llvm/lib/Target/AMDGPU/AMDGPUPrintfRuntimeBinding.cpp - toolchain/llvm-project - Git at Google

 //=== AMDGPUPrintfRuntimeBinding.cpp - OpenCL printf implementation -------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 // \file
 //
 // The pass bind printfs to a kernel arg pointer that will be bound to a buffer
 // later by the runtime.
 //
 // This pass traverses the functions in the module and converts
 // each call to printf to a sequence of operations that
 // store the following into the printf buffer:
 // - format string (passed as a module's metadata unique ID)
 // - bitwise copies of printf arguments
 // The backend passes will need to store metadata in the kernel
 //===----------------------------------------------------------------------===//

 #include "AMDGPU.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/DataExtractor.h"
 #include "llvm/TargetParser/Triple.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"

 using namespace llvm;

 #define DEBUG_TYPE "printfToRuntime"
 enum { DWORD_ALIGN = 4 };

 namespace {
 class AMDGPUPrintfRuntimeBinding final : public ModulePass {

 public:
   static char ID;

   explicit AMDGPUPrintfRuntimeBinding();

 private:
   bool runOnModule(Module &M) override;
 };

 class AMDGPUPrintfRuntimeBindingImpl {
 public:
   AMDGPUPrintfRuntimeBindingImpl() = default;
   bool run(Module &M);

 private:
   void getConversionSpecifiers(SmallVectorImpl<char> &OpConvSpecifiers,
                                StringRef fmt, size_t num_ops) const;

   bool lowerPrintfForGpu(Module &M);

   const DataLayout *TD;
   SmallVector<CallInst *, 32> Printfs;
 };
 } // namespace

 char AMDGPUPrintfRuntimeBinding::ID = 0;

 INITIALIZE_PASS_BEGIN(AMDGPUPrintfRuntimeBinding,
                       "amdgpu-printf-runtime-binding", "AMDGPU Printf lowering",
                       false, false)
 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_END(AMDGPUPrintfRuntimeBinding, "amdgpu-printf-runtime-binding",
                     "AMDGPU Printf lowering", false, false)

 char &llvm::AMDGPUPrintfRuntimeBindingID = AMDGPUPrintfRuntimeBinding::ID;

 namespace llvm {
 ModulePass *createAMDGPUPrintfRuntimeBinding() {
   return new AMDGPUPrintfRuntimeBinding();
 }
 } // namespace llvm

 AMDGPUPrintfRuntimeBinding::AMDGPUPrintfRuntimeBinding() : ModulePass(ID) {
   initializeAMDGPUPrintfRuntimeBindingPass(*PassRegistry::getPassRegistry());
 }

 void AMDGPUPrintfRuntimeBindingImpl::getConversionSpecifiers(
     SmallVectorImpl<char> &OpConvSpecifiers, StringRef Fmt,
     size_t NumOps) const {
   // not all format characters are collected.
   // At this time the format characters of interest
   // are %p and %s, which use to know if we
   // are either storing a literal string or a
   // pointer to the printf buffer.
   static const char ConvSpecifiers[] = "cdieEfgGaosuxXp";
   size_t CurFmtSpecifierIdx = 0;
   size_t PrevFmtSpecifierIdx = 0;

   while ((CurFmtSpecifierIdx = Fmt.find_first_of(
               ConvSpecifiers, CurFmtSpecifierIdx)) != StringRef::npos) {
     bool ArgDump = false;
     StringRef CurFmt = Fmt.substr(PrevFmtSpecifierIdx,
                                   CurFmtSpecifierIdx - PrevFmtSpecifierIdx);
     size_t pTag = CurFmt.find_last_of('%');
     if (pTag != StringRef::npos) {
       ArgDump = true;
       while (pTag && CurFmt[--pTag] == '%') {
         ArgDump = !ArgDump;
       }
     }

     if (ArgDump)
       OpConvSpecifiers.push_back(Fmt[CurFmtSpecifierIdx]);

     PrevFmtSpecifierIdx = ++CurFmtSpecifierIdx;
   }
 }

 static bool shouldPrintAsStr(char Specifier, Type *OpType) {
   return Specifier == 's' && isa<PointerType>(OpType);
 }

 constexpr StringLiteral NonLiteralStr("???");
 static_assert(NonLiteralStr.size() == 3);

 static StringRef getAsConstantStr(Value *V) {
   StringRef S;
   if (!getConstantStringInfo(V, S))
     S = NonLiteralStr;

   return S;
 }

 static void diagnoseInvalidFormatString(const CallBase *CI) {
   DiagnosticInfoUnsupported UnsupportedFormatStr(
       *CI->getParent()->getParent(),
       "printf format string must be a trivially resolved constant string "
       "global variable",
       CI->getDebugLoc());
   CI->getContext().diagnose(UnsupportedFormatStr);
 }

 bool AMDGPUPrintfRuntimeBindingImpl::lowerPrintfForGpu(Module &M) {
   LLVMContext &Ctx = M.getContext();
   IRBuilder<> Builder(Ctx);
   Type *I32Ty = Type::getInt32Ty(Ctx);

