[llvm] r319096 - [SROA] Propagate !range metadata when moving loads.
Davide Italiano via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 27 13:25:13 PST 2017
Author: davide
Date: Mon Nov 27 13:25:13 2017
New Revision: 319096
URL: http://llvm.org/viewvc/llvm-project?rev=319096&view=rev
Log:
[SROA] Propagate !range metadata when moving loads.
This tries to propagate !range metadata to a pre-existing load
when a load is optimized out. This is done instead of adding an
assume because converting loads to and from assumes creates a
lot of IR.
Patch by Ariel Ben-Yehuda.
Differential Revision: https://reviews.llvm.org/D37216
Modified:
llvm/trunk/lib/Transforms/Scalar/SROA.cpp
llvm/trunk/lib/Transforms/Utils/Local.cpp
llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
llvm/trunk/test/Transforms/SROA/preserve-nonnull.ll
Modified: llvm/trunk/lib/Transforms/Scalar/SROA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SROA.cpp?rev=319096&r1=319095&r2=319096&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SROA.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SROA.cpp Mon Nov 27 13:25:13 2017
@@ -2455,15 +2455,10 @@ private:
// are different types, for example by mapping !nonnull metadata to
// !range metadata by modeling the null pointer constant converted to the
// integer type.
- // FIXME: Add support for range metadata here. Currently the utilities
- // for this don't propagate range metadata in trivial cases from one
- // integer load to another, don't handle non-addrspace-0 null pointers
- // correctly, and don't have any support for mapping ranges as the
- // integer type becomes winder or narrower.
if (MDNode *N = LI.getMetadata(LLVMContext::MD_nonnull))
copyNonnullMetadata(LI, N, *NewLI);
-
- // Try to preserve nonnull metadata
+ if (MDNode *N = LI.getMetadata(LLVMContext::MD_range))
+ copyRangeMetadata(DL, LI, N, *NewLI);
V = NewLI;
// If this is an integer load past the end of the slice (which means the
@@ -3654,7 +3649,7 @@ bool SROA::presplitLoadsAndStores(Alloca
PartPtrTy, BasePtr->getName() + "."),
getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false,
LI->getName());
- PLoad->copyMetadata(*LI, LLVMContext::MD_mem_parallel_loop_access);
+ PLoad->copyMetadata(*LI, LLVMContext::MD_mem_parallel_loop_access);
// Append this load onto the list of split loads so we can find it later
// to rewrite the stores.
Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=319096&r1=319095&r2=319096&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/Local.cpp Mon Nov 27 13:25:13 2017
@@ -1947,18 +1947,24 @@ void llvm::copyNonnullMetadata(const Loa
void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI,
MDNode *N, LoadInst &NewLI) {
auto *NewTy = NewLI.getType();
+ auto *OldTy = OldLI.getType();
- // Give up unless it is converted to a pointer where there is a single very
- // valuable mapping we can do reliably.
- // FIXME: It would be nice to propagate this in more ways, but the type
- // conversions make it hard.
- if (!NewTy->isPointerTy())
+ if (DL.getTypeStoreSizeInBits(NewTy) == DL.getTypeSizeInBits(OldTy) &&
+ NewTy->isIntegerTy()) {
+ // An integer with the same number of bits - give it the range
+ // metadata!.
+ NewLI.setMetadata(LLVMContext::MD_range, N);
return;
+ }
- unsigned BitWidth = DL.getTypeSizeInBits(NewTy);
- if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
- MDNode *NN = MDNode::get(OldLI.getContext(), None);
- NewLI.setMetadata(LLVMContext::MD_nonnull, NN);
+ if (NewTy->isPointerTy()) {
+ // Try to convert the !range metadata to !nonnull metadata on the
+ // new pointer.
+ unsigned BitWidth = DL.getTypeSizeInBits(NewTy);
+ if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
+ MDNode *NN = MDNode::get(OldLI.getContext(), None);
+ NewLI.setMetadata(LLVMContext::MD_nonnull, NN);
+ }
}
}
Modified: llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp?rev=319096&r1=319095&r2=319096&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp Mon Nov 27 13:25:13 2017
@@ -17,6 +17,7 @@
#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"
@@ -48,7 +49,7 @@
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <algorithm>
-#include <cassert>
+
#include <iterator>
#include <utility>
#include <vector>
@@ -177,6 +178,16 @@ 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.
///
@@ -190,14 +201,109 @@ 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 only looks at accesses to allocas.
