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[compiler] Only run ScheduleEarly if graph contains loops.

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The ScheduleEarly phase of the scheduler initializes the minimum_block
values which are only required for loop hoisting. If there are no loops,
running this step is unecessary overhead.

BUG=v8:9684

Change-Id: Iba181fd55ecd634c05d3f8eb4282bd0be3141c21
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2880538
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74445}
This commit is contained in:
Ross McIlroy 2021-05-07 16:34:25 +01:00 committed by V8 LUCI CQ
parent 350b0c38ad
commit be09ba1f12
1 changed files with 10 additions and 0 deletions
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10
src/compiler/scheduler.cc
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@ -727,6 +727,8 @@ class SpecialRPONumberer : public ZoneObject {
return empty_;
}
bool HasLoopBlocks() const { return loops_.size() != 0; }
private:
using Backedge = std::pair<BasicBlock*, size_t>;
@ -1382,6 +1384,11 @@ class ScheduleEarlyNodeVisitor {
void Scheduler::ScheduleEarly() {
if (!special_rpo_->HasLoopBlocks()) {
TRACE("--- NO LOOPS SO SKIPPING SCHEDULE EARLY --------------------\n");
return;
}
TRACE("--- SCHEDULE EARLY -----------------------------------------\n");
if (FLAG_trace_turbo_scheduler) {
TRACE("roots: ");
@ -1459,6 +1466,7 @@ class ScheduleLateNodeVisitor {
// The schedule early block dominates the schedule late block.
BasicBlock* min_block = scheduler_->GetData(node)->minimum_block_;
DCHECK_EQ(min_block, BasicBlock::GetCommonDominator(block, min_block));
TRACE(
"Schedule late of #%d:%s is id:%d at loop depth %d, minimum = id:%d\n",
node->id(), node->op()->mnemonic(), block->id().ToInt(),
@ -1470,6 +1478,7 @@ class ScheduleLateNodeVisitor {
BasicBlock* hoist_block = GetHoistBlock(block);
if (hoist_block &&
hoist_block->dominator_depth() >= min_block->dominator_depth()) {
DCHECK(scheduler_->special_rpo_->HasLoopBlocks());
do {
TRACE(" hoisting #%d:%s to block id:%d\n", node->id(),
node->op()->mnemonic(), hoist_block->id().ToInt());
@ -1599,6 +1608,7 @@ class ScheduleLateNodeVisitor {
}
BasicBlock* GetHoistBlock(BasicBlock* block) {
if (!scheduler_->special_rpo_->HasLoopBlocks()) return nullptr;
if (block->IsLoopHeader()) return block->dominator();
// We have to check to make sure that the {block} dominates all
// of the outgoing blocks. If it doesn't, then there is a path