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[turbofan] Consistently use String feedback for JSAdd.

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Currently we didn't always consistently use the String feedback on
JSAdd, but only if JSTypedLowering would already figure out statically
that one of the inputs is already a String. That leads to some odd
performance cliffs, as highlighted in the referenced bug.

This CL fixes the JSTypedLowering::ReduceJSAdd to always bake in the
String feedback. This improves the relevant performance tests from the
bug from

  console.timeEnd: Runtime join3, 967.512000
  console.timeEnd: Runtime join, 1004.599000
  console.timeEnd: Runtime join3, 1124.764000
  console.timeEnd: Runtime join, 966.164000
  console.timeEnd: Runtime join3, 1145.296000
  console.timeEnd: Runtime join, 966.176000
  console.timeEnd: Runtime join3, 1145.272000
  console.timeEnd: Runtime join, 931.266000

to

  console.timeEnd: Runtime join3, 903.050000
  console.timeEnd: Runtime join, 856.509000
  console.timeEnd: Runtime join3, 945.144000
  console.timeEnd: Runtime join, 840.038000
  console.timeEnd: Runtime join3, 927.965000
  console.timeEnd: Runtime join, 841.263000
  console.timeEnd: Runtime join3, 929.342000
  console.timeEnd: Runtime join, 858.143000

which corresponds to an 8-18% improvement.

Bug: v8:7415
Change-Id: I62e008298e4ee0864885b37817c91d055acf2a09
Reviewed-on: https://chromium-review.googlesource.com/936643
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51551}
This commit is contained in:
Benedikt Meurer 2018-02-26 09:39:15 +01:00 committed by Commit Bot
parent 80e0a759fd
commit d504203e93
1 changed files with 10 additions and 1 deletions
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11
src/compiler/js-typed-lowering.cc
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@ -504,6 +504,13 @@ Reduction JSTypedLowering::ReduceJSAdd(Node* node) {
r.ConvertInputsToNumber();
return r.ChangeToPureOperator(simplified()->NumberAdd(), Type::Number());
}
if (BinaryOperationHintOf(node->op()) == BinaryOperationHint::kString) {
// Always bake in String feedback into the graph.
// TODO(bmeurer): Consider adding a SpeculativeStringAdd operator,
// and use that in JSTypeHintLowering instead of looking at the
// binary operation feedback here.
r.CheckInputsToString();
}
if (r.OneInputIs(Type::String())) {
// We know that (at least) one input is already a String,
// so try to strength-reduce the non-String input.
@ -539,7 +546,7 @@ Reduction JSTypedLowering::ReduceJSAdd(Node* node) {
return ReduceCreateConsString(node);
}
// Eliminate useless concatenation of empty string.
if (BinaryOperationHintOf(node->op()) == BinaryOperationHint::kString) {
if (r.BothInputsAre(Type::String())) {
Node* effect = NodeProperties::GetEffectInput(node);
Node* control = NodeProperties::GetControlInput(node);
if (r.LeftInputIs(empty_string_type_)) {
@ -582,6 +589,8 @@ Reduction JSTypedLowering::ReduceJSAdd(Node* node) {
NodeProperties::ChangeOp(node, common()->Call(call_descriptor));
return Changed(node);
}
// We never get here when we had String feedback.
DCHECK_NE(BinaryOperationHint::kString, BinaryOperationHintOf(node->op()));
return NoChange();
}