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Support persistent MPI #2535

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8 changes: 5 additions & 3 deletions enzyme/Enzyme/ActivityAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -621,12 +621,14 @@ bool ActivityAnalyzer::isFunctionArgumentConstant(CallInst *CI, Value *val) {
return val != CI->getOperand(0);
}
// only the recv buffer and request is active for mpi isend/irecv
if (Name == "MPI_Irecv" || Name == "MPI_Isend" || Name == "PMPI_Irecv" ||
Name == "PMPI_Isend") {
if (Name == "MPI_Irecv" || Name == "MPI_Isend" || Name == "MPI_Send_init" || Name == "MPI_Recv_init" ||
Name == "PMPI_Irecv" || Name == "PMPI_Isend" || Name == "PMPI_Send_init" || Name == "PMPI_Recv_init") {
return val != CI->getOperand(0) && val != CI->getOperand(6);
}

// only request is active
if (Name == "MPI_Start" || Name == "PMPI_Start")
return val != CI->getOperand(0);

if (Name == "MPI_Wait" || Name == "PMPI_Wait")
return val != CI->getOperand(0);

Expand Down
40 changes: 34 additions & 6 deletions enzyme/Enzyme/CallDerivatives.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,8 +44,8 @@ void AdjointGenerator::handleMPI(llvm::CallInst &call, llvm::Function *called,
BuilderZ.setFastMathFlags(getFast());

// MPI send / recv can only send float/integers
if (funcName == "PMPI_Isend" || funcName == "MPI_Isend" ||
funcName == "PMPI_Irecv" || funcName == "MPI_Irecv") {
if (funcName == "PMPI_Isend" || funcName == "MPI_Isend" || funcName == "PMPI_Send_init" || funcName == "MPI_Send_init" ||
funcName == "PMPI_Irecv" || funcName == "MPI_Irecv" || funcName == "PMPI_Recv_init" || funcName == "MPI_Recv_init") {
if (!gutils->isConstantInstruction(&call)) {
if (Mode == DerivativeMode::ReverseModePrimal ||
Mode == DerivativeMode::ReverseModeCombined) {
Expand Down Expand Up @@ -73,7 +73,8 @@ void AdjointGenerator::handleMPI(llvm::CallInst &call, llvm::Function *called,
getMPIMemberPtr<MPI_Elem::Old>(BuilderZ, impialloc, impi));
BuilderZ.CreateStore(impialloc, d_req);

if (funcName == "MPI_Isend" || funcName == "PMPI_Isend") {
if (funcName == "MPI_Isend" || funcName == "PMPI_Isend" ||
funcName == "MPI_Send_init" || funcName == "PMPI_Send_init") {
Value *tysize =
MPI_TYPE_SIZE(gutils->getNewFromOriginal(call.getOperand(2)),
BuilderZ, call.getType(), called);
Expand Down Expand Up @@ -134,12 +135,22 @@ void AdjointGenerator::handleMPI(llvm::CallInst &call, llvm::Function *called,
BuilderZ.CreatePointerCast(comm, getInt8PtrTy(call.getContext())),
getMPIMemberPtr<MPI_Elem::Comm>(BuilderZ, impialloc, impi));

MPI_CallType callType;
if (funcName == "MPI_Isend" || funcName == "PMPI_Isend")
callType = MPI_CallType::ISEND;
else if (funcName == "MPI_Irecv" || funcName == "PMPI_Irecv")
callType = MPI_CallType::IRECV;
else if (funcName == "MPI_Send_init" || funcName == "PMPI_Send_init")
callType = MPI_CallType::SEND_INIT;
else if (funcName == "MPI_Recv_init" || funcName == "PMPI_Recv_init")
callType = MPI_CallType::RECV_INIT;
else
assert(0 && "illegal mpi");

BuilderZ.CreateStore(
ConstantInt::get(
Type::getInt8Ty(impialloc->getContext()),
(funcName == "MPI_Isend" || funcName == "PMPI_Isend")
? (int)MPI_CallType::ISEND
: (int)MPI_CallType::IRECV),
(int)callType),
getMPIMemberPtr<MPI_Elem::Call>(BuilderZ, impialloc, impi));
// TODO old
}
Expand Down Expand Up @@ -2178,6 +2189,23 @@ void AdjointGenerator::handleMPI(llvm::CallInst &call, llvm::Function *called,
return;
}

// Adjoint of MPI_Send is to place a MPI_send at the corresponding
// location in the reverse.
if (func == "MPI_Send" || func == "PMPI_Send") {
if (Mode == DerivativeMode::ReverseModeGradient ||
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@wsmoses wsmoses Nov 6, 2025

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did we miss this from earlier??

if so we should add a test

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@vchuravy vchuravy Nov 6, 2025

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Sorry this was a brain fart on my side this ought to be MPI_Start not MPI_Send

Mode == DerivativeMode::ReverseModeCombined) {
IRBuilder<> Builder2(&call);
getReverseBuilder(Builder2);
auto callval = call.getCalledOperand();
Value *args[] = {
lookup(gutils->getNewFromOriginal(call.getOperand(0)), Builder2)};
Builder2.CreateCall(call.getFunctionType(), callval, args);
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@wsmoses wsmoses Nov 6, 2025

