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Unified Diff: src/hydrogen-uint32-analysis.cc

Issue 18487003: Turn UInt32 analysis into a proper HPhase. (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: Fix typos. Created 7 years, 6 months ago
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Index: src/hydrogen-uint32-analysis.cc
diff --git a/src/hydrogen-uint32-analysis.cc b/src/hydrogen-uint32-analysis.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d796b37e789382e59b8c02a6175783f46464b375
--- /dev/null
+++ b/src/hydrogen-uint32-analysis.cc
@@ -0,0 +1,227 @@
+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following
+// disclaimer in the documentation and/or other materials provided
+// with the distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived
+// from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "hydrogen-uint32-analysis.h"
+
+namespace v8 {
+namespace internal {
+
+
+bool HUint32AnalysisPhase::IsSafeUint32Use(HValue* val, HValue* use) {
+ // Operations that operate on bits are safe.
+ if (use->IsBitwise() ||
+ use->IsShl() ||
+ use->IsSar() ||
+ use->IsShr() ||
+ use->IsBitNot()) {
+ return true;
+ } else if (use->IsChange() || use->IsSimulate()) {
+ // Conversions and deoptimization have special support for unt32.
+ return true;
+ } else if (use->IsStoreKeyed()) {
+ HStoreKeyed* store = HStoreKeyed::cast(use);
+ if (store->is_external()) {
+ // Storing a value into an external integer array is a bit level
+ // operation.
+ if (store->value() == val) {
+ // Clamping or a conversion to double should have beed inserted.
+ ASSERT(store->elements_kind() != EXTERNAL_PIXEL_ELEMENTS);
+ ASSERT(store->elements_kind() != EXTERNAL_FLOAT_ELEMENTS);
+ ASSERT(store->elements_kind() != EXTERNAL_DOUBLE_ELEMENTS);
+ return true;
+ }
+ }
+ }
+
+ return false;
+}
+
+
+// Iterate over all uses and verify that they are uint32 safe: either don't
+// distinguish between int32 and uint32 due to their bitwise nature or
+// have special support for uint32 values.
+// Encountered phis are optimistically treated as safe uint32 uses,
+// marked with kUint32 flag and collected in the phis_ list. A separate
+// pass will be performed later by UnmarkUnsafePhis to clear kUint32 from
+// phis that are not actually uint32-safe (it requires fix point iteration).
+bool HUint32AnalysisPhase::Uint32UsesAreSafe(HValue* uint32val) {
+ bool collect_phi_uses = false;
+ for (HUseIterator it(uint32val->uses()); !it.Done(); it.Advance()) {
+ HValue* use = it.value();
+
+ if (use->IsPhi()) {
+ if (!use->CheckFlag(HInstruction::kUint32)) {
+ // There is a phi use of this value from a phi that is not yet
+ // collected in phis_ array. Separate pass is required.
+ collect_phi_uses = true;
+ }
+
+ // Optimistically treat phis as uint32 safe.
+ continue;
+ }
+
+ if (!IsSafeUint32Use(uint32val, use)) {
+ return false;
+ }
+ }
+
+ if (collect_phi_uses) {
+ for (HUseIterator it(uint32val->uses()); !it.Done(); it.Advance()) {
+ HValue* use = it.value();
+
+ // There is a phi use of this value from a phi that is not yet
+ // collected in phis_ array. Separate pass is required.
+ if (use->IsPhi() && !use->CheckFlag(HInstruction::kUint32)) {
+ use->SetFlag(HInstruction::kUint32);
+ phis_.Add(HPhi::cast(use), zone());
+ }
+ }
+ }
+
+ return true;
+}
+
+
+// Check if all operands to the given phi are marked with kUint32 flag.
+bool HUint32AnalysisPhase::CheckPhiOperands(HPhi* phi) {
+ if (!phi->CheckFlag(HInstruction::kUint32)) {
+ // This phi is not uint32 safe. No need to check operands.
+ return false;
+ }
+
+ for (int j = 0; j < phi->OperandCount(); j++) {
+ HValue* operand = phi->OperandAt(j);
+ if (!operand->CheckFlag(HInstruction::kUint32)) {
+ // Lazily mark constants that fit into uint32 range with kUint32 flag.
