LLVM API Documentation

X86AsmPrinter.cpp

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00001 //===-- X86AsmPrinter.cpp - Convert X86 LLVM IR to X86 assembly -----------===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file the shared super class printer that converts from our internal
00011 // representation of machine-dependent LLVM code to Intel and AT&T format
00012 // assembly language.
00013 // This printer is the output mechanism used by `llc'.
00014 //
00015 //===----------------------------------------------------------------------===//
00016 
00017 #include "X86AsmPrinter.h"
00018 #include "X86ATTAsmPrinter.h"
00019 #include "X86IntelAsmPrinter.h"
00020 #include "X86Subtarget.h"
00021 #include "llvm/Constants.h"
00022 #include "llvm/Module.h"
00023 #include "llvm/Type.h"
00024 #include "llvm/Assembly/Writer.h"
00025 #include "llvm/Support/Mangler.h"
00026 #include "llvm/Support/CommandLine.h"
00027 using namespace llvm;
00028 
00029 Statistic<> llvm::EmittedInsts("asm-printer",
00030                                "Number of machine instrs printed");
00031 
00032 enum AsmWriterFlavorTy { att, intel };
00033 cl::opt<AsmWriterFlavorTy>
00034 AsmWriterFlavor("x86-asm-syntax",
00035                 cl::desc("Choose style of code to emit from X86 backend:"),
00036                 cl::values(
00037                            clEnumVal(att,   "  Emit AT&T-style assembly"),
00038                            clEnumVal(intel, "  Emit Intel-style assembly"),
00039                            clEnumValEnd),
00040 #ifdef _MSC_VER
00041                 cl::init(intel)
00042 #else
00043                 cl::init(att)
00044 #endif
00045                 );
00046 
00047 // Out of line virtual function to home classes.
00048 void X86DwarfWriter::virtfn() {}
00049 
00050 
00051 /// doInitialization
00052 bool X86SharedAsmPrinter::doInitialization(Module &M) {
00053   PrivateGlobalPrefix = ".L";
00054   DefaultTextSection = ".text";
00055   DefaultDataSection = ".data";
00056   
00057   switch (Subtarget->TargetType) {
00058   case X86Subtarget::isDarwin:
00059     AlignmentIsInBytes = false;
00060     GlobalPrefix = "_";
00061     Data64bitsDirective = 0;       // we can't emit a 64-bit unit
00062     ZeroDirective = "\t.space\t";  // ".space N" emits N zeros.
00063     PrivateGlobalPrefix = "L";     // Marker for constant pool idxs
00064     ConstantPoolSection = "\t.const\n";
00065     JumpTableDataSection = "\t.const\n"; // FIXME: depends on PIC mode
00066     FourByteConstantSection = "\t.literal4\n";
00067     EightByteConstantSection = "\t.literal8\n";
00068     LCOMMDirective = "\t.lcomm\t";
00069     COMMDirectiveTakesAlignment = false;
00070     HasDotTypeDotSizeDirective = false;
00071     StaticCtorsSection = ".mod_init_func";
00072     StaticDtorsSection = ".mod_term_func";
00073     InlineAsmStart = "# InlineAsm Start";
00074     InlineAsmEnd = "# InlineAsm End";
00075     break;
00076   case X86Subtarget::isCygwin:
00077     GlobalPrefix = "_";
00078     COMMDirectiveTakesAlignment = false;
00079     HasDotTypeDotSizeDirective = false;
00080     StaticCtorsSection = "\t.section .ctors,\"aw\"";
00081     StaticDtorsSection = "\t.section .dtors,\"aw\"";
00082     break;
00083   case X86Subtarget::isWindows:
00084     GlobalPrefix = "_";
00085     HasDotTypeDotSizeDirective = false;
00086     break;
00087   default: break;
00088   }
00089   
00090   if (Subtarget->isTargetDarwin()) {
00091     // Emit initial debug information.
00092     DW.BeginModule(&M);
00093   }
00094 
00095   return AsmPrinter::doInitialization(M);
00096 }
00097 
00098 bool X86SharedAsmPrinter::doFinalization(Module &M) {
00099   // Note: this code is not shared by the Intel printer as it is too different
00100   // from how MASM does things.  When making changes here don't forget to look
00101   // at X86IntelAsmPrinter::doFinalization().
00102   const TargetData *TD = TM.getTargetData();
00103 
00104   // Print out module-level global variables here.
00105   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
00106        I != E; ++I) {
00107     if (!I->hasInitializer()) continue;   // External global require no code
00108     
00109     // Check to see if this is a special global used by LLVM, if so, emit it.
