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Z: Short circuit memCmp methods if addresses are equal
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If addresses of two blocks of memory are equal, the content is equal too.
We can jump to the end label without comparing the content.
Four methods are updated to handle signed and unsigned result as well as constant and variable length.

Signed-off-by: Ehsan Kiani Far <ehsan.kianifar@gmail.com>
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@ehsankianifar
ehsankianifar committed Jan 23, 2024
1 parent a2b3b25 commit 4af016d
Showing 1 changed file with 46 additions and 73 deletions.
119 changes: 46 additions & 73 deletions compiler/z/codegen/OpMemToMem.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1503,6 +1503,20 @@ generateCmpResult(TR::CodeGenerator * cg, TR::Node * rootNode, TR::Register * ds
return cursor;
}

static TR::Instruction *
generateShortCircuitInstructions(TR::CodeGenerator * cg, TR::Node * node, TR::Register * result, TR::Register * src, TR::Register * dst, TR::LabelSymbol * label)
{
TR::LabelSymbol * cFlowRegionStart = generateLabelSymbol(cg);
// If "src" equals "dst", "result" would be zero and jumps to "label".
generateRRFInstruction(cg, TR::InstOpCode::getSubtractThreeRegOpCode(), node, result, src, dst);
// This is the first compare and branch instruction therefore control flow starts here.
generateS390LabelInstruction(cg, TR::InstOpCode::label, node, cFlowRegionStart);
cFlowRegionStart->setStartInternalControlFlow();
TR::Instruction * cursor = generateS390BranchInstruction(cg, TR::InstOpCode::BRC, TR::InstOpCode::COND_BRZ, node, label);

return cursor;
}

TR::Instruction *
MemCmpVarLenMacroOp::generate(TR::Register* dstReg, TR::Register* srcReg, TR::Register* tmpReg, int32_t offset, TR::Instruction *cursor)
{
Expand All @@ -1514,32 +1528,19 @@ MemCmpVarLenMacroOp::generate(TR::Register* dstReg, TR::Register* srcReg, TR::Re
_offset = offset;
_cursor = cursor;
_litReg = NULL;
TR::Compilation *comp = _cg->comp();
TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

if(cursorBefore == NULL) cursorBefore = _cg->getAppendInstruction();
generateShortCircuitInstructions(_cg, _rootNode, _resultReg, _srcReg, _dstReg, _doneLabel);
generateLoop();
setInRemainder(true);
generateRemainder();

_cursor = generateCmpResult(_cg, _rootNode, _dstReg, _srcReg, _resultReg, _falseLabel, _trueLabel, _doneLabel);
TR::RegisterDependencyConditions * dependencies = generateDependencies();
_cursor->setDependencyConditions(dependencies);
if(_startControlFlow==NULL)
{
_startControlFlow=cursorBefore->getNext();
if(_startControlFlow->getOpCodeValue() == TR::InstOpCode::assocreg) _startControlFlow=_startControlFlow->getNext();
}
if(_startControlFlow != _cursor)
{
TR::LabelSymbol * cFlowRegionStart = generateLabelSymbol(_cg);
TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionStart, dependencies, _startControlFlow->getPrev());
cFlowRegionStart->setStartInternalControlFlow();
TR::RegisterDependencyConditions * dependencies = generateDependencies();
generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, dependencies);
cFlowRegionEnd->setEndInternalControlFlow();

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, _cursor->getPrev());
cFlowRegionEnd->setEndInternalControlFlow();
}
return _cursor;
}

Expand All @@ -1556,32 +1557,24 @@ MemCmpConstLenMacroOp::generate(TR::Register* dstReg, TR::Register* srcReg, TR::
_litReg = NULL;
TR::Compilation *comp = _cg->comp();

if (_length == 0)
{
_cursor = generateRRInstruction(_cg, TR::InstOpCode::getXORRegOpCode(), _rootNode, _resultReg, _resultReg);
return _cursor;
}

TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

if(cursorBefore == NULL) cursorBefore = _cg->getAppendInstruction();
generateShortCircuitInstructions(_cg, _rootNode, _resultReg, _srcReg, _dstReg, _doneLabel);
generateLoop();
setInRemainder(true);
generateRemainder();

_cursor = generateCmpResult(_cg, _rootNode, _dstReg, _srcReg, _resultReg, _falseLabel, _trueLabel, _doneLabel);

