[AArch64][Windows] Check sret attribute also for inreg attribute

[bcl5980]

Summary

Fix the issue: #57684

[DavidSpickett]

I have zero idea what either InReg or SRet are, I'll leave the actual review to others.

llvm/test/CodeGen/AArch64/aarch64-windows-inreg-without-sret.ll

3

Please comment the intent of the test. E.g.

"When there is inreg but not sret, we should emit..."

[efriedma]

Code change looks fine

llvm/test/CodeGen/AArch64/aarch64-windows-inreg-without-sret.ll

7

Is there some other file we could put this in with other Windows calling convention stuff?

[bcl5980]

move the test to arm64-windows-calls.ll

[efriedma]

LGTM

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

if (isVarArg) {
     }
   }
 
   // On Windows, InReg pointers must be returned, so record the pointer in a
   // virtual register at the start of the function so it can be returned in the
   // epilogue.
   if (IsWin64) {
     for (unsigned I = 0, E = Ins.size(); I != E; ++I) {
-      if (Ins[I].Flags.isInReg()) {
+      if (Ins[I].Flags.isInReg() && Ins[I].Flags.isSRet()) {
         assert(!FuncInfo->getSRetReturnReg());
 
         MVT PtrTy = getPointerTy(DAG.getDataLayout());
         Register Reg =
             MF.getRegInfo().createVirtualRegister(getRegClassFor(PtrTy));
         FuncInfo->setSRetReturnReg(Reg);
 
         SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), DL, Reg, InVals[I]);

llvm/test/CodeGen/AArch64/aarch64-windows-inreg-without-sret.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-pc-windows-msvc"
+
+define i64 @foobar(i64* inreg %0) {
+; CHECK-LABEL: foobar:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    ldr x0, [x0]
+; CHECK-NEXT:    ret
+entry:
+  %1 = load i64, i64* %0
+  ret i64 %1
+}