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//===-- SnippetGenerator.cpp ------------------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include <array>
#include <string>
#include "Assembler.h"
#include "MCInstrDescView.h"
#include "SnippetGenerator.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/Program.h"
namespace exegesis {
SnippetGeneratorFailure::SnippetGeneratorFailure(const llvm::Twine &S)
: llvm::StringError(S, llvm::inconvertibleErrorCode()) {}
SnippetGenerator::SnippetGenerator(const LLVMState &State)
: State(State), RATC(State.getRegInfo(),
getFunctionReservedRegs(State.getTargetMachine())) {}
SnippetGenerator::~SnippetGenerator() = default;
llvm::Expected<std::vector<BenchmarkCode>>
SnippetGenerator::generateConfigurations(unsigned Opcode) const {
if (auto E = generateCodeTemplate(Opcode)) {
CodeTemplate &CT = E.get();
std::vector<BenchmarkCode> Output;
// TODO: Generate as many BenchmarkCode as needed.
{
BenchmarkCode BC;
BC.Info = CT.Info;
for (InstructionTemplate &IT : CT.Instructions) {
IT.randomizeUnsetVariables(
CT.ScratchSpacePointerInReg
? RATC.getRegister(CT.ScratchSpacePointerInReg).aliasedBits()
: RATC.emptyRegisters());
BC.Instructions.push_back(IT.build());
}
if (CT.ScratchSpacePointerInReg)
BC.LiveIns.push_back(CT.ScratchSpacePointerInReg);
BC.RegisterInitialValues = computeRegisterInitialValues(CT.Instructions);
Output.push_back(std::move(BC));
}
return Output;
} else
return E.takeError();
}
std::vector<RegisterValue> SnippetGenerator::computeRegisterInitialValues(
const std::vector<InstructionTemplate> &Instructions) const {
// Collect all register uses and create an assignment for each of them.
// Ignore memory operands which are handled separately.
// Loop invariant: DefinedRegs[i] is true iif it has been set at least once
// before the current instruction.
llvm::BitVector DefinedRegs = RATC.emptyRegisters();
std::vector<RegisterValue> RIV;
for (const InstructionTemplate &IT : Instructions) {
// Returns the register that this Operand sets or uses, or 0 if this is not
// a register.
const auto GetOpReg = [&IT](const Operand &Op) -> unsigned {
if (Op.IsMem)
return 0;
if (Op.ImplicitReg)
return *Op.ImplicitReg;
if (Op.IsExplicit && IT.getValueFor(Op).isReg())
return IT.getValueFor(Op).getReg();
return 0;
};
// Collect used registers that have never been def'ed.
for (const Operand &Op : IT.Instr.Operands) {
if (!Op.IsDef) {
const unsigned Reg = GetOpReg(Op);
if (Reg > 0 && !DefinedRegs.test(Reg)) {
RIV.push_back(RegisterValue{Reg, llvm::APInt()});
DefinedRegs.set(Reg);
}
}
}
// Mark defs as having been def'ed.
for (const Operand &Op : IT.Instr.Operands) {
if (Op.IsDef) {
const unsigned Reg = GetOpReg(Op);
if (Reg > 0)
DefinedRegs.set(Reg);
}
}
}
return RIV;
}
llvm::Expected<CodeTemplate> SnippetGenerator::generateSelfAliasingCodeTemplate(
const Instruction &Instr) const {
const AliasingConfigurations SelfAliasing(Instr, Instr);
if (SelfAliasing.empty()) {
return llvm::make_error<SnippetGeneratorFailure>("empty self aliasing");
}
CodeTemplate CT;
InstructionTemplate IT(Instr);
if (SelfAliasing.hasImplicitAliasing()) {
CT.Info = "implicit Self cycles, picking random values.";
} else {
CT.Info = "explicit self cycles, selecting one aliasing Conf.";
// This is a self aliasing instruction so defs and uses are from the same
// instance, hence twice IT in the following call.
setRandomAliasing(SelfAliasing, IT, IT);
}
CT.Instructions.push_back(std::move(IT));
return std::move(CT);
}
llvm::Expected<CodeTemplate>
SnippetGenerator::generateUnconstrainedCodeTemplate(const Instruction &Instr,
llvm::StringRef Msg) const {
CodeTemplate CT;
CT.Info = llvm::formatv("{0}, repeating an unconstrained assignment", Msg);
CT.Instructions.emplace_back(Instr);
return std::move(CT);
}
} // namespace exegesis
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