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doesn't cover fwd mode, so we shouldn't return in that case

}
if (Mode == DerivativeMode::ReverseModeGradient)
eraseIfUnused(call, /*erase*/ true, /*check*/ false);
return;
}

// Remove free's in forward pass so the comm can be used in the reverse
// pass
if (funcName == "MPI_Comm_free" || funcName == "MPI_Comm_disconnect") {
Expand Down
8 changes: 6 additions & 2 deletions enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4952,8 +4952,8 @@ void TypeAnalyzer::visitCallBase(CallBase &call) {
updateAnalysis(&call, TypeTree(BaseType::Integer).Only(-1, &call), &call);
return;
}
if (funcName == "MPI_Isend" || funcName == "MPI_Irecv" ||
funcName == "PMPI_Isend" || funcName == "PMPI_Irecv") {
if (funcName == "MPI_Isend" || funcName == "MPI_Irecv" || funcName == "MPI_Send_init" || funcName == "MPI_Recv_init" ||
funcName == "PMPI_Isend" || funcName == "PMPI_Irecv" || funcName == "PMPI_Send_init" || funcName == "PMPI_Recv_init") {
TypeTree buf = TypeTree(BaseType::Pointer);

if (Constant *C = dyn_cast<Constant>(call.getOperand(2))) {
Expand Down Expand Up @@ -4989,6 +4989,10 @@ void TypeAnalyzer::visitCallBase(CallBase &call) {
TypeTree(BaseType::Pointer).Only(-1, &call), &call);
return;
}
if (funcName == "MPI_Start" || funcName == "PMPI_Start") {
// TODO
return;
}
if (funcName == "MPI_Wait") {
updateAnalysis(call.getOperand(0),
TypeTree(BaseType::Pointer).Only(-1, &call), &call);
Expand Down
39 changes: 36 additions & 3 deletions enzyme/Enzyme/Utils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1771,6 +1771,9 @@ llvm::Function *getOrInsertDifferentialMPI_Wait(llvm::Module &M,
BasicBlock *entry = BasicBlock::Create(M.getContext(), "entry", F);
BasicBlock *isend = BasicBlock::Create(M.getContext(), "invertISend", F);
BasicBlock *irecv = BasicBlock::Create(M.getContext(), "invertIRecv", F);
BasicBlock *send_init = BasicBlock::Create(M.getContext(), "invertSendInit", F);
BasicBlock *recv_init = BasicBlock::Create(M.getContext(), "invertRecvInit", F);
BasicBlock *error = BasicBlock::Create(M.getContext(), "invertError", F);

#if 0
/*0 */getInt8PtrTy(call.getContext())
Expand Down Expand Up @@ -1831,10 +1834,25 @@ llvm::Function *getOrInsertDifferentialMPI_Wait(llvm::Module &M,
buf, count, datatype, source, tag, comm, d_req,
};

B.CreateCondBr(B.CreateICmpEQ(fn, ConstantInt::get(fn->getType(),
(int)MPI_CallType::ISEND)),
isend, irecv);
auto *SI = B.CreateSwitch(fn, error, 4);

SI->addCase(
ConstantInt::get(fn->getType(), (int)MPI_CallType::ISEND),
isend);
SI->addCase(
ConstantInt::get(fn->getType(), (int)MPI_CallType::IRECV),
irecv);
SI->addCase(
ConstantInt::get(fn->getType(), (int)MPI_CallType::SEND_INIT),
send_init);
SI->addCase(
ConstantInt::get(fn->getType(), (int)MPI_CallType::RECV_INIT),
recv_init);

{
B.SetInsertPoint(error);
B.CreateUnreachable();
}
{
B.SetInsertPoint(isend);
auto fcall = B.CreateCall(irecvfn, args);
Expand All @@ -1848,6 +1866,21 @@ llvm::Function *getOrInsertDifferentialMPI_Wait(llvm::Module &M,
fcall->setCallingConv(isendfn->getCallingConv());
B.CreateRetVoid();
}

{
B.SetInsertPoint(send_init);
auto fcall = B.CreateCall(recv_initfn, args);
fcall->setCallingConv(isendfn->getCallingConv());
B.CreateRetVoid();
}

{
B.SetInsertPoint(recv_init);
auto fcall = B.CreateCall(send_initfn, args);
fcall->setCallingConv(isendfn->getCallingConv());
B.CreateRetVoid();
}

return F;
}

Expand Down
2 changes: 2 additions & 0 deletions enzyme/Enzyme/Utils.h
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Expand Up @@ -1132,6 +1132,8 @@ allInstructionsBetween(llvm::LoopInfo &LI, llvm::Instruction *inst1,
enum class MPI_CallType {
ISEND = 1,
IRECV = 2,
SEND_INIT = 3,
RECV_INIT = 4
};

enum class MPI_Elem {
Expand Down
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