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      1 /*
      2  * Copyright (C) 2015 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 #include "pc_relative_fixups_x86.h"
     18 #include "code_generator_x86.h"
     19 #include "intrinsics_x86.h"
     20 
     21 namespace art {
     22 namespace x86 {
     23 
     24 /**
     25  * Finds instructions that need the constant area base as an input.
     26  */
     27 class PCRelativeHandlerVisitor : public HGraphVisitor {
     28  public:
     29   PCRelativeHandlerVisitor(HGraph* graph, CodeGenerator* codegen)
     30       : HGraphVisitor(graph),
     31         codegen_(down_cast<CodeGeneratorX86*>(codegen)),
     32         base_(nullptr) {}
     33 
     34   void MoveBaseIfNeeded() {
     35     if (base_ != nullptr) {
     36       // Bring the base closer to the first use (previously, it was in the
     37       // entry block) and relieve some pressure on the register allocator
     38       // while avoiding recalculation of the base in a loop.
     39       base_->MoveBeforeFirstUserAndOutOfLoops();
     40     }
     41   }
     42 
     43  private:
     44   void VisitAdd(HAdd* add) override {
     45     BinaryFP(add);
     46   }
     47 
     48   void VisitSub(HSub* sub) override {
     49     BinaryFP(sub);
     50   }
     51 
     52   void VisitMul(HMul* mul) override {
     53     BinaryFP(mul);
     54   }
     55 
     56   void VisitDiv(HDiv* div) override {
     57     BinaryFP(div);
     58   }
     59 
     60   void VisitCompare(HCompare* compare) override {
     61     BinaryFP(compare);
     62   }
     63 
     64   void VisitReturn(HReturn* ret) override {
     65     HConstant* value = ret->InputAt(0)->AsConstant();
     66     if ((value != nullptr && DataType::IsFloatingPointType(value->GetType()))) {
     67       ReplaceInput(ret, value, 0, true);
     68     }
     69   }
     70 
     71   void VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) override {
     72     HandleInvoke(invoke);
     73   }
     74 
     75   void VisitInvokeVirtual(HInvokeVirtual* invoke) override {
     76     HandleInvoke(invoke);
     77   }
     78 
     79   void VisitInvokeInterface(HInvokeInterface* invoke) override {
     80     HandleInvoke(invoke);
     81   }
     82 
     83   void VisitLoadClass(HLoadClass* load_class) override {
     84     if (load_class->HasPcRelativeLoadKind()) {
     85       HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(load_class);
     86       load_class->AddSpecialInput(method_address);
     87     }
     88   }
     89 
     90   void VisitLoadString(HLoadString* load_string) override {
     91     if (load_string->HasPcRelativeLoadKind()) {
     92       HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(load_string);
     93       load_string->AddSpecialInput(method_address);
     94     }
     95   }
     96 
     97   void BinaryFP(HBinaryOperation* bin) {
     98     HConstant* rhs = bin->InputAt(1)->AsConstant();
     99     if (rhs != nullptr && DataType::IsFloatingPointType(rhs->GetType())) {
    100       ReplaceInput(bin, rhs, 1, false);
    101     }
    102   }
    103 
    104   void VisitEqual(HEqual* cond) override {
    105     BinaryFP(cond);
    106   }
    107 
    108   void VisitNotEqual(HNotEqual* cond) override {
    109     BinaryFP(cond);
    110   }
    111 
    112   void VisitLessThan(HLessThan* cond) override {
    113     BinaryFP(cond);
    114   }
    115 
    116   void VisitLessThanOrEqual(HLessThanOrEqual* cond) override {
    117     BinaryFP(cond);
    118   }
    119 
    120   void VisitGreaterThan(HGreaterThan* cond) override {
    121     BinaryFP(cond);
    122   }
    123 
    124   void VisitGreaterThanOrEqual(HGreaterThanOrEqual* cond) override {
    125     BinaryFP(cond);
    126   }
    127 
    128   void VisitNeg(HNeg* neg) override {
    129     if (DataType::IsFloatingPointType(neg->GetType())) {
    130       // We need to replace the HNeg with a HX86FPNeg in order to address the constant area.
    131       HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(neg);
    132       HGraph* graph = GetGraph();
    133       HBasicBlock* block = neg->GetBlock();
    134       HX86FPNeg* x86_fp_neg = new (graph->GetAllocator()) HX86FPNeg(
    135           neg->GetType(),
    136           neg->InputAt(0),
    137           method_address,
    138           neg->GetDexPc());
    139       block->ReplaceAndRemoveInstructionWith(neg, x86_fp_neg);
    140     }
    141   }
    142 
    143   void VisitPackedSwitch(HPackedSwitch* switch_insn) override {
    144     if (switch_insn->GetNumEntries() <=
    145         InstructionCodeGeneratorX86::kPackedSwitchJumpTableThreshold) {
    146       return;
    147     }
    148     // We need to replace the HPackedSwitch with a HX86PackedSwitch in order to
    149     // address the constant area.
