Author: Narayan
Date: 2026-05-07T16:28:10+05:30
New Revision: 07b5dfe9473c6f864027855b68fa5775d0adf2d9

URL: 
https://github.com/llvm/llvm-project/commit/07b5dfe9473c6f864027855b68fa5775d0adf2d9
DIFF: 
https://github.com/llvm/llvm-project/commit/07b5dfe9473c6f864027855b68fa5775d0adf2d9.diff

LOG:  [clang] Integrate LLVMABI for function call ABI lowering  (#194460)

This PR wires the LLVM ABI library (prototyped in
https://github.com/llvm/llvm-project/pull/140112) into Clang's function
call ABI lowering pipeline, behind a new `-fexperimental-abi-lowering`
cc1 flag.

When the flag is enabled and the active target has an LLVMABI
implementation, `CodeGenTypes::arrangeLLVMFunctionInfo` constructs an
`llvm::abi::FunctionInfo` from the call's argument and result types
(using QualTypeMapper(https://github.com/llvm/llvm-project/pull/174634)
to translate Clang QualTypes into ABI types).

Asks the target's `llvm::abi::TargetInfo` to classify it, and then
translates each `llvm::abi::ArgInfo` back into the ABIArgInfo consumed
by the rest of CodeGen. The translation is handled by a new
`convertABIArgInfo` helper covering the Direct, Extend, Indirect, and
Ignore kinds, with coerce-to types lifted back into LLVM IR via a new
IRTypeMapper.

The integration is intentionally narrow and existing code paths are
untouched. `CodeGenModule::shouldUseLLVMABILowering` only opts in for
targets explicitly wired to the new library(currently only BPF).

Added: 
    llvm/include/llvm/ABI/IRTypeMapper.h
    llvm/lib/ABI/IRTypeMapper.cpp

Modified: 
    clang/include/clang/Basic/CodeGenOptions.def
    clang/include/clang/Options/Options.td
    clang/lib/CodeGen/CGCall.cpp
    clang/lib/CodeGen/CMakeLists.txt
    clang/lib/CodeGen/CodeGenModule.cpp
    clang/lib/CodeGen/CodeGenModule.h
    clang/lib/CodeGen/QualTypeMapper.h
    clang/test/CodeGen/bpf-abiinfo.c
    clang/test/CodeGen/bpf-struct-argument.c
    clang/test/CodeGen/bpf-union-argument.c
    llvm/lib/ABI/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/CodeGenOptions.def 
b/clang/include/clang/Basic/CodeGenOptions.def
index 0d1bf83eaec9f..fd0b6d9096f50 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -28,6 +28,10 @@ CODEGENOPT(Name, Bits, Default, Compatibility)
 #endif
 
 CODEGENOPT(DisableIntegratedAS, 1, 0, Benign) ///< -no-integrated-as
+CODEGENOPT(ExperimentalABILowering, 1, 0, Benign) ///< 
-fexperimental-abi-lowering:
+                                                  ///< route function ABI 
lowering
+                                                  ///< through the in-tree 
LLVMABI
+                                                  ///< library where supported.
 CODEGENOPT(Crel, 1, 0, Benign) ///< -Wa,--crel
 ENUM_CODEGENOPT(RelocSectionSym, RelocSectionSymType, 2,
                 RelocSectionSymType::All, Benign) ///< -Wa,--reloc-section-sym=

diff  --git a/clang/include/clang/Options/Options.td 
b/clang/include/clang/Options/Options.td
index 863e6b3d0871f..38cd7d4b86a0b 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -3578,6 +3578,10 @@ defm modules_reduced_bmi : BoolOption<"f", 
"modules-reduced-bmi",
 def experimental_modules_reduced_bmi : Flag<["-"], 
"fexperimental-modules-reduced-bmi">,
   Group<f_Group>, Visibility<[ClangOption, CC1Option]>, 
Alias<fmodules_reduced_bmi>;
 
