[clang] [clang][bytecode] Add an `ExplicitThisParam` flag to `Function` (PR #203672)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/203672

We unfortunately have to check this for every function call, so don't consult the decl every time here.

>From e2d715ec9a2987fb267736b64e4d2ca90595ab73 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Fri, 12 Jun 2026 15:31:19 +0200
Subject: [PATCH] func explicit flag

---
 clang/lib/AST/ByteCode/Function.cpp |  5 +++++
 clang/lib/AST/ByteCode/Function.h   | 19 ++++++++-----------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/clang/lib/AST/ByteCode/Function.cpp b/clang/lib/AST/ByteCode/Function.cpp
index e08e2790dbd4f..cd0f7eb125230 100644
--- a/clang/lib/AST/ByteCode/Function.cpp
+++ b/clang/lib/AST/ByteCode/Function.cpp
@@ -29,12 +29,15 @@ Function::Function(Program &P, FunctionDeclTy Source, unsigned ArgSize,
     Constexpr = F->isConstexpr();
     if (const auto *CD = dyn_cast<CXXConstructorDecl>(F)) {
       Virtual = CD->isVirtual();
+      ExplicitThisPointer = CD->isExplicitObjectMemberFunction();
       Kind = CD->isCopyOrMoveConstructor() ? FunctionKind::CopyOrMoveCtor
                                            : FunctionKind::Ctor;
     } else if (const auto *CD = dyn_cast<CXXDestructorDecl>(F)) {
+      ExplicitThisPointer = CD->isExplicitObjectMemberFunction();
       Virtual = CD->isVirtual();
       Kind = FunctionKind::Dtor;
     } else if (const auto *MD = dyn_cast<CXXMethodDecl>(F)) {
+      ExplicitThisPointer = MD->isExplicitObjectMemberFunction();
       Virtual = MD->isVirtual();
       if (IsLambdaStaticInvoker)
         Kind = FunctionKind::LambdaStaticInvoker;
@@ -43,9 +46,11 @@ Function::Function(Program &P, FunctionDeclTy Source, unsigned ArgSize,
       else if (MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator())
         Kind = FunctionKind::CopyOrMoveOperator;
     } else {
+      ExplicitThisPointer = false;
       Virtual = false;
     }
   } else {
+    ExplicitThisPointer = false;
     Variadic = false;
     Virtual = false;
     Immediate = false;
diff --git a/clang/lib/AST/ByteCode/Function.h b/clang/lib/AST/ByteCode/Function.h
index d9a286937cadd..2ef529b6d586b 100644
--- a/clang/lib/AST/ByteCode/Function.h
+++ b/clang/lib/AST/ByteCode/Function.h
@@ -233,6 +233,12 @@ class Function final {
 
   bool isVariadic() const { return Variadic; }
 
+  bool isThisPointerExplicit() const { return ExplicitThisPointer; }
+
+  bool hasImplicitThisParam() const {
+    return hasThisPointer() && !ExplicitThisPointer;
+  }
+
   unsigned getNumParams() const {
     return ParamDescriptors.size() + hasThisPointer() + hasRVO();
   }
@@ -247,17 +253,6 @@ class Function final {
     return ArgSize - (align(primSize(PT_Ptr)) * (hasThisPointer() + hasRVO()));
   }
 
-  bool isThisPointerExplicit() const {
-    if (const auto *MD = dyn_cast_if_present<CXXMethodDecl>(
-            dyn_cast<const FunctionDecl *>(Source)))
-      return MD->isExplicitObjectMemberFunction();
-    return false;
-  }
-
-  bool hasImplicitThisParam() const {
-    return hasThisPointer() && !isThisPointerExplicit();
-  }
-
 private:
   /// Construct a function representing an actual function.
   Function(Program &P, FunctionDeclTy Source, unsigned ArgSize,
@@ -315,6 +310,8 @@ class Function final {
   /// as the first implicit argument
   LLVM_PREFERRED_TYPE(bool)
   unsigned HasThisPointer : 1;
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned ExplicitThisPointer : 1;
   /// Whether this function has Return Value Optimization, i.e.
   /// the return value is constructed in the caller's stack frame.
   /// This is done for functions that return non-primive values.