[turbofan] Add fast-path for Math.hypot().

This adds a fast-path to inline `Math.hypot(v1,...,vn)` into optimized
code assuming that v1,...,vn are already numbers. The inlining follows
the general C++ implementation (which was also simplified a bit), and
thus uses Kahan summation to avoid rounding errors.

This improves the benchmark in [1] from around

  testHypot: 656 ms.
  testSqrt: 105 ms.
  testExp: 103 ms.

to

  testHypot: 147 ms.
  testSqrt: 103 ms.
  testExp: 102 ms.

so its roughly a **4.5x improvement**.

[1] 60a34c0dd2/bench-math-hypot.js

Bug: chromium:979893
Change-Id: Id834d5613bc22aa7ce27b9d6eca1f1f1979aa3e7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1684178
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62483}

src/builtins/builtins-math.cc

@@ -20,7 +20,6 @@ BUILTIN(MathHypot) {
   if (length == 0) return Smi::kZero;
   DCHECK_LT(0, length);
   double max = 0;
-  bool one_arg_is_nan = false;
   std::vector<double> abs_values;
   abs_values.reserve(length);
   for (int i = 0; i < length; i++) {
@@ -28,29 +27,20 @@ BUILTIN(MathHypot) {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, x,
                                        Object::ToNumber(isolate, x));
     double abs_value = std::abs(x->Number());
-
-    if (std::isnan(abs_value)) {
-      one_arg_is_nan = true;
-    } else {
-      abs_values.push_back(abs_value);
-      if (max < abs_value) {
-        max = abs_value;
-      }
+    abs_values.push_back(abs_value);
+    // Use negation here to make sure that {max} is NaN
+    // in the end in case any of the arguments was NaN.
+    if (!(abs_value <= max)) {
+      max = abs_value;
     }
   }
 
-  if (max == V8_INFINITY) {
-    return *isolate->factory()->NewNumber(V8_INFINITY);
-  }
-
-  if (one_arg_is_nan) {
-    return ReadOnlyRoots(isolate).nan_value();
-  }
-
   if (max == 0) {
     return Smi::kZero;
+  } else if (max == V8_INFINITY) {
+    return ReadOnlyRoots(isolate).infinity_value();
   }
-  DCHECK_GT(max, 0);
+  DCHECK(!(max <= 0));
 
   // Kahan summation to avoid rounding errors.
   // Normalize the numbers to the largest one to avoid overflow.

src/compiler/js-call-reducer.cc

@@ -179,6 +179,100 @@ Reduction JSCallReducer::ReduceMathMinMax(Node* node, const Operator* op,
   return Replace(value);
 }
 
