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                 cl::init(att));
00041 
00042 /// doInitialization
00043 bool X86SharedAsmPrinter::doInitialization(Module &M) {
00044   const X86Subtarget *Subtarget = &TM.getSubtarget<X86Subtarget>();
00045   
00046   forDarwin = false;
00047   PrivateGlobalPrefix = ".L";
00048   
00049   switch (Subtarget->TargetType) {
00050   case X86Subtarget::isDarwin:
00051     AlignmentIsInBytes = false;
00052     GlobalPrefix = "_";
00053     Data64bitsDirective = 0;       // we can't emit a 64-bit unit
00054     ZeroDirective = "\t.space\t";  // ".space N" emits N zeros.
00055     PrivateGlobalPrefix = "L";     // Marker for constant pool idxs
00056     ConstantPoolSection = "\t.const\n";
00057     LCOMMDirective = "\t.lcomm\t";
00058     COMMDirectiveTakesAlignment = false;
00059     HasDotTypeDotSizeDirective = false;
00060     forDarwin = true;
00061     StaticCtorsSection = ".mod_init_func";
00062     StaticDtorsSection = ".mod_term_func";
00063     InlineAsmStart = InlineAsmEnd = "";  // Don't use #APP/#NO_APP
00064     break;
00065   case X86Subtarget::isCygwin:
00066     GlobalPrefix = "_";
00067     COMMDirectiveTakesAlignment = false;
00068     HasDotTypeDotSizeDirective = false;
00069     break;
00070   case X86Subtarget::isWindows:
00071     GlobalPrefix = "_";
00072     HasDotTypeDotSizeDirective = false;
00073     break;
00074   default: break;
00075   }
00076   
00077   if (forDarwin) {
00078     // Emit initial debug information.
00079     DW.BeginModule(&M);
00080   }
00081 
00082   return AsmPrinter::doInitialization(M);
00083 }
00084 
00085 bool X86SharedAsmPrinter::doFinalization(Module &M) {
00086   const TargetData &TD = TM.getTargetData();
00087 
00088   // Print out module-level global variables here.
00089   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
00090        I != E; ++I) {
00091     if (!I->hasInitializer()) continue;   // External global require no code
00092     
00093     // Check to see if this is a special global used by LLVM, if so, emit it.
00094     if (EmitSpecialLLVMGlobal(I))
00095       continue;
00096     
00097     std::string name = Mang->getValueName(I);
00098     Constant *C = I->getInitializer();
00099     unsigned Size = TD.getTypeSize(C->getType());
00100     unsigned Align = getPreferredAlignmentLog(I);
00101 
00102     if (C->isNullValue() && /* FIXME: Verify correct */
00103         (I->hasInternalLinkage() || I->hasWeakLinkage() ||
00104          I->hasLinkOnceLinkage() ||
00105          (forDarwin && I->hasExternalLinkage() && !I->hasSection()))) {
00106       if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
00107       if (I->hasExternalLinkage()) {
00108           O << "\t.globl\t" << name << "\n";
00109           O << "\t.zerofill __DATA__, __common, " << name << ", "
00110             << Size << ", " << Align;
00111       } else {
00112         SwitchSection(".data", I);
00113         if (LCOMMDirective != NULL) {
00114           if (I->hasInternalLinkage()) {
00115             O << LCOMMDirective << name << "," << Size;
00116             if (forDarwin)
00117               O << "," << (AlignmentIsInBytes ? (1 << Align) : Align);
00118           } else
00119             O << COMMDirective  << name << "," << Size;
00120         } else {
00121           if (I->hasInternalLinkage())
00122             O << "\t.local\t" << name << "\n";
00123           O << COMMDirective  << name << "," << Size;
00124           if (COMMDirectiveTakesAlignment)
00125             O << "," << (AlignmentIsInBytes ? (1 << Align) : Align);
00126         }
00127       }
00128       O << "\t\t" << CommentString << " " << I->getName() << "\n";
00129     } else {
00130       switch (I->getLinkage()) {
00131       case GlobalValue::LinkOnceLinkage:
00132       case GlobalValue::WeakLinkage:
00133         if (forDarwin) {
00134           O << "\t.globl " << name << "\n"
00135             << "\t.weak_definition " << name << "\n";
00136           SwitchSection(".section __DATA,__datacoal_nt,coalesced", I);
00137         } else {
00138           O << "\t.section\t.llvm.linkonce.d." << name << ",\"aw\",@progbits\n";
00139           O << "\t.weak " << name << "\n";
00140         }
00141         break;
00142       case GlobalValue::AppendingLinkage:
00143         // FIXME: appending linkage variables should go into a section of
00144         // their name or something.  For now, just emit them as external.
