[flang-commits] [flang] [flang] Add struct passing target rewrite hooks and partial X86-64 impl (PR #74829)

[Slava Zakharin via flang-commits]

================
@@ -318,6 +382,251 @@ struct TargetX86_64 : public GenericTarget<TargetX86_64> {
     }
     return marshal;
   }
+
+  /// X86-64 argument classes from System V ABI version 1.0 section 3.2.3.
+  enum ArgClass {
+    Integer = 0,
+    SSE,
+    SSEUp,
+    X87,
+    X87Up,
+    ComplexX87,
+    NoClass,
+    Memory
+  };
+
+  /// Classify an argument type or a field of an aggregate type argument.
+  /// See ystem V ABI version 1.0 section 3.2.3.
+  /// The Lo and Hi class are set to the class of the lower eight eightbytes
+  /// and upper eight eightbytes on return.
+  /// If this is called for an aggregate field, the caller is responsible to
+  /// do the post-merge.
+  void classify(mlir::Location loc, mlir::Type type, std::uint64_t byteOffset,
+                ArgClass &Lo, ArgClass &Hi) const {
+    Hi = Lo = ArgClass::NoClass;
+    ArgClass &current = byteOffset < 8 ? Lo : Hi;
+    // System V AMD64 ABI 3.2.3. version 1.0
+    llvm::TypeSwitch<mlir::Type>(type)
+        .template Case<mlir::IntegerType>([&](mlir::IntegerType intTy) {
+          if (intTy.getWidth() == 128)
+            Hi = Lo = ArgClass::Integer;
+          else
+            current = ArgClass::Integer;
+        })
+        .template Case<mlir::FloatType, fir::RealType>([&](mlir::Type floatTy) {
+          const auto *sem = &floatToSemantics(kindMap, floatTy);
+          if (sem == &llvm::APFloat::x87DoubleExtended()) {
+            Lo = ArgClass::X87;
+            Hi = ArgClass::X87Up;
+          } else if (sem == &llvm::APFloat::IEEEquad()) {
+            Lo = ArgClass::SSE;
+            Hi = ArgClass::SSEUp;
+          } else {
+            current = ArgClass::SSE;
+          }
+        })
+        .template Case<fir::ComplexType>([&](fir::ComplexType cmplx) {
+          const auto *sem = &floatToSemantics(kindMap, cmplx.getElementType());
+          if (sem == &llvm::APFloat::x87DoubleExtended()) {
+            current = ArgClass::ComplexX87;
+          } else {
+            fir::SequenceType::Shape shape{2};
+            classifyArray(loc,
+                          fir::SequenceType::get(shape, cmplx.getElementType()),
+                          byteOffset, Lo, Hi);
+          }
+        })
+        .template Case<fir::LogicalType>([&](fir::LogicalType logical) {
+          if (kindMap.getLogicalBitsize(logical.getFKind()) == 128)
+            Hi = Lo = ArgClass::Integer;
+          else
+            current = ArgClass::Integer;
+        })
+        .template Case<fir::CharacterType>(
+            [&](fir::CharacterType character) { current = ArgClass::Integer; })
+        .template Case<fir::SequenceType>([&](fir::SequenceType seqTy) {
+          // Array component.
+          classifyArray(loc, seqTy, byteOffset, Lo, Hi);
+        })
+        .template Case<fir::RecordType>([&](fir::RecordType recTy) {
+          // Component that is a derived type.
+          classifyStruct(loc, recTy, byteOffset, Lo, Hi);
+        })
+        .template Case<fir::VectorType>([&](fir::VectorType vecTy) {
+          // Previously marshalled SSE eight byte for a previous struct
+          // argument.
+          auto *sem = fir::isa_real(vecTy.getEleTy())
+                          ? &floatToSemantics(kindMap, vecTy.getEleTy())
+                          : nullptr;
+          // Note expecting to hit this todo in standard code (it would
----------------
vzakhari wrote:

typo?
```suggestion
          // Not expecting to hit this todo in standard code (it would
```

https://github.com/llvm/llvm-project/pull/74829