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[turbofan] Avoid unnecessary bit materialization in CheckedInt32Mod.

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The slow-path of CheckedInt32Mod(x,y) when x is found to be negative
still had the power of two right hand side optimization, and thus would
perform a dynamic check on y. Now the same dynamic check was done for
the fast-path, and the word operations for this check were pure, leading
to weird bit materialization in TurboFan (due to sea of nodes). But
there's not really a point to be clever for the slow-path, so we just
insert the Uint32Mod operation directly here, which completely avoids
the problem.

This improves the Kraken/audio-oscillator test from around 73ms to 69ms.

Bug: v8:8069
Change-Id: Ie8ea667136c95df2bd8c5ba56ebbc6bd2442ff23
Reviewed-on: https://chromium-review.googlesource.com/c/1259063
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56370}
This commit is contained in:
Benedikt Meurer 2018-10-04 06:45:10 +02:00 committed by Commit Bot
parent 513a5bdd04
commit 7cd2cacf50
2 changed files with 28 additions and 3 deletions
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7
src/compiler/effect-control-linearizer.cc
View File

@ -1862,8 +1862,11 @@ Node* EffectControlLinearizer::LowerCheckedInt32Mod(Node* node,
__ Bind(&if_lhs_negative);
{
// The {lhs} is a negative integer.
Node* res = BuildUint32Mod(__ Int32Sub(zero, lhs), rhs);
// The {lhs} is a negative integer. This is very unlikely and
// we intentionally don't use the BuildUint32Mod() here, which
// would try to figure out whether {rhs} is a power of two,
// since this is intended to be a slow-path.
Node* res = __ Uint32Mod(__ Int32Sub(zero, lhs), rhs);
// Check if we would have to return -0.
__ DeoptimizeIf(DeoptimizeReason::kMinusZero, VectorSlotPair(),

24
test/mjsunit/compiler/number-modulus.js
View File

@ -2,7 +2,7 @@
// 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
// Flags: --allow-natives-syntax --opt --noalways-opt
// Test that NumberModulus with Number feedback works if only in the
// end SimplifiedLowering figures out that the inputs to this operation
@ -154,3 +154,25 @@
assertEquals(1, foo(-1));
assertOptimized(foo);
})();
// Test that CheckedInt32Mod handles the slow-path (when
// the left hand side is negative) correctly.
(function() {
// We need a SpeculativeNumberModulus with SignedSmall feedback.
function foo(x, y) {
return x % y;
}
assertEquals(0, foo(2, 1));
assertEquals(0, foo(2, 2));
assertEquals(-1, foo(-3, 2));
%OptimizeFunctionOnNextCall(foo);
assertEquals(0, foo(2, 1));
assertEquals(0, foo(2, 2));
assertEquals(-1, foo(-3, 2));
assertOptimized(foo);
// Now `foo` should deoptimize if the result is -0.
assertEquals(-0, foo(-2, 2));
assertUnoptimized(foo);
})();