caio/clang-p2996
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[flang] add option to generate runtime type info as external (#145901)

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So far flang generates runtime derived type info global definitions (as
opposed to declarations) for all the types used in the current
compilation unit even when the derived types are defined in other
compilation units. It is using linkonce_odr to achieve derived type
descriptor address "uniqueness" aspect needed to match two derived type
inside the runtime.

This comes at a big compile time cost because of all the extra globals
and their definitions in apps with many and complex derived types.

This patch adds and experimental option to only generate the rtti
definition for the types defined in the current compilation unit and to
only generate external declaration for the derived type descriptor
object of types defined elsewhere.

Note that objects compiled with this option are not compatible with
object files compiled without because files compiled without it may drop
the rtti for type they defined if it is not used in the compilation unit
because of the linkonce_odr aspect.

I am adding the option so that we can better measure the extra cost of
the current approach on apps and allow speeding up some compilation
where devirtualization does not matter (and the build config links to
all module file object anyway).
This commit is contained in:
jeanPerier
2025-06-27 13:00:29 +02:00
committed by GitHub
parent f0f46e25ec
commit e816817bbb
15 changed files with 256 additions and 153 deletions
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102
flang/lib/Optimizer/CodeGen/CodeGen.cpp
View File

@@ -1294,6 +1294,51 @@ genCUFAllocDescriptor(mlir::Location loc,
.getResult();
}
/// Get the address of the type descriptor global variable that was created by
/// lowering for derived type \p recType.
template <typename ModOpTy>
static mlir::Value
getTypeDescriptor(ModOpTy mod, mlir::ConversionPatternRewriter &rewriter,
mlir::Location loc, fir::RecordType recType,
const fir::FIRToLLVMPassOptions &options) {
std::string name =
options.typeDescriptorsRenamedForAssembly
? fir::NameUniquer::getTypeDescriptorAssemblyName(recType.getName())
: fir::NameUniquer::getTypeDescriptorName(recType.getName());
mlir::Type llvmPtrTy = ::getLlvmPtrType(mod.getContext());
if (auto global = mod.template lookupSymbol<fir::GlobalOp>(name))
return rewriter.create<mlir::LLVM::AddressOfOp>(loc, llvmPtrTy,
global.getSymName());
// The global may have already been translated to LLVM.
if (auto global = mod.template lookupSymbol<mlir::LLVM::GlobalOp>(name))
return rewriter.create<mlir::LLVM::AddressOfOp>(loc, llvmPtrTy,
global.getSymName());
// Type info derived types do not have type descriptors since they are the
// types defining type descriptors.
if (options.ignoreMissingTypeDescriptors ||
fir::NameUniquer::belongsToModule(
name, Fortran::semantics::typeInfoBuiltinModule))
return rewriter.create<mlir::LLVM::ZeroOp>(loc, llvmPtrTy);
if (!options.skipExternalRttiDefinition)
fir::emitFatalError(loc,
"runtime derived type info descriptor was not "
"generated and skipExternalRttiDefinition and "
"ignoreMissingTypeDescriptors options are not set");
// Rtti for a derived type defined in another compilation unit and for which
// rtti was not defined in lowering because of the skipExternalRttiDefinition
// option. Generate the object declaration now.
auto insertPt = rewriter.saveInsertionPoint();
rewriter.setInsertionPoint(mod.getBody(), mod.getBody()->end());
mlir::LLVM::GlobalOp global = rewriter.create<mlir::LLVM::GlobalOp>(
loc, llvmPtrTy, /*constant=*/true, mlir::LLVM::Linkage::External, name,
mlir::Attribute());
rewriter.restoreInsertionPoint(insertPt);
