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/*
* Copyright (C) 2011 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 "DFGOSREntry.h"
#if ENABLE(DFG_JIT)
#include "CallFrame.h"
#include "CodeBlock.h"
#include "DFGNode.h"
#include "JIT.h"
#include "Operations.h"
namespace JSC { namespace DFG {
void* prepareOSREntry(ExecState* exec, CodeBlock* codeBlock, unsigned bytecodeIndex)
{
#if DFG_ENABLE(OSR_ENTRY)
ASSERT(codeBlock->getJITType() == JITCode::DFGJIT);
ASSERT(codeBlock->alternative());
ASSERT(codeBlock->alternative()->getJITType() == JITCode::BaselineJIT);
ASSERT(!codeBlock->jitCodeMap());
#if ENABLE(JIT_VERBOSE_OSR)
dataLog("OSR in ", *codeBlock->alternative(), " -> ", *codeBlock, " from bc#", bytecodeIndex, "\n");
#endif
VM* vm = &exec->vm();
OSREntryData* entry = codeBlock->dfgOSREntryDataForBytecodeIndex(bytecodeIndex);
if (!entry) {
#if ENABLE(JIT_VERBOSE_OSR)
dataLogF(" OSR failed because the entrypoint was optimized out.\n");
#endif
return 0;
}
ASSERT(entry->m_bytecodeIndex == bytecodeIndex);
// The code below checks if it is safe to perform OSR entry. It may find
// that it is unsafe to do so, for any number of reasons, which are documented
// below. If the code decides not to OSR then it returns 0, and it's the caller's
// responsibility to patch up the state in such a way as to ensure that it's
// both safe and efficient to continue executing baseline code for now. This
// should almost certainly include calling either codeBlock->optimizeAfterWarmUp()
// or codeBlock->dontOptimizeAnytimeSoon().
// 1) Verify predictions. If the predictions are inconsistent with the actual
// values, then OSR entry is not possible at this time. It's tempting to
// assume that we could somehow avoid this case. We can certainly avoid it
// for first-time loop OSR - that is, OSR into a CodeBlock that we have just
// compiled. Then we are almost guaranteed that all of the predictions will
// check out. It would be pretty easy to make that a hard guarantee. But
// then there would still be the case where two call frames with the same
// baseline CodeBlock are on the stack at the same time. The top one
// triggers compilation and OSR. In that case, we may no longer have
// accurate value profiles for the one deeper in the stack. Hence, when we
// pop into the CodeBlock that is deeper on the stack, we might OSR and
// realize that the predictions are wrong. Probably, in most cases, this is
// just an anomaly in the sense that the older CodeBlock simply went off
// into a less-likely path. So, the wisest course of action is to simply not
// OSR at this time.
for (size_t argument = 0; argument < entry->m_expectedValues.numberOfArguments(); ++argument) {
if (argument >= exec->argumentCountIncludingThis()) {
#if ENABLE(JIT_VERBOSE_OSR)
dataLogF(" OSR failed because argument %zu was not passed, expected ", argument);
entry->m_expectedValues.argument(argument).dump(WTF::dataFile());
dataLogF(".\n");
#endif
return 0;
}
JSValue value;
if (!argument)
value = exec->hostThisValue();
else
value = exec->argument(argument - 1);
if (!entry->m_expectedValues.argument(argument).validate(value)) {
#if ENABLE(JIT_VERBOSE_OSR)
dataLog(" OSR failed because argument ", argument, " is ", value, ", expected ", entry->m_expectedValues.argument(argument), ".\n");
#endif
return 0;
}
}
for (size_t local = 0; local < entry->m_expectedValues.numberOfLocals(); ++local) {
if (entry->m_localsForcedDouble.get(local)) {
if (!exec->registers()[local].jsValue().isNumber()) {
#if ENABLE(JIT_VERBOSE_OSR)
dataLog(" OSR failed because variable ", local, " is ", exec->registers()[local].jsValue(), ", expected number.\n");
#endif
return 0;
}
continue;
}
if (!entry->m_expectedValues.local(local).validate(exec->registers()[local].jsValue())) {
#if ENABLE(JIT_VERBOSE_OSR)
dataLog(" OSR failed because variable ", local, " is ", exec->registers()[local].jsValue(), ", expected ", entry->m_expectedValues.local(local), ".\n");
#endif
return 0;
}
}
// 2) Check the stack height. The DFG JIT may require a taller stack than the
// baseline JIT, in some cases. If we can't grow the stack, then don't do
// OSR right now. That's the only option we have unless we want basic block
// boundaries to start throwing RangeErrors. Although that would be possible,
// it seems silly: you'd be diverting the program to error handling when it
// would have otherwise just kept running albeit less quickly.
if (!vm->interpreter->stack().grow(&exec->registers()[codeBlock->m_numCalleeRegisters])) {
#if ENABLE(JIT_VERBOSE_OSR)
dataLogF(" OSR failed because stack growth failed.\n");
#endif
return 0;
}
#if ENABLE(JIT_VERBOSE_OSR)
dataLogF(" OSR should succeed.\n");
#endif
// 3) Perform data format conversions.
for (size_t local = 0; local < entry->m_expectedValues.numberOfLocals(); ++local) {
if (entry->m_localsForcedDouble.get(local))
*bitwise_cast<double*>(exec->registers() + local) = exec->registers()[local].jsValue().asNumber();
}
// 4) Fix the call frame.
exec->setCodeBlock(codeBlock);
// 5) Find and return the destination machine code address.
void* result = codeBlock->getJITCode().executableAddressAtOffset(entry->m_machineCodeOffset);
#if ENABLE(JIT_VERBOSE_OSR)
dataLogF(" OSR returning machine code address %p.\n", result);
#endif
return result;
#else // DFG_ENABLE(OSR_ENTRY)
UNUSED_PARAM(exec);
UNUSED_PARAM(codeBlock);
UNUSED_PARAM(bytecodeIndex);
return 0;
#endif
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)
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