   // Instead of creating global variables, the printf format strings are
   // extracted and passed as metadata. This avoids polluting llvm's symbol
   // tables in this module. Metadata is going to be extracted by the backend
   // passes and inserted into the OpenCL binary as appropriate.
   NamedMDNode *metaD = M.getOrInsertNamedMetadata("llvm.printf.fmts");
   unsigned UniqID = metaD->getNumOperands();

   for (auto *CI : Printfs) {
     unsigned NumOps = CI->arg_size();

     SmallString<16> OpConvSpecifiers;
     Value *Op = CI->getArgOperand(0);

     StringRef FormatStr;
     if (!getConstantStringInfo(Op, FormatStr)) {
       Value *Stripped = Op->stripPointerCasts();
       if (!isa<UndefValue>(Stripped) && !isa<ConstantPointerNull>(Stripped))
         diagnoseInvalidFormatString(CI);
       continue;
     }

     // We need this call to ascertain that we are printing a string or a
     // pointer. It takes out the specifiers and fills up the first arg.
     getConversionSpecifiers(OpConvSpecifiers, FormatStr, NumOps - 1);

     // Add metadata for the string
     std::string AStreamHolder;
     raw_string_ostream Sizes(AStreamHolder);
     int Sum = DWORD_ALIGN;
     Sizes << CI->arg_size() - 1;
     Sizes << ':';
     for (unsigned ArgCount = 1;
          ArgCount < CI->arg_size() && ArgCount <= OpConvSpecifiers.size();
          ArgCount++) {
       Value *Arg = CI->getArgOperand(ArgCount);
       Type *ArgType = Arg->getType();
       unsigned ArgSize = TD->getTypeAllocSize(ArgType);
       //
       // ArgSize by design should be a multiple of DWORD_ALIGN,
       // expand the arguments that do not follow this rule.
       //
       if (ArgSize % DWORD_ALIGN != 0) {
         Type *ResType = Type::getInt32Ty(Ctx);
         if (auto *VecType = dyn_cast<VectorType>(ArgType))
           ResType = VectorType::get(ResType, VecType->getElementCount());
         Builder.SetInsertPoint(CI);
         Builder.SetCurrentDebugLocation(CI->getDebugLoc());

         if (ArgType->isFloatingPointTy()) {
           Arg = Builder.CreateBitCast(
               Arg,
               IntegerType::getIntNTy(Ctx, ArgType->getPrimitiveSizeInBits()));
         }

         if (OpConvSpecifiers[ArgCount - 1] == 'x' ||
             OpConvSpecifiers[ArgCount - 1] == 'X' ||
             OpConvSpecifiers[ArgCount - 1] == 'u' ||
             OpConvSpecifiers[ArgCount - 1] == 'o')
           Arg = Builder.CreateZExt(Arg, ResType);
         else
           Arg = Builder.CreateSExt(Arg, ResType);
         ArgType = Arg->getType();
         ArgSize = TD->getTypeAllocSize(ArgType);
         CI->setOperand(ArgCount, Arg);
       }
       if (OpConvSpecifiers[ArgCount - 1] == 'f') {
         ConstantFP *FpCons = dyn_cast<ConstantFP>(Arg);
         if (FpCons)
           ArgSize = 4;
         else {
           FPExtInst *FpExt = dyn_cast<FPExtInst>(Arg);
           if (FpExt && FpExt->getType()->isDoubleTy() &&
               FpExt->getOperand(0)->getType()->isFloatTy())
             ArgSize = 4;
         }
       }
       if (shouldPrintAsStr(OpConvSpecifiers[ArgCount - 1], ArgType))
         ArgSize = alignTo(getAsConstantStr(Arg).size() + 1, 4);

       LLVM_DEBUG(dbgs() << "Printf ArgSize (in buffer) = " << ArgSize
                         << " for type: " << *ArgType << '\n');
       Sizes << ArgSize << ':';
       Sum += ArgSize;
     }
     LLVM_DEBUG(dbgs() << "Printf format string in source = " << FormatStr
                       << '\n');
     for (char C : FormatStr) {
       // Rest of the C escape sequences (e.g. \') are handled correctly
       // by the MDParser
       switch (C) {
       case '\a':
         Sizes << "\\a";
         break;
       case '\b':
         Sizes << "\\b";
         break;
       case '\f':
         Sizes << "\\f";
         break;
       case '\n':
         Sizes << "\\n";
         break;
       case '\r':
         Sizes << "\\r";
         break;
       case '\v':
         Sizes << "\\v";
         break;
       case ':':
         // ':' cannot be scanned by Flex, as it is defined as a delimiter
         // Replace it with it's octal representation \72
         Sizes << "\\72";
         break;
       default:
         Sizes << C;
         break;
       }
     }