+def fexperimental_abi_lowering : Flag<["-"], "fexperimental-abi-lowering">,
+  Group<f_Group>, Visibility<[CC1Option]>,
+  MarshallingInfoFlag<CodeGenOpts<"ExperimentalABILowering">>;
+
 def fmodules_embed_all_files : Joined<["-"], "fmodules-embed-all-files">,
   Visibility<[ClangOption, CC1Option, CLOption]>,
   HelpText<"Embed the contents of all files read by this compilation into "

diff  --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index c584f2eeef937..1cafe364c4c42 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -22,6 +22,7 @@
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "CodeGenPGO.h"
+#include "QualTypeMapper.h"
 #include "TargetInfo.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/Decl.h"
@@ -32,6 +33,10 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
 #include "clang/CodeGen/SwiftCallingConv.h"
+#include "llvm/ABI/FunctionInfo.h"
+#include "llvm/ABI/IRTypeMapper.h"
+#include "llvm/ABI/TargetInfo.h"
+#include "llvm/ABI/Types.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/ValueTracking.h"
@@ -824,9 +829,70 @@ const CGFunctionInfo &CodeGenTypes::arrangeCall(const 
CGFunctionInfo &signature,
 namespace clang {
 namespace CodeGen {
 void computeSPIRKernelABIInfo(CodeGenModule &CGM, CGFunctionInfo &FI);
-}
+} // namespace CodeGen
 } // namespace clang
 
+void CodeGenModule::computeABIInfoUsingLib(CGFunctionInfo &FI) {
+  SmallVector<const llvm::abi::Type *> MappedArgTypes;
+  MappedArgTypes.reserve(FI.arg_size());
+  for (const auto &Arg : FI.arguments())
+    MappedArgTypes.push_back(AbiMapper->convertType(Arg.type));
+
+  std::optional<unsigned> NumRequired;
+  RequiredArgs Required = FI.getRequiredArgs();
+  if (Required.allowsOptionalArgs())
+    NumRequired = Required.getNumRequiredArgs();
+
+  llvm::abi::FunctionInfo *AbiFI = llvm::abi::FunctionInfo::create(
+      FI.getCallingConvention(), AbiMapper->convertType(FI.getReturnType()),
+      MappedArgTypes, NumRequired);
+
+  getLLVMABITargetInfo(AbiMapper->getTypeBuilder()).computeInfo(*AbiFI);
+
+  FI.getReturnInfo() =
+      convertABIArgInfo(AbiFI->getReturnInfo(), FI.getReturnType());
+
+  for (auto [CGArg, AbiArg] :
+       llvm::zip_equal(FI.arguments(), AbiFI->arguments()))
+    CGArg.info = convertABIArgInfo(AbiArg.Info, CGArg.type);
+}
+
+ABIArgInfo CodeGenModule::convertABIArgInfo(const llvm::abi::ArgInfo &AbiInfo,
+                                            QualType Type) {
+  switch (AbiInfo.getKind()) {
+  case llvm::abi::ArgInfo::Direct: {
+    llvm::Type *CoercedType = nullptr;
+    if (AbiInfo.getCoerceToType())
+      CoercedType = AbiReverseMapper->convertType(AbiInfo.getCoerceToType());
+    if (!CoercedType)
+      CoercedType = getTypes().ConvertType(Type);
+    return ABIArgInfo::getDirect(CoercedType, AbiInfo.getDirectOffset());
+  }
+  case llvm::abi::ArgInfo::Extend: {
+    llvm::Type *CoercedType = nullptr;
+    if (AbiInfo.getCoerceToType())
+      CoercedType = AbiReverseMapper->convertType(AbiInfo.getCoerceToType());
+    if (!CoercedType)
+      CoercedType = getTypes().ConvertType(Type);
+    if (AbiInfo.isSignExt())
+      return ABIArgInfo::getSignExtend(Type, CoercedType);
+    if (AbiInfo.isZeroExt())
+      return ABIArgInfo::getZeroExtend(Type, CoercedType);
+    return ABIArgInfo::getExtend(Type, CoercedType);
+  }
+  case llvm::abi::ArgInfo::Indirect: {
+    CharUnits Alignment =
+        CharUnits::fromQuantity(AbiInfo.getIndirectAlign().value());
+    return ABIArgInfo::getIndirect(Alignment, AbiInfo.getIndirectAddrSpace(),
+                                   AbiInfo.getIndirectByVal(),
+                                   AbiInfo.getIndirectRealign());
+  }
+  case llvm::abi::ArgInfo::Ignore:
+    return ABIArgInfo::getIgnore();
+  }
+  llvm_unreachable("Unexpected llvm::abi::ArgInfo kind");
+}
+
 /// Arrange the argument and result information for an abstract value
 /// of a given function type.  This is the method which all of the
 /// above functions ultimately defer to.
@@ -876,6 +942,8 @@ const CGFunctionInfo &CodeGenTypes::arrangeLLVMFunctionInfo(
     computeSPIRKernelABIInfo(CGM, *FI);
   } else if (info.getCC() == CC_Swift || info.getCC() == CC_SwiftAsync) {
     swiftcall::computeABIInfo(CGM, *FI);
+  } else if (CGM.shouldUseLLVMABILowering()) {
+    CGM.computeABIInfoUsingLib(*FI);
   } else {
     CGM.getABIInfo().computeInfo(*FI);
   }

