[WIP][IR][Constants] Change the semantic of ConstantPointerNull to represent an actual nullptr instead of a zero-value pointer
#166667
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,5 @@ | ||
| // RUN: %clang_cc1 %s -O0 -triple amdgcn -emit-llvm -o - | FileCheck %s | ||
| // RUN: %clang_cc1 %s -O0 -triple amdgcn---opencl -emit-llvm -o - | FileCheck %s | ||
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| // CHECK: target datalayout = "e-m:e-p:64:64-p1:64:64-po2:32:32-po3:32:32-p4:64:64-po5:32:32-p6:32:32-p7:160:256:256:32-p8:128:128:128:48-p9:192:256:256:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5-G1-ni:7:8:9" | ||
| void foo(void) {} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -3768,9 +3768,18 @@ bool IRTranslator::translate(const Constant &C, Register Reg) { | |
| EntryBuilder->buildFConstant(Reg, *CF); | ||
| } else if (isa<UndefValue>(C)) | ||
| EntryBuilder->buildUndef(Reg); | ||
| else if (auto *NullPtr = dyn_cast<ConstantPointerNull>(&C)) { | ||
| const DataLayout &DL = EntryBuilder->getMF().getDataLayout(); | ||
| if (std::optional<APInt> NullPtrValue = | ||
| DL.getNullPtrValue(NullPtr->getType()->getAddressSpace())) { | ||
| if (NullPtrValue->isZero()) | ||
| EntryBuilder->buildConstant(Reg, 0); | ||
| else if (NullPtrValue->isAllOnes()) | ||
| EntryBuilder->buildConstant(Reg, -1); | ||
| else | ||
| llvm_unreachable("unknown null pointer value"); | ||
| } | ||
| } else if (auto GV = dyn_cast<GlobalValue>(&C)) | ||
| EntryBuilder->buildGlobalValue(Reg, GV); | ||
| else if (auto CPA = dyn_cast<ConstantPtrAuth>(&C)) { | ||
| Register Addr = getOrCreateVReg(*CPA->getPointer()); | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -1872,8 +1872,18 @@ SDValue SelectionDAGBuilder::getValueImpl(const Value *V) { | |
| getValue(CPA->getDiscriminator())); | ||
| } | ||
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| if (auto *NullPtr = dyn_cast<ConstantPointerNull>(C)) { | ||
| const DataLayout &DL = DAG.getDataLayout(); | ||
| if (std::optional<APInt> NullPtrValue = | ||
| DL.getNullPtrValue(NullPtr->getType()->getAddressSpace())) { | ||
| if (NullPtrValue->isZero()) | ||
| return DAG.getConstant(0, getCurSDLoc(), VT); | ||
| else if (NullPtrValue->isAllOnes()) | ||
| return DAG.getAllOnesConstant(getCurSDLoc(), VT); | ||
| else | ||
| llvm_unreachable("unknown null pointer value"); | ||
| } | ||
| } | ||
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| if (match(C, m_VScale())) | ||
| return DAG.getVScale(getCurSDLoc(), VT, APInt(VT.getSizeInBits(), 1)); | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -1806,6 +1806,15 @@ static void writeConstantInternal(raw_ostream &Out, const Constant *CV, | |
| } | ||
| } | ||
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| // Use zeroinitializer for inttoptr(0) constant expression. | ||
| if (CE->getOpcode() == Instruction::IntToPtr) { | ||
| Constant *SrcCI = cast<Constant>(CE->getOperand(0)); | ||
| if (SrcCI->isZeroValue()) { | ||
| Out << "zeroinitializer"; | ||
| return; | ||
| } | ||
| } | ||
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| Out << CE->getOpcodeName(); | ||
| writeOptimizationInfo(Out, CE); | ||
| Out << " ("; | ||
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| Original file line number | Diff line number | Diff line change | ||||||||||||||
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@@ -126,6 +126,40 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, | |||||||||||||||
| if (isa<PoisonValue>(V)) | ||||||||||||||||
| return PoisonValue::get(DestTy); | ||||||||||||||||
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| if (opc == Instruction::IntToPtr) { | ||||||||||||||||
| // We can't fold inttoptr(0) to ConstantPointerNull without checking the | ||||||||||||||||
| // target data layout. However, since data layout is not available here, we | ||||||||||||||||
| // can't do this. | ||||||||||||||||
| if (V->isZeroValue()) | ||||||||||||||||
| return nullptr; | ||||||||||||||||
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Member
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Suggested change
I don't think we need the early return here? Although I guess it's a cheap check and so might actually be better to have it.
Member
There was a problem hiding this comment. Ah is this because of the |
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| // If the input is a ptrtoint(0), we can fold it to the corresponding zero | ||||||||||||||||
| // value pointer. | ||||||||||||||||
| if (auto *CE = dyn_cast<ConstantExpr>(V)) { | ||||||||||||||||
| if (CE->getOpcode() == Instruction::PtrToInt) { | ||||||||||||||||
| if (CE->getOperand(0)->isZeroValue()) | ||||||||||||||||
| return Constant::getZeroValue(DestTy); | ||||||||||||||||
| } | ||||||||||||||||
| } | ||||||||||||||||
| } | ||||||||||||||||
| if (opc == Instruction::PtrToInt) { | ||||||||||||||||
| // Similarly, we can't fold ptrtoint(nullptr) to null. | ||||||||||||||||
| if (V->isNullValue()) | ||||||||||||||||
| return nullptr; | ||||||||||||||||
| // If the input is a inttoptr(0), we can fold it to the corresponding | ||||||||||||||||
| // zero value. | ||||||||||||||||
| if (auto *CE = dyn_cast<ConstantExpr>(V)) { | ||||||||||||||||
| if (CE->getOpcode() == Instruction::IntToPtr) { | ||||||||||||||||
| if (CE->getOperand(0)->isZeroValue()) | ||||||||||||||||
| return Constant::getZeroValue(DestTy); | ||||||||||||||||
| } | ||||||||||||||||
| } | ||||||||||||||||
| } | ||||||||||||||||
| // However, since the recent change of the semantic of `ptr addrspace(N) | ||||||||||||||||
| // null`, we can fold address space cast of a nullptr to the corresponding | ||||||||||||||||
| // nullptr in the destination address space. | ||||||||||||||||
| if (opc == Instruction::AddrSpaceCast && V->isNullValue()) | ||||||||||||||||
| return Constant::getNullValue(DestTy); | ||||||||||||||||
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| if (isa<UndefValue>(V)) { | ||||||||||||||||
| // zext(undef) = 0, because the top bits will be zero. | ||||||||||||||||
| // sext(undef) = 0, because the top bits will all be the same. | ||||||||||||||||
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I believe this is equivalent and a bit simpler.