00110     if (EmitSpecialLLVMGlobal(I))
00111       continue;
00112     
00113     std::string name = Mang->getValueName(I);
00114     Constant *C = I->getInitializer();
00115     unsigned Size = TD->getTypeSize(C->getType());
00116     unsigned Align = getPreferredAlignmentLog(I);
00117 
00118     if (C->isNullValue() && /* FIXME: Verify correct */
00119         (I->hasInternalLinkage() || I->hasWeakLinkage() ||
00120          I->hasLinkOnceLinkage() ||
00121          (Subtarget->isTargetDarwin() && 
00122           I->hasExternalLinkage() && !I->hasSection()))) {
00123       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
00124       if (I->hasExternalLinkage()) {
00125           O << "\t.globl\t" << name << "\n";
00126           O << "\t.zerofill __DATA__, __common, " << name << ", "
00127             << Size << ", " << Align;
00128       } else {
00129         SwitchToDataSection(DefaultDataSection, I);
00130         if (LCOMMDirective != NULL) {
00131           if (I->hasInternalLinkage()) {
00132             O << LCOMMDirective << name << "," << Size;
00133             if (Subtarget->isTargetDarwin())
00134               O << "," << (AlignmentIsInBytes ? (1 << Align) : Align);
00135           } else
00136             O << COMMDirective  << name << "," << Size;
00137         } else {
00138           if (Subtarget->TargetType != X86Subtarget::isCygwin) {
00139             if (I->hasInternalLinkage())
00140               O << "\t.local\t" << name << "\n";
00141           }
00142           O << COMMDirective  << name << "," << Size;
00143           if (COMMDirectiveTakesAlignment)
00144             O << "," << (AlignmentIsInBytes ? (1 << Align) : Align);
00145         }
00146       }
00147       O << "\t\t" << CommentString << " " << I->getName() << "\n";
00148     } else {
00149       switch (I->getLinkage()) {
00150       case GlobalValue::LinkOnceLinkage:
00151       case GlobalValue::WeakLinkage:
00152         if (Subtarget->isTargetDarwin()) {
00153           O << "\t.globl " << name << "\n"
00154             << "\t.weak_definition " << name << "\n";
00155           SwitchToDataSection(".section __DATA,__const_coal,coalesced", I);
00156         } else if (Subtarget->TargetType == X86Subtarget::isCygwin) {
00157           O << "\t.section\t.llvm.linkonce.d." << name << ",\"aw\"\n"
00158             << "\t.weak " << name << "\n";
00159         } else {
00160           O << "\t.section\t.llvm.linkonce.d." << name << ",\"aw\",@progbits\n"
00161             << "\t.weak " << name << "\n";
00162         }
00163         break;
00164       case GlobalValue::AppendingLinkage:
00165         // FIXME: appending linkage variables should go into a section of
00166         // their name or something.  For now, just emit them as external.
00167       case GlobalValue::ExternalLinkage:
00168         // If external or appending, declare as a global symbol
00169         O << "\t.globl " << name << "\n";
00170         // FALL THROUGH
00171       case GlobalValue::InternalLinkage:
00172         SwitchToDataSection(DefaultDataSection, I);
00173         break;
00174       default:
00175         assert(0 && "Unknown linkage type!");
00176       }
00177 
00178       EmitAlignment(Align, I);
00179       O << name << ":\t\t\t\t" << CommentString << " " << I->getName()
00180         << "\n";
00181       if (HasDotTypeDotSizeDirective)
00182         O << "\t.size " << name << ", " << Size << "\n";
00183 
00184       EmitGlobalConstant(C);
00185       O << '\n';
00186     }
00187   }
00188   
00189   if (Subtarget->isTargetDarwin()) {
00190     SwitchToDataSection("", 0);
00191 
00192     // Output stubs for dynamically-linked functions
00193     unsigned j = 1;
00194     for (std::set<std::string>::iterator i = FnStubs.begin(), e = FnStubs.end();
00195          i != e; ++i, ++j) {
00196       SwitchToDataSection(".section __IMPORT,__jump_table,symbol_stubs,"
00197                           "self_modifying_code+pure_instructions,5", 0);
00198       O << "L" << *i << "$stub:\n";
00199       O << "\t.indirect_symbol " << *i << "\n";
00200       O << "\thlt ; hlt ; hlt ; hlt ; hlt\n";
00201     }
00202 
00203     O << "\n";
00204 
00205     // Output stubs for external and common global variables.
00206     if (GVStubs.begin() != GVStubs.end())
00207       SwitchToDataSection(
00208                     ".section __IMPORT,__pointers,non_lazy_symbol_pointers", 0);
00209     for (std::set<std::string>::iterator i = GVStubs.begin(), e = GVStubs.end();
00210          i != e; ++i) {
00211       O << "L" << *i << "$non_lazy_ptr:\n";
00212       O << "\t.indirect_symbol " << *i << "\n";
00213       O << "\t.long\t0\n";
00214     }
00215 
00216     // Emit initial debug information.
00217     DW.EndModule();
00218 
00219     // Funny Darwin hack: This flag tells the linker that no global symbols
00220     // contain code that falls through to other global symbols (e.g. the obvious
00221     // implementation of multiple entry points).  If this doesn't occur, the
00222     // linker can safely perform dead code stripping.  Since LLVM never
00223     // generates code that does this, it is always safe to set.
00224     O << "\t.subsections_via_symbols\n";
00225   }
00226 
00227   AsmPrinter::doFinalization(M);
00228   return false; // success
00229 }
00230 
00231 /// createX86CodePrinterPass - Returns a pass that prints the X86 assembly code
00232 /// for a MachineFunction to the given output stream, using the given target
00233 /// machine description.
00234 ///
00235 FunctionPass *llvm::createX86CodePrinterPass(std::ostream &o,
00236                                              X86TargetMachine &tm){
00237   switch (AsmWriterFlavor) {
00238   default:
00239     assert(0 && "Unknown asm flavor!");
00240   case intel:
00241     return new X86IntelAsmPrinter(o, tm);
00242   case att:
00243     return new X86ATTAsmPrinter(o, tm);
00244   }
00245 }