[TurboFan] Streamline BigInt.asUintN lowering

This CL applies the following changes:
- JSCallReducer no longer generates a CheckBigInt in front of the
  generated BigIntAsUintN.
- This results in a slight change of the semantics of the latter, which
  now includes the necessary type check. Typer and Verifier are changed
  accordingly.
- The BigIntAsUintN operator is now effectful, since it can now deopt.
- IrOpcode::kBigIntAsUintN is now lowered in SimplifedLowering instead
  of EffectControlLinearizer, the necessary type check is introduced
  by the RepresentationChanger.
- Adds a small mjsunit test to check the correct deoptimization behavior
  of optimized BigInt.asUintN.
==> Remove UseInfo::TruncatingWord64()!

Drive-by: Fix an issue in ChangeUnaryToPureBinaryOp when the new_input
is at index 1.
Drive-by: Introduce an %Is64Bit() intrinsic to allow tests to
distinguish 32 and 64 bit architectures.

Bug: v8:11682
Change-Id: I448f892d3bd2280d731ae5b248c833de8faf1bd5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2843816
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74147}

src/compiler/effect-control-linearizer.cc

@@ -113,7 +113,6 @@ class EffectControlLinearizer {
   Node* LowerCheckedTaggedToFloat64(Node* node, Node* frame_state);
   Node* LowerCheckedTaggedToTaggedSigned(Node* node, Node* frame_state);
   Node* LowerCheckedTaggedToTaggedPointer(Node* node, Node* frame_state);
-  Node* LowerBigIntAsUintN(Node* node, Node* frame_state);
   Node* LowerChangeUint64ToBigInt(Node* node);
   Node* LowerTruncateBigIntToUint64(Node* node);
   Node* LowerChangeTaggedToFloat64(Node* node);
@@ -1061,9 +1060,6 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
     case IrOpcode::kCheckedTaggedToTaggedPointer:
       result = LowerCheckedTaggedToTaggedPointer(node, frame_state);
       break;
-    case IrOpcode::kBigIntAsUintN:
-      result = LowerBigIntAsUintN(node, frame_state);
-      break;
     case IrOpcode::kChangeUint64ToBigInt:
       result = LowerChangeUint64ToBigInt(node);
       break;
@@ -2936,22 +2932,6 @@ Node* EffectControlLinearizer::LowerCheckBigInt(Node* node, Node* frame_state) {
   return value;
 }
 
-Node* EffectControlLinearizer::LowerBigIntAsUintN(Node* node,
-                                                  Node* frame_state) {
-  DCHECK(machine()->Is64());
-
-  const int bits = OpParameter<int>(node->op());
-  DCHECK(0 <= bits && bits <= 64);
-
-  if (bits == 64) {
-    // Reduce to nop.
-    return node->InputAt(0);
-  } else {
-    const uint64_t msk = (1ULL << bits) - 1ULL;
-    return __ Word64And(node->InputAt(0), __ Int64Constant(msk));
-  }
-}
-
 Node* EffectControlLinearizer::LowerChangeUint64ToBigInt(Node* node) {
   DCHECK(machine()->Is64());
 

src/compiler/js-call-reducer.cc

@@ -7829,9 +7829,9 @@ Reduction JSCallReducer::ReduceBigIntAsUintN(Node* node) {
   NumberMatcher matcher(bits);
   if (matcher.IsInteger() && matcher.IsInRange(0, 64)) {
     const int bits_value = static_cast<int>(matcher.ResolvedValue());
-    value = effect = graph()->NewNode(simplified()->CheckBigInt(p.feedback()),
-                                      value, effect, control);
-    value = graph()->NewNode(simplified()->BigIntAsUintN(bits_value), value);
+    value = effect = graph()->NewNode(
+        simplified()->SpeculativeBigIntAsUintN(bits_value, p.feedback()), value,
+        effect, control);
     ReplaceWithValue(node, value, effect);
     return Replace(value);
   }

src/compiler/opcodes.h

@@ -385,7 +385,6 @@
   V(NumberSilenceNaN)
 