+// ES section #sec-math.hypot Math.hypot ( value1, value2, ...values )
+Reduction JSCallReducer::ReduceMathHypot(Node* node) {
+  CallParameters const& p = CallParametersOf(node->op());
+  if (p.speculation_mode() == SpeculationMode::kDisallowSpeculation) {
+    return NoChange();
+  }
+  if (node->op()->ValueInputCount() < 3) {
+    Node* value = jsgraph()->ZeroConstant();
+    ReplaceWithValue(node, value);
+    return Replace(value);
+  }
+  Node* effect = NodeProperties::GetEffectInput(node);
+  Node* control = NodeProperties::GetControlInput(node);
+  NodeVector values(graph()->zone());
+
+  Node* max = effect =
+      graph()->NewNode(simplified()->SpeculativeToNumber(
+                           NumberOperationHint::kNumberOrOddball, p.feedback()),
+                       NodeProperties::GetValueInput(node, 2), effect, control);
+  max = graph()->NewNode(simplified()->NumberAbs(), max);
+  values.push_back(max);
+  for (int i = 3; i < node->op()->ValueInputCount(); ++i) {
+    Node* input = effect = graph()->NewNode(
+        simplified()->SpeculativeToNumber(NumberOperationHint::kNumberOrOddball,
+                                          p.feedback()),
+        NodeProperties::GetValueInput(node, i), effect, control);
+    input = graph()->NewNode(simplified()->NumberAbs(), input);
+    values.push_back(input);
+
+    // Make sure {max} is NaN in the end in case any argument was NaN.
+    max = graph()->NewNode(
+        common()->Select(MachineRepresentation::kTagged),
+        graph()->NewNode(simplified()->NumberLessThanOrEqual(), input, max),
+        max, input);
+  }
+
+  Node* check0 = graph()->NewNode(simplified()->NumberEqual(), max,
+                                  jsgraph()->ZeroConstant());
+  Node* branch0 =
+      graph()->NewNode(common()->Branch(BranchHint::kFalse), check0, control);
+
+  Node* if_true0 = graph()->NewNode(common()->IfTrue(), branch0);
+  Node* vtrue0 = jsgraph()->ZeroConstant();
+
+  Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
+  Node* vfalse0;
+  {
+    Node* check1 = graph()->NewNode(simplified()->NumberEqual(), max,
+                                    jsgraph()->Constant(V8_INFINITY));
+    Node* branch1 = graph()->NewNode(common()->Branch(BranchHint::kFalse),
+                                     check1, if_false0);
+
+    Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
+    Node* vtrue1 = jsgraph()->Constant(V8_INFINITY);
+
+    Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
+    Node* vfalse1;
+    {
+      // Kahan summation to avoid rounding errors.
+      // Normalize the numbers to the largest one to avoid overflow.
+      Node* sum = jsgraph()->ZeroConstant();
+      Node* compensation = jsgraph()->ZeroConstant();
+      for (Node* value : values) {
+        Node* n = graph()->NewNode(simplified()->NumberDivide(), value, max);
+        Node* summand = graph()->NewNode(
+            simplified()->NumberSubtract(),
+            graph()->NewNode(simplified()->NumberMultiply(), n, n),
+            compensation);
+        Node* preliminary =
+            graph()->NewNode(simplified()->NumberAdd(), sum, summand);
+        compensation = graph()->NewNode(
+            simplified()->NumberSubtract(),
+            graph()->NewNode(simplified()->NumberSubtract(), preliminary, sum),
+            summand);
+        sum = preliminary;
+      }
+      vfalse1 = graph()->NewNode(
+          simplified()->NumberMultiply(),
+          graph()->NewNode(simplified()->NumberSqrt(), sum), max);
+    }
+
+    if_false0 = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
+    vfalse0 = graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
+                               vtrue1, vfalse1, if_false0);
+  }
+
+  control = graph()->NewNode(common()->Merge(2), if_true0, if_false0);
+  Node* value =
+      graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2), vtrue0,
+                       vfalse0, control);
+  ReplaceWithValue(node, value, effect, control);
+  return Replace(value);
+}
+
 Reduction JSCallReducer::Reduce(Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kJSConstruct:
@@ -3518,6 +3612,8 @@ Reduction JSCallReducer::ReduceJSCall(Node* node,
       return ReduceMathUnary(node, simplified()->NumberFloor());
     case Builtins::kMathFround:
       return ReduceMathUnary(node, simplified()->NumberFround());
+    case Builtins::kMathHypot:
+      return ReduceMathHypot(node);
     case Builtins::kMathLog:
       return ReduceMathUnary(node, simplified()->NumberLog());
     case Builtins::kMathLog1p:

src/compiler/js-call-reducer.h

@@ -156,6 +156,7 @@ class V8_EXPORT_PRIVATE JSCallReducer final : public AdvancedReducer {
   Reduction ReduceMathImul(Node* node);
   Reduction ReduceMathClz32(Node* node);
   Reduction ReduceMathMinMax(Node* node, const Operator* op, Node* empty_value);
+  Reduction ReduceMathHypot(Node* node);
 
   Reduction ReduceNumberIsFinite(Node* node);
   Reduction ReduceNumberIsInteger(Node* node);