[ConstantRange] Add API for intrinsics (NFC)

[nikic]

Summary

This adds a common API for compute constant ranges of intrinsics. The intention here is that
a) we can reuse the same code across different passes that handle constant ranges, i.e. this can be reused in SCCP
b) we only have to add knowledge about supported intrinsics to ConstantRange, not any consumers.

[fhahn]

LGTM, this makes sense to enable wider use and is in line with existing members like binaryOp. Thanks!

llvm/include/llvm/IR/ConstantRange.h

153

Nit: mentioning explicitly what is returned seems a bit clearer to me, .e.g Returns true if ConstantRange calculations are supported for intrinsic with \p IntrinsicID.

llvm/lib/IR/ConstantRange.cpp

863

maybe we should assert(!isIntrinsicSupported(IntrinsicID)) here, to catch (some) inconsistencies between isIntrinsicSupported and intrinsic

llvm/include/llvm/IR/ConstantRange.h

static ConstantRange makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
                                                   unsigned NoWrapKind);
 
   /// Produce the range that contains X if and only if "X BinOp Other" does
   /// not wrap.
   static ConstantRange makeExactNoWrapRegion(Instruction::BinaryOps BinOp,
                                              const APInt &Other,
                                              unsigned NoWrapKind);
 
+  /// Whether ConstantRange calculations for this intrinsic are supported.
+  static bool isIntrinsicSupported(Intrinsic::ID IntrinsicID);
+
+  /// Compute range of intrinsic result for the given operand ranges.
+  static ConstantRange intrinsic(Intrinsic::ID IntrinsicID,
+                                 ArrayRef<ConstantRange> Ops);
+
   /// Set up \p Pred and \p RHS such that
   /// ConstantRange::makeExactICmpRegion(Pred, RHS) == *this.  Return true if
   /// successful.
   bool getEquivalentICmp(CmpInst::Predicate &Pred, APInt &RHS) const;
 
   /// Return the lower value for this range.
   const APInt &getLower() const { return Lower; }
 

llvm/lib/Analysis/LazyValueInfo.cpp

Optional<ValueLatticeElement> solveBlockValueBinaryOpImpl(
       std::function<ConstantRange(const ConstantRange &,
                                   const ConstantRange &)> OpFn);
   Optional<ValueLatticeElement> solveBlockValueBinaryOp(BinaryOperator *BBI,
                                                         BasicBlock *BB);
   Optional<ValueLatticeElement> solveBlockValueCast(CastInst *CI,
                                                     BasicBlock *BB);
   Optional<ValueLatticeElement> solveBlockValueOverflowIntrinsic(
       WithOverflowInst *WO, BasicBlock *BB);
-  Optional<ValueLatticeElement> solveBlockValueSaturatingIntrinsic(
-      SaturatingInst *SI, BasicBlock *BB);
   Optional<ValueLatticeElement> solveBlockValueIntrinsic(IntrinsicInst *II,
                                                          BasicBlock *BB);
   Optional<ValueLatticeElement> solveBlockValueExtractValue(
       ExtractValueInst *EVI, BasicBlock *BB);
   void intersectAssumeOrGuardBlockValueConstantRange(Value *Val,
                                                      ValueLatticeElement &BBLV,
                                                      Instruction *BBI);
 

 LazyValueInfoImpl::solveBlockValueOverflowIntrinsic(WithOverflowInst *WO,
                                                     BasicBlock *BB) {
   return solveBlockValueBinaryOpImpl(
       WO, BB, [WO](const ConstantRange &CR1, const ConstantRange &CR2) {
         return CR1.binaryOp(WO->getBinaryOp(), CR2);
       });
 }
 
