[CIR] Implement non-virtual thunk generation for multiple inheritance #2006
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lanza
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xlauko
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lanza
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Nov 23, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: eaf1735
Pull-Request: #2006
This was referenced Nov 23, 2025
lanza
added a commit
that referenced
this pull request
Nov 23, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: 16477e8
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 23, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: 62c915d
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 23, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: d6515e1
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 23, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: ae6fa6a
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 24, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: eb03968
Pull-Request: #2006
This was referenced Nov 24, 2025
Draft
lanza
added a commit
that referenced
this pull request
Nov 25, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: eb03968
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 25, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: eb03968
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 26, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: eb03968
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 26, 2025
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.
Implementation details:
1. **CIRGenVTables.cpp**:
- Implemented `generateThunk()` to create thunk function bodies with
proper scope management (SymTableScopeTy + LexicalScope)
- Implemented `emitCallAndReturnForThunk()` to emit the call sequence
- Implemented `setThunkProperties()` to set linkage and properties
- Fixed VTable double-insertion bug in vtable emission
2. **CIRGenCXXABI.h/cpp**:
- Added virtual methods `performThisAdjustment()` and
`performReturnAdjustment()` to base class
- Implemented `EmitReturnFromThunk()` default implementation
3. **CIRGenItaniumCXXABI.cpp**:
- Implemented `performThisAdjustment()` for non-virtual adjustments
using cir.ptr_stride operations
- Implemented `performReturnAdjustment()` for covariant return types
- Virtual adjustments marked as NYI with llvm_unreachable
4. **CIRGenFunction.h/cpp**:
- Added `startThunk()`, `generateThunk()`, `emitCallAndReturnForThunk()`,
`finishThunk()`, and `emitMustTailThunk()` methods
- Implemented `finishThunk()` to properly cleanup after thunk generation
5. **CIRGenModule.cpp**:
- Removed assertion blocking thunks in `setFunctionAttributes()`
- Fixed insertion point management in vtable creation
6. **CIRGenCXX.cpp**:
- Added null checks for GlobalDecl in XRay attributes for thunks
7. **Test Updates**:
- Added `clang/test/CIR/CodeGen/vtable-thunk.cpp` for CIR generation
- Added `clang/test/CIR/Lowering/vtable-thunk.cpp` for LLVM lowering
- Fixed offset expectations (16 bytes for x86_64 layout)
- Reordered FileCheck patterns to match actual CIR output order
This implementation closely follows CodeGen's approach in
CodeGenVTables.cpp and CodeGenItaniumCXXABI.cpp, with adaptations for
CIR's MLIR-based infrastructure (e.g., location requirements, operation
builders, scope management).
Limitations:
- Virtual adjustments (vcall offsets) not yet implemented
- Musttail thunks for variadic functions not yet implemented
- Return adjustments implemented but not extensively tested
Test Plan:
```
bin/llvm-lit -v ../../clang/test/CIR/CodeGen/vtable-thunk.cpp
bin/llvm-lit -v ../../clang/test/CIR/Lowering/vtable-thunk.cpp
```
Both tests pass, verifying:
- CIR generation with correct thunk mangling and operations
- Vtable contains thunk references
- Lowering to LLVM IR produces correct getelementptr operations
ghstack-source-id: eb03968
Pull-Request: #2006
lanza
added a commit
that referenced
this pull request
Nov 26, 2025
This patch implements complete support for generating non-virtual thunks in ClangIR for multiple inheritance scenarios. Thunks are small adapter functions that adjust the 'this' pointer and forward calls to the actual target function when virtual functions are overridden in derived classes with multiple base classes. ghstack-source-id: a80ef29 Pull-Request: #2006
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Stack from ghstack (oldest at bottom):
This patch implements complete support for generating non-virtual thunks
in ClangIR for multiple inheritance scenarios. Thunks are small adapter
functions that adjust the 'this' pointer and forward calls to the actual
target function when virtual functions are overridden in derived classes
with multiple base classes.