1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_VMAP_TABLE_H_ 18 #define ART_RUNTIME_VMAP_TABLE_H_ 19 20 #include "base/logging.h" 21 #include "leb128.h" 22 #include "stack.h" 23 24 namespace art { 25 26 class VmapTable { 27 public: 28 // For efficient encoding of special values, entries are adjusted by 2. 29 static constexpr uint16_t kEntryAdjustment = 2u; 30 static constexpr uint16_t kAdjustedFpMarker = static_cast<uint16_t>(0xffffu + kEntryAdjustment); 31 VmapTable(const uint8_t * table)32 explicit VmapTable(const uint8_t* table) : table_(table) { 33 } 34 35 // Look up nth entry, not called from performance critical code. 36 uint16_t operator[](size_t n) const { 37 const uint8_t* table = table_; 38 size_t size = DecodeUnsignedLeb128(&table); 39 CHECK_LT(n, size); 40 uint16_t adjusted_entry = DecodeUnsignedLeb128(&table); 41 for (size_t i = 0; i < n; ++i) { 42 adjusted_entry = DecodeUnsignedLeb128(&table); 43 } 44 return adjusted_entry - kEntryAdjustment; 45 } 46 Size()47 size_t Size() const { 48 const uint8_t* table = table_; 49 return DecodeUnsignedLeb128(&table); 50 } 51 52 // Is the dex register 'vreg' in the context or on the stack? Should not be called when the 53 // 'kind' is unknown or constant. IsInContext(size_t vreg,VRegKind kind,uint32_t * vmap_offset)54 bool IsInContext(size_t vreg, VRegKind kind, uint32_t* vmap_offset) const { 55 DCHECK(kind == kReferenceVReg || kind == kIntVReg || kind == kFloatVReg || 56 kind == kLongLoVReg || kind == kLongHiVReg || kind == kDoubleLoVReg || 57 kind == kDoubleHiVReg || kind == kImpreciseConstant); 58 *vmap_offset = 0xEBAD0FF5; 59 // TODO: take advantage of the registers being ordered 60 // TODO: we treat kImpreciseConstant as an integer below, need to ensure that such values 61 // are never promoted to floating point registers. 62 bool is_float = (kind == kFloatVReg) || (kind == kDoubleLoVReg) || (kind == kDoubleHiVReg); 63 bool in_floats = false; 64 const uint8_t* table = table_; 65 uint16_t adjusted_vreg = vreg + kEntryAdjustment; 66 size_t end = DecodeUnsignedLeb128(&table); 67 bool high_reg = (kind == kLongHiVReg) || (kind == kDoubleHiVReg); 68 bool target64 = (kRuntimeISA == kArm64) || (kRuntimeISA == kX86_64); 69 if (target64 && high_reg) { 70 // Wide promoted registers are associated with the sreg of the low portion. 71 adjusted_vreg--; 72 } 73 for (size_t i = 0; i < end; ++i) { 74 // Stop if we find what we are are looking for. 75 uint16_t adjusted_entry = DecodeUnsignedLeb128(&table); 76 if ((adjusted_entry == adjusted_vreg) && (in_floats == is_float)) { 77 *vmap_offset = i; 78 return true; 79 } 80 // 0xffff is the marker for LR (return PC on x86), following it are spilled float registers. 81 if (adjusted_entry == kAdjustedFpMarker) { 82 in_floats = true; 83 } 84 } 85 return false; 86 } 87 88 // Compute the register number that corresponds to the entry in the vmap (vmap_offset, computed 89 // by IsInContext above). If the kind is floating point then the result will be a floating point 90 // register number, otherwise it will be an integer register number. ComputeRegister(uint32_t spill_mask,uint32_t vmap_offset,VRegKind kind)91 uint32_t ComputeRegister(uint32_t spill_mask, uint32_t vmap_offset, VRegKind kind) const { 92 // Compute the register we need to load from the context. 93 DCHECK(kind == kReferenceVReg || kind == kIntVReg || kind == kFloatVReg || 94 kind == kLongLoVReg || kind == kLongHiVReg || kind == kDoubleLoVReg || 95 kind == kDoubleHiVReg || kind == kImpreciseConstant); 96 // TODO: we treat kImpreciseConstant as an integer below, need to ensure that such values 97 // are never promoted to floating point registers. 98 bool is_float = (kind == kFloatVReg) || (kind == kDoubleLoVReg) || (kind == kDoubleHiVReg); 99 uint32_t matches = 0; 100 if (UNLIKELY(is_float)) { 101 const uint8_t* table = table_; 102 DecodeUnsignedLeb128(&table); // Skip size. 103 while (DecodeUnsignedLeb128(&table) != kAdjustedFpMarker) { 104 matches++; 105 } 106 matches++; 107 } 108 CHECK_LT(vmap_offset - matches, static_cast<uint32_t>(POPCOUNT(spill_mask))); 109 uint32_t spill_shifts = 0; 110 while (matches != (vmap_offset + 1)) { 111 DCHECK_NE(spill_mask, 0u); 112 matches += spill_mask & 1; // Add 1 if the low bit is set 113 spill_mask >>= 1; 114 spill_shifts++; 115 } 116 spill_shifts--; // wind back one as we want the last match 117 return spill_shifts; 118 } 119 120 private: 121 const uint8_t* const table_; 122 }; 123 124 } // namespace art 125 126 #endif // ART_RUNTIME_VMAP_TABLE_H_ 127