00145       case GlobalValue::ExternalLinkage:
00146         // If external or appending, declare as a global symbol
00147         O << "\t.globl " << name << "\n";
00148         // FALL THROUGH
00149       case GlobalValue::InternalLinkage:
00150         SwitchSection(".data", I);
00151         break;
00152       default:
00153         assert(0 && "Unknown linkage type!");
00154       }
00155 
00156       EmitAlignment(Align, I);
00157       O << name << ":\t\t\t\t" << CommentString << " " << I->getName()
00158         << "\n";
00159       if (HasDotTypeDotSizeDirective)
00160         O << "\t.size " << name << ", " << Size << "\n";
00161 
00162       EmitGlobalConstant(C);
00163       O << '\n';
00164     }
00165   }
00166   
00167   if (forDarwin) {
00168     SwitchSection("", 0);
00169 
00170     // Output stubs for dynamically-linked functions
00171     unsigned j = 1;
00172     for (std::set<std::string>::iterator i = FnStubs.begin(), e = FnStubs.end();
00173          i != e; ++i, ++j) {
00174       SwitchSection(".section __IMPORT,__jump_table,symbol_stubs,"
00175                     "self_modifying_code+pure_instructions,5", 0);
00176       O << "L" << *i << "$stub:\n";
00177       O << "\t.indirect_symbol " << *i << "\n";
00178       O << "\thlt ; hlt ; hlt ; hlt ; hlt\n";
00179     }
00180 
00181     O << "\n";
00182 
00183     // Output stubs for external and common global variables.
00184     if (GVStubs.begin() != GVStubs.end())
00185       SwitchSection(".section __IMPORT,__pointers,non_lazy_symbol_pointers", 0);
00186     for (std::set<std::string>::iterator i = GVStubs.begin(), e = GVStubs.end();
00187          i != e; ++i) {
00188       O << "L" << *i << "$non_lazy_ptr:\n";
00189       O << "\t.indirect_symbol " << *i << "\n";
00190       O << "\t.long\t0\n";
00191     }
00192 
00193     // Emit initial debug information.
00194     DW.EndModule();
00195 
00196     // Funny Darwin hack: This flag tells the linker that no global symbols
00197     // contain code that falls through to other global symbols (e.g. the obvious
00198     // implementation of multiple entry points).  If this doesn't occur, the
00199     // linker can safely perform dead code stripping.  Since LLVM never
00200     // generates code that does this, it is always safe to set.
00201     O << "\t.subsections_via_symbols\n";
00202   }
00203 
00204   AsmPrinter::doFinalization(M);
00205   return false; // success
00206 }
00207 
00208 /// createX86CodePrinterPass - Returns a pass that prints the X86 assembly code
00209 /// for a MachineFunction to the given output stream, using the given target
00210 /// machine description.
00211 ///
00212 FunctionPass *llvm::createX86CodePrinterPass(std::ostream &o,
00213                                              X86TargetMachine &tm){
00214   switch (AsmWriterFlavor) {
00215   default:
00216     assert(0 && "Unknown asm flavor!");
00217   case intel:
00218     return new X86IntelAsmPrinter(o, tm);
00219   case att:
00220     return new X86ATTAsmPrinter(o, tm);
00221   }
00222 }