Revision: 16645
Author: [email protected]
Date: Wed Sep 11 10:53:56 2013 UTC
Log: Implement simplistic local alias analysis, which will be used in
both check elimination and load elimination.
BUG=
[email protected]
Review URL: https://codereview.chromium.org/23516010
http://code.google.com/p/v8/source/detail?r=16645
Added:
/branches/bleeding_edge/src/hydrogen-alias-analysis.h
Modified:
/branches/bleeding_edge/tools/gyp/v8.gyp
=======================================
--- /dev/null
+++ /branches/bleeding_edge/src/hydrogen-alias-analysis.h Wed Sep 11
10:53:56 2013 UTC
@@ -0,0 +1,101 @@
+// 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.
+
+#ifndef V8_HYDROGEN_ALIAS_ANALYSIS_H_
+#define V8_HYDROGEN_ALIAS_ANALYSIS_H_
+
+#include "hydrogen.h"
+
+namespace v8 {
+namespace internal {
+
+enum HAliasing {
+ kMustAlias,
+ kMayAlias,
+ kNoAlias
+};
+
+
+// Defines the interface to alias analysis for the rest of the compiler.
+// A simple implementation can use only local reasoning, but a more
powerful
+// analysis might employ points-to analysis.
+class HAliasAnalyzer : public ZoneObject {
+ public:
+ // Simple alias analysis distinguishes allocations, parameters,
+ // and constants using only local reasoning.
+ HAliasing Query(HValue* a, HValue* b) {
+ // The same SSA value always references the same object.
+ if (a == b) return kMustAlias;
+
+ if (a->IsAllocate() || a->IsInnerAllocatedObject()) {
+ // Two non-identical allocations can never be aliases.
+ if (b->IsAllocate()) return kNoAlias;
+ if (b->IsInnerAllocatedObject()) return kNoAlias;
+ // An allocation can never alias a parameter or a constant.
+ if (b->IsParameter()) return kNoAlias;
+ if (b->IsConstant()) return kNoAlias;
+ }
+ if (b->IsAllocate() || b->IsInnerAllocatedObject()) {
+ // An allocation can never alias a parameter or a constant.
+ if (a->IsParameter()) return kNoAlias;
+ if (a->IsConstant()) return kNoAlias;
+ }
+
+ // TODO(titzer): return MustAlias for two equivalent constants.
+ return kMayAlias;
+ }
+
+ // Checks whether the objects referred to by the given instructions may
+ // ever be aliases. Note that this is more conservative than checking
+ // {Query(a, b) == kMayAlias}, since this method considers kMustAlias
+ // objects to also be may-aliasing.
+ inline bool MayAlias(HValue* a, HValue* b) {
+ return Query(a, b) != kNoAlias;
+ }
+
+ inline bool MustAlias(HValue* a, HValue* b) {
+ return Query(a, b) == kMayAlias;
+ }
+
+ inline bool NoAlias(HValue* a, HValue* b) {
+ return Query(a, b) == kNoAlias;
+ }
+
+ // Returns the actual value of an instruction. In the case of a chain
+ // of informative definitions, return the root of the chain.
+ HValue* ActualValue(HValue* obj) {
+ while (obj->IsInformativeDefinition()) { // Walk a chain of idefs.
+ obj = obj->RedefinedOperand();
+ }
+ return obj;
+ }
+};
+
+
+} } // namespace v8::internal
+
+#endif // V8_HYDROGEN_ALIAS_ANALYSIS_H_
=======================================
--- /branches/bleeding_edge/tools/gyp/v8.gyp Wed Sep 11 08:47:02 2013 UTC
+++ /branches/bleeding_edge/tools/gyp/v8.gyp Wed Sep 11 10:53:56 2013 UTC
@@ -336,6 +336,7 @@
'../../src/heap-snapshot-generator.h',
'../../src/heap.cc',
'../../src/heap.h',
+ '../../src/hydrogen-alias-analysis.h',
'../../src/hydrogen-bce.cc',
'../../src/hydrogen-bce.h',
'../../src/hydrogen-bch.cc',
--
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
---
You received this message because you are subscribed to the Google Groups "v8-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.