 #define SIMPLIFIED_BIGINT_UNOP_LIST(V) \
-  V(BigIntAsUintN)                     \
   V(BigIntNegate)                      \
   V(CheckBigInt)
 
@@ -497,7 +496,9 @@
   V(SpeculativeBigIntAdd)                           \
   V(SpeculativeBigIntSubtract)
 
-#define SIMPLIFIED_SPECULATIVE_BIGINT_UNOP_LIST(V) V(SpeculativeBigIntNegate)
+#define SIMPLIFIED_SPECULATIVE_BIGINT_UNOP_LIST(V) \
+  V(SpeculativeBigIntAsUintN)                      \
+  V(SpeculativeBigIntNegate)
 
 #define SIMPLIFIED_OP_LIST(V)                 \
   SIMPLIFIED_CHANGE_OP_LIST(V)                \

src/compiler/operation-typer.cc

@@ -576,8 +576,7 @@ Type OperationTyper::NumberSilenceNaN(Type type) {
   return type;
 }
 
-Type OperationTyper::BigIntAsUintN(Type type) {
-  DCHECK(type.Is(Type::BigInt()));
+Type OperationTyper::SpeculativeBigIntAsUintN(Type type) {
   return Type::BigInt();
 }
 

src/compiler/representation-change.h

@@ -180,10 +180,10 @@ class UseInfo {
   static UseInfo TruncatingWord32() {
     return UseInfo(MachineRepresentation::kWord32, Truncation::Word32());
   }
-  static UseInfo TruncatingWord64() {
-    return UseInfo(MachineRepresentation::kWord64, Truncation::Word64());
-  }
   static UseInfo CheckedBigIntTruncatingWord64(const FeedbackSource& feedback) {
+    // Note that Trunction::Word64() can safely use kIdentifyZero, because
+    // TypeCheckKind::kBigInt will make sure we deopt for anything other than
+    // type BigInt anyway.
     return UseInfo(MachineRepresentation::kWord64, Truncation::Word64(),
                    TypeCheckKind::kBigInt, feedback);
   }

src/compiler/simplified-lowering.cc

@@ -836,7 +836,13 @@ class RepresentationSelector {
     } else {
       DCHECK_EQ(0, node->op()->ControlInputCount());
     }
-    node->InsertInput(jsgraph_->zone(), new_input_index, new_input);
+    if (new_input_index == 0) {
+      node->InsertInput(jsgraph_->zone(), 0, new_input);
+    } else {
+      DCHECK_EQ(new_input_index, 1);
+      DCHECK_EQ(node->InputCount(), 1);
+      node->AppendInput(jsgraph_->zone(), new_input);
+    }
     ChangeOp(node, new_op);
   }
 
@@ -2830,9 +2836,25 @@ class RepresentationSelector {
         }
         return;
       }
-      case IrOpcode::kBigIntAsUintN: {
-        ProcessInput<T>(node, 0, UseInfo::TruncatingWord64());
+      case IrOpcode::kSpeculativeBigIntAsUintN: {
+        const auto p = SpeculativeBigIntAsUintNParametersOf(node->op());
+        DCHECK_LE(0, p.bits());
+        DCHECK_LE(p.bits(), 64);
+
+        ProcessInput<T>(node, 0,
+                        UseInfo::CheckedBigIntTruncatingWord64(p.feedback()));
         SetOutput<T>(node, MachineRepresentation::kWord64, Type::BigInt());
+        if (lower<T>()) {
+          if (p.bits() == 0) {
+            DeferReplacement(node, jsgraph_->ZeroConstant());
+          } else if (p.bits() == 64) {
+            DeferReplacement(node, node->InputAt(0));
+          } else {
+            const uint64_t mask = (1ULL << p.bits()) - 1ULL;
+            ChangeUnaryToPureBinaryOp(node, lowering->machine()->Word64And(), 1,
+                                      jsgraph_->Int64Constant(mask));
+          }
+        }
         return;
       }
       case IrOpcode::kNumberAcos:

src/compiler/simplified-operator.cc

@@ -615,6 +615,27 @@ NumberOperationParameters const& NumberOperationParametersOf(
   return OpParameter<NumberOperationParameters>(op);
 }
 
