[GISel] Add KnownFPClass Analysis to GISelValueTrackingPass

llvm/include/llvm/CodeGen/GlobalISel/GISelValueTracking.h

@@ -14,13 +14,16 @@
 #ifndef LLVM_CODEGEN_GLOBALISEL_GISELVALUETRACKING_H
 #define LLVM_CODEGEN_GLOBALISEL_GISELVALUETRACKING_H
 
+#include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/Register.h"
+#include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/KnownBits.h"
+#include "llvm/Support/KnownFPClass.h"
 
 namespace llvm {
 
@@ -35,13 +38,72 @@ class GISelValueTracking : public GISelChangeObserver {
   unsigned MaxDepth;
   /// Cache maintained during a computeKnownBits request.
   SmallDenseMap<Register, KnownBits, 16> ComputeKnownBitsCache;
+  SmallDenseMap<Register, KnownFPClass, 16> ComputeKnownFPClassCache;
 
   void computeKnownBitsMin(Register Src0, Register Src1, KnownBits &Known,
                            const APInt &DemandedElts, unsigned Depth = 0);
 
   unsigned computeNumSignBitsMin(Register Src0, Register Src1,
                                  const APInt &DemandedElts, unsigned Depth = 0);
 
+  /// Returns a pair of values, which if passed to llvm.is.fpclass, returns the
+  /// same result as an fcmp with the given operands.
+  ///
+  /// If \p LookThroughSrc is true, consider the input value when computing the
+  /// mask.
+  ///
+  /// If \p LookThroughSrc is false, ignore the source value (i.e. the first
+  /// pair element will always be LHS.
+  std::pair<Register, FPClassTest> fcmpToClassTest(CmpInst::Predicate Pred,
+                                                   const MachineFunction &MF,
+                                                   Register LHS, Value *RHS,
+                                                   bool LookThroughSrc = true);
+  std::pair<Register, FPClassTest> fcmpToClassTest(CmpInst::Predicate Pred,
+                                                   const MachineFunction &MF,
+                                                   Register LHS,
+                                                   const APFloat *ConstRHS,
+                                                   bool LookThroughSrc = true);
+
+  /// Compute the possible floating-point classes that \p LHS could be based on
+  /// fcmp \Pred \p LHS, \p RHS.
+  ///
+  /// \returns { TestedValue, ClassesIfTrue, ClassesIfFalse }
+  ///
+  /// If the compare returns an exact class test, ClassesIfTrue ==
+  /// ~ClassesIfFalse
+  ///
+  /// This is a less exact version of fcmpToClassTest (e.g. fcmpToClassTest will
+  /// only succeed for a test of x > 0 implies positive, but not x > 1).
+  ///
+  /// If \p LookThroughSrc is true, consider the input value when computing the
+  /// mask. This may look through sign bit operations.
+  ///
+  /// If \p LookThroughSrc is false, ignore the source value (i.e. the first
+  /// pair element will always be LHS.
+  ///
+  std::tuple<Register, FPClassTest, FPClassTest>
+  fcmpImpliesClass(CmpInst::Predicate Pred, const MachineFunction &MF,
+                   Register LHS, Register RHS, bool LookThroughSrc = true);
+  std::tuple<Register, FPClassTest, FPClassTest>
+  fcmpImpliesClass(CmpInst::Predicate Pred, const MachineFunction &MF,
+                   Register LHS, FPClassTest RHS, bool LookThroughSrc = true);
+  std::tuple<Register, FPClassTest, FPClassTest>
+  fcmpImpliesClass(CmpInst::Predicate Pred, const MachineFunction &MF,
+                   Register LHS, const APFloat &RHS,
+                   bool LookThroughSrc = true);
+
+  void computeKnownFPClass(Register R, KnownFPClass &Known,
+                           FPClassTest InterestedClasses, unsigned Depth);
+
+  void computeKnownFPClassForFPTrunc(const MachineInstr &MI,
+                                     const APInt &DemandedElts,
+                                     FPClassTest InterestedClasses,
+                                     KnownFPClass &Known, unsigned Depth);
+
+  void computeKnownFPClass(Register R, const APInt &DemandedElts,
+                           FPClassTest InterestedClasses, KnownFPClass &Known,
+                           unsigned Depth);
+
 public:
   GISelValueTracking(MachineFunction &MF, unsigned MaxDepth = 6);
   virtual ~GISelValueTracking() = default;
@@ -87,6 +149,34 @@ class GISelValueTracking : public GISelChangeObserver {
   /// \return The known alignment for the pointer-like value \p R.
   Align computeKnownAlignment(Register R, unsigned Depth = 0);
 
+  /// Determine which floating-point classes are valid for \p V, and return them
+  /// in KnownFPClass bit sets.
+  ///
+  /// This function is defined on values with floating-point type, values
+  /// vectors of floating-point type, and arrays of floating-point type.
+
+  /// \p InterestedClasses is a compile time optimization hint for which
+  /// floating point classes should be queried. Queries not specified in \p
+  /// InterestedClasses should be reliable if they are determined during the
+  /// query.
+  KnownFPClass computeKnownFPClass(Register R, const APInt &DemandedElts,
+                                   FPClassTest InterestedClasses,
+                                   unsigned Depth);
+
+  KnownFPClass computeKnownFPClass(Register R,
+                                   FPClassTest InterestedClasses = fcAllFlags,
+                                   unsigned Depth = 0);
+
+  /// Wrapper to account for known fast math flags at the use instruction.
+  KnownFPClass computeKnownFPClass(Register R, const APInt &DemandedElts,
+                                   uint32_t Flags,
+                                   FPClassTest InterestedClasses,
+                                   unsigned Depth);
+
+  KnownFPClass computeKnownFPClass(Register R, uint32_t Flags,
+                                   FPClassTest InterestedClasses,
+                                   unsigned Depth);
+
   // Observer API. No-op for non-caching implementation.
   void erasingInstr(MachineInstr &MI) override {}
   void createdInstr(MachineInstr &MI) override {}

