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/*========================== begin_copyright_notice ============================
Copyright (C) 2017-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
//
/// GenXRematerialization
/// ---------------------
///
/// This pass performs rematerialization to reduce register pressure.
///
//===----------------------------------------------------------------------===//
#include "GenX.h"
#include "GenXBaling.h"
#include "GenXLiveness.h"
#include "GenXModule.h"
#include "GenXNumbering.h"
#include "GenXPressureTracker.h"
#include "GenXUtil.h"
#include "llvm/Pass.h"
#include "Probe/Assertion.h"
using namespace llvm;
using namespace genx;
namespace {
class GenXRematerialization : public FGPassImplInterface,
public IDMixin<GenXRematerialization> {
GenXBaling *Baling = nullptr;
GenXLiveness *Liveness = nullptr;
GenXNumbering *Numbering = nullptr;
bool Modified = false;
public:
explicit GenXRematerialization() {}
static StringRef getPassName() { return "GenX rematerialization pass"; }
static void getAnalysisUsage(AnalysisUsage &AU);
bool runOnFunctionGroup(FunctionGroup &FG) override;
private:
void remat(Function *F, PressureTracker &RP);
};
} // namespace
namespace llvm {
void initializeGenXRematerializationWrapperPass(PassRegistry &);
using GenXRematerializationWrapper =
FunctionGroupWrapperPass<GenXRematerialization>;
} // namespace llvm
INITIALIZE_PASS_BEGIN(GenXRematerializationWrapper,
"GenXRematerializationWrapper",
"GenXRematerializationWrapper", false, false)
INITIALIZE_PASS_DEPENDENCY(GenXGroupBalingWrapper)
INITIALIZE_PASS_DEPENDENCY(GenXLivenessWrapper)
INITIALIZE_PASS_DEPENDENCY(GenXNumberingWrapper)
INITIALIZE_PASS_END(GenXRematerializationWrapper,
"GenXRematerializationWrapper",
"GenXRematerializationWrapper", false, false)
ModulePass *llvm::createGenXRematerializationWrapperPass() {
initializeGenXRematerializationWrapperPass(*PassRegistry::getPassRegistry());
return new GenXRematerializationWrapper;
}
void GenXRematerialization::getAnalysisUsage(AnalysisUsage &AU) {
AU.addRequired<GenXGroupBaling>();
AU.addRequired<GenXLiveness>();
AU.addRequired<GenXNumbering>();
AU.addPreserved<GenXModule>();
AU.addPreserved<FunctionGroupAnalysis>();
AU.setPreservesCFG();
}
bool GenXRematerialization::runOnFunctionGroup(FunctionGroup &FG) {
if (skipOptWithLargeBlock(FG))
return false;
Modified = false;
Baling = &getAnalysis<GenXGroupBaling>();
Liveness = &getAnalysis<GenXLiveness>();
Numbering = &getAnalysis<GenXNumbering>();
const auto &DL = FG.getModule()->getDataLayout();
PressureTracker RP(DL, FG, Liveness);
for (auto fgi = FG.begin(), fge = FG.end(); fgi != fge; ++fgi)
remat(*fgi, RP);
return Modified;
}
void GenXRematerialization::remat(Function *F, PressureTracker &RP) {
// Collect rematerialization candidates.
std::vector<Use *> Candidates;
for (auto &BB : F->getBasicBlockList()) {
for (auto &Inst : BB.getInstList()) {
// (1) upward cast
if (auto CI = dyn_cast<CastInst>(&Inst)) {
if (CI->getOpcode() != Instruction::UIToFP &&
CI->getOpcode() != Instruction::SIToFP)
continue;
if (!CI->getType()->isVectorTy())
continue;
if (CI->getSrcTy()->getScalarSizeInBits() >=
CI->getDestTy()->getScalarSizeInBits())
continue;
if (Inst.isUsedOutsideOfBlock(&BB) || !Inst.hasNUsesOrMore(3))
continue;
LiveRange *LR = Liveness->getLiveRangeOrNull(CI);
if (!LR || LR->value_size() != 1)
continue;
IGC_ASSERT(LR->value_begin()->getValue() == CI);
unsigned B = Numbering->getNumber(CI);
for (auto &U : CI->uses()) {
auto UI = U.getUser();
unsigned E = Numbering->getNumber(UI);
if (E > B && RP.intersectWithRedRegion(B, E))
Candidates.push_back(&U);
}
}
}
}
// Do rematerialization.
for (auto U : Candidates) {
Instruction *Inst = cast<Instruction>(U->get());
Instruction *UI = cast<Instruction>(U->getUser());
Instruction *Clone = Inst->clone();
Clone->insertBefore(UI);
U->set(Clone);
Modified = true;
}
}
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