+bool operator==(SpeculativeBigIntAsUintNParameters const& lhs,
+                SpeculativeBigIntAsUintNParameters const& rhs) {
+  return lhs.bits() == rhs.bits() && lhs.feedback() == rhs.feedback();
+}
+
+size_t hash_value(SpeculativeBigIntAsUintNParameters const& p) {
+  FeedbackSource::Hash feedback_hash;
+  return base::hash_combine(p.bits(), feedback_hash(p.feedback()));
+}
+
+std::ostream& operator<<(std::ostream& os,
+                         SpeculativeBigIntAsUintNParameters const& p) {
+  return os << p.bits() << ", " << p.feedback();
+}
+
+SpeculativeBigIntAsUintNParameters const& SpeculativeBigIntAsUintNParametersOf(
+    Operator const* op) {
+  DCHECK_EQ(IrOpcode::kSpeculativeBigIntAsUintN, op->opcode());
+  return OpParameter<SpeculativeBigIntAsUintNParameters>(op);
+}
+
 size_t hash_value(AllocateParameters info) {
   return base::hash_combine(info.type(),
                             static_cast<int>(info.allocation_type()));
@@ -1296,11 +1317,14 @@ const Operator* SimplifiedOperatorBuilder::RuntimeAbort(AbortReason reason) {
       static_cast<int>(reason));                // parameter
 }
 
-const Operator* SimplifiedOperatorBuilder::BigIntAsUintN(int bits) {
+const Operator* SimplifiedOperatorBuilder::SpeculativeBigIntAsUintN(
+    int bits, const FeedbackSource& feedback) {
   CHECK(0 <= bits && bits <= 64);
 
-  return zone()->New<Operator1<int>>(IrOpcode::kBigIntAsUintN, Operator::kPure,
-                                     "BigIntAsUintN", 1, 0, 0, 1, 0, 0, bits);
+  return zone()->New<Operator1<SpeculativeBigIntAsUintNParameters>>(
+      IrOpcode::kSpeculativeBigIntAsUintN, Operator::kNoProperties,
+      "SpeculativeBigIntAsUintN", 1, 1, 1, 1, 1, 0,
+      SpeculativeBigIntAsUintNParameters(bits, feedback));
 }
 
 const Operator* SimplifiedOperatorBuilder::UpdateInterruptBudget(int delta) {

src/compiler/simplified-operator.h

@@ -606,6 +606,30 @@ bool operator==(NumberOperationParameters const&,
 const NumberOperationParameters& NumberOperationParametersOf(const Operator* op)
     V8_WARN_UNUSED_RESULT;
 
+class SpeculativeBigIntAsUintNParameters {
+ public:
+  SpeculativeBigIntAsUintNParameters(int bits, const FeedbackSource& feedback)
+      : bits_(bits), feedback_(feedback) {
+    DCHECK_GE(bits_, 0);
+    DCHECK_LE(bits_, 64);
+  }
+
+  int bits() const { return bits_; }
+  const FeedbackSource& feedback() const { return feedback_; }
+
+ private:
+  int bits_;
+  FeedbackSource feedback_;
+};
+
+size_t hash_value(SpeculativeBigIntAsUintNParameters const&);
+V8_EXPORT_PRIVATE std::ostream& operator<<(
+    std::ostream&, const SpeculativeBigIntAsUintNParameters&);
+bool operator==(SpeculativeBigIntAsUintNParameters const&,
+                SpeculativeBigIntAsUintNParameters const&);
+const SpeculativeBigIntAsUintNParameters& SpeculativeBigIntAsUintNParametersOf(
+    const Operator* op) V8_WARN_UNUSED_RESULT;
+
 int FormalParameterCountOf(const Operator* op) V8_WARN_UNUSED_RESULT;
 