llvm/include/llvm/CodeGen/GlobalISel/MIPatternMatch.h

@@ -14,8 +14,11 @@
 #define LLVM_CODEGEN_GLOBALISEL_MIPATTERNMATCH_H
 
 #include "llvm/ADT/APInt.h"
+#include "llvm/ADT/FloatingPointMode.h"
+#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
 #include "llvm/CodeGen/GlobalISel/Utils.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetOpcodes.h"
 #include "llvm/IR/InstrTypes.h"
 
 namespace llvm {
@@ -393,6 +396,7 @@ inline bind_ty<const MachineInstr *> m_MInstr(const MachineInstr *&MI) {
 inline bind_ty<LLT> m_Type(LLT &Ty) { return Ty; }
 inline bind_ty<CmpInst::Predicate> m_Pred(CmpInst::Predicate &P) { return P; }
 inline operand_type_match m_Pred() { return operand_type_match(); }
+inline bind_ty<FPClassTest> m_FPClassTest(FPClassTest &T) { return T; }
 
 template <typename BindTy> struct deferred_helper {
   static bool match(const MachineRegisterInfo &MRI, BindTy &VR, BindTy &V) {
@@ -762,6 +766,32 @@ struct CompareOp_match {
   }
 };
 
+template <typename LHS_P, typename Test_P, unsigned Opcode>
+struct ClassifyOp_match {
+  LHS_P L;
+  Test_P T;
+
+  ClassifyOp_match(const LHS_P &LHS, const Test_P &Tst) : L(LHS), T(Tst) {}
+
+  template <typename OpTy>
+  bool match(const MachineRegisterInfo &MRI, OpTy &&Op) {
+    MachineInstr *TmpMI;
+    if (!mi_match(Op, MRI, m_MInstr(TmpMI)) || TmpMI->getOpcode() != Opcode)
+      return false;
+
+    Register LHS = TmpMI->getOperand(1).getReg();
+    if (!L.match(MRI, LHS))
+      return false;
+
+    FPClassTest TmpClass =
+        static_cast<FPClassTest>(TmpMI->getOperand(2).getImm());
+    if (T.match(MRI, TmpClass))
+      return true;
+
+    return false;
+  }
+};
+
 template <typename Pred, typename LHS, typename RHS>
 inline CompareOp_match<Pred, LHS, RHS, TargetOpcode::G_ICMP>
 m_GICmp(const Pred &P, const LHS &L, const RHS &R) {
@@ -804,6 +834,14 @@ m_c_GFCmp(const Pred &P, const LHS &L, const RHS &R) {
   return CompareOp_match<Pred, LHS, RHS, TargetOpcode::G_FCMP, true>(P, L, R);
 }
 
+/// Matches the register and immediate used in a fpclass test
+/// G_IS_FPCLASS %val, 96
+template <typename LHS, typename Test>
+inline ClassifyOp_match<LHS, Test, TargetOpcode::G_IS_FPCLASS>
+m_GIsFPClass(const LHS &L, const Test &T) {
+  return ClassifyOp_match<LHS, Test, TargetOpcode::G_IS_FPCLASS>(L, T);
+}
+
 // Helper for checking if a Reg is of specific type.
 struct CheckType {
   LLT Ty;

llvm/include/llvm/CodeGen/GlobalISel/Utils.h

@@ -655,6 +655,9 @@ class GIConstant {
 /// }
 /// provides low-level access.
 class GFConstant {
+  using VecTy = SmallVector<APFloat>;
+  using const_iterator = VecTy::const_iterator;
+
 public:
   enum class GFConstantKind { Scalar, FixedVector, ScalableVector };
 
@@ -672,6 +675,23 @@ class GFConstant {
   /// Returns the kind of of this constant, e.g, Scalar.
   GFConstantKind getKind() const { return Kind; }
 
+  const_iterator begin() const {
+    assert(Kind != GFConstantKind::ScalableVector &&
+           "Expected fixed vector or scalar constant");
+    return Values.begin();
+  }
+
+  const_iterator end() const {
+    assert(Kind != GFConstantKind::ScalableVector &&
+           "Expected fixed vector or scalar constant");
+    return Values.end();
+  }
+
+  size_t size() const {
+    assert(Kind == GFConstantKind::FixedVector && "Expected fixed vector");
+    return Values.size();
+  }
+
   /// Returns the value, if this constant is a scalar.
   APFloat getScalarValue() const;
 

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -51,6 +51,7 @@
 #include "llvm/Support/AtomicOrdering.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/KnownFPClass.h"
 #include <algorithm>
 #include <cassert>
 #include <climits>
@@ -4230,6 +4231,13 @@ class TargetLowering : public TargetLoweringBase {
                                               const MachineRegisterInfo &MRI,
                                               unsigned Depth = 0) const;
 
+  virtual void computeKnownFPClassForTargetInstr(GISelValueTracking &Analysis,
+                                                 Register R,
+                                                 KnownFPClass &Known,
+                                                 const APInt &DemandedElts,
+                                                 const MachineRegisterInfo &MRI,
+                                                 unsigned Depth = 0) const;
+
   /// Determine the known alignment for the pointer value \p R. This is can
   /// typically be inferred from the number of low known 0 bits. However, for a
   /// pointer with a non-integral address space, the alignment value may be