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[flang][cuda] Fix false positive on unsupported CUDA data transfer #148295

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Merged
merged 1 commit into from
Jul 11, 2025
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[flang][cuda] Fix false positive on unsupported CUDA data transfer #148295

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25 changes: 15 additions & 10 deletions flang/lib/Evaluate/tools.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1157,23 +1157,28 @@ template semantics::UnorderedSymbolSet CollectCudaSymbols(
bool HasCUDAImplicitTransfer(const Expr<SomeType> &expr) {
semantics::UnorderedSymbolSet hostSymbols;
semantics::UnorderedSymbolSet deviceSymbols;
semantics::UnorderedSymbolSet cudaSymbols{CollectCudaSymbols(expr)};

SymbolVector symbols{GetSymbolVector(expr)};
std::reverse(symbols.begin(), symbols.end());
bool skipNext{false};
for (const Symbol &sym : symbols) {
bool isComponent{sym.owner().IsDerivedType()};
bool skipComponent{false};
if (!skipNext) {
if (IsCUDADeviceSymbol(sym)) {
deviceSymbols.insert(sym);
} else if (isComponent) {
skipComponent = true; // Component is not device. Look on the base.
} else {
hostSymbols.insert(sym);
if (cudaSymbols.find(sym) != cudaSymbols.end()) {
bool isComponent{sym.owner().IsDerivedType()};
bool skipComponent{false};
if (!skipNext) {
if (IsCUDADeviceSymbol(sym)) {
deviceSymbols.insert(sym);
} else if (isComponent) {
skipComponent = true; // Component is not device. Look on the base.
} else {
hostSymbols.insert(sym);
}
}
skipNext = isComponent && !skipComponent;
} else {
skipNext = false;
}
skipNext = isComponent && !skipComponent;
}
bool hasConstant{HasConstant(expr)};
return (hasConstant || (hostSymbols.size() > 0)) && deviceSymbols.size() > 0;
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8 changes: 8 additions & 0 deletions flang/test/Lower/CUDA/cuda-data-transfer.cuf
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Expand Up @@ -436,3 +436,11 @@ end subroutine

! CHECK-LABEL: func.func @_QPsub22()
! CHECK: cuf.data_transfer

subroutine sub23(n)
integer :: n
real(8), device :: d(n,n), x(n)
x = sum(d,dim=2) ! Was triggering Unsupported CUDA data transfer
end subroutine

! CHECK-LABEL: func.func @_QPsub23
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