     // Insert the printf_alloc call
     Builder.SetInsertPoint(CI);
     Builder.SetCurrentDebugLocation(CI->getDebugLoc());

     AttributeList Attr = AttributeList::get(Ctx, AttributeList::FunctionIndex,
                                             Attribute::NoUnwind);

     Type *SizetTy = Type::getInt32Ty(Ctx);

     Type *Tys_alloc[1] = {SizetTy};
     Type *I8Ty = Type::getInt8Ty(Ctx);
     Type *I8Ptr = PointerType::get(I8Ty, 1);
     FunctionType *FTy_alloc = FunctionType::get(I8Ptr, Tys_alloc, false);
     FunctionCallee PrintfAllocFn =
         M.getOrInsertFunction(StringRef("__printf_alloc"), FTy_alloc, Attr);

     LLVM_DEBUG(dbgs() << "Printf metadata = " << Sizes.str() << '\n');
     std::string fmtstr = itostr(++UniqID) + ":" + Sizes.str();
     MDString *fmtStrArray = MDString::get(Ctx, fmtstr);

     MDNode *myMD = MDNode::get(Ctx, fmtStrArray);
     metaD->addOperand(myMD);
     Value *sumC = ConstantInt::get(SizetTy, Sum, false);
     SmallVector<Value *, 1> alloc_args;
     alloc_args.push_back(sumC);
     CallInst *pcall = CallInst::Create(PrintfAllocFn, alloc_args,
                                        "printf_alloc_fn", CI->getIterator());

     //
     // Insert code to split basicblock with a
     // piece of hammock code.
     // basicblock splits after buffer overflow check
     //
     ConstantPointerNull *zeroIntPtr =
         ConstantPointerNull::get(PointerType::get(I8Ty, 1));
     auto *cmp = cast<ICmpInst>(Builder.CreateICmpNE(pcall, zeroIntPtr, ""));
     if (!CI->use_empty()) {
       Value *result =
           Builder.CreateSExt(Builder.CreateNot(cmp), I32Ty, "printf_res");
       CI->replaceAllUsesWith(result);
     }
     SplitBlock(CI->getParent(), cmp);
     Instruction *Brnch =
         SplitBlockAndInsertIfThen(cmp, cmp->getNextNode(), false);
     BasicBlock::iterator BrnchPoint = Brnch->getIterator();

     Builder.SetInsertPoint(Brnch);

     // store unique printf id in the buffer
     //
     GetElementPtrInst *BufferIdx = GetElementPtrInst::Create(
         I8Ty, pcall, ConstantInt::get(Ctx, APInt(32, 0)), "PrintBuffID",
         BrnchPoint);

     Type *idPointer = PointerType::get(I32Ty, AMDGPUAS::GLOBAL_ADDRESS);
     Value *id_gep_cast =
         new BitCastInst(BufferIdx, idPointer, "PrintBuffIdCast", BrnchPoint);

     new StoreInst(ConstantInt::get(I32Ty, UniqID), id_gep_cast, BrnchPoint);

     // 1st 4 bytes hold the printf_id
     // the following GEP is the buffer pointer
     BufferIdx = GetElementPtrInst::Create(I8Ty, pcall,
                                           ConstantInt::get(Ctx, APInt(32, 4)),
                                           "PrintBuffGep", BrnchPoint);

     Type *Int32Ty = Type::getInt32Ty(Ctx);
     for (unsigned ArgCount = 1;
          ArgCount < CI->arg_size() && ArgCount <= OpConvSpecifiers.size();
          ArgCount++) {
       Value *Arg = CI->getArgOperand(ArgCount);
       Type *ArgType = Arg->getType();
       SmallVector<Value *, 32> WhatToStore;
       if (ArgType->isFPOrFPVectorTy() && !isa<VectorType>(ArgType)) {
         if (OpConvSpecifiers[ArgCount - 1] == 'f') {
           if (auto *FpCons = dyn_cast<ConstantFP>(Arg)) {
             APFloat Val(FpCons->getValueAPF());
             bool Lost = false;
             Val.convert(APFloat::IEEEsingle(), APFloat::rmNearestTiesToEven,
                         &Lost);
             Arg = ConstantFP::get(Ctx, Val);
           } else if (auto *FpExt = dyn_cast<FPExtInst>(Arg)) {
             if (FpExt->getType()->isDoubleTy() &&
                 FpExt->getOperand(0)->getType()->isFloatTy()) {
               Arg = FpExt->getOperand(0);
             }
           }
         }
         WhatToStore.push_back(Arg);
       } else if (isa<PointerType>(ArgType)) {
         if (shouldPrintAsStr(OpConvSpecifiers[ArgCount - 1], ArgType)) {
           StringRef S = getAsConstantStr(Arg);
           if (!S.empty()) {
             const uint64_t ReadSize = 4;

