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AMDGPU: Improve vector of pointer handling in amdgpu-promote-alloca #114144

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merged 2 commits into from
Nov 6, 2024
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AMDGPU: Improve vector of pointer handling in amdgpu-promote-alloca #114144

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7e356e2
AMDGPU: Improve vector of pointer handling in amdgpu-promote-alloca
arsenm Oct 29, 2024
5c33264
variadic isa
arsenm Nov 5, 2024
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73 changes: 34 additions & 39 deletions llvm/lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1115,9 +1115,10 @@ bool AMDGPUPromoteAllocaImpl::binaryOpIsDerivedFromSameAlloca(
if (Val == OtherOp)
OtherOp = Inst->getOperand(OpIdx1);

if (isa<ConstantPointerNull>(OtherOp))
if (isa<ConstantPointerNull, ConstantAggregateZero>(OtherOp))
return true;

// TODO: getUnderlyingObject will not work on a vector getelementptr
Value *OtherObj = getUnderlyingObject(OtherOp);
if (!isa<AllocaInst>(OtherObj))
return false;
Expand Down Expand Up @@ -1195,36 +1196,19 @@ bool AMDGPUPromoteAllocaImpl::collectUsesWithPtrTypes(
continue;
}

// TODO: If we know the address is only observed through flat pointers, we
// could still promote.
if (UseInst->getOpcode() == Instruction::AddrSpaceCast)
return false;

// Do not promote vector/aggregate type instructions. It is hard to track
// their users.
if (isa<InsertValueInst>(User) || isa<InsertElementInst>(User))
return false;

// TODO: Handle vectors of pointers.
if (!User->getType()->isPointerTy())
return false;

if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UseInst)) {
// Be conservative if an address could be computed outside the bounds of
// the alloca.
if (!GEP->isInBounds())
return false;
}

// Only promote a select if we know that the other select operand is from
// another pointer that will also be promoted.
if (SelectInst *SI = dyn_cast<SelectInst>(UseInst)) {
} else if (SelectInst *SI = dyn_cast<SelectInst>(UseInst)) {
// Only promote a select if we know that the other select operand is from
// another pointer that will also be promoted.
if (!binaryOpIsDerivedFromSameAlloca(BaseAlloca, Val, SI, 1, 2))
return false;
}
} else if (PHINode *Phi = dyn_cast<PHINode>(UseInst)) {
// Repeat for phis.

// Repeat for phis.
if (PHINode *Phi = dyn_cast<PHINode>(UseInst)) {
// TODO: Handle more complex cases. We should be able to replace loops
// over arrays.
switch (Phi->getNumIncomingValues()) {
Expand All @@ -1237,6 +1221,15 @@ bool AMDGPUPromoteAllocaImpl::collectUsesWithPtrTypes(
default:
return false;
}
} else if (!isa<ExtractElementInst>(User)) {
// Do not promote vector/aggregate type instructions. It is hard to track
// their users.

// Do not promote addrspacecast.
//
// TODO: If we know the address is only observed through flat pointers, we
// could still promote.
return false;
}

WorkList.push_back(User);
Expand Down Expand Up @@ -1490,17 +1483,21 @@ bool AMDGPUPromoteAllocaImpl::tryPromoteAllocaToLDS(AllocaInst &I,

SmallVector<IntrinsicInst *> DeferredIntrs;

PointerType *NewPtrTy = PointerType::get(Context, AMDGPUAS::LOCAL_ADDRESS);

for (Value *V : WorkList) {
CallInst *Call = dyn_cast<CallInst>(V);
if (!Call) {
if (ICmpInst *CI = dyn_cast<ICmpInst>(V)) {
PointerType *NewTy = PointerType::get(Context, AMDGPUAS::LOCAL_ADDRESS);
Value *LHS = CI->getOperand(0);
Value *RHS = CI->getOperand(1);

if (isa<ConstantPointerNull>(CI->getOperand(0)))
CI->setOperand(0, ConstantPointerNull::get(NewTy));
Type *NewTy = LHS->getType()->getWithNewType(NewPtrTy);
if (isa<ConstantPointerNull, ConstantAggregateZero>(LHS))
CI->setOperand(0, Constant::getNullValue(NewTy));

if (isa<ConstantPointerNull>(CI->getOperand(1)))
CI->setOperand(1, ConstantPointerNull::get(NewTy));
if (isa<ConstantPointerNull, ConstantAggregateZero>(RHS))
CI->setOperand(1, Constant::getNullValue(NewTy));

continue;
}
Expand All @@ -1510,25 +1507,23 @@ bool AMDGPUPromoteAllocaImpl::tryPromoteAllocaToLDS(AllocaInst &I,
if (isa<AddrSpaceCastInst>(V))
continue;

PointerType *NewTy = PointerType::get(Context, AMDGPUAS::LOCAL_ADDRESS);

assert(isa<PointerType>(V->getType()));
assert(V->getType()->isPtrOrPtrVectorTy());

// FIXME: It doesn't really make sense to try to do this for all
// instructions.
Type *NewTy = V->getType()->getWithNewType(NewPtrTy);
V->mutateType(NewTy);

// Adjust the types of any constant operands.
if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
if (isa<ConstantPointerNull>(SI->getOperand(1)))
SI->setOperand(1, ConstantPointerNull::get(NewTy));
if (isa<ConstantPointerNull, ConstantAggregateZero>(SI->getOperand(1)))
SI->setOperand(1, Constant::getNullValue(NewTy));

if (isa<ConstantPointerNull>(SI->getOperand(2)))
SI->setOperand(2, ConstantPointerNull::get(NewTy));
if (isa<ConstantPointerNull, ConstantAggregateZero>(SI->getOperand(2)))
SI->setOperand(2, Constant::getNullValue(NewTy));
} else if (PHINode *Phi = dyn_cast<PHINode>(V)) {
for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
if (isa<ConstantPointerNull>(Phi->getIncomingValue(I)))
Phi->setIncomingValue(I, ConstantPointerNull::get(NewTy));
if (isa<ConstantPointerNull, ConstantAggregateZero>(
Phi->getIncomingValue(I)))
Phi->setIncomingValue(I, Constant::getNullValue(NewTy));
}
}

Expand Down
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