Reapply [IR] Lazily initialize the class to pass name mapping (NFC) (#96321) (#96462)

On MSVC the `this` uses inside `decltype` require a lambda capture. On
clang they result in an unused capture warning instead. Add the capture
and suppress the warning with `(void)this`.

-----

Initializing this map is somewhat expensive (especially for O0), so we
currently only do it if certain flags are used. I would like to make use
of it for crash dumps (#96078), where we don't know in advance whether
it will be needed or not.

This patch changes the initialization to a lazy approach, where a
callback is registered that does the actual initialization. The
callbacks will be run the first time the pass name is requested.

This way there is no compile-time impact if the mapping is not used.

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
index c853393..e6dbb25 100644
--- a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
+++ b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
@@ -102,8 +102,7 @@ DirectXTargetMachine::DirectXTargetMachine(const Target &T, const Triple &TT,
 
 DirectXTargetMachine::~DirectXTargetMachine() {}
 
-void DirectXTargetMachine::registerPassBuilderCallbacks(
-    PassBuilder &PB, bool PopulateClassToPassNames) {
+void DirectXTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
 #define GET_PASS_REGISTRY "DirectXPassRegistry.def"
 #include "llvm/Passes/TargetPassRegistry.inc"
 }