             DataExtractor Extractor(S, /*IsLittleEndian=*/true, 8);
             DataExtractor::Cursor Offset(0);
             while (Offset && Offset.tell() < S.size()) {
               uint64_t ReadNow = std::min(ReadSize, S.size() - Offset.tell());
               uint64_t ReadBytes = 0;
               switch (ReadNow) {
               default: llvm_unreachable("min(4, X) > 4?");
               case 1:
                 ReadBytes = Extractor.getU8(Offset);
                 break;
               case 2:
                 ReadBytes = Extractor.getU16(Offset);
                 break;
               case 3:
                 ReadBytes = Extractor.getU24(Offset);
                 break;
               case 4:
                 ReadBytes = Extractor.getU32(Offset);
                 break;
               }

               cantFail(Offset.takeError(),
                        "failed to read bytes from constant array");

               APInt IntVal(8 * ReadSize, ReadBytes);

               // TODO: Should not bothering aligning up.
               if (ReadNow < ReadSize)
                 IntVal = IntVal.zext(8 * ReadSize);

               Type *IntTy = Type::getIntNTy(Ctx, IntVal.getBitWidth());
               WhatToStore.push_back(ConstantInt::get(IntTy, IntVal));
             }
           } else {
             // Empty string, give a hint to RT it is no NULL
             Value *ANumV = ConstantInt::get(Int32Ty, 0xFFFFFF00, false);
             WhatToStore.push_back(ANumV);
           }
         } else {
           WhatToStore.push_back(Arg);
         }
       } else {
         WhatToStore.push_back(Arg);
       }
       for (unsigned I = 0, E = WhatToStore.size(); I != E; ++I) {
         Value *TheBtCast = WhatToStore[I];
         unsigned ArgSize = TD->getTypeAllocSize(TheBtCast->getType());
         StoreInst *StBuff = new StoreInst(TheBtCast, BufferIdx, BrnchPoint);
         LLVM_DEBUG(dbgs() << "inserting store to printf buffer:\n"
                           << *StBuff << '\n');
         (void)StBuff;
         if (I + 1 == E && ArgCount + 1 == CI->arg_size())
           break;
         BufferIdx = GetElementPtrInst::Create(
             I8Ty, BufferIdx, {ConstantInt::get(I32Ty, ArgSize)},
             "PrintBuffNextPtr", BrnchPoint);
         LLVM_DEBUG(dbgs() << "inserting gep to the printf buffer:\n"
                           << *BufferIdx << '\n');
       }
     }
   }

   // erase the printf calls
   for (auto *CI : Printfs)
     CI->eraseFromParent();

   Printfs.clear();
   return true;
 }

 bool AMDGPUPrintfRuntimeBindingImpl::run(Module &M) {
   Triple TT(M.getTargetTriple());
   if (TT.getArch() == Triple::r600)
     return false;

   auto PrintfFunction = M.getFunction("printf");
   if (!PrintfFunction || !PrintfFunction->isDeclaration() ||
       M.getModuleFlag("openmp"))
     return false;

   for (auto &U : PrintfFunction->uses()) {
     if (auto *CI = dyn_cast<CallInst>(U.getUser())) {
       if (CI->isCallee(&U) && !CI->isNoBuiltin())
         Printfs.push_back(CI);
     }
   }

   if (Printfs.empty())
     return false;

   TD = &M.getDataLayout();

   return lowerPrintfForGpu(M);
 }

 bool AMDGPUPrintfRuntimeBinding::runOnModule(Module &M) {
   return AMDGPUPrintfRuntimeBindingImpl().run(M);
 }

 PreservedAnalyses
 AMDGPUPrintfRuntimeBindingPass::run(Module &M, ModuleAnalysisManager &AM) {
   bool Changed = AMDGPUPrintfRuntimeBindingImpl().run(M);
   return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
 }
	//=== AMDGPUPrintfRuntimeBinding.cpp - OpenCL printf implementation -------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	// \file
	//
	// The pass bind printfs to a kernel arg pointer that will be bound to a buffer
	// later by the runtime.
	//
	// This pass traverses the functions in the module and converts
	// each call to printf to a sequence of operations that
	// store the following into the printf buffer:
	// - format string (passed as a module's metadata unique ID)
	// - bitwise copies of printf arguments
	// The backend passes will need to store metadata in the kernel
	//===----------------------------------------------------------------------===//

