| //===- NVVMReflect.cpp - NVVM Emulate conditional compilation -------------===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass replaces occurrences of __nvvm_reflect("foo") and llvm.nvvm.reflect |
| // with an integer. |
| // |
| // We choose the value we use by looking at metadata in the module itself. Note |
| // that we intentionally only have one way to choose these values, because other |
| // parts of LLVM (particularly, InstCombineCall) rely on being able to predict |
| // the values chosen by this pass. |
| // |
| // If we see an unknown string, we replace its call with 0. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "NVPTX.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/StringMap.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/InstIterator.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/IntrinsicsNVPTX.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/IR/PassManager.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_os_ostream.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/Scalar.h" |
| #include <sstream> |
| #include <string> |
| #define NVVM_REFLECT_FUNCTION "__nvvm_reflect" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "nvptx-reflect" |
| |
| namespace llvm { void initializeNVVMReflectPass(PassRegistry &); } |
| |
| namespace { |
| class NVVMReflect : public FunctionPass { |
| public: |
| static char ID; |
| unsigned int SmVersion; |
| NVVMReflect() : NVVMReflect(0) {} |
| explicit NVVMReflect(unsigned int Sm) : FunctionPass(ID), SmVersion(Sm) { |
| initializeNVVMReflectPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool runOnFunction(Function &) override; |
| }; |
| } |
| |
| FunctionPass *llvm::createNVVMReflectPass(unsigned int SmVersion) { |
| return new NVVMReflect(SmVersion); |
| } |
| |
| static cl::opt<bool> |
| NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden, |
| cl::desc("NVVM reflection, enabled by default")); |
| |
| char NVVMReflect::ID = 0; |
| INITIALIZE_PASS(NVVMReflect, "nvvm-reflect", |
| "Replace occurrences of __nvvm_reflect() calls with 0/1", false, |
| false) |
| |
| static bool runNVVMReflect(Function &F, unsigned SmVersion) { |
| if (!NVVMReflectEnabled) |
| return false; |
| |
| if (F.getName() == NVVM_REFLECT_FUNCTION) { |
| assert(F.isDeclaration() && "_reflect function should not have a body"); |
| assert(F.getReturnType()->isIntegerTy() && |
| "_reflect's return type should be integer"); |
| return false; |
| } |
| |
| SmallVector<Instruction *, 4> ToRemove; |
| |
| // Go through the calls in this function. Each call to __nvvm_reflect or |
| // llvm.nvvm.reflect should be a CallInst with a ConstantArray argument. |
| // First validate that. If the c-string corresponding to the ConstantArray can |
| // be found successfully, see if it can be found in VarMap. If so, replace the |
| // uses of CallInst with the value found in VarMap. If not, replace the use |
| // with value 0. |
| |
| // The IR for __nvvm_reflect calls differs between CUDA versions. |
| // |
| // CUDA 6.5 and earlier uses this sequence: |
| // %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8 |
| // (i8 addrspace(4)* getelementptr inbounds |
| // ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0)) |
| // %reflect = tail call i32 @__nvvm_reflect(i8* %ptr) |
| // |
| // The value returned by Sym->getOperand(0) is a Constant with a |
| // ConstantDataSequential operand which can be converted to string and used |
| // for lookup. |
| // |
| // CUDA 7.0 does it slightly differently: |
| // %reflect = call i32 @__nvvm_reflect(i8* addrspacecast |
| // (i8 addrspace(1)* getelementptr inbounds |
| // ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*)) |
| // |
| // In this case, we get a Constant with a GlobalVariable operand and we need |
| // to dig deeper to find its initializer with the string we'll use for lookup. |
| for (Instruction &I : instructions(F)) { |
| CallInst *Call = dyn_cast<CallInst>(&I); |
| if (!Call) |
| continue; |
| Function *Callee = Call->getCalledFunction(); |
| if (!Callee || (Callee->getName() != NVVM_REFLECT_FUNCTION && |
| Callee->getIntrinsicID() != Intrinsic::nvvm_reflect)) |
| continue; |
| |
| // FIXME: Improve error handling here and elsewhere in this pass. |
| assert(Call->getNumOperands() == 2 && |
| "Wrong number of operands to __nvvm_reflect function"); |
| |
| // In cuda 6.5 and earlier, we will have an extra constant-to-generic |
| // conversion of the string. |
| const Value *Str = Call->getArgOperand(0); |
| if (const CallInst *ConvCall = dyn_cast<CallInst>(Str)) { |
| // FIXME: Add assertions about ConvCall. |
| Str = ConvCall->getArgOperand(0); |
| } |
| assert(isa<ConstantExpr>(Str) && |
| "Format of __nvvm__reflect function not recognized"); |
| const ConstantExpr *GEP = cast<ConstantExpr>(Str); |
| |
| const Value *Sym = GEP->getOperand(0); |
| assert(isa<Constant>(Sym) && |
| "Format of __nvvm_reflect function not recognized"); |
| |
| const Value *Operand = cast<Constant>(Sym)->getOperand(0); |
| if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand)) { |
| // For CUDA-7.0 style __nvvm_reflect calls, we need to find the operand's |
| // initializer. |
| assert(GV->hasInitializer() && |
| "Format of _reflect function not recognized"); |
| const Constant *Initializer = GV->getInitializer(); |
| Operand = Initializer; |
| } |
| |
| assert(isa<ConstantDataSequential>(Operand) && |
| "Format of _reflect function not recognized"); |
| assert(cast<ConstantDataSequential>(Operand)->isCString() && |
| "Format of _reflect function not recognized"); |
| |
| StringRef ReflectArg = cast<ConstantDataSequential>(Operand)->getAsString(); |
| ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1); |
| LLVM_DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n"); |
| |
| int ReflectVal = 0; // The default value is 0 |
| if (ReflectArg == "__CUDA_FTZ") { |
| // Try to pull __CUDA_FTZ from the nvvm-reflect-ftz module flag. Our |
| // choice here must be kept in sync with AutoUpgrade, which uses the same |
| // technique to detect whether ftz is enabled. |
| if (auto *Flag = mdconst::extract_or_null<ConstantInt>( |
| F.getParent()->getModuleFlag("nvvm-reflect-ftz"))) |
| ReflectVal = Flag->getSExtValue(); |
| } else if (ReflectArg == "__CUDA_ARCH") { |
| ReflectVal = SmVersion * 10; |
| } |
| Call->replaceAllUsesWith(ConstantInt::get(Call->getType(), ReflectVal)); |
| ToRemove.push_back(Call); |
| } |
| |
| for (Instruction *I : ToRemove) |
| I->eraseFromParent(); |
| |
| return ToRemove.size() > 0; |
| } |
| |
| bool NVVMReflect::runOnFunction(Function &F) { |
| return runNVVMReflect(F, SmVersion); |
| } |
| |
| NVVMReflectPass::NVVMReflectPass() : NVVMReflectPass(0) {} |
| |
| PreservedAnalyses NVVMReflectPass::run(Function &F, |
| FunctionAnalysisManager &AM) { |
| return runNVVMReflect(F, SmVersion) ? PreservedAnalyses::none() |
| : PreservedAnalyses::all(); |
| } |