diff  --git a/clang/lib/CodeGen/CMakeLists.txt 
b/clang/lib/CodeGen/CMakeLists.txt
index 434781b3c4f02..117438c616ab5 100644
--- a/clang/lib/CodeGen/CMakeLists.txt
+++ b/clang/lib/CodeGen/CMakeLists.txt
@@ -1,4 +1,5 @@
 set(LLVM_LINK_COMPONENTS
+  ABI
   AggressiveInstCombine
   Analysis
   BitReader

diff  --git a/clang/lib/CodeGen/CodeGenModule.cpp 
b/clang/lib/CodeGen/CodeGenModule.cpp
index e88fed1296667..106f1e63cd904 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -26,6 +26,7 @@
 #include "CodeGenPGO.h"
 #include "ConstantEmitter.h"
 #include "CoverageMappingGen.h"
+#include "QualTypeMapper.h"
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTLambda.h"
@@ -47,6 +48,8 @@
 #include "clang/Basic/Version.h"
 #include "clang/CodeGen/BackendUtil.h"
 #include "clang/CodeGen/ConstantInitBuilder.h"
+#include "llvm/ABI/IRTypeMapper.h"
+#include "llvm/ABI/TargetInfo.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -336,6 +339,25 @@ const TargetCodeGenInfo 
&CodeGenModule::getTargetCodeGenInfo() {
   return *TheTargetCodeGenInfo;
 }
 
+bool CodeGenModule::shouldUseLLVMABILowering() const {
+  if (!CodeGenOpts.ExperimentalABILowering)
+    return false;
+  // Only opt in for targets that have an LLVMABI implementation; others
+  // continue through the legacy ABIInfo path.
+  return getTriple().isBPF();
+}
+
+const llvm::abi::TargetInfo &
+CodeGenModule::getLLVMABITargetInfo(llvm::abi::TypeBuilder &TB) {
+  if (TheLLVMABITargetInfo)
+    return *TheLLVMABITargetInfo;
+
+  assert(getTriple().isBPF() &&
+         "LLVMABI lowering requested for an unsupported target");
+  TheLLVMABITargetInfo = llvm::abi::createBPFTargetInfo(TB);
+  return *TheLLVMABITargetInfo;
+}
+
 static void checkDataLayoutConsistency(const TargetInfo &Target,
                                        llvm::LLVMContext &Context,
                                        const LangOptions &Opts) {
@@ -420,6 +442,10 @@ CodeGenModule::CodeGenModule(ASTContext &C,
       SanitizerMD(new SanitizerMetadata(*this)),
       AtomicOpts(Target.getAtomicOpts()) {
 
+  AbiMapper = std::make_unique<QualTypeMapper>(C, M.getDataLayout(), AbiAlloc);
+  AbiReverseMapper = std::make_unique<llvm::abi::IRTypeMapper>(
+      M.getContext(), M.getDataLayout());
+
   // Initialize the type cache.
   Types.reset(new CodeGenTypes(*this));
   llvm::LLVMContext &LLVMContext = M.getContext();

diff  --git a/clang/lib/CodeGen/CodeGenModule.h 
b/clang/lib/CodeGen/CodeGenModule.h
index c7e168433e42c..b7dab4ef583ff 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -38,6 +38,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ValueHandle.h"
+#include "llvm/Support/Allocator.h"
 #include "llvm/Transforms/Utils/SanitizerStats.h"
 #include <optional>
 
