[clang] [llvm] [PowerPC] add TargetParser for PPC target (PR #97541)

[David Tenty via cfe-commits]

================
@@ -0,0 +1,120 @@
+//===---- PPCTargetParser.cpp - Parser for target features ------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a target parser to recognise hardware features
+// for PPC CPUs.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/TargetParser/PPCTargetParser.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/TargetParser/Host.h"
+
+namespace llvm {
+namespace PPC {
+
+struct CPUInfo {
+  StringLiteral Name;
+  // FIXME: add the features field for this CPU.
+};
+
+constexpr CPUInfo PPCCPUInfo[] = {
+#define PPC_CPU(Name, Linux_SUPPORT_METHOD, LinuxID, AIX_SUPPORT_METHOD,       \
+                AIXID)                                                         \
+  Name,
+#include "llvm/TargetParser/PPCTargetParser.def"
+};
+
+static const CPUInfo *getCPUInfoByName(StringRef CPU) {
+  for (auto &C : PPCCPUInfo)
+    if (C.Name == CPU)
+      return &C;
+  return nullptr;
+}
+
+StringRef normalizeCPUName(StringRef CPUName) {
+  // Clang/LLVM does not actually support code generation
+  // for the 405 CPU. However, there are uses of this CPU ID
+  // in projects that previously used GCC and rely on Clang
+  // accepting it. Clang has always ignored it and passed the
+  // generic CPU ID to the back end.
+  return StringSwitch<StringRef>(CPUName)
+      .Cases("common", "405", "generic")
+      .Cases("ppc440", "440fp", "440")
+      .Cases("630", "power3", "pwr3")
+      .Case("G3", "g3")
+      .Case("G4", "g4")
+      .Case("G4+", "g4+")
+      .Case("8548", "e500")
+      .Case("ppc970", "970")
+      .Case("G5", "g5")
+      .Case("ppca2", "a2")
+      .Case("power4", "pwr4")
+      .Case("power5", "pwr5")
+      .Case("power5x", "pwr5x")
+      .Case("power5+", "pwr5+")
+      .Case("power6", "pwr6")
+      .Case("power6x", "pwr6x")
+      .Case("power7", "pwr7")
+      .Case("power8", "pwr8")
+      .Case("power9", "pwr9")
+      .Case("power10", "pwr10")
+      .Cases("powerpc", "powerpc32", "ppc")
+      .Case("powerpc64", "ppc64")
+      .Case("powerpc64le", "ppc64le")
+      .Default(CPUName);
+}
+
+void fillValidCPUList(SmallVectorImpl<StringRef> &Values) {
+  for (const auto &C : PPCCPUInfo)
+    Values.emplace_back(C.Name);
+}
+
+void fillValidTuneCPUList(SmallVectorImpl<StringRef> &Values) {
+  for (const auto &C : PPCCPUInfo)
+    Values.emplace_back(C.Name);
+}
+
+bool isValidCPU(StringRef CPU) {
+  const CPUInfo *Info = getCPUInfoByName(CPU);
+  if (!Info)
+    return false;
+  return true;
+}
+
+StringRef getPPCGenericTargetCPU(const Triple &T, StringRef CPUName) {
+  if (!CPUName.empty()) {
+    if (CPUName == "native") {
+      std::string CPU = std::string(sys::getHostCPUName());
+      if (!CPU.empty() && CPU != "generic")
+        return CPU;
+    }
+
+    StringRef CPU = normalizeCPUName(CPUName);
+    if (CPU != "generic")
+      return CPU;
+  }
+
+  // LLVM may default to generating code for the native CPU, but, like gcc, we
+  // default to a more generic option for each architecture. (except on AIX)
+  if (T.isOSAIX())
+    return "pwr7";
+  else if (T.getArch() == Triple::ppc64le)
+    return "ppc64le";
+  else if (T.getArch() == Triple::ppc64)
+    return "ppc64";
----------------
daltenty wrote:

I'm not sure that the AIX changes should be part of this patch (to keep the scope of what's changing clear), but if it is, I'd suggest we key this to the minimum supported CPUs per OS level: 

```suggestion
  if (T.isOSAIX()) {
    if (T.isOSVersionLT(7, 2))
      return "pwr4";
    else if (T.isOSVersionLT(7, 3))
      return "pwr7";
    else // AIX 7.3 and above
      return "pwr8";
  }
  else if (T.getArch() == Triple::ppc64le)
    return "ppc64le";
  else if (T.getArch() == Triple::ppc64)
    return "ppc64";
```

https://github.com/llvm/llvm-project/pull/97541