Refactor fgInitArgInfo to track non standard arg kinds (#58324)

This changes the JIT to keep track of the non standard arg kinds that
are added to the arg info table. We currently have several places
(`fgResetArgInfo`, morph for tailcall-via-helpers) that make "blind"
assumptions on which arg is which depending on certain flags set in the
call. This change makes `fgResetArgInfo` more general and allows us to
add asserts to the tailcall logic to verify that we are removing the
args we expect.

Author: jakobbotsch

src/coreclr/jit/compiler.h

@@ -1461,6 +1461,26 @@ struct FuncInfoDsc
     // that isn't shared between the main function body and funclets.
 };
 
+enum class NonStandardArgKind : unsigned
+{
+    None,
+    PInvokeFrame,
+    PInvokeTarget,
+    PInvokeCookie,
+    WrapperDelegateCell,
+    ShiftLow,
+    ShiftHigh,
+    FixedRetBuffer,
+    VirtualStubCell,
+    R2RIndirectionCell,
+
+    // If changing this enum also change getNonStandardArgKindName and isNonStandardArgAddedLate below
+};
+
+#ifdef DEBUG
+const char* getNonStandardArgKindName(NonStandardArgKind kind);
+#endif
+
 struct fgArgTabEntry
 {
     GenTreeCall::Use* use;     // Points to the argument's GenTreeCall::Use in gtCallArgs or gtCallThisArg.
@@ -1521,17 +1541,18 @@ struct fgArgTabEntry
                        // struct is passed as a scalar type, this is that type.
                        // Note that if a struct is passed by reference, this will still be the struct type.
 
-    bool needTmp : 1;       // True when we force this argument's evaluation into a temp LclVar
-    bool needPlace : 1;     // True when we must replace this argument with a placeholder node
-    bool isTmp : 1;         // True when we setup a temp LclVar for this argument due to size issues with the struct
-    bool processed : 1;     // True when we have decided the evaluation order for this argument in the gtCallLateArgs
-    bool isBackFilled : 1;  // True when the argument fills a register slot skipped due to alignment requirements of
-                            // previous arguments.
-    bool isNonStandard : 1; // True if it is an arg that is passed in a reg other than a standard arg reg, or is forced
-                            // to be on the stack despite its arg list position.
-    bool isStruct : 1;      // True if this is a struct arg
-    bool _isVararg : 1;     // True if the argument is in a vararg context.
-    bool passedByRef : 1;   // True iff the argument is passed by reference.
+    bool needTmp : 1;      // True when we force this argument's evaluation into a temp LclVar
+    bool needPlace : 1;    // True when we must replace this argument with a placeholder node
+    bool isTmp : 1;        // True when we setup a temp LclVar for this argument due to size issues with the struct
+    bool processed : 1;    // True when we have decided the evaluation order for this argument in the gtCallLateArgs
+    bool isBackFilled : 1; // True when the argument fills a register slot skipped due to alignment requirements of
+                           // previous arguments.
+    NonStandardArgKind nonStandardArgKind : 4; // The non-standard arg kind. Non-standard args are args that are forced
+                                               // to be in certain registers or on the stack, regardless of where they
+                                               // appear in the arg list.
+    bool isStruct : 1;                         // True if this is a struct arg
+    bool _isVararg : 1;                        // True if the argument is in a vararg context.
+    bool passedByRef : 1;                      // True iff the argument is passed by reference.
 #ifdef FEATURE_ARG_SPLIT
     bool _isSplit : 1; // True when this argument is split between the registers and OutArg area
 #endif                 // FEATURE_ARG_SPLIT
@@ -1557,6 +1578,34 @@ struct fgArgTabEntry
 #endif
     }
 
+    bool isNonStandard() const
+    {
+        return nonStandardArgKind != NonStandardArgKind::None;
+    }
+
+    // Returns true if the IR node for this non-standarg arg is added by fgInitArgInfo.
+    // In this case, it must be removed by GenTreeCall::ResetArgInfo.
+    bool isNonStandardArgAddedLate() const
+    {
+        switch (nonStandardArgKind)
+        {
+            case NonStandardArgKind::None:
+            case NonStandardArgKind::PInvokeFrame:
+            case NonStandardArgKind::ShiftLow:
+            case NonStandardArgKind::ShiftHigh:
+            case NonStandardArgKind::FixedRetBuffer:
+                return false;
+            case NonStandardArgKind::WrapperDelegateCell:
+            case NonStandardArgKind::VirtualStubCell:
+            case NonStandardArgKind::PInvokeCookie:
+            case NonStandardArgKind::PInvokeTarget:
+            case NonStandardArgKind::R2RIndirectionCell:
+                return true;
+            default:
+                unreached();
+        }
+    }
+
     bool isLateArg() const
     {
         bool isLate = (_lateArgInx != UINT_MAX);

src/coreclr/jit/gentree.cpp

@@ -1226,18 +1226,31 @@ void GenTreeCall::ResetArgInfo()
     // only sets up fgArgInfo, it also adds non-standard args to the IR, and we need
     // to remove that extra IR so it doesn't get added again.
     //
-    // NOTE: this doesn't handle all possible cases. There might be cases where we
-    // should be removing non-standard arg IR but currently aren't.
-    CLANG_FORMAT_COMMENT_ANCHOR;
+    unsigned argNum = 0;
+    if (gtCallThisArg != nullptr)
+    {
+        argNum++;
+    }
 
-#if !defined(TARGET_X86)
-    if (IsVirtualStub())
+    Use** link = &gtCallArgs;
+    while ((*link) != nullptr)
     {
-        JITDUMP("Removing VSD non-standard arg [%06u] to prepare for re-morphing call [%06u]\n",
-                Compiler::dspTreeID(gtCallArgs->GetNode()), gtTreeID);
-        gtCallArgs = gtCallArgs->GetNext();
+        const fgArgTabEntry* entry = fgArgInfo->GetArgEntry(argNum);
+        if (entry->isNonStandard() && entry->isNonStandardArgAddedLate())
+        {
+            JITDUMP("Removing non-standarg arg %s [%06u] to prepare for re-morphing call [%06u]\n",
+                    getNonStandardArgKindName(entry->nonStandardArgKind), Compiler::dspTreeID((*link)->GetNode()),
+                    gtTreeID);
+
+            *link = (*link)->GetNext();
+        }
+        else
+        {
+            link = &(*link)->NextRef();
+        }
+
+        argNum++;
     }
-#endif // !defined(TARGET_X86)
 
     fgArgInfo = nullptr;
 }