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https://github.com/c64scene-ar/llvm-6502.git
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Fix Transforms/ScalarRepl/2007-05-29-MemcpyPreserve.ll and the second
half of PR1421, by not decimating structs with holes that are the source and destination of a memcpy. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37358 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
parent
661c2ce9c5
commit
39a1c04323
@ -65,11 +65,41 @@ namespace {
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}
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private:
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int isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI);
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int isSafeUseOfAllocation(Instruction *User, AllocationInst *AI);
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bool isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI);
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bool isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI);
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/// AllocaInfo - When analyzing uses of an alloca instruction, this captures
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/// information about the uses. All these fields are initialized to false
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/// and set to true when something is learned.
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struct AllocaInfo {
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/// isUnsafe - This is set to true if the alloca cannot be SROA'd.
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bool isUnsafe : 1;
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/// needsCanon - This is set to true if there is some use of the alloca
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/// that requires canonicalization.
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bool needsCanon : 1;
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/// isMemCpySrc - This is true if this aggregate is memcpy'd from.
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bool isMemCpySrc : 1;
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/// isMemCpyDst - This is true if this aggregate is memcpy'd info.
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bool isMemCpyDst : 1;
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AllocaInfo()
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: isUnsafe(false), needsCanon(false),
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isMemCpySrc(false), isMemCpyDst(false) {}
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};
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void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
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int isSafeAllocaToScalarRepl(AllocationInst *AI);
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void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
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AllocaInfo &Info);
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void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
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AllocaInfo &Info);
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void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
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unsigned OpNo, AllocaInfo &Info);
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void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
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AllocaInfo &Info);
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void DoScalarReplacement(AllocationInst *AI,
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std::vector<AllocationInst*> &WorkList);
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void CanonicalizeAllocaUsers(AllocationInst *AI);
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@ -320,7 +350,8 @@ void SROA::DoScalarReplacement(AllocationInst *AI,
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/// getelementptr instruction of an array aggregate allocation. isFirstElt
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/// indicates whether Ptr is known to the start of the aggregate.
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///
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int SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI) {
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void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
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AllocaInfo &Info) {
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for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
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I != E; ++I) {
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Instruction *User = cast<Instruction>(*I);
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@ -328,7 +359,7 @@ int SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI) {
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case Instruction::Load: break;
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case Instruction::Store:
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// Store is ok if storing INTO the pointer, not storing the pointer
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if (User->getOperand(0) == Ptr) return 0;
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if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
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break;
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case Instruction::GetElementPtr: {
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GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
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@ -336,7 +367,8 @@ int SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI) {
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if (GEP->getNumOperands() > 1) {
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if (!isa<ConstantInt>(GEP->getOperand(1)) ||
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!cast<ConstantInt>(GEP->getOperand(1))->isZero())
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return 0; // Using pointer arithmetic to navigate the array.
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// Using pointer arithmetic to navigate the array.
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return MarkUnsafe(Info);
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if (AreAllZeroIndices) {
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for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i) {
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@ -348,28 +380,34 @@ int SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI) {
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}
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}
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}
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if (!isSafeElementUse(GEP, AreAllZeroIndices, AI)) return 0;
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isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
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if (Info.isUnsafe) return;
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break;
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}
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case Instruction::BitCast:
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if (isFirstElt &&
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isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI))
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if (isFirstElt) {
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isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
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if (Info.isUnsafe) return;
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break;
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DOUT << " Transformation preventing inst: " << *User;
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return 0;
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case Instruction::Call:
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if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
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if (isFirstElt && isSafeMemIntrinsicOnAllocation(MI, AI))
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break;
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}
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DOUT << " Transformation preventing inst: " << *User;
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return 0;
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return MarkUnsafe(Info);
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case Instruction::Call:
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if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
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if (isFirstElt) {
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isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
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if (Info.isUnsafe) return;
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break;
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}
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}
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DOUT << " Transformation preventing inst: " << *User;
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return MarkUnsafe(Info);
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default:
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DOUT << " Transformation preventing inst: " << *User;
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return 0;
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return MarkUnsafe(Info);
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}
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}
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return 3; // All users look ok :)
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return; // All users look ok :)
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}
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/// AllUsersAreLoads - Return true if all users of this value are loads.
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@ -384,21 +422,25 @@ static bool AllUsersAreLoads(Value *Ptr) {
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/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
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/// aggregate allocation.
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///
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int SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI) {
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void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
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AllocaInfo &Info) {
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if (BitCastInst *C = dyn_cast<BitCastInst>(User))
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return isSafeUseOfBitCastedAllocation(C, AI) ? 3 : 0;
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if (!isa<GetElementPtrInst>(User)) return 0;
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return isSafeUseOfBitCastedAllocation(C, AI, Info);
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GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
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if (GEPI == 0)
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return MarkUnsafe(Info);
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GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
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gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
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// The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
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if (I == E ||
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I.getOperand() != Constant::getNullValue(I.getOperand()->getType()))
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return 0;
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I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
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return MarkUnsafe(Info);
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}
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++I;
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if (I == E) return 0; // ran out of GEP indices??
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if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
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bool IsAllZeroIndices = true;
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@ -413,7 +455,7 @@ int SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI) {
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// something funny is going on, so we won't do the optimization.
