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[turbofan] splinters should spill if there is no register use

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When allocating for splinters, we were prematurely reverting to the
hot range behavior, even when the range didn't actually have any
positions requiring a register. This could cause unnecessary moves.

BUG=

Review-Url: https://chromiumcodereview.appspot.com/2436813003
Cr-Commit-Position: refs/heads/master@{#40472}
This commit is contained in:
mtrofin 2016-10-20 07:17:52 -07:00 committed by Commit bot
parent 510b56d3f2
commit d2784b985f
1 changed files with 4 additions and 2 deletions
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6
src/compiler/register-allocator.cc
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@ -2661,14 +2661,16 @@ void LinearScanAllocator::AllocateRegisters() {
bool LinearScanAllocator::TrySplitAndSpillSplinter(LiveRange* range) {
DCHECK(range->TopLevel()->IsSplinter());
// If there was no hint, apply regular (hot path) heuristics.
if (range->FirstHintPosition() == nullptr) return false;
// If we can spill the whole range, great. Otherwise, split above the
// first use needing a register and spill the top part.
const UsePosition* next_reg = range->NextRegisterPosition(range->Start());
if (next_reg == nullptr) {
Spill(range);
return true;
} else if (range->FirstHintPosition() == nullptr) {
// If there was no hint, but we have a use position requiring a
// register, apply the hot path heuristics.
return false;
} else if (next_reg->pos().PrevStart() > range->Start()) {
LiveRange* tail = SplitRangeAt(range, next_reg->pos().PrevStart());
AddToUnhandledSorted(tail);