+ if (operand->IsInteger32Constant() &&
+ operand->GetInteger32Constant() >= 0) {
+ operand->SetFlag(HInstruction::kUint32);
+ continue;
+ }
+
+ // This phi is not safe, some operands are not uint32 values.
+ return false;
+ }
+ }
+
+ return true;
+}
+
+
+// Remove kUint32 flag from the phi itself and its operands. If any operand
+// was a phi marked with kUint32 place it into a worklist for
+// transitive clearing of kUint32 flag.
+void HUint32AnalysisPhase::UnmarkPhi(HPhi* phi, ZoneList<HPhi*>* worklist) {
+ phi->ClearFlag(HInstruction::kUint32);
+ for (int j = 0; j < phi->OperandCount(); j++) {
+ HValue* operand = phi->OperandAt(j);
+ if (operand->CheckFlag(HInstruction::kUint32)) {
+ operand->ClearFlag(HInstruction::kUint32);
+ if (operand->IsPhi()) {
+ worklist->Add(HPhi::cast(operand), zone());
+ }
+ }
+ }
+}
+
+
+void HUint32AnalysisPhase::UnmarkUnsafePhis() {
+ // No phis were collected. Nothing to do.
+ if (phis_.length() == 0) return;
+
+ // Worklist used to transitively clear kUint32 from phis that
+ // are used as arguments to other phis.
+ ZoneList<HPhi*> worklist(phis_.length(), zone());
+
+ // Phi can be used as a uint32 value if and only if
+ // all its operands are uint32 values and all its
+ // uses are uint32 safe.
+
+ // Iterate over collected phis and unmark those that
+ // are unsafe. When unmarking phi unmark its operands
+ // and add it to the worklist if it is a phi as well.
+ // Phis that are still marked as safe are shifted down
+ // so that all safe phis form a prefix of the phis_ array.
+ int phi_count = 0;
+ for (int i = 0; i < phis_.length(); i++) {
+ HPhi* phi = phis_[i];
+
+ if (CheckPhiOperands(phi) && Uint32UsesAreSafe(phi)) {
+ phis_[phi_count++] = phi;
+ } else {
+ UnmarkPhi(phi, &worklist);
+ }
+ }
+
+ // Now phis array contains only those phis that have safe
+ // non-phi uses. Start transitively clearing kUint32 flag
+ // from phi operands of discovered non-safe phis until
+ // only safe phis are left.
+ while (!worklist.is_empty()) {
+ while (!worklist.is_empty()) {
+ HPhi* phi = worklist.RemoveLast();
+ UnmarkPhi(phi, &worklist);
+ }
+
+ // Check if any operands to safe phis were unmarked
+ // turning a safe phi into unsafe. The same value
+ // can flow into several phis.
+ int new_phi_count = 0;
+ for (int i = 0; i < phi_count; i++) {
+ HPhi* phi = phis_[i];
+
+ if (CheckPhiOperands(phi)) {
+ phis_[new_phi_count++] = phi;
+ } else {
+ UnmarkPhi(phi, &worklist);
+ }
+ }
+ phi_count = new_phi_count;
+ }
+}
+
+
+void HUint32AnalysisPhase::Run() {
+ if (!graph()->has_uint32_instructions()) return;
+
+ ZoneList<HInstruction*>* uint32_instructions = graph()->uint32_instructions();
+ for (int i = 0; i < uint32_instructions->length(); ++i) {
+ // Analyze instruction and mark it with kUint32 if all
+ // its uses are uint32 safe.
+ HInstruction* current = uint32_instructions->at(i);
+ if (Uint32UsesAreSafe(current)) current->SetFlag(HInstruction::kUint32);
+ }
+
+ // Some phis might have been optimistically marked with kUint32 flag.
+ // Remove this flag from those phis that are unsafe and propagate
+ // this information transitively potentially clearing kUint32 flag
+ // from some non-phi operations that are used as operands to unsafe phis.
+ UnmarkUnsafePhis();
+}
+
+
+} } // namespace v8::internal
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