@@ -55,6 +56,13 @@ class IndexedInstrProfReader;
 namespace vfs {
 class FileSystem;
 }
+
+namespace abi {
+class ArgInfo;
+class IRTypeMapper;
+class TargetInfo;
+class TypeBuilder;
+} // namespace abi
 }
 
 namespace clang {
@@ -95,7 +103,9 @@ class CGOpenCLRuntime;
 class CGOpenMPRuntime;
 class CGCUDARuntime;
 class CGHLSLRuntime;
+class CGFunctionInfo;
 class CoverageMappingModuleGen;
+class QualTypeMapper;
 class TargetCodeGenInfo;
 
 enum ForDefinition_t : bool {
@@ -363,6 +373,18 @@ class CodeGenModule : public CodeGenTypeCache {
 
   mutable std::unique_ptr<TargetCodeGenInfo> TheTargetCodeGenInfo;
 
+  /// Cached LLVMABI target lowering info, lazily constructed when the
+  /// experimental ABI lowering path is taken.
+  mutable std::unique_ptr<llvm::abi::TargetInfo> TheLLVMABITargetInfo;
+
+  /// Allocator and mappers used by the experimental LLVMABI-based lowering
+  /// path (gated on -fexperimental-abi-lowering). Constructed unconditionally
+  /// so the path can be entered without re-checking initialization, but the
+  /// caches stay empty when the flag is off.
+  llvm::BumpPtrAllocator AbiAlloc;
+  std::unique_ptr<QualTypeMapper> AbiMapper;
+  std::unique_ptr<llvm::abi::IRTypeMapper> AbiReverseMapper;
+
   // This should not be moved earlier, since its initialization depends on some
   // of the previous reference members being already initialized and also 
checks
   // if TheTargetCodeGenInfo is NULL
@@ -877,6 +899,21 @@ class CodeGenModule : public CodeGenTypeCache {
   void maybeSetTrivialComdat(const Decl &D, llvm::GlobalObject &GO);
 
   const ABIInfo &getABIInfo();
+
+  /// Lazily build and return the LLVMABI library's TargetInfo for the current
+  /// target. Used by the experimental ABI lowering path
+  /// (-fexperimental-abi-lowering).
+  const llvm::abi::TargetInfo &getLLVMABITargetInfo(llvm::abi::TypeBuilder 
&TB);
+
+  /// True when -fexperimental-abi-lowering is in effect AND the active target
+  /// has an LLVMABI implementation we can route to.
+  bool shouldUseLLVMABILowering() const;
+
+  /// Drive the experimental LLVMABI-based lowering path: map argument and
+  /// return types into the LLVMABI library, ask its target lowering to fill
+  /// in classification, and write the results back into FI.
+  void computeABIInfoUsingLib(CGFunctionInfo &FI);
+
   CGCXXABI &getCXXABI() const { return *ABI; }
   llvm::LLVMContext &getLLVMContext() { return VMContext; }
 
@@ -1902,6 +1939,12 @@ class CodeGenModule : public CodeGenTypeCache {
   llvm::GlobalValue *getPFPDeactivationSymbol(const FieldDecl *FD);
 
 private:
+  /// Translate an llvm::abi::ArgInfo (computed by the LLVMABI library) into
+  /// the clang ABIArgInfo consumed by the rest of CodeGen. Used by the
+  /// experimental ABI lowering path.
+  ABIArgInfo convertABIArgInfo(const llvm::abi::ArgInfo &AbiInfo,
+                               QualType Type);
+
   bool shouldDropDLLAttribute(const Decl *D, const llvm::GlobalValue *GV) 
const;
 
   llvm::Constant *GetOrCreateLLVMFunction(

diff  --git a/clang/lib/CodeGen/QualTypeMapper.h 
b/clang/lib/CodeGen/QualTypeMapper.h
index 11e8ba86cfcdf..35876f44f3aba 100644
--- a/clang/lib/CodeGen/QualTypeMapper.h
+++ b/clang/lib/CodeGen/QualTypeMapper.h
@@ -71,7 +71,7 @@ class QualTypeMapper {
 
   void clearCache() { TypeCache.clear(); }
 
-  llvm::abi::TypeBuilder getTypeBuilder() { return Builder; }
+  llvm::abi::TypeBuilder &getTypeBuilder() { return Builder; }
 };
 
