//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "arm-atomic-expand"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+
using namespace llvm;
+#define DEBUG_TYPE "arm-atomic-expand"
+
namespace {
class AtomicExpandLoadLinked : public FunctionPass {
- const TargetLowering *TLI;
+ const TargetMachine *TM;
public:
static char ID; // Pass identification, replacement for typeid
- explicit AtomicExpandLoadLinked(const TargetMachine *TM = 0)
- : FunctionPass(ID), TLI(TM ? TM->getTargetLowering() : 0) {
+ explicit AtomicExpandLoadLinked(const TargetMachine *TM = nullptr)
+ : FunctionPass(ID), TM(TM) {
initializeAtomicExpandLoadLinkedPass(*PassRegistry::getPassRegistry());
}
char AtomicExpandLoadLinked::ID = 0;
char &llvm::AtomicExpandLoadLinkedID = AtomicExpandLoadLinked::ID;
-
-static void *initializeAtomicExpandLoadLinkedPassOnce(PassRegistry &Registry) {
- PassInfo *PI = new PassInfo(
- "Expand Atomic calls in terms of load-linked & store-conditional",
- "atomic-ll-sc", &AtomicExpandLoadLinked::ID,
- PassInfo::NormalCtor_t(callDefaultCtor<AtomicExpandLoadLinked>), false,
- false, PassInfo::TargetMachineCtor_t(
- callTargetMachineCtor<AtomicExpandLoadLinked>));
- Registry.registerPass(*PI, true);
- return PI;
-}
-
-void llvm::initializeAtomicExpandLoadLinkedPass(PassRegistry &Registry) {
- CALL_ONCE_INITIALIZATION(initializeAtomicExpandLoadLinkedPassOnce)
-}
-
+INITIALIZE_TM_PASS(AtomicExpandLoadLinked, "atomic-ll-sc",
+ "Expand Atomic calls in terms of load-linked & store-conditional",
+ false, false)
FunctionPass *llvm::createAtomicExpandLoadLinkedPass(const TargetMachine *TM) {
return new AtomicExpandLoadLinked(TM);
}
bool AtomicExpandLoadLinked::runOnFunction(Function &F) {
- if (!TLI)
+ if (!TM || !TM->getSubtargetImpl()->enableAtomicExpandLoadLinked())
return false;
SmallVector<Instruction *, 1> AtomicInsts;
bool MadeChange = false;
for (Instruction *Inst : AtomicInsts) {
- if (!TLI->shouldExpandAtomicInIR(Inst))
+ if (!TM->getSubtargetImpl()->getTargetLowering()->shouldExpandAtomicInIR(
+ Inst))
continue;
if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(Inst))
// Load instructions don't actually need a leading fence, even in the
// SequentiallyConsistent case.
AtomicOrdering MemOpOrder =
- TLI->getInsertFencesForAtomic() ? Monotonic : LI->getOrdering();
+ TM->getSubtargetImpl()->getTargetLowering()->getInsertFencesForAtomic()
+ ? Monotonic
+ : LI->getOrdering();
- // The only 64-bit load guaranteed to be single-copy atomic by the ARM ARM is
+ // The only 64-bit load guaranteed to be single-copy atomic by the ARM is
// an ldrexd (A3.5.3).
IRBuilder<> Builder(LI);
- Value *Val =
- TLI->emitLoadLinked(Builder, LI->getPointerOperand(), MemOpOrder);
+ Value *Val = TM->getSubtargetImpl()->getTargetLowering()->emitLoadLinked(
+ Builder, LI->getPointerOperand(), MemOpOrder);
insertTrailingFence(Builder, LI->getOrdering());
// Start the main loop block now that we've taken care of the preliminaries.
