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compiler/arm64: change nops to use EmitIdentity

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This affects VisitChangeUint32ToUint64 and VisitTruncateInt64ToInt32.

The geometric mean of changes across octane, ares6-1.0.1, jetstream2,
and web-tooling-0.5.3, was an improvement of 1.2% when running on a
Cortex-A53.

Change-Id: Ib551641fb78ce4060100129e12f23cd02b0b3b27
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1669690
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62327}
This commit is contained in:
Stephen Kyle 2019-06-20 16:43:18 +01:00 committed by Commit Bot
parent 7e5d6304cd
commit 6ddbb54fc2
1 changed files with 3 additions and 4 deletions
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7
src/compiler/backend/arm64/instruction-selector-arm64.cc
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@ -1599,7 +1599,7 @@ void InstructionSelector::VisitChangeUint32ToUint64(Node* node) {
// 32-bit operations will write their result in a W register (implicitly
// clearing the top 32-bit of the corresponding X register) so the
// zero-extension is a no-op.
Emit(kArchNop, g.DefineSameAsFirst(node), g.Use(value));
EmitIdentity(node);
return;
}
case IrOpcode::kLoad: {
@ -1610,7 +1610,7 @@ void InstructionSelector::VisitChangeUint32ToUint64(Node* node) {
case MachineRepresentation::kWord8:
case MachineRepresentation::kWord16:
case MachineRepresentation::kWord32:
Emit(kArchNop, g.DefineSameAsFirst(node), g.Use(value));
EmitIdentity(node);
return;
default:
break;
@ -1665,10 +1665,9 @@ void InstructionSelector::VisitChangeCompressedSignedToTaggedSigned(
void InstructionSelector::VisitTruncateInt64ToInt32(Node* node) {
Arm64OperandGenerator g(this);
Node* value = node->InputAt(0);
// The top 32 bits in the 64-bit register will be undefined, and
// must not be used by a dependent node.
Emit(kArchNop, g.DefineSameAsFirst(node), g.UseRegister(value));
EmitIdentity(node);
}
void InstructionSelector::VisitFloat64Mod(Node* node) {