return rewriter.create<mlir::LLVM::AddressOfOp>(loc, llvmPtrTy,
global.getSymName());
}
/// Common base class for embox to descriptor conversion.
template <typename OP>
struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
@@ -1406,36 +1451,6 @@ struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
stride);
}
/// Get the address of the type descriptor global variable that was created by
/// lowering for derived type \p recType.
template <typename ModOpTy>
mlir::Value
getTypeDescriptor(ModOpTy mod, mlir::ConversionPatternRewriter &rewriter,
mlir::Location loc, fir::RecordType recType) const {
std::string name =
this->options.typeDescriptorsRenamedForAssembly
? fir::NameUniquer::getTypeDescriptorAssemblyName(recType.getName())
: fir::NameUniquer::getTypeDescriptorName(recType.getName());
mlir::Type llvmPtrTy = ::getLlvmPtrType(mod.getContext());
if (auto global = mod.template lookupSymbol<fir::GlobalOp>(name)) {
return rewriter.create<mlir::LLVM::AddressOfOp>(loc, llvmPtrTy,
global.getSymName());
}
if (auto global = mod.template lookupSymbol<mlir::LLVM::GlobalOp>(name)) {
// The global may have already been translated to LLVM.
return rewriter.create<mlir::LLVM::AddressOfOp>(loc, llvmPtrTy,
global.getSymName());
}
// Type info derived types do not have type descriptors since they are the
// types defining type descriptors.
if (!this->options.ignoreMissingTypeDescriptors &&
!fir::NameUniquer::belongsToModule(
name, Fortran::semantics::typeInfoBuiltinModule))
fir::emitFatalError(
loc, "runtime derived type info descriptor was not generated");
return rewriter.create<mlir::LLVM::ZeroOp>(loc, llvmPtrTy);
}
template <typename ModOpTy>
mlir::Value populateDescriptor(mlir::Location loc, ModOpTy mod,
fir::BaseBoxType boxTy, mlir::Type inputType,
@@ -1500,7 +1515,8 @@ struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
mlir::Type innerType = fir::unwrapInnerType(inputType);
if (innerType && mlir::isa<fir::RecordType>(innerType)) {
auto recTy = mlir::dyn_cast<fir::RecordType>(innerType);
typeDesc = getTypeDescriptor(mod, rewriter, loc, recTy);
typeDesc =
getTypeDescriptor(mod, rewriter, loc, recTy, this->options);
} else {
// Unlimited polymorphic type descriptor with no record type. Set
// type descriptor address to a clean state.
@@ -1508,8 +1524,8 @@ struct EmboxCommonConversion : public fir::FIROpConversion<OP> {
loc, ::getLlvmPtrType(mod.getContext()));
}
} else {
typeDesc = getTypeDescriptor(mod, rewriter, loc,
fir::unwrapIfDerived(boxTy));
typeDesc = getTypeDescriptor(
mod, rewriter, loc, fir::unwrapIfDerived(boxTy), this->options);
}
}
if (typeDesc)
@@ -3021,22 +3037,10 @@ struct TypeDescOpConversion : public fir::FIROpConversion<fir::TypeDescOp> {
assert(mlir::isa<fir::RecordType>(inTy) && "expecting fir.type");
auto recordType = mlir::dyn_cast<fir::RecordType>(inTy);
auto module = typeDescOp.getOperation()->getParentOfType<mlir::ModuleOp>();
std::string typeDescName =
this->options.typeDescriptorsRenamedForAssembly
? fir::NameUniquer::getTypeDescriptorAssemblyName(
recordType.getName())
: fir::NameUniquer::getTypeDescriptorName(recordType.getName());
auto llvmPtrTy = ::getLlvmPtrType(typeDescOp.getContext());
if (auto global = module.lookupSymbol<mlir::LLVM::GlobalOp>(typeDescName)) {
rewriter.replaceOpWithNewOp<mlir::LLVM::AddressOfOp>(
typeDescOp, llvmPtrTy, global.getSymName());
return mlir::success();
} else if (auto global = module.lookupSymbol<fir::GlobalOp>(typeDescName)) {
rewriter.replaceOpWithNewOp<mlir::LLVM::AddressOfOp>(
typeDescOp, llvmPtrTy, global.getSymName());
return mlir::success();
}
return mlir::failure();
mlir::Value typeDesc = getTypeDescriptor(
module, rewriter, typeDescOp.getLoc(), recordType, this->options);
rewriter.replaceOp(typeDescOp, typeDesc);
return mlir::success();
}
};