1249259Sdim//===- NVVMReflect.cpp - NVVM Emulate conditional compilation -------------===// 2249259Sdim// 3353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4353358Sdim// See https://llvm.org/LICENSE.txt for license information. 5353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6249259Sdim// 7249259Sdim//===----------------------------------------------------------------------===// 8249259Sdim// 9309124Sdim// This pass replaces occurrences of __nvvm_reflect("foo") and llvm.nvvm.reflect 10309124Sdim// with an integer. 11249259Sdim// 12321369Sdim// We choose the value we use by looking at metadata in the module itself. Note 13321369Sdim// that we intentionally only have one way to choose these values, because other 14321369Sdim// parts of LLVM (particularly, InstCombineCall) rely on being able to predict 15321369Sdim// the values chosen by this pass. 16309124Sdim// 17309124Sdim// If we see an unknown string, we replace its call with 0. 18309124Sdim// 19249259Sdim//===----------------------------------------------------------------------===// 20249259Sdim 21251662Sdim#include "NVPTX.h" 22249259Sdim#include "llvm/ADT/SmallVector.h" 23249259Sdim#include "llvm/ADT/StringMap.h" 24276479Sdim#include "llvm/IR/Constants.h" 25276479Sdim#include "llvm/IR/DerivedTypes.h" 26249259Sdim#include "llvm/IR/Function.h" 27309124Sdim#include "llvm/IR/InstIterator.h" 28276479Sdim#include "llvm/IR/Instructions.h" 29276479Sdim#include "llvm/IR/Intrinsics.h" 30360784Sdim#include "llvm/IR/IntrinsicsNVPTX.h" 31249259Sdim#include "llvm/IR/Module.h" 32249259Sdim#include "llvm/IR/Type.h" 33276479Sdim#include "llvm/Pass.h" 34249259Sdim#include "llvm/Support/CommandLine.h" 35249259Sdim#include "llvm/Support/Debug.h" 36249259Sdim#include "llvm/Support/raw_os_ostream.h" 37288943Sdim#include "llvm/Support/raw_ostream.h" 38249259Sdim#include "llvm/Transforms/Scalar.h" 39249259Sdim#include <sstream> 40249259Sdim#include <string> 41249259Sdim#define NVVM_REFLECT_FUNCTION "__nvvm_reflect" 42249259Sdim 43249259Sdimusing namespace llvm; 44249259Sdim 45276479Sdim#define DEBUG_TYPE "nvptx-reflect" 46276479Sdim 47249259Sdimnamespace llvm { void initializeNVVMReflectPass(PassRegistry &); } 48249259Sdim 49249259Sdimnamespace { 50309124Sdimclass NVVMReflect : public FunctionPass { 51249259Sdimpublic: 52249259Sdim static char ID; 53344779Sdim unsigned int SmVersion; 54344779Sdim NVVMReflect() : NVVMReflect(0) {} 55344779Sdim explicit NVVMReflect(unsigned int Sm) : FunctionPass(ID), SmVersion(Sm) { 56251662Sdim initializeNVVMReflectPass(*PassRegistry::getPassRegistry()); 57251662Sdim } 58251662Sdim 59309124Sdim bool runOnFunction(Function &) override; 60249259Sdim}; 61249259Sdim} 62249259Sdim 63344779SdimFunctionPass *llvm::createNVVMReflectPass(unsigned int SmVersion) { 64344779Sdim return new NVVMReflect(SmVersion); 65344779Sdim} 66251662Sdim 67249259Sdimstatic cl::opt<bool> 68261991SdimNVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden, 69249259Sdim cl::desc("NVVM reflection, enabled by default")); 70249259Sdim 71249259Sdimchar NVVMReflect::ID = 0; 72249259SdimINITIALIZE_PASS(NVVMReflect, "nvvm-reflect", 73276479Sdim "Replace occurrences of __nvvm_reflect() calls with 0/1", false, 74249259Sdim false) 75249259Sdim 76309124Sdimbool NVVMReflect::runOnFunction(Function &F) { 77309124Sdim if (!NVVMReflectEnabled) 78309124Sdim return false; 79249259Sdim 80309124Sdim if (F.getName() == NVVM_REFLECT_FUNCTION) { 81309124Sdim assert(F.isDeclaration() && "_reflect function should not have a body"); 82309124Sdim assert(F.getReturnType()->isIntegerTy() && 83309124Sdim "_reflect's return type should be integer"); 84309124Sdim return false; 85309124Sdim } 86249259Sdim 87309124Sdim SmallVector<Instruction *, 4> ToRemove; 88288943Sdim 89309124Sdim // Go through the calls in this function. Each call to __nvvm_reflect or 90309124Sdim // llvm.nvvm.reflect should be a CallInst with a ConstantArray argument. 91309124Sdim // First validate that. If the c-string corresponding to the ConstantArray can 92309124Sdim // be found successfully, see if it can be found in VarMap. If so, replace the 93309124Sdim // uses of CallInst with the value found in VarMap. If not, replace the use 94309124Sdim // with value 0. 95309124Sdim 96309124Sdim // The IR for __nvvm_reflect calls differs between CUDA versions. 