[clang] [llvm] [WIP] ABI Lowering Library (PR #140112)

[Nikita Popov via llvm-commits]

================
@@ -0,0 +1,337 @@
+//===----- ABIFunctionInfo.h - ABI Function Information ----- C++ ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines ABIFunctionInfo and associated types used in representing the
+// ABI-coerced types for function arguments and return values.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ABI_ABIFUNCTIONINFO_H
+#define LLVM_ABI_ABIFUNCTIONINFO_H
+
+#include "llvm/ABI/Types.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/IR/CallingConv.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/TrailingObjects.h"
+
+namespace llvm {
+namespace abi {
+
+/// ABIArgInfo - Helper class to encapsulate information about how a
+/// specific type should be passed to or returned from a function.
+class ABIArgInfo {
+public:
+  enum Kind {
+    Direct,
+    Extend,
+    Indirect,
+    IndirectAliased,
+    Ignore,
+    Expand,
+    CoerceAndExpand,
+    InAlloca
+  };
+
+private:
+  Kind TheKind;
+  const Type *CoercionType;
+  const Type *PaddingType;
+  struct DirectAttrInfo {
+    unsigned Offset;
+    unsigned Align;
+  };
+
+  struct IndirectAttrInfo {
+    unsigned Align;
+    unsigned AddrSpace;
+  };
+
+  union {
+    DirectAttrInfo DirectAttr;
+    IndirectAttrInfo IndirectAttr;
+  };
+  bool InReg : 1;
+  bool PaddingInReg : 1;
+  bool SignExt : 1;
+  bool ZeroExt : 1;
+  unsigned IndirectAlign : 16;
+  bool IndirectByVal : 1;
+  bool IndirectRealign : 1;
+  bool CanBeFlattened : 1;
+
+  ABIArgInfo(Kind K = Direct)
+      : TheKind(K), CoercionType(nullptr), InReg(false), PaddingInReg(false),
+        SignExt(false), ZeroExt(false), IndirectAlign(0), IndirectByVal(false) {
+  }
+
+public:
+  static ABIArgInfo getDirect(const Type *T = nullptr, unsigned Offset = 0,
+                              const Type *Padding = nullptr,
+                              bool CanBeFlattened = true, unsigned Align = 0) {
+    ABIArgInfo AI(Direct);
+    AI.CoercionType = T;
+    AI.PaddingType = Padding;
+    AI.DirectAttr.Offset = Offset;
+    AI.DirectAttr.Align = Align;
+    AI.CanBeFlattened = CanBeFlattened;
+    return AI;
+  }
+
+  static ABIArgInfo getIndirectAliased(unsigned Align, unsigned AddrSpace = 0,
+                                       bool Realign = false,
+                                       const Type *Padding = nullptr) {
+    ABIArgInfo AI(IndirectAliased);
+    AI.IndirectAttr.Align = Align;
+    AI.IndirectAttr.AddrSpace = AddrSpace;
+    AI.IndirectRealign = Realign;
+    AI.PaddingType = Padding;
+    return AI;
+  }
+  static ABIArgInfo getDirectInReg(const Type *T = nullptr) {
+    ABIArgInfo AI = getDirect(T);
+    AI.InReg = true;
+    return AI;
+  }
+  static ABIArgInfo getExtend(const Type *T = nullptr) {
----------------
nikic wrote:

```suggestion
  static ABIArgInfo getExtend(const Type *T) {
```
Shouldn't have nullptr default if next line asserts it's not nullptr :)

https://github.com/llvm/llvm-project/pull/140112