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//===- UniformityAnalysis.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
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/UniformityAnalysis.h"
#include "llvm/ADT/GenericUniformityImpl.h"
#include "llvm/Analysis/CycleAnalysis.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/InitializePasses.h"
using namespace llvm;
template <>
bool llvm::GenericUniformityAnalysisImpl<SSAContext>::hasDivergentDefs(
const Instruction &I) const {
return isDivergent((const Value *)&I);
}
template <>
bool llvm::GenericUniformityAnalysisImpl<SSAContext>::markDefsDivergent(
const Instruction &Instr) {
return markDivergent(cast<Value>(&Instr));
}
template <> void llvm::GenericUniformityAnalysisImpl<SSAContext>::initialize() {
for (auto &I : instructions(F)) {
if (TTI->isSourceOfDivergence(&I))
markDivergent(I);
else if (TTI->isAlwaysUniform(&I))
addUniformOverride(I);
}
for (auto &Arg : F.args()) {
if (TTI->isSourceOfDivergence(&Arg)) {
markDivergent(&Arg);
}
}
}
template <>
void llvm::GenericUniformityAnalysisImpl<SSAContext>::pushUsers(
const Value *V) {
for (const auto *User : V->users()) {
if (const auto *UserInstr = dyn_cast<const Instruction>(User)) {
markDivergent(*UserInstr);
}
}
}
template <>
void llvm::GenericUniformityAnalysisImpl<SSAContext>::pushUsers(
const Instruction &Instr) {
assert(!isAlwaysUniform(Instr));
if (Instr.isTerminator())
return;
pushUsers(cast<Value>(&Instr));
}
template <>
bool llvm::GenericUniformityAnalysisImpl<SSAContext>::usesValueFromCycle(
const Instruction &I, const Cycle &DefCycle) const {
assert(!isAlwaysUniform(I));
for (const Use &U : I.operands()) {
if (auto *I = dyn_cast<Instruction>(&U)) {
if (DefCycle.contains(I->getParent()))
return true;
}
}
return false;
}
template <>
void llvm::GenericUniformityAnalysisImpl<
SSAContext>::propagateTemporalDivergence(const Instruction &I,
const Cycle &DefCycle) {
for (auto *User : I.users()) {
auto *UserInstr = cast<Instruction>(User);
if (DefCycle.contains(UserInstr->getParent()))
continue;
markDivergent(*UserInstr);
recordTemporalDivergence(&I, UserInstr, &DefCycle);
}
}
template <>
bool llvm::GenericUniformityAnalysisImpl<SSAContext>::isDivergentUse(
const Use &U) const {
const auto *V = U.get();
if (isDivergent(V))
return true;
if (const auto *DefInstr = dyn_cast<Instruction>(V)) {
const auto *UseInstr = cast<Instruction>(U.getUser());
return isTemporalDivergent(*UseInstr->getParent(), *DefInstr);
}
return false;
}
// This ensures explicit instantiation of
// GenericUniformityAnalysisImpl::ImplDeleter::operator()
template class llvm::GenericUniformityInfo<SSAContext>;
template struct llvm::GenericUniformityAnalysisImplDeleter<
llvm::GenericUniformityAnalysisImpl<SSAContext>>;
//===----------------------------------------------------------------------===//
// UniformityInfoAnalysis and related pass implementations
//===----------------------------------------------------------------------===//
llvm::UniformityInfo UniformityInfoAnalysis::run(Function &F,
FunctionAnalysisManager &FAM) {
auto &DT = FAM.getResult<DominatorTreeAnalysis>(F);
auto &TTI = FAM.getResult<TargetIRAnalysis>(F);
auto &CI = FAM.getResult<CycleAnalysis>(F);
UniformityInfo UI{DT, CI, &TTI};
// Skip computation if we can assume everything is uniform.
if (TTI.hasBranchDivergence(&F))
UI.compute();
return UI;
}
AnalysisKey UniformityInfoAnalysis::Key;
UniformityInfoPrinterPass::UniformityInfoPrinterPass(raw_ostream &OS)
: OS(OS) {}
PreservedAnalyses UniformityInfoPrinterPass::run(Function &F,
FunctionAnalysisManager &AM) {
OS << "UniformityInfo for function '" << F.getName() << "':\n";
AM.getResult<UniformityInfoAnalysis>(F).print(OS);
return PreservedAnalyses::all();
}
//===----------------------------------------------------------------------===//
// UniformityInfoWrapperPass Implementation
//===----------------------------------------------------------------------===//
char UniformityInfoWrapperPass::ID = 0;
UniformityInfoWrapperPass::UniformityInfoWrapperPass() : FunctionPass(ID) {}
INITIALIZE_PASS_BEGIN(UniformityInfoWrapperPass, "uniformity",
"Uniformity Analysis", false, true)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(CycleInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_END(UniformityInfoWrapperPass, "uniformity",
"Uniformity Analysis", false, true)
void UniformityInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequiredTransitive<CycleInfoWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
}
bool UniformityInfoWrapperPass::runOnFunction(Function &F) {
auto &cycleInfo = getAnalysis<CycleInfoWrapperPass>().getResult();
auto &domTree = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto &targetTransformInfo =
getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
m_function = &F;
m_uniformityInfo = UniformityInfo{domTree, cycleInfo, &targetTransformInfo};
// Skip computation if we can assume everything is uniform.
if (targetTransformInfo.hasBranchDivergence(m_function))
m_uniformityInfo.compute();
return false;
}
void UniformityInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
OS << "UniformityInfo for function '" << m_function->getName() << "':\n";
}
void UniformityInfoWrapperPass::releaseMemory() {
m_uniformityInfo = UniformityInfo{};
m_function = nullptr;
}
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