 } // namespace CodeGen

diff  --git a/clang/test/CodeGen/bpf-abiinfo.c 
b/clang/test/CodeGen/bpf-abiinfo.c
index 366e8003f4557..f3f421fcde520 100644
--- a/clang/test/CodeGen/bpf-abiinfo.c
+++ b/clang/test/CodeGen/bpf-abiinfo.c
@@ -1,5 +1,6 @@
 // REQUIRES: bpf-registered-target
 // RUN: %clang_cc1 -triple bpf -O2 -emit-llvm -disable-llvm-passes %s -o - | 
FileCheck %s
+// RUN: %clang_cc1 -triple bpf -O2 -emit-llvm -disable-llvm-passes 
-fexperimental-abi-lowering %s -o - | FileCheck %s
 
 _Bool bar_bool(void);
 unsigned char bar_char(void);

diff  --git a/clang/test/CodeGen/bpf-struct-argument.c 
b/clang/test/CodeGen/bpf-struct-argument.c
index d4fcf16af2e28..bdfdbbb61770f 100644
--- a/clang/test/CodeGen/bpf-struct-argument.c
+++ b/clang/test/CodeGen/bpf-struct-argument.c
@@ -1,5 +1,6 @@
 // REQUIRES: bpf-registered-target
 // RUN: %clang_cc1 -triple bpf -O2 -emit-llvm -disable-llvm-passes %s -o - | 
FileCheck %s
+// RUN: %clang_cc1 -triple bpf -O2 -emit-llvm -disable-llvm-passes 
-fexperimental-abi-lowering %s -o - | FileCheck %s
 
 struct t1 {};
 struct t2 {

diff  --git a/clang/test/CodeGen/bpf-union-argument.c 
b/clang/test/CodeGen/bpf-union-argument.c
index 5f3a0bc5a9261..7020f2f999d44 100644
--- a/clang/test/CodeGen/bpf-union-argument.c
+++ b/clang/test/CodeGen/bpf-union-argument.c
@@ -1,5 +1,6 @@
 // REQUIRES: bpf-registered-target
 // RUN: %clang_cc1 -triple bpf -O2 -emit-llvm -disable-llvm-passes %s -o - | 
FileCheck %s
+// RUN: %clang_cc1 -triple bpf -O2 -emit-llvm -disable-llvm-passes 
-fexperimental-abi-lowering %s -o - | FileCheck %s
 
 union t1 {};
 union t2 {

diff  --git a/llvm/include/llvm/ABI/IRTypeMapper.h 
b/llvm/include/llvm/ABI/IRTypeMapper.h
new file mode 100644
index 0000000000000..1a77cfd91bca9
--- /dev/null
+++ b/llvm/include/llvm/ABI/IRTypeMapper.h
@@ -0,0 +1,60 @@
+//===---- IRTypeMapper.h - Maps LLVM ABI Types to LLVM IR Types ---------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Maps LLVM ABI type representations back to corresponding LLVM IR types.
+/// Used by frontends after the ABI library has computed argument/return
+/// classification: coerce-to types in the ABI representation must be
+/// translated to llvm::Type before being handed back to the IR builder.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ABI_IRTYPEMAPPER_H
+#define LLVM_ABI_IRTYPEMAPPER_H
+
+#include "llvm/ABI/Types.h"
+#include "llvm/ADT/DenseMap.h"
+
+namespace llvm {
+class LLVMContext;
+class Type;
+class StructType;
+class DataLayout;
+
+namespace abi {
+
+class IRTypeMapper {
+public:
+  IRTypeMapper(LLVMContext &Ctx, const DataLayout &DL) : Context(Ctx), DL(DL) 
{}
+
+  llvm::Type *convertType(const abi::Type *ABIType);
+
+  void clearCache() { TypeCache.clear(); }
+
+private:
+  LLVMContext &Context;
+  const DataLayout &DL;
+
+  llvm::DenseMap<const abi::Type *, llvm::Type *> TypeCache;
+
+  llvm::Type *convertArrayType(const abi::ArrayType *AT);
+  llvm::Type *convertVectorType(const abi::VectorType *VT);
+  llvm::Type *convertRecordType(const abi::RecordType *RT);
+  llvm::Type *convertComplexType(const abi::ComplexType *CT);
+  llvm::Type *convertMemberPointerType(const abi::MemberPointerType *MPT);
+
+  llvm::StructType *createStructFromFields(ArrayRef<abi::FieldInfo> Fields,
+                                           TypeSize Size, Align Alignment,
+                                           bool IsUnion);
+  llvm::Type *createPaddingType(uint64_t PaddingBits);
+};
+
+} // namespace abi
+} // namespace llvm
+
+#endif // LLVM_ABI_ABITYPEMAPPER_H

