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B3EliminateDeadCode.cpp
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B3EliminateDeadCode.cpp
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/*
* Copyright (C) 2015-2019 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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
"
config.h
"
#
include
"
B3EliminateDeadCode.h
"
#
if
ENABLE(B3_JIT)
#
include
"
B3BasicBlock.h
"
#
include
"
B3PhaseScope.h
"
#
include
"
B3ValueInlines.h
"
#
include
"
B3Variable.h
"
#
include
"
B3VariableValue.h
"
#
include
<
wtf/GraphNodeWorklist.h
>
#
include
<
wtf/IndexSet.h
>
#
include
<
wtf/Vector.h
>
namespace
JSC
{
namespace
B3
{
//
FIXME: this pass currently only eliminates values and variables, it does not seem to eliminate dead blocks.
bool
eliminateDeadCodeImpl
(Procedure& proc)
{
bool
changed =
false
;
GraphNodeWorklist<Value*, IndexSet<Value*>> worklist;
Vector<UpsilonValue*,
128
> upsilons;
for
(BasicBlock* block : proc) {
for
(Value* value : *block) {
//
We don't care about effects of SSA operations, since we model them more
//
accurately than the effects() method does.
if
(value->
opcode
() != Phi && value->
opcode
() != Upsilon) {
if
(value->
mustExecute
())
worklist.
push
(value);
}
if
(UpsilonValue* upsilon = value->
as
<UpsilonValue>())
upsilons.
append
(upsilon);
}
}
for
(;;) {
while
(Value* value = worklist.
pop
()) {
for
(Value* child : value->
children
())
worklist.
push
(child);
}
bool
didPush =
false
;
for
(
size_t
upsilonIndex =
0
; upsilonIndex < upsilons.
size
(); ++upsilonIndex) {
UpsilonValue* upsilon = upsilons[upsilonIndex];
if
(worklist.
saw
(upsilon->
phi
())) {
worklist.
push
(upsilon);
upsilons[upsilonIndex--] = upsilons.
last
();
upsilons.
takeLast
();
didPush =
true
;
}
}
if
(!didPush)
break
;
}
IndexSet<Variable*> liveVariables;
for
(BasicBlock* block : proc) {
size_t
sourceIndex =
0
;
size_t
targetIndex =
0
;
while
(sourceIndex < block->
size
()) {
Value* value = block->
at
(sourceIndex++);
if
(worklist.
saw
(value)) {
if
(VariableValue* variableValue = value->
as
<VariableValue>())
liveVariables.
add
(variableValue->
variable
());
block->
at
(targetIndex++) = value;
}
else
{
proc.
deleteValue
(value);
changed =
true
;
}
}
block->
values
().
shrink
(targetIndex);
}
for
(Variable* variable : proc.
variables
()) {
if
(!liveVariables.
contains
(variable))
proc.
deleteVariable
(variable);
}
return
changed;
}
bool
eliminateDeadCode
(Procedure& proc)
{
PhaseScope
phaseScope
(proc,
"
eliminateDeadCode
"
_s);
return
eliminateDeadCodeImpl
(proc);
}
} }
//
namespace JSC::B3
#
endif
//
ENABLE(B3_JIT)
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