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[maglev] Disable stack-slot reuse

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It doesn't take into account stack-slot liveness at time of spill, so
it can cause false sharing.

Bug: v8:7700
Change-Id: Ib8a00d00d857fad40f14fce1d1496fea071e334f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3568465
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79737}
This commit is contained in:
Leszek Swirski 2022-04-04 13:17:10 +02:00 committed by V8 LUCI CQ
parent 1f0d7d2072
commit f6a23fb87d
2 changed files with 1 additions and 14 deletions
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14
src/maglev/maglev-regalloc.cc
View File

@ -314,12 +314,6 @@ void StraightForwardRegisterAllocator::UpdateUse(
// If a value is dead, make sure it's cleared. // If a value is dead, make sure it's cleared.
FreeRegisters(node); FreeRegisters(node);
// If the stack slot is a local slot, free it so it can be reused.
if (node->is_spilled()) {
compiler::AllocatedOperand slot = node->spill_slot();
if (slot.index() > 0) free_slots_.push_back(slot.index());
}
} }
void StraightForwardRegisterAllocator::UpdateUse( void StraightForwardRegisterAllocator::UpdateUse(
@ -632,13 +626,7 @@ void StraightForwardRegisterAllocator::SpillAndClearRegisters() {
void StraightForwardRegisterAllocator::AllocateSpillSlot(ValueNode* node) { void StraightForwardRegisterAllocator::AllocateSpillSlot(ValueNode* node) {
DCHECK(!node->is_spilled()); DCHECK(!node->is_spilled());
uint32_t free_slot; uint32_t free_slot = top_of_stack_++;
if (free_slots_.empty()) {
free_slot = top_of_stack_++;
} else {
free_slot = free_slots_.back();
free_slots_.pop_back();
}
node->Spill(compiler::AllocatedOperand(compiler::AllocatedOperand::STACK_SLOT, node->Spill(compiler::AllocatedOperand(compiler::AllocatedOperand::STACK_SLOT,
MachineRepresentation::kTagged, MachineRepresentation::kTagged,
free_slot)); free_slot));

1
src/maglev/maglev-regalloc.h
View File

@ -33,7 +33,6 @@ class StraightForwardRegisterAllocator {
int top_of_stack_ = 0; int top_of_stack_ = 0;
RegList free_registers_ = kAllocatableGeneralRegisters; RegList free_registers_ = kAllocatableGeneralRegisters;
std::vector<uint32_t> free_slots_;
RegList used_registers() const { RegList used_registers() const {
// Only allocatable registers should be free. // Only allocatable registers should be free.