TR::RegisterDependencyConditions * dependencies = generateDependencies();
_cursor->setDependencyConditions(dependencies);
if(_startControlFlow==NULL)
{
_startControlFlow=cursorBefore->getNext();
if(_startControlFlow->getOpCodeValue() == TR::InstOpCode::assocreg) _startControlFlow=_startControlFlow->getNext();
}
if(_startControlFlow != _cursor)
{
TR::LabelSymbol * cFlowRegionStart = generateLabelSymbol(_cg);
TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionStart, dependencies, _startControlFlow->getPrev());
cFlowRegionStart->setStartInternalControlFlow();

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, _cursor->getPrev());
cFlowRegionEnd->setEndInternalControlFlow();
}
generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, dependencies);
cFlowRegionEnd->setEndInternalControlFlow();

return _cursor;
}
Expand Down Expand Up @@ -1651,31 +1644,18 @@ MemCmpVarLenSignMacroOp::generate(TR::Register* dstReg, TR::Register* srcReg, TR
_offset = offset;
_cursor = cursor;
_litReg = NULL;
TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

if(cursorBefore == NULL) cursorBefore = _cg->getAppendInstruction();
generateShortCircuitInstructions(_cg, _rootNode, _resultReg, _srcReg, _dstReg, _doneLabel);
generateLoop();
setInRemainder(true);
generateRemainder();

_cursor = generateCmpSignResult(_cg, _rootNode, _dstReg, _srcReg, _resultReg, _falseLabel, _gtLabel, _trueLabel, _doneLabel);
TR::RegisterDependencyConditions * dependencies = generateDependencies();
_cursor->setDependencyConditions(dependencies);
if(_startControlFlow==NULL)
{
_startControlFlow=cursorBefore->getNext();
if(_startControlFlow->getOpCodeValue() == TR::InstOpCode::assocreg) _startControlFlow=_startControlFlow->getNext();
}
if(_startControlFlow != _cursor)
{
TR::LabelSymbol * cFlowRegionStart = generateLabelSymbol(_cg);
TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionStart, dependencies, _startControlFlow->getPrev());
cFlowRegionStart->setStartInternalControlFlow();

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, _cursor->getPrev());
cFlowRegionEnd->setEndInternalControlFlow();
}
TR::RegisterDependencyConditions * dependencies = generateDependencies();
generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, dependencies);
cFlowRegionEnd->setEndInternalControlFlow();

return _cursor;
}
Expand All @@ -1699,32 +1679,25 @@ MemCmpConstLenSignMacroOp::generate(TR::Register* dstReg, TR::Register* srcReg,
_offset = offset;
_cursor = cursor;
_litReg = NULL;
TR::Compilation *comp = _cg->comp();

if(cursorBefore == NULL) cursorBefore = _cg->getAppendInstruction();
if (_length == 0)
{
_cursor = generateRRInstruction(_cg, TR::InstOpCode::getXORRegOpCode(), _rootNode, _resultReg, _resultReg);
return _cursor;
}

TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

generateShortCircuitInstructions(_cg, _rootNode, _resultReg, _srcReg, _dstReg, _doneLabel);
generateLoop();
setInRemainder(true);
generateRemainder();

_cursor = generateCmpSignResult(_cg, _rootNode, _dstReg, _srcReg, _resultReg, _falseLabel, _gtLabel, _trueLabel, _doneLabel);
TR::RegisterDependencyConditions * dependencies = generateDependencies();
_cursor->setDependencyConditions(dependencies);
if(_startControlFlow==NULL)
{
_startControlFlow=cursorBefore->getNext();
if(_startControlFlow->getOpCodeValue() == TR::InstOpCode::assocreg) _startControlFlow=_startControlFlow->getNext();
}
if(_startControlFlow != _cursor)
{
TR::LabelSymbol * cFlowRegionStart = generateLabelSymbol(_cg);
TR::LabelSymbol * cFlowRegionEnd = generateLabelSymbol(_cg);

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionStart, dependencies, _startControlFlow->getPrev());
cFlowRegionStart->setStartInternalControlFlow();

generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, _cursor->getPrev());
cFlowRegionEnd->setEndInternalControlFlow();
}
TR::RegisterDependencyConditions * dependencies = generateDependencies();
generateS390LabelInstruction(_cg, TR::InstOpCode::label, _rootNode, cFlowRegionEnd, dependencies);
cFlowRegionEnd->setEndInternalControlFlow();

return _cursor;
}
Expand Down

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