[AArch64] Produce the right kind of va_arg for windows

[mstorsjo]

Summary

On windows on arm64, the va_list is a plain pointer.

[efriedma]

Needs a testcase (to check the emitted IR).

lib/CodeGen/TargetInfo.cpp

4769 ↗

(On Diff #105253)

Can we extend ABIKind rather than adding a separate boolean?

[mstorsjo]

lib/CodeGen/TargetInfo.cpp

4769 ↗

(On Diff #105253)

Sure. I was afraid there was a lot of checks like Kind == AAPCS which would need to be changed into Kind == AAPCS || Kind == Win64, but it didn't turn out to be an issue.

[mstorsjo]

Added a testcase, using a different Kind instead of adding a separate bool.

[mstorsjo]

Ping - the dependency, D35006, has now been committed.

[rnk]

lgtm

lib/CodeGen/TargetInfo.cpp

8463 ↗

(On Diff #105392)

Triple.isOSWindows() is probably cleaner.

cfe/trunk/lib/CodeGen/TargetInfo.cpp

 //===----------------------------------------------------------------------===//
 
 namespace {
 
 class AArch64ABIInfo : public SwiftABIInfo {
 public:
   enum ABIKind {
     AAPCS = 0,
-    DarwinPCS
+    DarwinPCS,
+    Win64
   };
 
 private:
   ABIKind Kind;
 
 public:
   AArch64ABIInfo(CodeGenTypes &CGT, ABIKind Kind)
     : SwiftABIInfo(CGT), Kind(Kind) {}
private:
   Address EmitDarwinVAArg(Address VAListAddr, QualType Ty,
                           CodeGenFunction &CGF) const;
 
   Address EmitAAPCSVAArg(Address VAListAddr, QualType Ty,
                          CodeGenFunction &CGF) const;
 
   Address EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
                     QualType Ty) const override {
-    return isDarwinPCS() ? EmitDarwinVAArg(VAListAddr, Ty, CGF)
+    return Kind == Win64 ? EmitMSVAArg(CGF, VAListAddr, Ty)
+                         : isDarwinPCS() ? EmitDarwinVAArg(VAListAddr, Ty, CGF)
                                          : EmitAAPCSVAArg(VAListAddr, Ty, CGF);
   }
 
+  Address EmitMSVAArg(CodeGenFunction &CGF, Address VAListAddr,
+                      QualType Ty) const override;
+
   bool shouldPassIndirectlyForSwift(CharUnits totalSize,
                                     ArrayRef<llvm::Type*> scalars,
                                     bool asReturnValue) const override {
     return occupiesMoreThan(CGT, scalars, /*total*/ 4);
   }
   bool isSwiftErrorInRegister() const override {
     return true;
   }
if (TyInfo.first.getQuantity() > 16) {
     uint64_t Members = 0;
     IsIndirect = !isHomogeneousAggregate(Ty, Base, Members);
   }
 
   return emitVoidPtrVAArg(CGF, VAListAddr, Ty, IsIndirect,
                           TyInfo, SlotSize, /*AllowHigherAlign*/ true);
 }
 
+Address AArch64ABIInfo::EmitMSVAArg(CodeGenFunction &CGF, Address VAListAddr,
+                                    QualType Ty) const {
+  return emitVoidPtrVAArg(CGF, VAListAddr, Ty, /*indirect*/ false,
+                          CGF.getContext().getTypeInfoInChars(Ty),
+                          CharUnits::fromQuantity(8),
+                          /*allowHigherAlign*/ false);
+}
+
 //===----------------------------------------------------------------------===//
 // ARM ABI Implementation
 //===----------------------------------------------------------------------===//
 
 namespace {
 
 class ARMABIInfo : public SwiftABIInfo {
 public:
const TargetCodeGenInfo &CodeGenModule::getTargetCodeGenInfo() {
   case llvm::Triple::avr:
     return SetCGInfo(new AVRTargetCodeGenInfo(Types));
 
   case llvm::Triple::aarch64:
   case llvm::Triple::aarch64_be: {
     AArch64ABIInfo::ABIKind Kind = AArch64ABIInfo::AAPCS;
     if (getTarget().getABI() == "darwinpcs")
       Kind = AArch64ABIInfo::DarwinPCS;
+    else if (Triple.isOSWindows())
+      Kind = AArch64ABIInfo::Win64;
 
     return SetCGInfo(new AArch64TargetCodeGenInfo(Types, Kind));
   }
 
   case llvm::Triple::wasm32:
   case llvm::Triple::wasm64:
     return SetCGInfo(new WebAssemblyTargetCodeGenInfo(Types));
 

cfe/trunk/test/CodeGen/aarch64-varargs-ms.c

+// RUN: %clang_cc1 -triple arm64-windows-msvc -emit-llvm -o - %s | FileCheck --check-prefix=CHECK %s
+
+#include <stdarg.h>
+
+int simple_int(va_list ap) {
+// CHECK-LABEL: define i32 @simple_int
+  return va_arg(ap, int);
+// CHECK: [[ADDR:%[a-z_0-9]+]] = bitcast i8* %argp.cur to i32*
+// CHECK: [[RESULT:%[a-z_0-9]+]] = load i32, i32* [[ADDR]]
+// CHECK: ret i32 [[RESULT]]
+}