Builder.SetInsertPoint(LoopBB);
- Value *Loaded = TLI->emitLoadLinked(Builder, Addr, MemOpOrder);
+ Value *Loaded = TM->getSubtargetImpl()->getTargetLowering()->emitLoadLinked(
+ Builder, Addr, MemOpOrder);
Value *NewVal;
switch (AI->getOperation()) {
NewVal = Builder.CreateAnd(Loaded, AI->getValOperand(), "new");
break;
case AtomicRMWInst::Nand:
- NewVal = Builder.CreateAnd(Loaded, Builder.CreateNot(AI->getValOperand()),
+ NewVal = Builder.CreateNot(Builder.CreateAnd(Loaded, AI->getValOperand()),
"new");
break;
case AtomicRMWInst::Or:
}
Value *StoreSuccess =
- TLI->emitStoreConditional(Builder, NewVal, Addr, MemOpOrder);
+ TM->getSubtargetImpl()->getTargetLowering()->emitStoreConditional(
+ Builder, NewVal, Addr, MemOpOrder);
Value *TryAgain = Builder.CreateICmpNE(
StoreSuccess, ConstantInt::get(IntegerType::get(Ctx, 32), 0), "tryagain");
Builder.CreateCondBr(TryAgain, LoopBB, ExitBB);
// %loaded = @load.linked(%addr)
// %should_store = icmp eq %loaded, %desired
// br i1 %should_store, label %cmpxchg.trystore,
- // label %cmpxchg.end/%cmpxchg.barrier
+ // label %cmpxchg.failure
// cmpxchg.trystore:
// %stored = @store_conditional(%new, %addr)
- // %try_again = icmp i32 ne %stored, 0
- // br i1 %try_again, label %loop, label %cmpxchg.end
- // cmpxchg.barrier:
+ // %success = icmp eq i32 %stored, 0
+ // br i1 %success, label %cmpxchg.success, label %loop/%cmpxchg.failure
+ // cmpxchg.success:
+ // fence?
+ // br label %cmpxchg.end
+ // cmpxchg.failure:
// fence?
// br label %cmpxchg.end
// cmpxchg.end:
+ // %success = phi i1 [true, %cmpxchg.success], [false, %cmpxchg.failure]
+ // %restmp = insertvalue { iN, i1 } undef, iN %loaded, 0
+ // %res = insertvalue { iN, i1 } %restmp, i1 %success, 1
// [...]
BasicBlock *ExitBB = BB->splitBasicBlock(CI, "cmpxchg.end");
- auto BarrierBB = BasicBlock::Create(Ctx, "cmpxchg.barrier", F, ExitBB);
- auto TryStoreBB = BasicBlock::Create(Ctx, "cmpxchg.trystore", F, BarrierBB);
+ auto FailureBB = BasicBlock::Create(Ctx, "cmpxchg.failure", F, ExitBB);
+ auto SuccessBB = BasicBlock::Create(Ctx, "cmpxchg.success", F, FailureBB);
+ auto TryStoreBB = BasicBlock::Create(Ctx, "cmpxchg.trystore", F, SuccessBB);
auto LoopBB = BasicBlock::Create(Ctx, "cmpxchg.start", F, TryStoreBB);
// This grabs the DebugLoc from CI
// Start the main loop block now that we've taken care of the preliminaries.
Builder.SetInsertPoint(LoopBB);
- Value *Loaded = TLI->emitLoadLinked(Builder, Addr, MemOpOrder);
+ Value *Loaded = TM->getSubtargetImpl()->getTargetLowering()->emitLoadLinked(
+ Builder, Addr, MemOpOrder);
Value *ShouldStore =
Builder.CreateICmpEQ(Loaded, CI->getCompareOperand(), "should_store");
// If the the cmpxchg doesn't actually need any ordering when it fails, we can
// jump straight past that fence instruction (if it exists).
