Reviewers: Jarin, Benedikt Meurer, Mircea Trofin,
Message:
Created Revert of [turbofan] Greedy: using hints
Description:
Revert of [turbofan] Greedy: using hints (patchset #2 id:60001 of
https://codereview.chromium.org/1329493004/ )
Reason for revert:
http://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20debug%20-%20greedy%20allocator/builds/1338
Original issue's description:
[turbofan] Greedy: using hints
This is a rudimentary introduction of hints. Primarily this helps with
allocating on the same register variables are defined (from instructions)
For dealing with phis, we need to introduce groups, in a subsequent
CL.
From the last CL (memory ops heuristics), this CL improves some
benchmarks - notably Life (11.94%) in Emscripten x64, and Memops
(Emscripten), 24% on x86; notable regressions: Memops in
AreWeFastYet (-14%, x64) and Corrections -25% on x86.
BUG=
Committed: https://crrev.com/038f5eaf3bd6796ed6b7519de83c21d4e1f54850
Cr-Commit-Position: refs/heads/master@{#30534}
[email protected],[email protected],[email protected]
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=
Please review this at https://codereview.chromium.org/1324763005/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+27, -36 lines):
M src/compiler/greedy-allocator.cc
Index: src/compiler/greedy-allocator.cc
diff --git a/src/compiler/greedy-allocator.cc
b/src/compiler/greedy-allocator.cc
index
63a2e436ee42e82390cc867dd473dfae5815beb6..aad322e3588eb90823fd05d51a09699fc20b78f5
100644
--- a/src/compiler/greedy-allocator.cc
+++ b/src/compiler/greedy-allocator.cc
@@ -21,11 +21,12 @@
namespace {
-void UpdateOperands(LiveRange* range, RegisterAllocationData* data) {
+
+void UpdateOperands(TopLevelLiveRange* range, RegisterAllocationData*
data) {
int reg_id = range->assigned_register();
range->SetUseHints(reg_id);
- if (range->IsTopLevel() && range->TopLevel()->is_phi()) {
-
data->GetPhiMapValueFor(range->TopLevel())->set_assigned_register(reg_id);
+ if (range->is_phi()) {
+ data->GetPhiMapValueFor(range)->set_assigned_register(reg_id);
}
}
@@ -139,7 +140,6 @@
TRACE("Assigning %s to range %d%d.\n", RegisterName(reg_id),
range->TopLevel()->vreg(), range->relative_id());
range->set_assigned_register(reg_id);
- UpdateOperands(range, data());
}
@@ -189,42 +189,24 @@
range->relative_id());
int free_reg = -1;
int evictable_reg = -1;
- int hinted_reg = -1;
-
EnsureValidRangeWeight(range);
DCHECK(range->weight() != LiveRange::kInvalidWeight);
- // Can we allocate at the hinted register?
- if (range->FirstHintPosition(&hinted_reg) != nullptr) {
- DCHECK(hinted_reg >= 0);
- float max_conflict_weight = GetMaximumConflictingWeight(hinted_reg,
range);
+ float smallest_weight = LiveRange::kMaxWeight;
+
+ // Seek either the first free register, or, from the set of registers
+ // where the maximum conflict is lower than the candidate's weight, the
one
+ // with the smallest such weight.
+ for (int i = 0; i < num_registers(); i++) {
+ float max_conflict_weight = GetMaximumConflictingWeight(i, range);
if (max_conflict_weight == LiveRange::kInvalidWeight) {
- free_reg = hinted_reg;
- } else if (max_conflict_weight < range->weight()) {
- evictable_reg = hinted_reg;
- }
- }
-
- if (free_reg < 0 && evictable_reg < 0) {
- // There was no hinted reg, or we cannot allocate there.
- float smallest_weight = LiveRange::kMaxWeight;
-
- // Seek either the first free register, or, from the set of registers
- // where the maximum conflict is lower than the candidate's weight,
the one
- // with the smallest such weight.
- for (int i = 0; i < num_registers(); i++) {
- // Skip unnecessarily re-visiting the hinted register, if any.
- if (i == hinted_reg) continue;
- float max_conflict_weight = GetMaximumConflictingWeight(i, range);
- if (max_conflict_weight == LiveRange::kInvalidWeight) {
- free_reg = i;
- break;
- }
- if (max_conflict_weight < range->weight() &&
- max_conflict_weight < smallest_weight) {
- smallest_weight = max_conflict_weight;
- evictable_reg = i;
- }
+ free_reg = i;
+ break;
+ }
+ if (max_conflict_weight < range->weight() &&
+ max_conflict_weight < smallest_weight) {
+ smallest_weight = max_conflict_weight;
+ evictable_reg = i;
}
}
@@ -322,6 +304,15 @@
TryAllocateCandidate(candidate);
}
+
+ // We do not rely on the hint mechanism used by LinearScan, so no need to
+ // actively update/reset operands until the end.
+ for (auto range : data()->live_ranges()) {
+ if (CanProcessRange(range) && range->HasRegisterAssigned()) {
+ UpdateOperands(range, data());
+ }
+ }
+
for (size_t i = 0; i < allocations_.size(); ++i) {
if (!allocations_[i]->empty()) {
data()->MarkAllocated(mode(), static_cast<int>(i));
--
--
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