[llvm] [AMDGPU] Add AMDGPU specific variadic operation MCExprs (PR #82022)

[Pierre van Houtryve via llvm-commits]

================
@@ -0,0 +1,94 @@
+//===- AMDGPUMCExpr.cpp - AMDGPU specific MC expression classes -----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPUMCExpr.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/raw_ostream.h"
+#include <optional>
+
+using namespace llvm;
+
+const AMDGPUVariadicMCExpr *
+AMDGPUVariadicMCExpr::create(AMDGPUVariadicKind Kind,
+                             ArrayRef<const MCExpr *> Args, MCContext &Ctx) {
+  return new (Ctx) AMDGPUVariadicMCExpr(Kind, Args);
+}
+
+const MCExpr *AMDGPUVariadicMCExpr::GetSubExpr(size_t index) const {
+  assert(index < Args.size() &&
+         "Indexing out of bounds AMDGPUVariadicMCExpr sub-expr");
+  return Args[index];
+}
+
+void AMDGPUVariadicMCExpr::printImpl(raw_ostream &OS,
+                                     const MCAsmInfo *MAI) const {
+  switch (Kind) {
+  default:
+    llvm_unreachable("Unknown AMDGPUVariadicMCExpr kind.");
+  case AGVK_Or:
+    OS << "or(";
+    break;
+  case AGVK_Max:
+    OS << "max(";
+    break;
+  }
+  for (auto It = Args.begin(); It != Args.end(); ++It) {
+    (*It)->print(OS, MAI, /*InParens=*/false);
+    if ((It + 1) != Args.end())
+      OS << ", ";
+  }
+  OS << ')';
+}
+
+static int64_t Op(AMDGPUVariadicMCExpr::AMDGPUVariadicKind Kind, int64_t Arg1,
+                  int64_t Arg2) {
+  switch (Kind) {
+  default:
+    llvm_unreachable("Unknown AMDGPUVariadicMCExpr kind.");
+  case AMDGPUVariadicMCExpr::AMDGPUVariadicKind::AGVK_Max:
+    return std::max(Arg1, Arg2);
+  case AMDGPUVariadicMCExpr::AMDGPUVariadicKind::AGVK_Or:
+    return Arg1 || Arg2;
----------------
Pierre-vh wrote:

```suggestion
  case AMDGPUVariadicMCExpr::AGVK_Max:
    return std::max(Arg1, Arg2);
  case AMDGPUVariadicMCExpr::AGVK_Or:
    return Arg1 || Arg2;
```

https://github.com/llvm/llvm-project/pull/82022