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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_VMAP_TABLE_H_
#define ART_RUNTIME_VMAP_TABLE_H_
#include "base/logging.h"
#include "leb128.h"
#include "stack.h"
namespace art {
class VmapTable {
public:
// For efficient encoding of special values, entries are adjusted by 2.
static constexpr uint16_t kEntryAdjustment = 2u;
static constexpr uint16_t kAdjustedFpMarker = static_cast<uint16_t>(0xffffu + kEntryAdjustment);
explicit VmapTable(const uint8_t* table) : table_(table) {
}
// Look up nth entry, not called from performance critical code.
uint16_t operator[](size_t n) const {
const uint8_t* table = table_;
size_t size = DecodeUnsignedLeb128(&table);
CHECK_LT(n, size);
uint16_t adjusted_entry = DecodeUnsignedLeb128(&table);
for (size_t i = 0; i < n; ++i) {
adjusted_entry = DecodeUnsignedLeb128(&table);
}
return adjusted_entry - kEntryAdjustment;
}
size_t Size() const {
const uint8_t* table = table_;
return DecodeUnsignedLeb128(&table);
}
// Is the dex register 'vreg' in the context or on the stack? Should not be called when the
// 'kind' is unknown or constant.
bool IsInContext(size_t vreg, VRegKind kind, uint32_t* vmap_offset) const {
DCHECK(kind == kReferenceVReg || kind == kIntVReg || kind == kFloatVReg ||
kind == kLongLoVReg || kind == kLongHiVReg || kind == kDoubleLoVReg ||
kind == kDoubleHiVReg || kind == kImpreciseConstant);
*vmap_offset = 0xEBAD0FF5;
// TODO: take advantage of the registers being ordered
// TODO: we treat kImpreciseConstant as an integer below, need to ensure that such values
// are never promoted to floating point registers.
bool is_float = (kind == kFloatVReg) || (kind == kDoubleLoVReg) || (kind == kDoubleHiVReg);
bool in_floats = false;
const uint8_t* table = table_;
uint16_t adjusted_vreg = vreg + kEntryAdjustment;
size_t end = DecodeUnsignedLeb128(&table);
for (size_t i = 0; i < end; ++i) {
// Stop if we find what we are are looking for.
uint16_t adjusted_entry = DecodeUnsignedLeb128(&table);
if ((adjusted_entry == adjusted_vreg) && (in_floats == is_float)) {
*vmap_offset = i;
return true;
}
// 0xffff is the marker for LR (return PC on x86), following it are spilled float registers.
if (adjusted_entry == kAdjustedFpMarker) {
in_floats = true;
}
}
return false;
}
// Compute the register number that corresponds to the entry in the vmap (vmap_offset, computed
// by IsInContext above). If the kind is floating point then the result will be a floating point
// register number, otherwise it will be an integer register number.
uint32_t ComputeRegister(uint32_t spill_mask, uint32_t vmap_offset, VRegKind kind) const {
// Compute the register we need to load from the context.
DCHECK(kind == kReferenceVReg || kind == kIntVReg || kind == kFloatVReg ||
kind == kLongLoVReg || kind == kLongHiVReg || kind == kDoubleLoVReg ||
kind == kDoubleHiVReg || kind == kImpreciseConstant);
// TODO: we treat kImpreciseConstant as an integer below, need to ensure that such values
// are never promoted to floating point registers.
bool is_float = (kind == kFloatVReg) || (kind == kDoubleLoVReg) || (kind == kDoubleHiVReg);
uint32_t matches = 0;
if (UNLIKELY(is_float)) {
const uint8_t* table = table_;
DecodeUnsignedLeb128(&table); // Skip size.
while (DecodeUnsignedLeb128(&table) != kAdjustedFpMarker) {
matches++;
}
matches++;
}
CHECK_LT(vmap_offset - matches, static_cast<uint32_t>(__builtin_popcount(spill_mask)));
uint32_t spill_shifts = 0;
while (matches != (vmap_offset + 1)) {
DCHECK_NE(spill_mask, 0u);
matches += spill_mask & 1; // Add 1 if the low bit is set
spill_mask >>= 1;
spill_shifts++;
}
spill_shifts--; // wind back one as we want the last match
return spill_shifts;
}
private:
const uint8_t* const table_;
};
} // namespace art
#endif // ART_RUNTIME_VMAP_TABLE_H_
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