	#include "AMDGPU.h"
	#include "llvm/ADT/StringExtras.h"
	#include "llvm/Analysis/ValueTracking.h"
	#include "llvm/IR/DiagnosticInfo.h"
	#include "llvm/IR/Dominators.h"
	#include "llvm/IR/IRBuilder.h"
	#include "llvm/IR/Instructions.h"
	#include "llvm/IR/Module.h"
	#include "llvm/InitializePasses.h"
	#include "llvm/Support/DataExtractor.h"
	#include "llvm/TargetParser/Triple.h"
	#include "llvm/Transforms/Utils/BasicBlockUtils.h"

	using namespace llvm;

	#define DEBUG_TYPE "printfToRuntime"
	enum { DWORD_ALIGN = 4 };

	namespace {
	class AMDGPUPrintfRuntimeBinding final : public ModulePass {

	public:
	static char ID;

	explicit AMDGPUPrintfRuntimeBinding();

	private:
	bool runOnModule(Module &M) override;
	};

	class AMDGPUPrintfRuntimeBindingImpl {
	public:
	AMDGPUPrintfRuntimeBindingImpl() = default;
	bool run(Module &M);

	private:
	void getConversionSpecifiers(SmallVectorImpl<char> &OpConvSpecifiers,
	StringRef fmt, size_t num_ops) const;

	bool lowerPrintfForGpu(Module &M);

	const DataLayout *TD;
	SmallVector<CallInst *, 32> Printfs;
	};
	} // namespace

	char AMDGPUPrintfRuntimeBinding::ID = 0;

	INITIALIZE_PASS_BEGIN(AMDGPUPrintfRuntimeBinding,
	"amdgpu-printf-runtime-binding", "AMDGPU Printf lowering",
	false, false)
	INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
	INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
	INITIALIZE_PASS_END(AMDGPUPrintfRuntimeBinding, "amdgpu-printf-runtime-binding",
	"AMDGPU Printf lowering", false, false)

	char &llvm::AMDGPUPrintfRuntimeBindingID = AMDGPUPrintfRuntimeBinding::ID;

	namespace llvm {
	ModulePass *createAMDGPUPrintfRuntimeBinding() {
	return new AMDGPUPrintfRuntimeBinding();
	}
	} // namespace llvm

	AMDGPUPrintfRuntimeBinding::AMDGPUPrintfRuntimeBinding() : ModulePass(ID) {
	initializeAMDGPUPrintfRuntimeBindingPass(*PassRegistry::getPassRegistry());
	}

	void AMDGPUPrintfRuntimeBindingImpl::getConversionSpecifiers(
	SmallVectorImpl<char> &OpConvSpecifiers, StringRef Fmt,
	size_t NumOps) const {
	// not all format characters are collected.
	// At this time the format characters of interest
	// are %p and %s, which use to know if we
	// are either storing a literal string or a
	// pointer to the printf buffer.
	static const char ConvSpecifiers[] = "cdieEfgGaosuxXp";
	size_t CurFmtSpecifierIdx = 0;
	size_t PrevFmtSpecifierIdx = 0;

	while ((CurFmtSpecifierIdx = Fmt.find_first_of(
	ConvSpecifiers, CurFmtSpecifierIdx)) != StringRef::npos) {
	bool ArgDump = false;
	StringRef CurFmt = Fmt.substr(PrevFmtSpecifierIdx,
	CurFmtSpecifierIdx - PrevFmtSpecifierIdx);
	size_t pTag = CurFmt.find_last_of('%');
	if (pTag != StringRef::npos) {
	ArgDump = true;
	while (pTag && CurFmt[--pTag] == '%') {
	ArgDump = !ArgDump;
	}
	}

	if (ArgDump)
	OpConvSpecifiers.push_back(Fmt[CurFmtSpecifierIdx]);