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//
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if (Idx->getZExtValue() >= NumElements)
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return 0;
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return MarkUnsafe(Info);
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// We cannot scalar repl this level of the array unless any array
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// sub-indices are in-range constants. In particular, consider:
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@ -430,9 +472,9 @@ int SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI) {
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NumElements = cast<VectorType>(*I)->getNumElements();
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ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
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if (!IdxVal) return 0;
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if (!IdxVal) return MarkUnsafe(Info);
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if (IdxVal->getZExtValue() >= NumElements)
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return 0;
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return MarkUnsafe(Info);
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IsAllZeroIndices &= IdxVal->isZero();
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}
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@ -444,53 +486,62 @@ int SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI) {
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// it, in which case we CAN promote it, but we have to canonicalize this
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// out if this is the only problem.
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if ((NumElements == 1 || NumElements == 2) &&
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AllUsersAreLoads(GEPI))
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return 1; // Canonicalization required!
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return 0;
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AllUsersAreLoads(GEPI)) {
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Info.needsCanon = true;
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return; // Canonicalization required!
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}
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return MarkUnsafe(Info);
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}
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}
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// If there are any non-simple uses of this getelementptr, make sure to reject
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// them.
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return isSafeElementUse(GEPI, IsAllZeroIndices, AI);
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return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
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}
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/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
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/// intrinsic can be promoted by SROA. At this point, we know that the operand
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/// of the memintrinsic is a pointer to the beginning of the allocation.
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bool SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI){
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void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
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unsigned OpNo, AllocaInfo &Info) {
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// If not constant length, give up.
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ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
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if (!Length) return false;
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if (!Length) return MarkUnsafe(Info);
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// If not the whole aggregate, give up.
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const TargetData &TD = getAnalysis<TargetData>();
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if (Length->getZExtValue() != TD.getTypeSize(AI->getType()->getElementType()))
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return false;
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return MarkUnsafe(Info);
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// We only know about memcpy/memset/memmove.
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if (!isa<MemCpyInst>(MI) && !isa<MemSetInst>(MI) && !isa<MemMoveInst>(MI))
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return false;
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// Otherwise, we can transform it.
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return true;
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return MarkUnsafe(Info);
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// Otherwise, we can transform it. Determine whether this is a memcpy/set
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// into or out of the aggregate.
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if (OpNo == 1)
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Info.isMemCpyDst = true;
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else {
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assert(OpNo == 2);
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Info.isMemCpySrc = true;
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}
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}
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/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
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/// are
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bool SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI) {
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void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
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AllocaInfo &Info) {
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for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
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UI != E; ++UI) {
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if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
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if (!isSafeUseOfBitCastedAllocation(BCU, AI))
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return false;
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isSafeUseOfBitCastedAllocation(BCU, AI, Info);
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} else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
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if (!isSafeMemIntrinsicOnAllocation(MI, AI))
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return false;
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isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
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} else {
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return false;
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return MarkUnsafe(Info);
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}
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if (Info.isUnsafe) return;
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}
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return true;
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}
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/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
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@ -668,6 +719,44 @@ void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
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}
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}
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/// HasStructPadding - Return true if the specified type has any structure
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/// padding, false otherwise.
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static bool HasStructPadding(const Type *Ty, const TargetData &TD) {
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if (const StructType *STy = dyn_cast<StructType>(Ty)) {
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const StructLayout *SL = TD.getStructLayout(STy);
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unsigned PrevFieldBitOffset = 0;
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for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
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unsigned FieldBitOffset = SL->getElementOffset(i)*8;
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// Padding in sub-elements?
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if (HasStructPadding(STy->getElementType(i), TD))
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return true;
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// Check to see if there is any padding between this element and the
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// previous one.
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if (i) {
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unsigned PrevFieldEnd =
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PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
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if (PrevFieldEnd < FieldBitOffset)
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return true;
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}
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PrevFieldBitOffset = FieldBitOffset;
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}
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// Check for tail padding.
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if (unsigned EltCount = STy->getNumElements()) {
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unsigned PrevFieldEnd = PrevFieldBitOffset +
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TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
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if (PrevFieldEnd < SL->getSizeInBytes()*8)
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return true;
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}
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} else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
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return HasStructPadding(ATy->getElementType(), TD);
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}
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return false;
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}
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/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
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/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
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@ -676,18 +765,29 @@ void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
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int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
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// Loop over the use list of the alloca. We can only transform it if all of
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// the users are safe to transform.
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//
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int isSafe = 3;
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AllocaInfo Info;
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for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
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I != E; ++I) {
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isSafe &= isSafeUseOfAllocation(cast<Instruction>(*I), AI);
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if (isSafe == 0) {
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isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
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if (Info.isUnsafe) {
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DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
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return 0;
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}
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}
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// If we require cleanup, isSafe is now 1, otherwise it is 3.
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return isSafe;
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// Okay, we know all the users are promotable. If the aggregate is a memcpy
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// source and destination, we have to be careful. In particular, the memcpy
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// could be moving around elements that live in structure padding of the LLVM
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// types, but may actually be used. In these cases, we refuse to promote the
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// struct.
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if (Info.isMemCpySrc && Info.isMemCpyDst &&
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HasStructPadding(AI->getType()->getElementType(),
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getAnalysis<TargetData>()))
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return 0;
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// If we require cleanup, return 1, otherwise return 3.
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return Info.needsCanon ? 1 : 3;
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}
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/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified
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