llvm/llvm/lib/Target/PowerPC/PPCBoolRetToInt.cpp

//===- PPCBoolRetToInt.cpp ------------------------------------------------===//
//
// 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 file implements converting i1 values to i32/i64 if they could be more
// profitably allocated as GPRs rather than CRs. This pass will become totally
// unnecessary if Register Bank Allocation and Global Instruction Selection ever
// go upstream.
//
// Presently, the pass converts i1 Constants, and Arguments to i32/i64 if the
// transitive closure of their uses includes only PHINodes, CallInsts, and
// ReturnInsts. The rational is that arguments are generally passed and returned
// in GPRs rather than CRs, so casting them to i32/i64 at the LLVM IR level will
// actually save casts at the Machine Instruction level.
//
// It might be useful to expand this pass to add bit-wise operations to the list
// of safe transitive closure types. Also, we miss some opportunities when LLVM
// represents logical AND and OR operations with control flow rather than data
// flow. For example by lowering the expression: return (A && B && C)
//
// as: return A ? true : B && C.
//
// There's code in SimplifyCFG that code be used to turn control flow in data
// flow using SelectInsts. Selects are slow on some architectures (P7/P8), so
// this probably isn't good in general, but for the special case of i1, the
// Selects could be further lowered to bit operations that are fast everywhere.
//
//===----------------------------------------------------------------------===//

#include "PPC.h"
#include "PPCTargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/OperandTraits.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/Support/Casting.h"
#include <cassert>

usingnamespacellvm;

namespace … // end anonymous namespace

char PPCBoolRetToInt::ID = …;
INITIALIZE_PASS(…)

FunctionPass *llvm::createPPCBoolRetToIntPass() { … }