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[flang-rt] Add APIs to retrive base_addr and DataSizeInBytes from Descriptor. #152756

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[flang-rt] Add APIs to retrive base_addr and DataSizeInBytes from Descriptor. #152756

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e5a205a
[flang-rt] Add APIs to retrive base_addr and DataSizeInBytes from Des…
skc7 Aug 8, 2025
ed85f97
Add support apis to generate new runtime calls
skc7 Aug 12, 2025
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24 changes: 24 additions & 0 deletions flang-rt/lib/runtime/support.cpp
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Expand Up @@ -48,6 +48,30 @@ void RTDEF(CopyAndUpdateDescriptor)(Descriptor &to, const Descriptor &from,
}
}

void *RTDEF(DescriptorGetBaseAddress)(
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As Valentin said, there is fir.box_addr operation that allows taking the base address from a descriptor.

const Descriptor &desc, const char *sourceFile, int sourceLine) {
Terminator terminator{sourceFile, sourceLine};
void *baseAddr = desc.raw().base_addr;
if (!baseAddr) {
terminator.Crash("Could not retrieve Descriptor's base address");
}
return baseAddr;
}

std::size_t RTDEF(DescriptorGetDataSizeInBytes)(
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There is fir.box_total_elements (probably not implemented end-to-end right now) and fir.box_elesize, which can be used to compute the data size in bytes (of course, assuming that the data is contiguous).

So there are existing operations that should allow you to get all the data for omp_target_memcpy invocation and insert it in the compiler generated code rather than doing it in the Fortran runtime.

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Thanks @clementval and @vzakhari for feedback. Will check if these fir ops work in our scenario e2e. Closing the pull request for now.

const Descriptor &desc, const char *sourceFile, int sourceLine) {
Terminator terminator{sourceFile, sourceLine};
std::size_t descElements{desc.Elements()};
if (!descElements) {
terminator.Crash("Could not retrieve Descriptor's Elements");
}
std::size_t descElementBytes{desc.ElementBytes()};
if (!descElementBytes) {
terminator.Crash("Could not retrieve Descriptor's ElementBytes");
}
return descElements * descElementBytes;
}

RT_EXT_API_GROUP_END
} // extern "C"
} // namespace Fortran::runtime
23 changes: 23 additions & 0 deletions flang-rt/unittests/Runtime/Support.cpp
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Expand Up @@ -98,3 +98,26 @@ TEST(IsContiguous, Basic) {
EXPECT_TRUE(RTNAME(IsContiguousUpTo)(section, 1));
EXPECT_FALSE(RTNAME(IsContiguousUpTo)(section, 2));
}

TEST(DescriptorGetBaseAddress, Basic) {
auto array{MakeArray<TypeCategory::Integer, 4>(
std::vector<int>{2, 3}, std::vector<std::int32_t>{0, 1, 2, 3, 4, 5})};
void *baseAddr = RTNAME(DescriptorGetBaseAddress)(*array);
EXPECT_NE(baseAddr, nullptr);
EXPECT_EQ(baseAddr, array->raw().base_addr);
}

TEST(DescriptorGetDataSizeInBytes, Basic) {
// Test with a 2x3 integer*4 array
auto int4Array{MakeArray<TypeCategory::Integer, 4>({2, 3})};
EXPECT_EQ(RTNAME(DescriptorGetDataSizeInBytes)(*int4Array),
6 * sizeof(std::int32_t));
// Test with a 1D, 5-element real*8 array
auto real8Array{MakeArray<TypeCategory::Real, 8>({5})};
EXPECT_EQ(
RTNAME(DescriptorGetDataSizeInBytes)(*real8Array), 5 * sizeof(double));
// Test with a scalar logical*1
auto logical1Scalar{MakeArray<TypeCategory::Logical, 1>({})};
EXPECT_EQ(
RTNAME(DescriptorGetDataSizeInBytes)(*logical1Scalar), 1 * sizeof(bool));
}
13 changes: 13 additions & 0 deletions flang/include/flang/Optimizer/Builder/Runtime/Support.h
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Expand Up @@ -31,5 +31,18 @@ void genCopyAndUpdateDescriptor(fir::FirOpBuilder &builder, mlir::Location loc,
mlir::Value genIsAssumedSize(fir::FirOpBuilder &builder, mlir::Location loc,
mlir::Value box);

/// Generate call to `DescriptorGetBaseAddress` runtime routine.
mlir::Value genDescriptorGetBaseAddress(fir::FirOpBuilder &builder,
mlir::Location loc, mlir::Value desc,
mlir::Value sourceFile,
mlir::Value sourceLine);

/// Generate call to `DescriptorGetDataSizeInBytes` runtime routine.
mlir::Value genDescriptorGetDataSizeInBytes(fir::FirOpBuilder &builder,
mlir::Location loc,
mlir::Value desc,
mlir::Value sourceFile,
mlir::Value sourceLine);

} // namespace fir::runtime
#endif // FORTRAN_OPTIMIZER_BUILDER_RUNTIME_SUPPORT_H
8 changes: 8 additions & 0 deletions flang/include/flang/Runtime/support.h
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Expand Up @@ -49,6 +49,14 @@ void RTDECL(CopyAndUpdateDescriptor)(Descriptor &to, const Descriptor &from,
const typeInfo::DerivedType *newDynamicType,
ISO::CFI_attribute_t newAttribute, enum LowerBoundModifier newLowerBounds);

// Retrieve the base_addr from Descriptor
void *RTDECL(DescriptorGetBaseAddress)(const Descriptor &desc,
const char *sourceFile = nullptr, int sourceLine = 0);

// Retrieve the totalSizeInBytes of data from Descriptor
std::size_t RTDECL(DescriptorGetDataSizeInBytes)(const Descriptor &desc,
const char *sourceFile = nullptr, int sourceLine = 0);

} // extern "C"
} // namespace Fortran::runtime
#endif // FORTRAN_RUNTIME_SUPPORT_H_
21 changes: 21 additions & 0 deletions flang/lib/Optimizer/Builder/Runtime/Support.cpp
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Expand Up @@ -54,3 +54,24 @@ mlir::Value fir::runtime::genIsAssumedSize(fir::FirOpBuilder &builder,
auto args = fir::runtime::createArguments(builder, loc, fTy, box);
return fir::CallOp::create(builder, loc, func, args).getResult(0);
}

mlir::Value fir::runtime::genDescriptorGetBaseAddress(
fir::FirOpBuilder &builder, mlir::Location loc, mlir::Value desc,
mlir::Value sourceFile, mlir::Value sourceLine) {
mlir::func::FuncOp baseAddrFunc =
fir::runtime::getRuntimeFunc<mkRTKey(DescriptorGetBaseAddress)>(loc,
builder);
llvm::SmallVector<mlir::Value> args{desc, sourceFile, sourceLine};
return fir::CallOp::create(builder, loc, baseAddrFunc, args).getResult(0);
}

mlir::Value fir::runtime::genDescriptorGetDataSizeInBytes(
fir::FirOpBuilder &builder, mlir::Location loc, mlir::Value desc,
mlir::Value sourceFile, mlir::Value sourceLine) {
mlir::func::FuncOp getDataSizeInBytesFunc =
fir::runtime::getRuntimeFunc<mkRTKey(DescriptorGetDataSizeInBytes)>(
loc, builder);
llvm::SmallVector<mlir::Value> args{desc, sourceFile, sourceLine};
return fir::CallOp::create(builder, loc, getDataSizeInBytesFunc, args)
.getResult(0);
}