[RyuJIT/ARM32] Enable passing large split struct argument (#12050)

* [RyuJIT/ARM32] Enable passing large split struct

This enables passing split struct larger than 16 bytes.
To support splitted struct, it defines new GenTree type - GenTreePutArgSplit.
GenTreePutArgSplit is similar with GenTreePutArgStk,
but it is used for splitted struct only
and it has additional field to save register information.
GenTreePutArgSplit node is generated in lower phase.

* Apply reviews: split struct argument passing

- Fix some comments:
genPutArgSplit, GenTreePutArgStk, GenTreePutArgSplit, NuwPutArg, ArgComplete
- Add assertion check in genPutArgSplit, genCallInstruction
- Rename variable: baseReg
- Change flag for GenTreePutArgSplit: _TARGET_ARM && !LEGACY_BACKEND
- Change type of gtOtherRegs in GenTreePutArgSplit
- Remove duplicated code: NewPutArg
- Implement spill & restore flag for GenTreePutArgSplit

* Apply reviews

- Rebase
- Update managing spillFlag for split struct
- Implement spill & restore code generation
- Fix typos and rename variables
- Fix bug related to print gentree for split struct

* Fix bug and comments

- Fix bug in regset.cpp
- Add comments in morph.cpp's NYI_ARM
- Fix comments' typo in lsraarmarcp.cpp

1 files changed, 39 insertions, 2 deletions

diff --git a/src/jit/regset.cpp b/src/jit/regset.cpp
index 48ec6ea6f1..720466348c 100644
--- a/src/jit/regset.cpp
+++ b/src/jit/regset.cpp
@@ -1527,6 +1527,9 @@ void RegSet::rsSpillTree(regNumber reg, GenTreePtr tree, unsigned regIdx /* =0 *
 
     GenTreeCall* call = nullptr;
     var_types    treeType;
+#if !defined(LEGACY_BACKEND) && defined(_TARGET_ARM_)
+    GenTreePutArgSplit* splitArg = nullptr;
+#endif
 
 #ifndef LEGACY_BACKEND
     if (tree->IsMultiRegCall())
@@ -1535,8 +1538,15 @@ void RegSet::rsSpillTree(regNumber reg, GenTreePtr tree, unsigned regIdx /* =0 *
         ReturnTypeDesc* retTypeDesc = call->GetReturnTypeDesc();
         treeType                    = retTypeDesc->GetReturnRegType(regIdx);
     }
+#ifdef _TARGET_ARM_
+    else if (tree->OperIsPutArgSplit())
+    {
+        splitArg = tree->AsPutArgSplit();
+        treeType = splitArg->GetRegType(regIdx);
+    }
+#endif // _TARGET_ARM_
     else
-#endif
+#endif // !LEGACY_BACKEND
     {
         treeType = tree->TypeGet();
     }
@@ -1584,6 +1594,14 @@ void RegSet::rsSpillTree(regNumber reg, GenTreePtr tree, unsigned regIdx /* =0 *
         assert((regFlags & GTF_SPILL) != 0);
         regFlags &= ~GTF_SPILL;
     }
+#ifdef _TARGET_ARM_
+    else if (splitArg != nullptr)
+    {
+        regFlags = splitArg->GetRegSpillFlagByIdx(regIdx);
+        assert((regFlags & GTF_SPILL) != 0);
+        regFlags &= ~GTF_SPILL;
+    }
+#endif // _TARGET_ARM_
     else
     {
         assert(!varTypeIsMultiReg(tree));
@@ -1603,9 +1621,12 @@ void RegSet::rsSpillTree(regNumber reg, GenTreePtr tree, unsigned regIdx /* =0 *
         assert(tree->InReg());
         assert(tree->gtRegNum == reg);
     }
+#elif defined(_TARGET_ARM_)
+    assert(tree->gtRegNum == reg || (call != nullptr && call->GetRegNumByIdx(regIdx) == reg) ||
+           (splitArg != nullptr && splitArg->GetRegNumByIdx(regIdx) == reg));
 #else
     assert(tree->gtRegNum == reg || (call != nullptr && call->GetRegNumByIdx(regIdx) == reg));
-#endif // CPU_LONG_USES_REGPAIR
+#endif // !CPU_LONG_USES_REGPAIR && !_TARGET_ARM_
 
     // Are any registers free for spillage?
     SpillDsc* spill = SpillDsc::alloc(m_rsCompiler, this, tempType);
@@ -1726,6 +1747,13 @@ void RegSet::rsSpillTree(regNumber reg, GenTreePtr tree, unsigned regIdx /* =0 *
         regFlags |= GTF_SPILLED;
         call->SetRegSpillFlagByIdx(regFlags, regIdx);
     }
+#ifdef _TARGET_ARM_
+    else if (splitArg != nullptr)
+    {
+        regFlags |= GTF_SPILLED;
+        splitArg->SetRegSpillFlagByIdx(regFlags, regIdx);
+    }
+#endif // _TARGET_ARM_
 #endif //! LEGACY_BACKEND
 }
 
@@ -2355,6 +2383,15 @@ TempDsc* RegSet::rsUnspillInPlace(GenTreePtr tree, regNumber oldReg, unsigned re
         flags &= ~GTF_SPILLED;
         call->SetRegSpillFlagByIdx(flags, regIdx);
     }
+#if !defined(LEGACY_BACKEND) && defined(_TARGET_ARM_)
+    else if (tree->OperIsPutArgSplit())
+    {
+        GenTreePutArgSplit* splitArg = tree->AsPutArgSplit();
+        unsigned            flags    = splitArg->GetRegSpillFlagByIdx(regIdx);
+        flags &= ~GTF_SPILLED;
+        splitArg->SetRegSpillFlagByIdx(flags, regIdx);
+    }
+#endif // !LEGACY_BACKEND && _TARGET_ARM_
     else
     {
         tree->gtFlags &= ~GTF_SPILLED;