diff  --git a/llvm/lib/ABI/CMakeLists.txt b/llvm/lib/ABI/CMakeLists.txt
index eb1d6042a25cd..a5c102b57d074 100644
--- a/llvm/lib/ABI/CMakeLists.txt
+++ b/llvm/lib/ABI/CMakeLists.txt
@@ -2,6 +2,7 @@ add_llvm_component_library(LLVMABI
   Types.cpp
   FunctionInfo.cpp
   TargetInfo.cpp
+  IRTypeMapper.cpp
   Targets/BPF.cpp
 
   ADDITIONAL_HEADER_DIRS

diff  --git a/llvm/lib/ABI/IRTypeMapper.cpp b/llvm/lib/ABI/IRTypeMapper.cpp
new file mode 100644
index 0000000000000..3ba4553420375
--- /dev/null
+++ b/llvm/lib/ABI/IRTypeMapper.cpp
@@ -0,0 +1,162 @@
+//===---- IRTypeMapper.cpp - Maps LLVM ABI Types to LLVM IR Types -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ABI/IRTypeMapper.h"
+#include "llvm/ABI/Types.h"
+#include "llvm/ADT/APFloat.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Type.h"
+
+using namespace llvm::abi;
+
+llvm::Type *IRTypeMapper::convertType(const abi::Type *ABIType) {
+  assert(ABIType && "convertType requires a non-null ABI type");
+
+  auto It = TypeCache.find(ABIType);
+  if (It != TypeCache.end())
+    return It->second;
+
+  llvm::Type *Result = nullptr;
+
+  switch (ABIType->getKind()) {
+  case abi::TypeKind::Void:
+    Result = llvm::Type::getVoidTy(Context);
+    break;
+  case abi::TypeKind::Integer: {
+    const auto *IT = cast<abi::IntegerType>(ABIType);
+    Result =
+        llvm::IntegerType::get(Context, IT->getSizeInBits().getFixedValue());
+    break;
+  }
+  case abi::TypeKind::Float: {
+    const llvm::fltSemantics *Semantics =
+        cast<abi::FloatType>(ABIType)->getSemantics();
+    Result = llvm::Type::getFloatingPointTy(Context, *Semantics);
+    break;
+  }
+  case abi::TypeKind::Pointer:
+    Result = llvm::PointerType::get(
+        Context, cast<abi::PointerType>(ABIType)->getAddrSpace());
+    break;
+  case abi::TypeKind::Array:
+    Result = convertArrayType(cast<abi::ArrayType>(ABIType));
+    break;
+  case abi::TypeKind::Vector:
+    Result = convertVectorType(cast<abi::VectorType>(ABIType));
+    break;
+  case abi::TypeKind::Record:
+    Result = convertRecordType(cast<abi::RecordType>(ABIType));
+    break;
+  case abi::TypeKind::Complex:
+    Result = convertComplexType(cast<abi::ComplexType>(ABIType));
+    break;
+  case abi::TypeKind::MemberPointer:
+    Result = convertMemberPointerType(cast<abi::MemberPointerType>(ABIType));
+    break;
+  }
+
+  TypeCache[ABIType] = Result;
+  return Result;
+}
+
+llvm::Type *IRTypeMapper::convertArrayType(const abi::ArrayType *AT) {
+  llvm::Type *ElementType = convertType(AT->getElementType());
+  uint64_t NumElements = AT->getNumElements();
+  if (AT->isMatrixType())
+    return llvm::VectorType::get(ElementType,
+                                 ElementCount::getFixed(NumElements));
+  return llvm::ArrayType::get(ElementType, NumElements);
+}
+
+llvm::Type *IRTypeMapper::convertVectorType(const abi::VectorType *VT) {
+  llvm::Type *ElementType = convertType(VT->getElementType());
+  return llvm::VectorType::get(ElementType, VT->getNumElements());
+}
+
+llvm::Type *IRTypeMapper::convertRecordType(const abi::RecordType *RT) {
