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// Copyright 2016 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.
#include "src/compiler/backend/bitcast-elider.h"
#include "src/compiler/graph.h"
namespace v8 {
namespace internal {
namespace compiler {
namespace {
bool IsBitcast(Node* node) {
// We can only elide kBitcastTaggedToWordForTagAndSmiBits and
// kBitcastWordToTaggedSigned because others might affect GC / safepoint
// tables.
return node->opcode() == IrOpcode::kBitcastTaggedToWordForTagAndSmiBits ||
node->opcode() == IrOpcode::kBitcastWordToTaggedSigned;
}
bool OwnedByWord32Op(Node* node) {
#if V8_TARGET_ARCH_LOONG64 || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_RISCV64
return false;
#else
for (Node* const use : node->uses()) {
switch (use->opcode()) {
case IrOpcode::kWord32Equal:
case IrOpcode::kInt32LessThan:
case IrOpcode::kInt32LessThanOrEqual:
case IrOpcode::kUint32LessThan:
case IrOpcode::kUint32LessThanOrEqual:
case IrOpcode::kChangeInt32ToInt64:
#define Word32Op(Name) case IrOpcode::k##Name:
MACHINE_BINOP_32_LIST(Word32Op)
#undef Word32Op
break;
default:
return false;
}
}
return true;
#endif
}
void Replace(Node* node, Node* replacement) {
for (Edge edge : node->use_edges()) {
edge.UpdateTo(replacement);
}
node->Kill();
}
} // namespace
void BitcastElider::Enqueue(Node* node) {
if (seen_.Get(node)) return;
seen_.Set(node, true);
to_visit_.push(node);
}
void BitcastElider::Revisit(Node* node) { to_visit_.push(node); }
void BitcastElider::VisitNode(Node* node) {
for (int i = 0; i < node->InputCount(); i++) {
Node* input = node->InputAt(i);
if (input->opcode() == IrOpcode::kTruncateInt64ToInt32 &&
OwnedByWord32Op(input)) {
Replace(input, input->InputAt(0));
Revisit(node);
} else if (is_builtin_ && IsBitcast(input)) {
Replace(input, input->InputAt(0));
Revisit(node);
} else {
Enqueue(input);
}
}
}
void BitcastElider::ProcessGraph() {
Enqueue(graph_->end());
while (!to_visit_.empty()) {
Node* node = to_visit_.front();
to_visit_.pop();
VisitNode(node);
}
}
BitcastElider::BitcastElider(Zone* zone, Graph* graph, bool is_builtin)
: graph_(graph),
to_visit_(zone),
seen_(graph, 2),
is_builtin_(is_builtin) {}
void BitcastElider::Reduce() { ProcessGraph(); }
} // namespace compiler
} // namespace internal
} // namespace v8
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