	PrevFmtSpecifierIdx = ++CurFmtSpecifierIdx;
	}
	}

	static bool shouldPrintAsStr(char Specifier, Type *OpType) {
	return Specifier == 's' && isa<PointerType>(OpType);
	}

	constexpr StringLiteral NonLiteralStr("???");
	static_assert(NonLiteralStr.size() == 3);

	static StringRef getAsConstantStr(Value *V) {
	StringRef S;
	if (!getConstantStringInfo(V, S))
	S = NonLiteralStr;

	return S;
	}

	static void diagnoseInvalidFormatString(const CallBase *CI) {
	DiagnosticInfoUnsupported UnsupportedFormatStr(
	*CI->getParent()->getParent(),
	"printf format string must be a trivially resolved constant string "
	"global variable",
	CI->getDebugLoc());
	CI->getContext().diagnose(UnsupportedFormatStr);
	}

	bool AMDGPUPrintfRuntimeBindingImpl::lowerPrintfForGpu(Module &M) {
	LLVMContext &Ctx = M.getContext();
	IRBuilder<> Builder(Ctx);
	Type *I32Ty = Type::getInt32Ty(Ctx);

	// Instead of creating global variables, the printf format strings are
	// extracted and passed as metadata. This avoids polluting llvm's symbol
	// tables in this module. Metadata is going to be extracted by the backend
	// passes and inserted into the OpenCL binary as appropriate.
	NamedMDNode *metaD = M.getOrInsertNamedMetadata("llvm.printf.fmts");
	unsigned UniqID = metaD->getNumOperands();

	for (auto *CI : Printfs) {
	unsigned NumOps = CI->arg_size();

	SmallString<16> OpConvSpecifiers;
	Value *Op = CI->getArgOperand(0);

	StringRef FormatStr;
	if (!getConstantStringInfo(Op, FormatStr)) {
	Value *Stripped = Op->stripPointerCasts();
	if (!isa<UndefValue>(Stripped) && !isa<ConstantPointerNull>(Stripped))
	diagnoseInvalidFormatString(CI);
	continue;
	}

	// We need this call to ascertain that we are printing a string or a
	// pointer. It takes out the specifiers and fills up the first arg.
	getConversionSpecifiers(OpConvSpecifiers, FormatStr, NumOps - 1);

	// Add metadata for the string
	std::string AStreamHolder;
	raw_string_ostream Sizes(AStreamHolder);
	int Sum = DWORD_ALIGN;
	Sizes << CI->arg_size() - 1;
	Sizes << ':';
	for (unsigned ArgCount = 1;
	ArgCount < CI->arg_size() && ArgCount <= OpConvSpecifiers.size();
	ArgCount++) {
	Value *Arg = CI->getArgOperand(ArgCount);
	Type *ArgType = Arg->getType();
	unsigned ArgSize = TD->getTypeAllocSize(ArgType);
	//
	// ArgSize by design should be a multiple of DWORD_ALIGN,
	// expand the arguments that do not follow this rule.
	//
	if (ArgSize % DWORD_ALIGN != 0) {
	Type *ResType = Type::getInt32Ty(Ctx);
	if (auto *VecType = dyn_cast<VectorType>(ArgType))
	ResType = VectorType::get(ResType, VecType->getElementCount());
	Builder.SetInsertPoint(CI);
	Builder.SetCurrentDebugLocation(CI->getDebugLoc());

	if (ArgType->isFloatingPointTy()) {
	Arg = Builder.CreateBitCast(
	Arg,
	IntegerType::getIntNTy(Ctx, ArgType->getPrimitiveSizeInBits()));
	}

	if (OpConvSpecifiers[ArgCount - 1] == 'x' \|\|
	OpConvSpecifiers[ArgCount - 1] == 'X' \|\|
	OpConvSpecifiers[ArgCount - 1] == 'u' \|\|
	OpConvSpecifiers[ArgCount - 1] == 'o')
	Arg = Builder.CreateZExt(Arg, ResType);
	else
	Arg = Builder.CreateSExt(Arg, ResType);
	ArgType = Arg->getType();
	ArgSize = TD->getTypeAllocSize(ArgType);
	CI->setOperand(ArgCount, Arg);
	}
	if (OpConvSpecifiers[ArgCount - 1] == 'f') {
	ConstantFP *FpCons = dyn_cast<ConstantFP>(Arg);
	if (FpCons)
	ArgSize = 4;
	else {
	FPExtInst *FpExt = dyn_cast<FPExtInst>(Arg);
	if (FpExt && FpExt->getType()->isDoubleTy() &&
	FpExt->getOperand(0)->getType()->isFloatTy())
	ArgSize = 4;
	}
	}
	if (shouldPrintAsStr(OpConvSpecifiers[ArgCount - 1], ArgType))
	ArgSize = alignTo(getAsConstantStr(Arg).size() + 1, 4);