    150     HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(switch_insn);
    151     HGraph* graph = GetGraph();
    152     HBasicBlock* block = switch_insn->GetBlock();
    153     HX86PackedSwitch* x86_switch = new (graph->GetAllocator()) HX86PackedSwitch(
    154         switch_insn->GetStartValue(),
    155         switch_insn->GetNumEntries(),
    156         switch_insn->InputAt(0),
    157         method_address,
    158         switch_insn->GetDexPc());
    159     block->ReplaceAndRemoveInstructionWith(switch_insn, x86_switch);
    160   }
    161 
    162   HX86ComputeBaseMethodAddress* GetPCRelativeBasePointer(HInstruction* cursor) {
    163     bool has_irreducible_loops = GetGraph()->HasIrreducibleLoops();
    164     if (!has_irreducible_loops) {
    165       // Ensure we only initialize the pointer once.
    166       if (base_ != nullptr) {
    167         return base_;
    168       }
    169     }
    170     // Insert the base at the start of the entry block, move it to a better
    171     // position later in MoveBaseIfNeeded().
    172     HX86ComputeBaseMethodAddress* method_address =
    173         new (GetGraph()->GetAllocator()) HX86ComputeBaseMethodAddress();
    174     if (has_irreducible_loops) {
    175       cursor->GetBlock()->InsertInstructionBefore(method_address, cursor);
    176     } else {
    177       HBasicBlock* entry_block = GetGraph()->GetEntryBlock();
    178       entry_block->InsertInstructionBefore(method_address, entry_block->GetFirstInstruction());
    179       base_ = method_address;
    180     }
    181     return method_address;
    182   }
    183 
    184   void ReplaceInput(HInstruction* insn, HConstant* value, int input_index, bool materialize) {
    185     HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(insn);
    186     HX86LoadFromConstantTable* load_constant =
    187         new (GetGraph()->GetAllocator()) HX86LoadFromConstantTable(method_address, value);
    188     if (!materialize) {
    189       load_constant->MarkEmittedAtUseSite();
    190     }
    191     insn->GetBlock()->InsertInstructionBefore(load_constant, insn);
    192     insn->ReplaceInput(load_constant, input_index);
    193   }
    194 
    195   void HandleInvoke(HInvoke* invoke) {
    196     HInvokeStaticOrDirect* invoke_static_or_direct = invoke->AsInvokeStaticOrDirect();
    197 
    198     // We can't add the method address if we already have a current method pointer.
    199     // This may arise when sharpening doesn't remove the current method pointer from the invoke.
    200     if (invoke_static_or_direct != nullptr && invoke_static_or_direct->HasCurrentMethodInput()) {
    201       // Note: This happens only for recursive calls (including compiling an intrinsic
    202       // by faking a call to itself; we use kRuntimeCall for this case).
    203       DCHECK(!invoke_static_or_direct->HasPcRelativeMethodLoadKind());
    204       return;
    205     }
    206 
    207     // If this is an invoke-static/-direct with PC-relative addressing (within boot image
    208     // or using .bss or .data.bimg.rel.ro), we need the PC-relative address base.
    209     bool base_added = false;
    210     if (invoke_static_or_direct != nullptr &&
    211         invoke_static_or_direct->HasPcRelativeMethodLoadKind() &&
    212         !IsCallFreeIntrinsic<IntrinsicLocationsBuilderX86>(invoke, codegen_)) {
    213       HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(invoke);
    214       // Add the extra parameter.
    215       invoke_static_or_direct->AddSpecialInput(method_address);
    216       base_added = true;
    217     }
    218 
    219     // Ensure that we can load FP arguments from the constant area.
    220     HInputsRef inputs = invoke->GetInputs();
    221     for (size_t i = 0; i < inputs.size(); i++) {
    222       HConstant* input = inputs[i]->AsConstant();
    223       if (input != nullptr && DataType::IsFloatingPointType(input->GetType())) {
    224         ReplaceInput(invoke, input, i, true);
    225       }
    226     }
    227 
    228     switch (invoke->GetIntrinsic()) {
    229       case Intrinsics::kIntegerValueOf:
    230         // This intrinsic can be call free if it loads the address of the boot image object.
    231         // If we're compiling PIC, we need the address base for loading from .data.bimg.rel.ro.
    232         if (!codegen_->GetCompilerOptions().GetCompilePic()) {
    233           break;
    234         }
    235         FALLTHROUGH_INTENDED;
    236       case Intrinsics::kMathRoundFloat:
    237         // This intrinsic needs the constant area.
    238         if (!base_added) {
    239           DCHECK(invoke_static_or_direct != nullptr);
    240           DCHECK(!invoke_static_or_direct->HasCurrentMethodInput());
    241           HX86ComputeBaseMethodAddress* method_address = GetPCRelativeBasePointer(invoke);
    242           invoke_static_or_direct->AddSpecialInput(method_address);
    243         }
    244         break;
    245       default:
    246         break;
    247     }
    248   }
    249 
    250   CodeGeneratorX86* codegen_;
    251 
    252   // The generated HX86ComputeBaseMethodAddress in the entry block needed as an
    253   // input to the HX86LoadFromConstantTable instructions. Only set for
    254   // graphs with reducible loops.
    255   HX86ComputeBaseMethodAddress* base_;
    256 };
    257 
    258 bool PcRelativeFixups::Run() {
    259   PCRelativeHandlerVisitor visitor(graph_, codegen_);
    260   visitor.VisitInsertionOrder();
    261   visitor.MoveBaseIfNeeded();
    262   return true;
    263 }
    264 
    265 }  // namespace x86
    266 }  // namespace art
    267