Revert D109159 "[amdgpu] Enable selection of `s_cselect_b64`."

This reverts commit 640beb38e7710b939b3cfb3f4c54accc694b1d30.

That commit caused performance degradtion in Quicksilver test QS:sGPU and a functional test failure in (rocPRIM rocprim.device_segmented_radix_sort).
Reverting until we have a better solution to s_cselect_b64 codegen cleanup

Change-Id: Ibf8e397df94001f248fba609f072088a46abae08

Reviewed By: kzhuravl

Differential Revision: https://reviews.llvm.org/D115960

Change-Id: Id169459ce4dfffa857d5645a0af50b0063ce1105

1 files changed, 84 insertions, 0 deletions

diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp
new file mode 100644
index 000000000000..c0c819632851
--- /dev/null
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp
@@ -0,0 +1,84 @@
+//===-- LibCxxOptional.cpp ------------------------------------------------===//
+//
+// 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 "LibCxx.h"
+#include "lldb/DataFormatters/FormattersHelpers.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+namespace {
+
+class OptionalFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  OptionalFrontEnd(ValueObject &valobj) : SyntheticChildrenFrontEnd(valobj) {
+    Update();
+  }
+
+  size_t GetIndexOfChildWithName(ConstString name) override {
+    return formatters::ExtractIndexFromString(name.GetCString());
+  }
+
+  bool MightHaveChildren() override { return true; }
+  bool Update() override;
+  size_t CalculateNumChildren() override { return m_has_value ? 1U : 0U; }
+  ValueObjectSP GetChildAtIndex(size_t idx) override;
+
+private:
+  /// True iff the option contains a value.
+  bool m_has_value = false;
+};
+} // namespace
+
+bool OptionalFrontEnd::Update() {
+  ValueObjectSP engaged_sp(
+      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true));
+
+  if (!engaged_sp)
+    return false;
+
+  // __engaged_ is a bool flag and is true if the optional contains a value.
+  // Converting it to unsigned gives us a size of 1 if it contains a value
+  // and 0 if not.
+  m_has_value = engaged_sp->GetValueAsUnsigned(0) == 1;
+
+  return false;
+}
+
+ValueObjectSP OptionalFrontEnd::GetChildAtIndex(size_t idx) {
+  if (!m_has_value)
+    return ValueObjectSP();
+
+  // __val_ contains the underlying value of an optional if it has one.
+  // Currently because it is part of an anonymous union GetChildMemberWithName()
+  // does not peer through and find it unless we are at the parent itself.
+  // We can obtain the parent through __engaged_.
+  ValueObjectSP val_sp(
+      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
+          ->GetParent()
+          ->GetChildAtIndex(0, true)
+          ->GetChildMemberWithName(ConstString("__val_"), true));
+
+  if (!val_sp)
+    return ValueObjectSP();
+
+  CompilerType holder_type = val_sp->GetCompilerType();
+
+  if (!holder_type)
+    return ValueObjectSP();
+
+  return val_sp->Clone(ConstString("Value"));
+}
+
+SyntheticChildrenFrontEnd *
+formatters::LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
+                                          lldb::ValueObjectSP valobj_sp) {
+  if (valobj_sp)
+    return new OptionalFrontEnd(*valobj_sp);
+  return nullptr;
+}