6b62a9135a
I'd reverted this in 6c7805d5d1 after a bad stage. Original commit
messsage follows:
[NFC][RemoveDIs] Bulk update utilities to insert with iterators
As part of the RemoveDIs project we need LLVM to insert instructions using
iterators wherever possible, so that the iterators can carry a bit of
debug-info. This commit implements some of that by updating the contents of
llvm/lib/Transforms/Utils to always use iterator-versions of instruction
constructors.
There are two general flavours of update:
* Almost all call-sites just call getIterator on an instruction
* Several make use of an existing iterator (scenarios where the code is
actually significant for debug-info)
The underlying logic is that any call to getFirstInsertionPt or similar
APIs that identify the start of a block need to have that iterator passed
directly to the insertion function, without being converted to a bare
Instruction pointer along the way.
I've also switched DemotePHIToStack to take an optional iterator: it needs
to take an iterator, and having a no-insert-location behaviour appears to
be important. The constructors for ICmpInst and FCmpInst have been updated
too. They're the only instructions that take block _references_ rather than
pointers for certain calls, and a future patch is going to make use of
default-null block insertion locations.
All of this should be NFC.
108 lines
3.7 KiB
C++
108 lines
3.7 KiB
C++
//===- Reg2Mem.cpp - Convert registers to allocas -------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file demotes all registers to memory references. It is intended to be
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// the inverse of PromoteMemoryToRegister. By converting to loads, the only
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// values live across basic blocks are allocas and loads before phi nodes.
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// It is intended that this should make CFG hacking much easier.
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// To make later hacking easier, the entry block is split into two, such that
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// all introduced allocas and nothing else are in the entry block.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar/Reg2Mem.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <list>
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using namespace llvm;
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#define DEBUG_TYPE "reg2mem"
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STATISTIC(NumRegsDemoted, "Number of registers demoted");
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STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted");
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static bool valueEscapes(const Instruction &Inst) {
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if (!Inst.getType()->isSized())
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return false;
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const BasicBlock *BB = Inst.getParent();
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for (const User *U : Inst.users()) {
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const Instruction *UI = cast<Instruction>(U);
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if (UI->getParent() != BB || isa<PHINode>(UI))
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return true;
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}
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return false;
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}
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static bool runPass(Function &F) {
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// Insert all new allocas into entry block.
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BasicBlock *BBEntry = &F.getEntryBlock();
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assert(pred_empty(BBEntry) &&
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"Entry block to function must not have predecessors!");
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// Find first non-alloca instruction and create insertion point. This is
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// safe if block is well-formed: it always have terminator, otherwise
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// we'll get and assertion.
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BasicBlock::iterator I = BBEntry->begin();
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while (isa<AllocaInst>(I)) ++I;
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CastInst *AllocaInsertionPoint = new BitCastInst(
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Constant::getNullValue(Type::getInt32Ty(F.getContext())),
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Type::getInt32Ty(F.getContext()), "reg2mem alloca point", I);
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// Find the escaped instructions. But don't create stack slots for
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// allocas in entry block.
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std::list<Instruction*> WorkList;
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for (Instruction &I : instructions(F))
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if (!(isa<AllocaInst>(I) && I.getParent() == BBEntry) && valueEscapes(I))
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WorkList.push_front(&I);
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// Demote escaped instructions
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NumRegsDemoted += WorkList.size();
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for (Instruction *I : WorkList)
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DemoteRegToStack(*I, false, AllocaInsertionPoint->getIterator());
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WorkList.clear();
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// Find all phi's
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for (BasicBlock &BB : F)
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for (auto &Phi : BB.phis())
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WorkList.push_front(&Phi);
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// Demote phi nodes
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NumPhisDemoted += WorkList.size();
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for (Instruction *I : WorkList)
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DemotePHIToStack(cast<PHINode>(I), AllocaInsertionPoint->getIterator());
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return true;
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}
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PreservedAnalyses RegToMemPass::run(Function &F, FunctionAnalysisManager &AM) {
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auto *DT = &AM.getResult<DominatorTreeAnalysis>(F);
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auto *LI = &AM.getResult<LoopAnalysis>(F);
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unsigned N = SplitAllCriticalEdges(F, CriticalEdgeSplittingOptions(DT, LI));
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bool Changed = runPass(F);
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if (N == 0 && !Changed)
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return PreservedAnalyses::all();
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PreservedAnalyses PA;
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PA.preserve<DominatorTreeAnalysis>();
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PA.preserve<LoopAnalysis>();
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return PA;
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}
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