+ /// This code looks for stores to allocas, and for loads both for
+ /// allocas and for transferring metadata.
static bool isInterestingInstruction(const Instruction *I) {
- return (isa<LoadInst>(I) && isa<AllocaInst>(I->getOperand(0))) ||
+ return isa<LoadInst>(I) ||
(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) &&
@@ -213,9 +319,11 @@ 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?");
@@ -224,7 +332,10 @@ public:
void deleteValue(const Instruction *I) { InstNumbers.erase(I); }
- void clear() { InstNumbers.clear(); }
+ void clear() {
+ InstNumbers.clear();
+ GuaranteedExecutionIntervals.clear();
+ }
};
struct PromoteMem2Reg {
@@ -303,6 +414,7 @@ private:
SmallPtrSetImpl<BasicBlock *> &LiveInBlocks);
void RenamePass(BasicBlock *BB, BasicBlock *Pred,
RenamePassData::ValVector &IncVals,
+ LargeBlockInfo &LBI,
std::vector<RenamePassData> &Worklist);
bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx, unsigned &Version);
};
@@ -321,6 +433,32 @@ static void addAssumeNonNull(AssumptionC
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.
@@ -409,9 +547,7 @@ static bool rewriteSingleStoreAlloca(All
// 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.
- if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
- !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT))
- addAssumeNonNull(AC, LI);
+ addAssumptionsFromMetadata(LI, ReplVal, DT, DL, LBI, AC);
LI->replaceAllUsesWith(ReplVal);
LI->eraseFromParent();
@@ -505,9 +641,7 @@ static bool promoteSingleBlockAlloca(All
// 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);
- if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
- !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT))
- addAssumeNonNull(AC, LI);
+ addAssumptionsFromMetadata(LI, ReplVal, DT, DL, LBI, AC);
LI->replaceAllUsesWith(ReplVal);
}
@@ -643,7 +777,6 @@ 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
@@ -661,9 +794,10 @@ 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, RenamePassWorkList);
+ RenamePass(RPD.BB, RPD.Pred, RPD.Values, LBI, RenamePassWorkList);
} while (!RenamePassWorkList.empty());
+ LBI.clear();
// The renamer uses the Visited set to avoid infinite loops. Clear it now.
Visited.clear();
@@ -875,6 +1009,7 @@ bool PromoteMem2Reg::QueuePhiNode(BasicB
/// 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
@@ -941,13 +1076,12 @@ 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.
- if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
- !isKnownNonZero(V, SQ.DL, 0, AC, LI, &DT))
- addAssumeNonNull(AC, LI);
+ addAssumptionsFromMetadata(LI, V, DT, SQ.DL, LBI, AC);
// 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
@@ -965,6 +1099,7 @@ NextIteration:
for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[ai->second])
ConvertDebugDeclareToDebugValue(DII, SI, DIB);
BB->getInstList().erase(SI);
+ LBI.deleteValue(SI);
}
}
Modified: llvm/trunk/test/Transforms/SROA/preserve-nonnull.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SROA/preserve-nonnull.ll?rev=319096&r1=319095&r2=319096&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SROA/preserve-nonnull.ll (original)
+++ llvm/trunk/test/Transforms/SROA/preserve-nonnull.ll Mon Nov 27 13:25:13 2017
@@ -3,6 +3,8 @@
; Make sure that SROA doesn't lose nonnull metadata
; on loads from allocas that get optimized out.
+%pair = type { i64, [0 x i64], [1 x i64] }
+
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1)
; Check that we do basic propagation of nonnull when rewriting.
@@ -42,6 +44,23 @@ entry:
ret float* %ret
}
+; Make sure we propagate the !range attribute when we expand loads.
+define i64 @propagate_range(%pair* dereferenceable(16)) {
+; CHECK-LABEL: define i64 @propagate_range(
+; CHECK-NEXT: start:
+; CHECK-NEXT: %[[SROA_IDX:.*]] = getelementptr inbounds %pair
+; CHECK-NEXT: %[[RESULT:.*]] = load i64, i64* %[[SROA_IDX]], align 8, !range !1
+; CHECK: ret i64 %[[RESULT]]
+start:
+ %a = alloca %pair
+ %1 = bitcast %pair* %0 to i8*
+ %2 = bitcast %pair* %a to i8*
+ call void @llvm.memcpy.p0i8.p0i8.i64(i8* %2, i8* %1, i64 16, i32 8, i1 false)
+ %3 = getelementptr inbounds %pair, %pair* %a, i32 0, i32 0
+ %4 = load i64, i64* %3, !range !1
+ ret i64 %4
+}
+
; Make sure we properly handle the !nonnull attribute when we convert
; a pointer load to an integer load.
; FIXME: While this doesn't do anythnig actively harmful today, it really
@@ -90,3 +109,4 @@ entry:
}
!0 = !{}
+!1 = !{i64 0, i64 2}
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