- BasicBlock *FailureBB = FailureOrder == Monotonic ? ExitBB : BarrierBB;
Builder.CreateCondBr(ShouldStore, TryStoreBB, FailureBB);
Builder.SetInsertPoint(TryStoreBB);
- Value *StoreSuccess = TLI->emitStoreConditional(
- Builder, CI->getNewValOperand(), Addr, MemOpOrder);
- Value *TryAgain = Builder.CreateICmpNE(
+ Value *StoreSuccess =
+ TM->getSubtargetImpl()->getTargetLowering()->emitStoreConditional(
+ Builder, CI->getNewValOperand(), Addr, MemOpOrder);
+ StoreSuccess = Builder.CreateICmpEQ(
StoreSuccess, ConstantInt::get(Type::getInt32Ty(Ctx), 0), "success");
- Builder.CreateCondBr(TryAgain, LoopBB, BarrierBB);
+ Builder.CreateCondBr(StoreSuccess, SuccessBB,
+ CI->isWeak() ? FailureBB : LoopBB);
- // Finally, make sure later instructions don't get reordered with a fence if
- // necessary.
- Builder.SetInsertPoint(BarrierBB);
+ // Make sure later instructions don't get reordered with a fence if necessary.
+ Builder.SetInsertPoint(SuccessBB);
insertTrailingFence(Builder, SuccessOrder);
Builder.CreateBr(ExitBB);
- CI->replaceAllUsesWith(Loaded);
- CI->eraseFromParent();
+ Builder.SetInsertPoint(FailureBB);
+ insertTrailingFence(Builder, FailureOrder);
+ Builder.CreateBr(ExitBB);
+
+ // Finally, we have control-flow based knowledge of whether the cmpxchg
+ // succeeded or not. We expose this to later passes by converting any
+ // subsequent "icmp eq/ne %loaded, %oldval" into a use of an appropriate PHI.
+
+ // Setup the builder so we can create any PHIs we need.
+ Builder.SetInsertPoint(ExitBB, ExitBB->begin());
+ PHINode *Success = Builder.CreatePHI(Type::getInt1Ty(Ctx), 2);
+ Success->addIncoming(ConstantInt::getTrue(Ctx), SuccessBB);
+ Success->addIncoming(ConstantInt::getFalse(Ctx), FailureBB);
+
+ // Look for any users of the cmpxchg that are just comparing the loaded value
+ // against the desired one, and replace them with the CFG-derived version.
+ SmallVector<ExtractValueInst *, 2> PrunedInsts;
+ for (auto User : CI->users()) {
+ ExtractValueInst *EV = dyn_cast<ExtractValueInst>(User);
+ if (!EV)
+ continue;
+
+ assert(EV->getNumIndices() == 1 && EV->getIndices()[0] <= 1 &&
+ "weird extraction from { iN, i1 }");
+
+ if (EV->getIndices()[0] == 0)
+ EV->replaceAllUsesWith(Loaded);
+ else
+ EV->replaceAllUsesWith(Success);
+ PrunedInsts.push_back(EV);
+ }
+
+ // We can remove the instructions now we're no longer iterating through them.
+ for (auto EV : PrunedInsts)
+ EV->eraseFromParent();
+
+ if (!CI->use_empty()) {
+ // Some use of the full struct return that we don't understand has happened,
+ // so we've got to reconstruct it properly.
+ Value *Res;
+ Res = Builder.CreateInsertValue(UndefValue::get(CI->getType()), Loaded, 0);
+ Res = Builder.CreateInsertValue(Res, Success, 1);
+
+ CI->replaceAllUsesWith(Res);
+ }
+
+ CI->eraseFromParent();
return true;
}
AtomicOrdering AtomicExpandLoadLinked::insertLeadingFence(IRBuilder<> &Builder,
AtomicOrdering Ord) {
- if (!TLI->getInsertFencesForAtomic())
+ if (!TM->getSubtargetImpl()->getTargetLowering()->getInsertFencesForAtomic())
return Ord;
if (Ord == Release || Ord == AcquireRelease || Ord == SequentiallyConsistent)
void AtomicExpandLoadLinked::insertTrailingFence(IRBuilder<> &Builder,
AtomicOrdering Ord) {
- if (!TLI->getInsertFencesForAtomic())
+ if (!TM->getSubtargetImpl()->getTargetLowering()->getInsertFencesForAtomic())
return;
if (Ord == Acquire || Ord == AcquireRelease)
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