97309124Sdim // 98288943Sdim // CUDA 6.5 and earlier uses this sequence: 99288943Sdim // %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8 100288943Sdim // (i8 addrspace(4)* getelementptr inbounds 101288943Sdim // ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0)) 102288943Sdim // %reflect = tail call i32 @__nvvm_reflect(i8* %ptr) 103288943Sdim // 104309124Sdim // The value returned by Sym->getOperand(0) is a Constant with a 105288943Sdim // ConstantDataSequential operand which can be converted to string and used 106288943Sdim // for lookup. 107288943Sdim // 108288943Sdim // CUDA 7.0 does it slightly differently: 109288943Sdim // %reflect = call i32 @__nvvm_reflect(i8* addrspacecast 110288943Sdim // (i8 addrspace(1)* getelementptr inbounds 111288943Sdim // ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*)) 112288943Sdim // 113288943Sdim // In this case, we get a Constant with a GlobalVariable operand and we need 114288943Sdim // to dig deeper to find its initializer with the string we'll use for lookup. 115309124Sdim for (Instruction &I : instructions(F)) { 116309124Sdim CallInst *Call = dyn_cast<CallInst>(&I); 117309124Sdim if (!Call) 118309124Sdim continue; 119309124Sdim Function *Callee = Call->getCalledFunction(); 120309124Sdim if (!Callee || (Callee->getName() != NVVM_REFLECT_FUNCTION && 121309124Sdim Callee->getIntrinsicID() != Intrinsic::nvvm_reflect)) 122309124Sdim continue; 123288943Sdim 124309124Sdim // FIXME: Improve error handling here and elsewhere in this pass. 125309124Sdim assert(Call->getNumOperands() == 2 && 126309124Sdim "Wrong number of operands to __nvvm_reflect function"); 127249259Sdim 128309124Sdim // In cuda 6.5 and earlier, we will have an extra constant-to-generic 129309124Sdim // conversion of the string. 130309124Sdim const Value *Str = Call->getArgOperand(0); 131309124Sdim if (const CallInst *ConvCall = dyn_cast<CallInst>(Str)) { 132309124Sdim // FIXME: Add assertions about ConvCall. 133276479Sdim Str = ConvCall->getArgOperand(0); 134276479Sdim } 135276479Sdim assert(isa<ConstantExpr>(Str) && 136309124Sdim "Format of __nvvm__reflect function not recognized"); 137276479Sdim const ConstantExpr *GEP = cast<ConstantExpr>(Str); 138249259Sdim 139249259Sdim const Value *Sym = GEP->getOperand(0); 140309124Sdim assert(isa<Constant>(Sym) && 141309124Sdim "Format of __nvvm_reflect function not recognized"); 142249259Sdim 143288943Sdim const Value *Operand = cast<Constant>(Sym)->getOperand(0); 144288943Sdim if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand)) { 145309124Sdim // For CUDA-7.0 style __nvvm_reflect calls, we need to find the operand's 146288943Sdim // initializer. 147288943Sdim assert(GV->hasInitializer() && 148288943Sdim "Format of _reflect function not recognized"); 149288943Sdim const Constant *Initializer = GV->getInitializer(); 150288943Sdim Operand = Initializer; 151288943Sdim } 152249259Sdim 153288943Sdim assert(isa<ConstantDataSequential>(Operand) && 154249259Sdim "Format of _reflect function not recognized"); 155288943Sdim assert(cast<ConstantDataSequential>(Operand)->isCString() && 156249259Sdim "Format of _reflect function not recognized"); 157249259Sdim 158309124Sdim StringRef ReflectArg = cast<ConstantDataSequential>(Operand)->getAsString(); 159249259Sdim ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1); 160341825Sdim LLVM_DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n"); 161249259Sdim 162249259Sdim int ReflectVal = 0; // The default value is 0 163321369Sdim if (ReflectArg == "__CUDA_FTZ") { 164321369Sdim // Try to pull __CUDA_FTZ from the nvvm-reflect-ftz module flag. Our 165321369Sdim // choice here must be kept in sync with AutoUpgrade, which uses the same 166321369Sdim // technique to detect whether ftz is enabled. 167309124Sdim if (auto *Flag = mdconst::extract_or_null<ConstantInt>( 168309124Sdim F.getParent()->getModuleFlag("nvvm-reflect-ftz"))) 169309124Sdim ReflectVal = Flag->getSExtValue(); 170344779Sdim } else if (ReflectArg == "__CUDA_ARCH") { 171344779Sdim ReflectVal = SmVersion * 10; 172249259Sdim } 173309124Sdim Call->replaceAllUsesWith(ConstantInt::get(Call->getType(), ReflectVal)); 174309124Sdim ToRemove.push_back(Call); 175249259Sdim } 176249259Sdim 177309124Sdim for (Instruction *I : ToRemove) 178309124Sdim I->eraseFromParent(); 179276479Sdim 180309124Sdim return ToRemove.size() > 0; 181276479Sdim} 182