mirror of
https://github.com/intel/llvm.git
synced 2026-01-14 11:57:39 +08:00
d850ca3622
Summary: Add an implementation for shrink wrapping, a frame optimization that moves callee-saved register spills from hot prologues to cold successors. (cherry picked from FBD4983706)
113 lines
3.5 KiB
C++
113 lines
3.5 KiB
C++
//===--- Passes/StackReachingUses.cpp -------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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//===----------------------------------------------------------------------===//
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#include "StackReachingUses.h"
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#include "FrameAnalysis.h"
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#define DEBUG_TYPE "sru"
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namespace llvm {
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namespace bolt {
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bool StackReachingUses::isStoreUsed(const FrameIndexEntry &StoreFIE,
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ExprIterator Candidates,
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bool IncludeLocalAccesses) const {
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for (auto I = Candidates; I != expr_end(); ++I) {
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const MCInst *ReachingInst = *I;
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if (IncludeLocalAccesses) {
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if (auto FIEY = FA.getFIEFor(BC, *ReachingInst)) {
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assert(FIEY->IsLoad == 1);
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if (StoreFIE.StackOffset + StoreFIE.Size > FIEY->StackOffset &&
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StoreFIE.StackOffset < FIEY->StackOffset + FIEY->Size) {
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return true;
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}
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}
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}
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auto Args = FA.getArgAccessesFor(BC, *ReachingInst);
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if (!Args)
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continue;
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if (Args->AssumeEverything) {
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return true;
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}
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for (auto FIEY : Args->Set) {
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if (StoreFIE.StackOffset + StoreFIE.Size > FIEY.StackOffset &&
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StoreFIE.StackOffset < FIEY.StackOffset + FIEY.Size) {
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return true;
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}
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}
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}
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return false;
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}
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void StackReachingUses::preflight() {
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DEBUG(dbgs() << "Starting StackReachingUses on \"" << Func.getPrintName()
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<< "\"\n");
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// Populate our universe of tracked expressions. We are interested in
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// tracking reaching loads from frame position at any given point of the
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// program.
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for (auto &BB : Func) {
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for (auto &Inst : BB) {
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if (auto FIE = FA.getFIEFor(BC, Inst)) {
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if (FIE->IsLoad == true) {
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Expressions.push_back(&Inst);
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ExprToIdx[&Inst] = NumInstrs++;
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continue;
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}
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}
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auto AA = FA.getArgAccessesFor(BC, Inst);
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if (AA && (!AA->Set.empty() || AA->AssumeEverything)) {
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Expressions.push_back(&Inst);
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ExprToIdx[&Inst] = NumInstrs++;
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}
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}
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}
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}
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bool StackReachingUses::doesXKillsY(const MCInst *X, const MCInst *Y) {
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// if X is a store to the same stack location and the bytes fetched is a
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// superset of those bytes affected by the load in Y, return true
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auto FIEX = FA.getFIEFor(BC, *X);
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auto FIEY = FA.getFIEFor(BC, *Y);
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if (FIEX && FIEY) {
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if (FIEX->IsStore == true && FIEY->IsLoad == true &&
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FIEX->StackOffset <= FIEY->StackOffset &&
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FIEX->StackOffset + FIEX->Size >= FIEY->StackOffset + FIEY->Size)
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return true;
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}
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return false;
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}
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BitVector StackReachingUses::computeNext(const MCInst &Point,
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const BitVector &Cur) {
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BitVector Next = Cur;
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// Kill
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for (auto I = expr_begin(Next), E = expr_end(); I != E; ++I) {
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assert(*I != nullptr && "Lost pointers");
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if (doesXKillsY(&Point, *I)) {
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DEBUG(dbgs() << "\t\t\tKilling ");
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DEBUG((*I)->dump());
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Next.reset(I.getBitVectorIndex());
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}
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};
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// Gen
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if (auto FIE = FA.getFIEFor(BC, Point)) {
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if (FIE->IsLoad == true)
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Next.set(ExprToIdx[&Point]);
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}
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auto AA = FA.getArgAccessesFor(BC, Point);
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if (AA && (!AA->Set.empty() || AA->AssumeEverything))
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Next.set(ExprToIdx[&Point]);
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return Next;
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}
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} // namespace bolt
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} // namespace llvm
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