+  return createStructFromFields(RT->getFields(), RT->getSizeInBits(),
+                                RT->getAlignment(), RT->isUnion());
+}
+
+llvm::Type *IRTypeMapper::convertComplexType(const abi::ComplexType *CT) {
+  llvm::Type *ElementType = convertType(CT->getElementType());
+  llvm::Type *Fields[] = {ElementType, ElementType};
+  return llvm::StructType::get(Context, Fields, /*isPacked=*/false);
+}
+
+llvm::Type *
+IRTypeMapper::convertMemberPointerType(const abi::MemberPointerType *MPT) {
+  llvm::Type *IntPtrTy = DL.getIntPtrType(Context);
+  if (MPT->isFunctionPointer()) {
+    llvm::Type *Fields[] = {IntPtrTy, IntPtrTy};
+    return llvm::StructType::get(Context, Fields, /*isPacked=*/false);
+  }
+  return IntPtrTy;
+}
+
+llvm::Type *IRTypeMapper::createPaddingType(uint64_t PaddingBits) {
+  if (PaddingBits == 0)
+    return nullptr;
+  assert(PaddingBits % 8 == 0 &&
+         "sub-byte padding cannot be expressed as an llvm::Type");
+  return llvm::ArrayType::get(llvm::IntegerType::get(Context, 8),
+                              PaddingBits / 8);
+}
+
+llvm::StructType *
+IRTypeMapper::createStructFromFields(ArrayRef<abi::FieldInfo> Fields,
+                                     TypeSize Size, Align Alignment,
+                                     bool IsUnion) {
+  SmallVector<llvm::Type *, 16> FieldTypes;
+
+  if (IsUnion) {
+    llvm::Type *LargestFieldType = nullptr;
+    uint64_t LargestFieldSize = 0;
+    for (const auto &Field : Fields) {
+      llvm::Type *FieldType = convertType(Field.FieldType);
+      uint64_t FieldSize = Field.FieldType->getSizeInBits().getFixedValue();
+      if (FieldSize > LargestFieldSize) {
+        LargestFieldSize = FieldSize;
+        LargestFieldType = FieldType;
+      }
+    }
+    if (LargestFieldType) {
+      FieldTypes.push_back(LargestFieldType);
+      uint64_t UnionSizeBits = Size.getFixedValue();
+      if (LargestFieldSize < UnionSizeBits) {
+        if (llvm::Type *PaddingType =
+                createPaddingType(UnionSizeBits - LargestFieldSize))
+          FieldTypes.push_back(PaddingType);
+      }
+    }
+  } else {
+    uint64_t CurrentOffset = 0;
+    for (const auto &Field : Fields) {
+      if (Field.OffsetInBits > CurrentOffset) {
+        if (llvm::Type *PaddingType =
+                createPaddingType(Field.OffsetInBits - CurrentOffset))
+          FieldTypes.push_back(PaddingType);
+        CurrentOffset = Field.OffsetInBits;
+      }
+      assert(!Field.IsBitField && "bitfields should not reach IR type 
mapping");
+      llvm::Type *FieldType = convertType(Field.FieldType);
+      FieldTypes.push_back(FieldType);
+      CurrentOffset += Field.FieldType->getSizeInBits().getFixedValue();
+    }
+    uint64_t TotalSizeBits = Size.getFixedValue();
+    if (CurrentOffset < TotalSizeBits) {
+      if (llvm::Type *PaddingType =
+              createPaddingType(TotalSizeBits - CurrentOffset))
+        FieldTypes.push_back(PaddingType);
+    }
+  }
+
+  return StructType::get(Context, FieldTypes, /*isPacked=*/false);
+}


        
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