-//===-- NVPTXLowerKernelArgs.cpp - Lower kernel arguments -----------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// Pointer arguments to kernel functions need to be lowered specially.
-//
-// 1. Copy byval struct args to local memory. This is a preparation for handling
-// cases like
-//
-// kernel void foo(struct A arg, ...)
-// {
-// struct A *p = &arg;
-// ...
-// ... = p->filed1 ... (this is no generic address for .param)
-// p->filed2 = ... (this is no write access to .param)
-// }
-//
-// 2. Convert non-byval pointer arguments of CUDA kernels to pointers in the
-// global address space. This allows later optimizations to emit
-// ld.global.*/st.global.* for accessing these pointer arguments. For
-// example,
-//
-// define void @foo(float* %input) {
-// %v = load float, float* %input, align 4
-// ...
-// }
-//
-// becomes
-//
-// define void @foo(float* %input) {
-// %input2 = addrspacecast float* %input to float addrspace(1)*
-// %input3 = addrspacecast float addrspace(1)* %input2 to float*
-// %v = load float, float* %input3, align 4
-// ...
-// }
-//
-// Later, NVPTXFavorNonGenericAddrSpaces will optimize it to
-//
-// define void @foo(float* %input) {
-// %input2 = addrspacecast float* %input to float addrspace(1)*
-// %v = load float, float addrspace(1)* %input2, align 4
-// ...
-// }
-//
-// TODO: merge this pass with NVPTXFavorNonGenericAddrSpace so that other passes
-// don't cancel the addrspacecast pair this pass emits.
-//===----------------------------------------------------------------------===//
-
-#include "NVPTX.h"
-#include "NVPTXUtilities.h"
-#include "NVPTXTargetMachine.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/Type.h"
-#include "llvm/Pass.h"
-
-using namespace llvm;
-
-namespace llvm {
-void initializeNVPTXLowerKernelArgsPass(PassRegistry &);
-}
-
-namespace {
-class NVPTXLowerKernelArgs : public FunctionPass {
- bool runOnFunction(Function &F) override;
-
- // handle byval parameters
- void handleByValParam(Argument *);
- // handle non-byval pointer parameters
- void handlePointerParam(Argument *);
-
-public:
- static char ID; // Pass identification, replacement for typeid
- NVPTXLowerKernelArgs(const NVPTXTargetMachine *TM = nullptr)
- : FunctionPass(ID), TM(TM) {}
- const char *getPassName() const override {
- return "Lower pointer arguments of CUDA kernels";
- }
-
-private:
- const NVPTXTargetMachine *TM;
-};
-} // namespace
-
-char NVPTXLowerKernelArgs::ID = 1;
-
-INITIALIZE_PASS(NVPTXLowerKernelArgs, "nvptx-lower-kernel-args",
- "Lower kernel arguments (NVPTX)", false, false)
-
-// =============================================================================
-// If the function had a byval struct ptr arg, say foo(%struct.x *byval %d),
-// then add the following instructions to the first basic block:
-//
-// %temp = alloca %struct.x, align 8
-// %tempd = addrspacecast %struct.x* %d to %struct.x addrspace(101)*
-// %tv = load %struct.x addrspace(101)* %tempd
-// store %struct.x %tv, %struct.x* %temp, align 8
-//
-// The above code allocates some space in the stack and copies the incoming
-// struct from param space to local space.
-// Then replace all occurences of %d by %temp.
-// =============================================================================
-void NVPTXLowerKernelArgs::handleByValParam(Argument *Arg) {
- Function *Func = Arg->getParent();
- Instruction *FirstInst = &(Func->getEntryBlock().front());
- PointerType *PType = dyn_cast<PointerType>(Arg->getType());
-
- assert(PType && "Expecting pointer type in handleByValParam");
-
- Type *StructType = PType->getElementType();
- AllocaInst *AllocA = new AllocaInst(StructType, Arg->getName(), FirstInst);
- // Set the alignment to alignment of the byval parameter. This is because,
- // later load/stores assume that alignment, and we are going to replace
- // the use of the byval parameter with this alloca instruction.
- AllocA->setAlignment(Func->getParamAlignment(Arg->getArgNo() + 1));
- Arg->replaceAllUsesWith(AllocA);
-
- Value *ArgInParam = new AddrSpaceCastInst(
- Arg, PointerType::get(StructType, ADDRESS_SPACE_PARAM), Arg->getName(),
- FirstInst);
- LoadInst *LI = new LoadInst(ArgInParam, Arg->getName(), FirstInst);
- new StoreInst(LI, AllocA, FirstInst);
-}
-
-void NVPTXLowerKernelArgs::handlePointerParam(Argument *Arg) {
- assert(!Arg->hasByValAttr() &&
- "byval params should be handled by handleByValParam");
-
- Instruction *FirstInst = Arg->getParent()->getEntryBlock().begin();
- Instruction *ArgInGlobal = new AddrSpaceCastInst(
- Arg, PointerType::get(Arg->getType()->getPointerElementType(),
- ADDRESS_SPACE_GLOBAL),
- Arg->getName(), FirstInst);
- Value *ArgInGeneric = new AddrSpaceCastInst(ArgInGlobal, Arg->getType(),
- Arg->getName(), FirstInst);
- // Replace with ArgInGeneric all uses of Args except ArgInGlobal.
- Arg->replaceAllUsesWith(ArgInGeneric);
- ArgInGlobal->setOperand(0, Arg);
-}
-
-
-// =============================================================================
-// Main function for this pass.
-// =============================================================================
-bool NVPTXLowerKernelArgs::runOnFunction(Function &F) {
- // Skip non-kernels. See the comments at the top of this file.
- if (!isKernelFunction(F))
- return false;
-
- for (Argument &Arg : F.args()) {
- if (Arg.getType()->isPointerTy()) {
- if (Arg.hasByValAttr())
- handleByValParam(&Arg);
- else if (TM && TM->getDrvInterface() == NVPTX::CUDA)
- handlePointerParam(&Arg);
- }
- }
- return true;
-}
-
-FunctionPass *
-llvm::createNVPTXLowerKernelArgsPass(const NVPTXTargetMachine *TM) {
- return new NVPTXLowerKernelArgs(TM);
-}