-Optional<ValueLatticeElement>
-LazyValueInfoImpl::solveBlockValueSaturatingIntrinsic(SaturatingInst *SI,
-                                                      BasicBlock *BB) {
-  switch (SI->getIntrinsicID()) {
-  case Intrinsic::uadd_sat:
-    return solveBlockValueBinaryOpImpl(
-        SI, BB, [](const ConstantRange &CR1, const ConstantRange &CR2) {
-          return CR1.uadd_sat(CR2);
-        });
-  case Intrinsic::usub_sat:
-    return solveBlockValueBinaryOpImpl(
-        SI, BB, [](const ConstantRange &CR1, const ConstantRange &CR2) {
-          return CR1.usub_sat(CR2);
-        });
-  case Intrinsic::sadd_sat:
-    return solveBlockValueBinaryOpImpl(
-        SI, BB, [](const ConstantRange &CR1, const ConstantRange &CR2) {
-          return CR1.sadd_sat(CR2);
-        });
-  case Intrinsic::ssub_sat:
-    return solveBlockValueBinaryOpImpl(
-        SI, BB, [](const ConstantRange &CR1, const ConstantRange &CR2) {
-          return CR1.ssub_sat(CR2);
-        });
-  default:
-    llvm_unreachable("All llvm.sat intrinsic are handled.");
-  }
-}
-
 Optional<ValueLatticeElement> LazyValueInfoImpl::solveBlockValueIntrinsic(
     IntrinsicInst *II, BasicBlock *BB) {
-  if (auto *SI = dyn_cast<SaturatingInst>(II))
-    return solveBlockValueSaturatingIntrinsic(SI, BB);
-
+  if (!ConstantRange::isIntrinsicSupported(II->getIntrinsicID())) {
     LLVM_DEBUG(dbgs() << " compute BB '" << BB->getName()
                       << "' - overdefined (unknown intrinsic).\n");
     return ValueLatticeElement::getOverdefined();
   }
 
+  SmallVector<ConstantRange, 2> OpRanges;
+  for (Value *Op : II->args()) {
+    Optional<ConstantRange> Range = getRangeFor(Op, II, BB);
+    if (!Range)
+      return None;
+    OpRanges.push_back(*Range);
+  }
+
+  return ValueLatticeElement::getRange(
+      ConstantRange::intrinsic(II->getIntrinsicID(), OpRanges));
+}
+
 Optional<ValueLatticeElement> LazyValueInfoImpl::solveBlockValueExtractValue(
     ExtractValueInst *EVI, BasicBlock *BB) {
   if (auto *WO = dyn_cast<WithOverflowInst>(EVI->getAggregateOperand()))
     if (EVI->getNumIndices() == 1 && *EVI->idx_begin() == 0)
       return solveBlockValueOverflowIntrinsic(WO, BB);
 
   // Handle extractvalue of insertvalue to allow further simplification
   // based on replaced with.overflow intrinsics.

llvm/lib/IR/ConstantRange.cpp

 // ranges (other integral ranges use min/max values for special range values):
 //
 //  [F, F) = {}     = Empty set
 //  [T, F) = {T}
 //  [F, T) = {F}
 //  [T, T) = {F, T} = Full set
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/APInt.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/KnownBits.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
case Instruction::Sub:
     return subWithNoWrap(Other, NoWrapKind);
   default:
     // Don't know about this Overflowing Binary Operation.
     // Conservatively fallback to plain binop handling.
     return binaryOp(BinOp, Other);
   }
 }
 
+bool ConstantRange::isIntrinsicSupported(Intrinsic::ID IntrinsicID) {
+  switch (IntrinsicID) {
+  case Intrinsic::uadd_sat:
+  case Intrinsic::usub_sat:
+  case Intrinsic::sadd_sat:
+  case Intrinsic::ssub_sat:
+    return true;
+  default:
+    return false;
+  }
+}
+
+ConstantRange ConstantRange::intrinsic(Intrinsic::ID IntrinsicID,
+                                       ArrayRef<ConstantRange> Ops) {
+  switch (IntrinsicID) {
+  case Intrinsic::uadd_sat:
+    return Ops[0].uadd_sat(Ops[1]);
+  case Intrinsic::usub_sat:
+    return Ops[0].usub_sat(Ops[1]);
+  case Intrinsic::sadd_sat:
+    return Ops[0].sadd_sat(Ops[1]);
+  case Intrinsic::ssub_sat:
+    return Ops[0].ssub_sat(Ops[1]);
+  default:
+    llvm_unreachable("Unsupported intrinsic");
+  }
+}
+
 ConstantRange
 ConstantRange::add(const ConstantRange &Other) const {
   if (isEmptySet() || Other.isEmptySet())
     return getEmpty();
   if (isFullSet() || Other.isFullSet())
     return getFull();
 
   APInt NewLower = getLower() + Other.getLower();