 class AllocateParameters {
@@ -813,7 +837,8 @@ class V8_EXPORT_PRIVATE SimplifiedOperatorBuilder final
   const Operator* SpeculativeBigIntAdd(BigIntOperationHint hint);
   const Operator* SpeculativeBigIntSubtract(BigIntOperationHint hint);
   const Operator* SpeculativeBigIntNegate(BigIntOperationHint hint);
-  const Operator* BigIntAsUintN(int bits);
+  const Operator* SpeculativeBigIntAsUintN(int bits,
+                                           const FeedbackSource& feedback);
 
   const Operator* ReferenceEqual();
   const Operator* SameValue();

src/compiler/verifier.cc

@@ -954,8 +954,8 @@ void Verifier::Visitor::Check(Node* node, const AllNodes& all) {
     case IrOpcode::kSpeculativeBigIntNegate:
       CheckTypeIs(node, Type::BigInt());
       break;
-    case IrOpcode::kBigIntAsUintN:
-      CheckValueInputIs(node, 0, Type::BigInt());
+    case IrOpcode::kSpeculativeBigIntAsUintN:
+      CheckValueInputIs(node, 0, Type::Any());
       CheckTypeIs(node, Type::BigInt());
       break;
     case IrOpcode::kBigIntAdd:

src/runtime/runtime-test.cc

@@ -1348,5 +1348,11 @@ RUNTIME_FUNCTION(Runtime_NewRegExpWithBacktrackLimit) {
       isolate, JSRegExp::New(isolate, pattern, flags, backtrack_limit));
 }
 
+RUNTIME_FUNCTION(Runtime_Is64Bit) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(0, args.length());
+  return isolate->heap()->ToBoolean(kSystemPointerSize == 8);
+}
+
 }  // namespace internal
 }  // namespace v8

src/runtime/runtime.h

@@ -552,7 +552,8 @@ namespace internal {
   I(DeoptimizeNow, 0, 1)                      \
   F(PromiseSpeciesProtector, 0, 1)            \
   F(IsConcatSpreadableProtector, 0, 1)        \
-  F(RegExpSpeciesProtector, 0, 1)
+  F(RegExpSpeciesProtector, 0, 1)             \
+  F(Is64Bit, 0, 1)
 
 #define FOR_EACH_INTRINSIC_TYPEDARRAY(F, I) \
   F(ArrayBufferDetach, 1, 1)                \

test/mjsunit/compiler/bigint-asuintn.js

@@ -0,0 +1,37 @@
+// Copyright 2021 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --opt --no-always-opt
+
+
+function f(x) {
+  return BigInt.asUintN(3, x);
+}
+
+%PrepareFunctionForOptimization(f);
+assertEquals(7n, f(7n));
+assertEquals(1n, f(9n));
+%OptimizeFunctionOnNextCall(f);
+assertEquals(7n, f(7n));
+assertEquals(1n, f(9n));
+assertOptimized(f);
+
+// BigInt.asUintN throws TypeError for non-BigInt arguments.
+assertThrows(() => f(2), TypeError);
+if(%Is64Bit()) {
+  // On 64 bit architectures TurboFan optimizes BigInt.asUintN to native code
+  // that deoptimizes on non-BigInt arguments.
+  assertUnoptimized(f);
+
+  // The next time the function is optimized, speculation should be disabled
+  // so the builtin call is kept, which won't deoptimize again.
+  %PrepareFunctionForOptimization(f);
+  %OptimizeFunctionOnNextCall(f);
+}
+assertEquals(7n, f(7n));
+assertOptimized(f);
+
+// Re-optimized still throws but does not deopt-loop.
+assertThrows(() => f(2), TypeError);
+assertOptimized(f);