	LLVM_DEBUG(dbgs() << "Printf ArgSize (in buffer) = " << ArgSize
	<< " for type: " << *ArgType << '\n');
	Sizes << ArgSize << ':';
	Sum += ArgSize;
	}
	LLVM_DEBUG(dbgs() << "Printf format string in source = " << FormatStr
	<< '\n');
	for (char C : FormatStr) {
	// Rest of the C escape sequences (e.g. \') are handled correctly
	// by the MDParser
	switch (C) {
	case '\a':
	Sizes << "\\a";
	break;
	case '\b':
	Sizes << "\\b";
	break;
	case '\f':
	Sizes << "\\f";
	break;
	case '\n':
	Sizes << "\\n";
	break;
	case '\r':
	Sizes << "\\r";
	break;
	case '\v':
	Sizes << "\\v";
	break;
	case ':':
	// ':' cannot be scanned by Flex, as it is defined as a delimiter
	// Replace it with it's octal representation \72
	Sizes << "\\72";
	break;
	default:
	Sizes << C;
	break;
	}
	}

	// Insert the printf_alloc call
	Builder.SetInsertPoint(CI);
	Builder.SetCurrentDebugLocation(CI->getDebugLoc());

	AttributeList Attr = AttributeList::get(Ctx, AttributeList::FunctionIndex,
	Attribute::NoUnwind);

	Type *SizetTy = Type::getInt32Ty(Ctx);

	Type *Tys_alloc[1] = {SizetTy};
	Type *I8Ty = Type::getInt8Ty(Ctx);
	Type *I8Ptr = PointerType::get(I8Ty, 1);
	FunctionType *FTy_alloc = FunctionType::get(I8Ptr, Tys_alloc, false);
	FunctionCallee PrintfAllocFn =
	M.getOrInsertFunction(StringRef("__printf_alloc"), FTy_alloc, Attr);

	LLVM_DEBUG(dbgs() << "Printf metadata = " << Sizes.str() << '\n');
	std::string fmtstr = itostr(++UniqID) + ":" + Sizes.str();
	MDString *fmtStrArray = MDString::get(Ctx, fmtstr);

	MDNode *myMD = MDNode::get(Ctx, fmtStrArray);
	metaD->addOperand(myMD);
	Value *sumC = ConstantInt::get(SizetTy, Sum, false);
	SmallVector<Value *, 1> alloc_args;
	alloc_args.push_back(sumC);
	CallInst *pcall = CallInst::Create(PrintfAllocFn, alloc_args,
	"printf_alloc_fn", CI->getIterator());

	//
	// Insert code to split basicblock with a
	// piece of hammock code.
	// basicblock splits after buffer overflow check
	//
	ConstantPointerNull *zeroIntPtr =
	ConstantPointerNull::get(PointerType::get(I8Ty, 1));
	auto *cmp = cast<ICmpInst>(Builder.CreateICmpNE(pcall, zeroIntPtr, ""));
	if (!CI->use_empty()) {
	Value *result =
	Builder.CreateSExt(Builder.CreateNot(cmp), I32Ty, "printf_res");
	CI->replaceAllUsesWith(result);
	}
	SplitBlock(CI->getParent(), cmp);
	Instruction *Brnch =
	SplitBlockAndInsertIfThen(cmp, cmp->getNextNode(), false);
	BasicBlock::iterator BrnchPoint = Brnch->getIterator();

	Builder.SetInsertPoint(Brnch);

	// store unique printf id in the buffer
	//
	GetElementPtrInst *BufferIdx = GetElementPtrInst::Create(
	I8Ty, pcall, ConstantInt::get(Ctx, APInt(32, 0)), "PrintBuffID",
	BrnchPoint);

	Type *idPointer = PointerType::get(I32Ty, AMDGPUAS::GLOBAL_ADDRESS);
	Value *id_gep_cast =
	new BitCastInst(BufferIdx, idPointer, "PrintBuffIdCast", BrnchPoint);

	new StoreInst(ConstantInt::get(I32Ty, UniqID), id_gep_cast, BrnchPoint);

	// 1st 4 bytes hold the printf_id
	// the following GEP is the buffer pointer
	BufferIdx = GetElementPtrInst::Create(I8Ty, pcall,
	ConstantInt::get(Ctx, APInt(32, 4)),
	"PrintBuffGep", BrnchPoint);

