SDNode in SelectionDAGBuilder, clear the flag in SimplifyDemandedBits, and adds it to canCreateUndefOrPoison.

Uses of the flag will come in later patches.

[llvmbot]

@llvm/pr-subscribers-llvm-selectiondag

Author: Craig Topper (topperc)

Changes

This copies the flag from IR to the SDNode in SelectionDAGBuilder, clear the flag in SimplifyDemandedBits, and adds it to canCreateUndefOrPoison.

Uses of the flag will come in later patches.

---

Full diff: https://github.com/llvm/llvm-project/pull/76751.diff

5 Files Affected:

• (modified) llvm/include/llvm/CodeGen/SelectionDAGNodes.h (+9-4)
• (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (+4-1)
• (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (+2)
• (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp (+3)
• (modified) llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp (+13-3)

diff --git a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
index 5c44538fe69974..7f957878343a65 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -381,6 +381,7 @@ struct SDNodeFlags {
   bool NoUnsignedWrap : 1;
   bool NoSignedWrap : 1;
   bool Exact : 1;
+  bool Disjoint : 1;
   bool NonNeg : 1;
   bool NoNaNs : 1;
   bool NoInfs : 1;
@@ -402,10 +403,11 @@ struct SDNodeFlags {
 public:
   /// Default constructor turns off all optimization flags.
   SDNodeFlags()
-      : NoUnsignedWrap(false), NoSignedWrap(false), Exact(false), NonNeg(false),
-        NoNaNs(false), NoInfs(false), NoSignedZeros(false),
-        AllowReciprocal(false), AllowContract(false), ApproximateFuncs(false),
-        AllowReassociation(false), NoFPExcept(false), Unpredictable(false) {}
+      : NoUnsignedWrap(false), NoSignedWrap(false), Exact(false),
+        Disjoint(false), NonNeg(false), NoNaNs(false), NoInfs(false),
+        NoSignedZeros(false), AllowReciprocal(false), AllowContract(false),
+        ApproximateFuncs(false), AllowReassociation(false), NoFPExcept(false),
+        Unpredictable(false) {}
 
   /// Propagate the fast-math-flags from an IR FPMathOperator.
   void copyFMF(const FPMathOperator &FPMO) {
@@ -422,6 +424,7 @@ struct SDNodeFlags {
   void setNoUnsignedWrap(bool b) { NoUnsignedWrap = b; }
   void setNoSignedWrap(bool b) { NoSignedWrap = b; }
   void setExact(bool b) { Exact = b; }
+  void setDisjoint(bool b) { Disjoint = b; }
   void setNonNeg(bool b) { NonNeg = b; }
   void setNoNaNs(bool b) { NoNaNs = b; }
   void setNoInfs(bool b) { NoInfs = b; }
@@ -437,6 +440,7 @@ struct SDNodeFlags {
   bool hasNoUnsignedWrap() const { return NoUnsignedWrap; }
   bool hasNoSignedWrap() const { return NoSignedWrap; }
   bool hasExact() const { return Exact; }
+  bool hasDisjoint() const { return Disjoint; }
   bool hasNonNeg() const { return NonNeg; }
   bool hasNoNaNs() const { return NoNaNs; }
   bool hasNoInfs() const { return NoInfs; }
@@ -454,6 +458,7 @@ struct SDNodeFlags {
     NoUnsignedWrap &= Flags.NoUnsignedWrap;
     NoSignedWrap &= Flags.NoSignedWrap;
     Exact &= Flags.Exact;
+    Disjoint &= Flags.Disjoint;
     NonNeg &= Flags.NonNeg;
     NoNaNs &= Flags.NoNaNs;
     NoInfs &= Flags.NoInfs;
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 0e17bba2398ed2..75c10a74cdc44c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5022,7 +5022,6 @@ bool SelectionDAG::canCreateUndefOrPoison(SDValue Op, const APInt &DemandedElts,
   case ISD::CONCAT_VECTORS:
   case ISD::INSERT_SUBVECTOR:
   case ISD::AND:
-  case ISD::OR:
   case ISD::XOR:
   case ISD::ROTL:
   case ISD::ROTR:
@@ -5062,6 +5061,10 @@ bool SelectionDAG::canCreateUndefOrPoison(SDValue Op, const APInt &DemandedElts,
     return ConsiderFlags && (Op->getFlags().hasNoSignedWrap() ||
                              Op->getFlags().hasNoUnsignedWrap());
 
+  // Matches hasPoisonGeneratingFlags().
+  case ISD::OR:
+    return ConsiderFlags && Op->getFlags().hasDisjoint();
+
   case ISD::INSERT_VECTOR_ELT:{
     // Ensure that the element index is in bounds.
     EVT VecVT = Op.getOperand(0).getValueType();
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 3c4b285cb06747..192f7bc8d2aa1b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3354,6 +3354,8 @@ void SelectionDAGBuilder::visitBinary(const User &I, unsigned Opcode) {
   }
   if (auto *ExactOp = dyn_cast<PossiblyExactOperator>(&I))
     Flags.setExact(ExactOp->isExact());
+  if (auto *DisjointOp = dyn_cast<PossiblyDisjointInst>(&I))
+    Flags.setDisjoint(DisjointOp->isDisjoint());
   if (auto *FPOp = dyn_cast<FPMathOperator>(&I))
     Flags.copyFMF(*FPOp);
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
index 78cc60084068a5..4ae30000015e17 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
@@ -597,6 +597,9 @@ void SDNode::print_details(raw_ostream &OS, const SelectionDAG *G) const {
   if (getFlags().hasExact())
     OS << " exact";
 
+  if (getFlags().hasDisjoint())
+    OS << " disjoint";
+
   if (getFlags().hasNonNeg())
     OS << " nneg";
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index c5977546828f63..4581bb19e97ec3 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1468,14 +1468,24 @@ bool TargetLowering::SimplifyDemandedBits(
   case ISD::OR: {
     SDValue Op0 = Op.getOperand(0);
     SDValue Op1 = Op.getOperand(1);
-
+    SDNodeFlags Flags = Op.getNode()->getFlags();
     if (SimplifyDemandedBits(Op1, DemandedBits, DemandedElts, Known, TLO,
-                             Depth + 1))
+                             Depth + 1)) {
+      if (Flags.hasDisjoint()) {
+        Flags.setDisjoint(false);
+        Op->setFlags(Flags);
+      }
       return true;
+    }
     assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     if (SimplifyDemandedBits(Op0, ~Known.One & DemandedBits, DemandedElts,
-                             Known2, TLO, Depth + 1))
+                             Known2, TLO, Depth + 1)) {
+      if (Flags.hasDisjoint()) {
+        Flags.setDisjoint(false);
+        Op->setFlags(Flags);
+      }
       return true;
+    }
     assert(!Known2.hasConflict() && "Bits known to be one AND zero?");
 
     // If all of the demanded bits are known zero on one side, return the other.

[arsenm]

I thought this was unioned with the wrap flags. I guess we don't have enough of these bits to matter yet