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-rw-r--r--llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp164
1 files changed, 17 insertions, 147 deletions
diff --git a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index c14b4bd5f17..fcd3bd08482 100644
--- a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -17,7 +17,6 @@
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
@@ -49,7 +48,7 @@
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <algorithm>
-
+#include <cassert>
#include <iterator>
#include <utility>
#include <vector>
@@ -178,16 +177,6 @@ public:
ValVector Values;
};
-/// \brief Semi-open interval of instructions that are guaranteed to
-/// all execute if the first one does.
-class GuaranteedExecutionRange {
-public:
- unsigned Start;
- unsigned End;
-
- GuaranteedExecutionRange(unsigned S, unsigned E) : Start(S), End(E) {}
-};
-
/// \brief This assigns and keeps a per-bb relative ordering of load/store
/// instructions in the block that directly load or store an alloca.
///
@@ -201,108 +190,14 @@ class LargeBlockInfo {
/// the block.
DenseMap<const Instruction *, unsigned> InstNumbers;
- /// \brief For each basic block we track, keep track of the intervals
- /// of instruction numbers of instructions that transfer control
- /// to their successors, for propagating metadata.
- DenseMap<const BasicBlock *,
- Optional<SmallVector<GuaranteedExecutionRange, 4>>>
- GuaranteedExecutionIntervals;
-
public:
- /// This code looks for stores to allocas, and for loads both for
- /// allocas and for transferring metadata.
+
+ /// This code only looks at accesses to allocas.
static bool isInterestingInstruction(const Instruction *I) {
- return isa<LoadInst>(I) ||
+ return (isa<LoadInst>(I) && isa<AllocaInst>(I->getOperand(0))) ||
(isa<StoreInst>(I) && isa<AllocaInst>(I->getOperand(1)));
}
- /// Compute the GuaranteedExecutionIntervals for a given BB.
- ///
- /// This is valid and remains valid as long as each interesting
- /// instruction (see isInterestingInstruction) that
- /// A) existed when this LBI was cleared
- /// B) has not been deleted (deleting interesting instructions is fine)
- /// are run in the same program executions and in the same order
- /// as when this LBI was cleared.
- ///
- /// Because `PromoteMemoryToRegister` does not move memory loads at
- /// all, this assumption is satisfied in this pass.
- SmallVector<GuaranteedExecutionRange, 4> computeGEI(const BasicBlock *BB) {
- SmallVector<GuaranteedExecutionRange, 4> GuaranteedExecutionIntervals;
-
- unsigned InstNo = 0;
- bool InRange = false;
- unsigned FirstInstInRange = 0;
- for (const Instruction &BBI : *BB) {
- if (isGuaranteedToTransferExecutionToSuccessor(&BBI)) {
- if (!InRange && isInterestingInstruction(&BBI)) {
- InRange = true;
- FirstInstInRange = InstNo;
- }
- } else {
- if (InRange) {
- assert(FirstInstInRange < InstNo &&
- "Can't push an empty range here.");
- GuaranteedExecutionIntervals.emplace_back(FirstInstInRange, InstNo);
- }
- InRange = false;
- }
-
- if (isInterestingInstruction(&BBI)) {
- auto It = InstNumbers.find(&BBI);
- assert(It != InstNumbers.end() && InstNo <= It->second &&
- "missing number for interesting instruction");
- InstNo = It->second + 1;
- }
- }
-
- if (InRange) {
- assert(FirstInstInRange < InstNo && "Can't push an empty range here.");
- GuaranteedExecutionIntervals.emplace_back(FirstInstInRange, InstNo);
- }
-
- return GuaranteedExecutionIntervals;
- }
-
- /// Return true if, when CxtI executes, it is guaranteed that either
- /// I had executed already or that I is guaranteed to be later executed.
- ///
- /// The useful property this guarantees is that if I exhibits undefined
- /// behavior under some circumstances, then the whole program will exhibit
- /// undefined behavior at CxtI.
- bool isGuaranteedToBeExecuted(const Instruction *CxtI, const Instruction *I) {
- const BasicBlock *BB = CxtI->getParent();
-
- if (BB != I->getParent()) {
- // Instructions in different basic blocks, so control flow
- // can diverge between them (we could track this with
- // postdoms, but we don't bother).
- return false;
- }
-
- unsigned Index1 = getInstructionIndex(CxtI);
- unsigned Index2 = getInstructionIndex(I);
-
- auto &BBGEI = GuaranteedExecutionIntervals[BB];
- if (!BBGEI.hasValue()) {
- BBGEI.emplace(computeGEI(BB));
- }
-
- // We want to check whether I and CxtI are in the same range. To do that,
- // we notice that CxtI can only be in the first range R where
- // CxtI.end < R.end. If we find that range using binary search,
- // we can check whether I and CxtI are both in it.