	Type *Int32Ty = Type::getInt32Ty(Ctx);
	for (unsigned ArgCount = 1;
	ArgCount < CI->arg_size() && ArgCount <= OpConvSpecifiers.size();
	ArgCount++) {
	Value *Arg = CI->getArgOperand(ArgCount);
	Type *ArgType = Arg->getType();
	SmallVector<Value *, 32> WhatToStore;
	if (ArgType->isFPOrFPVectorTy() && !isa<VectorType>(ArgType)) {
	if (OpConvSpecifiers[ArgCount - 1] == 'f') {
	if (auto *FpCons = dyn_cast<ConstantFP>(Arg)) {
	APFloat Val(FpCons->getValueAPF());
	bool Lost = false;
	Val.convert(APFloat::IEEEsingle(), APFloat::rmNearestTiesToEven,
	&Lost);
	Arg = ConstantFP::get(Ctx, Val);
	} else if (auto *FpExt = dyn_cast<FPExtInst>(Arg)) {
	if (FpExt->getType()->isDoubleTy() &&
	FpExt->getOperand(0)->getType()->isFloatTy()) {
	Arg = FpExt->getOperand(0);
	}
	}
	}
	WhatToStore.push_back(Arg);
	} else if (isa<PointerType>(ArgType)) {
	if (shouldPrintAsStr(OpConvSpecifiers[ArgCount - 1], ArgType)) {
	StringRef S = getAsConstantStr(Arg);
	if (!S.empty()) {
	const uint64_t ReadSize = 4;

	DataExtractor Extractor(S, /IsLittleEndian=/true, 8);
	DataExtractor::Cursor Offset(0);
	while (Offset && Offset.tell() < S.size()) {
	uint64_t ReadNow = std::min(ReadSize, S.size() - Offset.tell());
	uint64_t ReadBytes = 0;
	switch (ReadNow) {
	default: llvm_unreachable("min(4, X) > 4?");
	case 1:
	ReadBytes = Extractor.getU8(Offset);
	break;
	case 2:
	ReadBytes = Extractor.getU16(Offset);
	break;
	case 3:
	ReadBytes = Extractor.getU24(Offset);
	break;
	case 4:
	ReadBytes = Extractor.getU32(Offset);
	break;
	}

	cantFail(Offset.takeError(),
	"failed to read bytes from constant array");

	APInt IntVal(8 * ReadSize, ReadBytes);

	// TODO: Should not bothering aligning up.
	if (ReadNow < ReadSize)
	IntVal = IntVal.zext(8 * ReadSize);

	Type *IntTy = Type::getIntNTy(Ctx, IntVal.getBitWidth());
	WhatToStore.push_back(ConstantInt::get(IntTy, IntVal));
	}
	} else {
	// Empty string, give a hint to RT it is no NULL
	Value *ANumV = ConstantInt::get(Int32Ty, 0xFFFFFF00, false);
	WhatToStore.push_back(ANumV);
	}
	} else {
	WhatToStore.push_back(Arg);
	}
	} else {
	WhatToStore.push_back(Arg);
	}
	for (unsigned I = 0, E = WhatToStore.size(); I != E; ++I) {
	Value *TheBtCast = WhatToStore[I];
	unsigned ArgSize = TD->getTypeAllocSize(TheBtCast->getType());
	StoreInst *StBuff = new StoreInst(TheBtCast, BufferIdx, BrnchPoint);
	LLVM_DEBUG(dbgs() << "inserting store to printf buffer:\n"
	<< *StBuff << '\n');
	(void)StBuff;
	if (I + 1 == E && ArgCount + 1 == CI->arg_size())
	break;
	BufferIdx = GetElementPtrInst::Create(
	I8Ty, BufferIdx, {ConstantInt::get(I32Ty, ArgSize)},
	"PrintBuffNextPtr", BrnchPoint);
	LLVM_DEBUG(dbgs() << "inserting gep to the printf buffer:\n"
	<< *BufferIdx << '\n');
	}
	}
	}

	// erase the printf calls
	for (auto *CI : Printfs)
	CI->eraseFromParent();

	Printfs.clear();
	return true;
	}

	bool AMDGPUPrintfRuntimeBindingImpl::run(Module &M) {
	Triple TT(M.getTargetTriple());
	if (TT.getArch() == Triple::r600)
	return false;

	auto PrintfFunction = M.getFunction("printf");
	if (!PrintfFunction \|\| !PrintfFunction->isDeclaration() \|\|
	M.getModuleFlag("openmp"))
	return false;

	for (auto &U : PrintfFunction->uses()) {
	if (auto *CI = dyn_cast<CallInst>(U.getUser())) {
	if (CI->isCallee(&U) && !CI->isNoBuiltin())
	Printfs.push_back(CI);
	}
	}

	if (Printfs.empty())
	return false;

	TD = &M.getDataLayout();

	return lowerPrintfForGpu(M);
	}

	bool AMDGPUPrintfRuntimeBinding::runOnModule(Module &M) {
	return AMDGPUPrintfRuntimeBindingImpl().run(M);
	}

	PreservedAnalyses
	AMDGPUPrintfRuntimeBindingPass::run(Module &M, ModuleAnalysisManager &AM) {
	bool Changed = AMDGPUPrintfRuntimeBindingImpl().run(M);
	return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
	}