[turbofan] Fix inconsistent typing of NumberFloor(NumberDivide(...))

In typed-optimization, Turbofan optimized NumberFloor(NumberDivide(...))
patterns where both inputs are known to be of Unsigned32 type, but the
replacement couldn't be typed consistently. This CL introduces a new
operator Unsigned32Divide, which has the same semantics, but can be
typed consistently and thus allows the simplified lowering verifier to
validate the graph correctly.

Bug: v8:12619
Change-Id: Iad77154d3d840c94edfd3ab91ffa37c840da0bc9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3644790
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80967}

src/compiler/opcodes.h

@@ -493,6 +493,7 @@
   V(TransitionAndStoreNumberElement)    \
   V(TransitionElementsKind)             \
   V(TypeOf)                             \
+  V(Unsigned32Divide)                   \
   V(VerifyType)
 
 #define SIMPLIFIED_SPECULATIVE_BIGINT_BINOP_LIST(V) \

src/compiler/simplified-lowering.cc

@@ -767,7 +767,7 @@ class RepresentationSelector {
       TurboJsonFile json_of(info, std::ios_base::app);
       JSONGraphWriter writer(json_of, graph(), source_positions_,
                              node_origins_);
-      writer.PrintPhase("V8.TFSimplifiedLowering [after retype]");
+      writer.PrintPhase("V8.TFSimplifiedLowering [after lower]");
     }
 
     // Verify all nodes.
@@ -797,7 +797,6 @@ class RepresentationSelector {
     RunPropagatePhase();
     RunRetypePhase();
     RunLowerPhase(lowering);
-
     if (verification_enabled()) {
       RunVerifyPhase(lowering->info_);
     }
@@ -2582,6 +2581,14 @@ class RepresentationSelector {
         if (lower<T>()) ChangeToPureOp(node, Float64Op(node));
         return;
       }
+      case IrOpcode::kUnsigned32Divide: {
+        CHECK(TypeOf(node->InputAt(0)).Is(Type::Unsigned32()));
+        CHECK(TypeOf(node->InputAt(1)).Is(Type::Unsigned32()));
+        // => unsigned Uint32Div
+        VisitWord32TruncatingBinop<T>(node);
+        if (lower<T>()) DeferReplacement(node, lowering->Uint32Div(node));
+        return;
+      }
       case IrOpcode::kSpeculativeNumberModulus:
         return VisitSpeculativeNumberModulus<T>(node, truncation, lowering);
       case IrOpcode::kNumberModulus: {

src/compiler/simplified-operator.cc

@@ -799,7 +799,8 @@ bool operator==(CheckMinusZeroParameters const& lhs,
   V(StringLessThan, Operator::kNoProperties, 2, 0)               \
   V(StringLessThanOrEqual, Operator::kNoProperties, 2, 0)        \
   V(ToBoolean, Operator::kNoProperties, 1, 0)                    \
-  V(NewConsString, Operator::kNoProperties, 3, 0)
+  V(NewConsString, Operator::kNoProperties, 3, 0)                \
+  V(Unsigned32Divide, Operator::kNoProperties, 2, 0)
 
 #define EFFECT_DEPENDENT_OP_LIST(V)                       \
   V(BigIntAdd, Operator::kNoProperties, 2, 1)             \

src/compiler/simplified-operator.h

@@ -1072,6 +1072,11 @@ class V8_EXPORT_PRIVATE SimplifiedOperatorBuilder final
 #endif
 
   const Operator* DateNow();
+  // Unsigned32Divide is a special operator to express the division of two
+  // Unsigned32 inputs and truncating the result to Unsigned32. It's semantics
+  // is equivalent to NumberFloor(NumberDivide(x:Unsigned32, y:Unsigned32)) but
+  // is required to allow consistent typing of the graph.
+  const Operator* Unsigned32Divide();
 
   // Represents the inputs necessary to construct a fast and a slow API call.
   const Operator* FastApiCall(

src/compiler/typed-optimization.cc

@@ -328,16 +328,14 @@ Reduction TypedOptimization::ReduceNumberFloor(Node* node) {
       //
       // with
       //
-      //   NumberToUint32(NumberDivide(lhs, rhs))
+      //   Unsigned32Divide(lhs, rhs)
       //
-      // and just smash the type [0...lhs.Max] on the {node},
+      // and have the new node typed to [0...lhs.Max],
       // as the truncated result must be lower than {lhs}'s maximum
       // value (note that {rhs} cannot be less than 1 due to the
       // plain-number type constraint on the {node}).
-      NodeProperties::ChangeOp(node, simplified()->NumberToUint32());
-      NodeProperties::SetType(node,
-                              Type::Range(0, lhs_type.Max(), graph()->zone()));
-      return Changed(node);
+      node = graph()->NewNode(simplified()->Unsigned32Divide(), lhs, rhs);
+      return Replace(node);
     }
   }
   return NoChange();

src/compiler/typer.cc

@@ -1525,6 +1525,11 @@ Type Typer::Visitor::TypeJSObjectIsArray(Node* node) { return Type::Boolean(); }
 
 Type Typer::Visitor::TypeDateNow(Node* node) { return Type::Number(); }
 
+Type Typer::Visitor::TypeUnsigned32Divide(Node* node) {
+  Type lhs = Operand(node, 0);
+  return Type::Range(0, lhs.Max(), zone());
+}
+
 Type Typer::Visitor::JSCallTyper(Type fun, Typer* t) {
   if (!fun.IsHeapConstant() || !fun.AsHeapConstant()->Ref().IsJSFunction()) {
     return Type::NonInternal();

src/compiler/verifier.cc

@@ -1096,6 +1096,11 @@ void Verifier::Visitor::Check(Node* node, const AllNodes& all) {
       CheckValueInputIs(node, 0, Type::Number());
       CheckTypeIs(node, Type::Unsigned32());
       break;
+    case IrOpcode::kUnsigned32Divide:
+      CheckValueInputIs(node, 0, Type::Unsigned32());
+      CheckValueInputIs(node, 1, Type::Unsigned32());
+      CheckTypeIs(node, Type::Unsigned32());
+      break;
     case IrOpcode::kSpeculativeToNumber:
       CheckValueInputIs(node, 0, Type::Any());
       CheckTypeIs(node, Type::Number());

test/mjsunit/regress/regress-1323602.js

+// Copyright 2022 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 --turbofan
+
+let g;
+
+function test() {
+  const ten = 10;
+  const x = 10 / ten;
+  const y = Math.floor(x);
+  g = x;
+  return y + 1;
+}
+
+%PrepareFunctionForOptimization(test);
+assertEquals(2, test());
+%OptimizeFunctionOnNextCall(test);
+assertEquals(2, test());