- GuaranteedExecutionRange Bound(Index1, Index1);
- auto R = std::upper_bound(
- BBGEI->begin(), BBGEI->end(), Bound,
- [](GuaranteedExecutionRange I_, GuaranteedExecutionRange R) {
- return I_.End < R.End;
- });
-
- return R != BBGEI->end() && R->Start <= Index1 && Index1 < R->End &&
- R->Start <= Index2 && Index2 < R->End;
- }
-
/// Get or calculate the index of the specified instruction.
unsigned getInstructionIndex(const Instruction *I) {
assert(isInterestingInstruction(I) &&
@@ -318,11 +213,9 @@ public:
// avoid gratuitus rescans.
const BasicBlock *BB = I->getParent();
unsigned InstNo = 0;
- GuaranteedExecutionIntervals.erase(BB);
for (const Instruction &BBI : *BB)
if (isInterestingInstruction(&BBI))
InstNumbers[&BBI] = InstNo++;
-
It = InstNumbers.find(I);
assert(It != InstNumbers.end() && "Didn't insert instruction?");
@@ -331,10 +224,7 @@ public:
void deleteValue(const Instruction *I) { InstNumbers.erase(I); }
- void clear() {
- InstNumbers.clear();
- GuaranteedExecutionIntervals.clear();
- }
+ void clear() { InstNumbers.clear(); }
};
struct PromoteMem2Reg {
@@ -412,7 +302,7 @@ private:
const SmallPtrSetImpl<BasicBlock *> &DefBlocks,
SmallPtrSetImpl<BasicBlock *> &LiveInBlocks);
void RenamePass(BasicBlock *BB, BasicBlock *Pred,
- RenamePassData::ValVector &IncVals, LargeBlockInfo &LBI,
+ RenamePassData::ValVector &IncVals,
std::vector<RenamePassData> &Worklist);
bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx, unsigned &Version);
};
@@ -431,29 +321,6 @@ static void addAssumeNonNull(AssumptionCache *AC, LoadInst *LI) {
AC->registerAssumption(CI);
}
-static void addAssumptionsFromMetadata(LoadInst *LI, Value *ReplVal,
- DominatorTree &DT, const DataLayout &DL,
- LargeBlockInfo &LBI,
- AssumptionCache *AC) {
- if (LI->getMetadata(LLVMContext::MD_nonnull) &&
- !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT)) {
- addAssumeNonNull(AC, LI);
- }
-
- if (auto *N = LI->getMetadata(LLVMContext::MD_range)) {
- // Range metadata is harder to use as an assumption,
- // so don't try to add one, but *do* try to copy
- // the metadata to a load in the same BB.
- if (LoadInst *NewLI = dyn_cast<LoadInst>(ReplVal)) {
- DEBUG(dbgs() << "trying to move !range metadata from" << *LI << " to"
- << *NewLI << "\n");
- if (LBI.isGuaranteedToBeExecuted(LI, NewLI)) {
- copyRangeMetadata(DL, *LI, N, *NewLI);
- }
- }
- }
-}
-
static void removeLifetimeIntrinsicUsers(AllocaInst *AI) {
// Knowing that this alloca is promotable, we know that it's safe to kill all
// instructions except for load and store.
@@ -542,7 +409,9 @@ static bool rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
// If the load was marked as nonnull we don't want to lose
// that information when we erase this Load. So we preserve
// it with an assume.
- addAssumptionsFromMetadata(LI, ReplVal, DT, DL, LBI, AC);
+ if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
+ !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT))
+ addAssumeNonNull(AC, LI);
LI->replaceAllUsesWith(ReplVal);
LI->eraseFromParent();
@@ -636,7 +505,9 @@ static bool promoteSingleBlockAlloca(AllocaInst *AI, const AllocaInfo &Info,
// Note, if the load was marked as nonnull we don't want to lose that
// information when we erase it. So we preserve it with an assume.
Value *ReplVal = std::prev(I)->second->getOperand(0);
- addAssumptionsFromMetadata(LI, ReplVal, DT, DL, LBI, AC);
+ if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
+ !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT))
+ addAssumeNonNull(AC, LI);
LI->replaceAllUsesWith(ReplVal);
}
@@ -772,6 +643,7 @@ void PromoteMem2Reg::run() {
if (Allocas.empty())
return; // All of the allocas must have been trivial!
+
LBI.clear();
// Set the incoming values for the basic block to be null values for all of
@@ -789,10 +661,9 @@ void PromoteMem2Reg::run() {
RenamePassData RPD = std::move(RenamePassWorkList.back());
RenamePassWorkList.pop_back();
// RenamePass may add new worklist entries.
- RenamePass(RPD.BB, RPD.Pred, RPD.Values, LBI, RenamePassWorkList);
+ RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList);
} while (!RenamePassWorkList.empty());
- LBI.clear();
// The renamer uses the Visited set to avoid infinite loops. Clear it now.
Visited.clear();
@@ -1004,7 +875,6 @@ bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo,
/// predecessor block Pred.
void PromoteMem2Reg::RenamePass(BasicBlock *BB, BasicBlock *Pred,
RenamePassData::ValVector &IncomingVals,
- LargeBlockInfo &LBI,
std::vector<RenamePassData> &Worklist) {
NextIteration:
// If we are inserting any phi nodes into this BB, they will already be in the
@@ -1071,12 +941,13 @@ NextIteration:
// If the load was marked as nonnull we don't want to lose
// that information when we erase this Load. So we preserve
// it with an assume.
- addAssumptionsFromMetadata(LI, V, DT, SQ.DL, LBI, AC);
+ if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
+ !isKnownNonZero(V, SQ.DL, 0, AC, LI, &DT))
+ addAssumeNonNull(AC, LI);
// Anything using the load now uses the current value.
LI->replaceAllUsesWith(V);
BB->getInstList().erase(LI);
- LBI.deleteValue(LI);
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
// Delete this instruction and mark the name as the current holder of the
// value
@@ -1094,7 +965,6 @@ NextIteration:
for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[ai->second])
ConvertDebugDeclareToDebugValue(DII, SI, DIB);
BB->getInstList().erase(SI);
- LBI.deleteValue(SI);
}
}
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