merge main into amd-staging (llvm#1075)

Author: ronlieb

clang/docs/ReleaseNotes.rst

@@ -294,6 +294,7 @@ Bug Fixes to C++ Support
   direct-list-initialized from an array is corrected to direct-initialization.
 - Clang no longer crashes when a coroutine is declared ``[[noreturn]]``. (#GH127327)
 - Clang now uses the parameter location for abbreviated function templates in ``extern "C"``. (#GH46386)
+- Clang now correctly parses ``if constexpr`` expressions in immediate function context. (#GH123524)
 
 Improvements to C++ diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/include/clang/Basic/LangOptions.def

@@ -530,7 +530,7 @@ VALUE_LANGOPT(FuchsiaAPILevel, 32, 0, "Fuchsia API level")
 // on large _BitInts.
 BENIGN_VALUE_LANGOPT(MaxBitIntWidth, 32, 128, "Maximum width of a _BitInt")
 
-COMPATIBLE_LANGOPT(IncrementalExtensions, 1, 0, " True if we want to process statements"
+COMPATIBLE_LANGOPT(IncrementalExtensions, 1, 0, "True if we want to process statements "
         "on the global scope, ignore EOF token and continue later on (thus "
         "avoid tearing the Lexer and etc. down). Controlled by "
         "-fincremental-extensions.")

clang/include/clang/Driver/Options.td

@@ -878,7 +878,7 @@ def Wa_COMMA : CommaJoined<["-"], "Wa,">,
   MetaVarName<"<arg>">;
 def warning_suppression_mappings_EQ : Joined<["--"],
   "warning-suppression-mappings=">, Group<Diag_Group>,
-  HelpText<"File containing diagnostic suppresion mappings. See user manual "
+  HelpText<"File containing diagnostic suppression mappings. See user manual "
   "for file format.">, Visibility<[ClangOption, CC1Option]>;
 def Wall : Flag<["-"], "Wall">, Group<W_Group>, Flags<[HelpHidden]>,
   Visibility<[ClangOption, CC1Option, FlangOption]>;
@@ -943,7 +943,7 @@ def Xarch__
   target matches the specified architecture. This can be used with the target
   CPU, triple architecture, or offloading host and device. It is most useful
   for separating behavior undesirable on one of the targets when combining many
-  compilation jobs, as is commong with offloading. For example, -Xarch_x86_64,
+  compilation jobs, as is common with offloading. For example, -Xarch_x86_64,
   -Xarch_gfx90a, and -Xarch_device are all valid selectors. -Xarch_device will
   forward the argument to the offloading device while -Xarch_host will target
   the host system, which can be used to suppress incompatible GPU arguments.}]>,
@@ -1683,7 +1683,7 @@ def fsample_profile_use_profi : Flag<["-"], "fsample-profile-use-profi">,
     HelpText<"Use profi to infer block and edge counts">,
     DocBrief<[{Infer block and edge counts. If the profiles have errors or missing
                blocks caused by sampling, profile inference (profi) can convert
-               basic block counts to branch probabilites to fix them by extended
+               basic block counts to branch probabilities to fix them by extended
                and re-engineered classic MCMF (min-cost max-flow) approach.}]>;
 def fno_profile_sample_accurate : Flag<["-"], "fno-profile-sample-accurate">, Group<f_Group>;
 def fno_auto_profile : Flag<["-"], "fno-auto-profile">, Group<f_Group>,

clang/lib/AST/ExprConstant.cpp

@@ -2419,6 +2419,16 @@ static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
           LVal.getLValueCallIndex() == 0) &&
          "have call index for global lvalue");
 
+  if (LVal.allowConstexprUnknown()) {
+    if (BaseVD) {
+      Info.FFDiag(Loc, diag::note_constexpr_var_init_non_constant, 1) << BaseVD;
+      NoteLValueLocation(Info, Base);
+    } else {
+      Info.FFDiag(Loc);
+    }
+    return false;
+  }
+
   if (Base.is<DynamicAllocLValue>()) {
     Info.FFDiag(Loc, diag::note_constexpr_dynamic_alloc)
         << IsReferenceType << !Designator.Entries.empty();
@@ -3597,7 +3607,8 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
   // expressions here; doing so would regress diagnostics for things like
   // reading from a volatile constexpr variable.
   if ((Info.getLangOpts().CPlusPlus && !VD->hasConstantInitialization() &&
-       VD->mightBeUsableInConstantExpressions(Info.Ctx)) ||
+       VD->mightBeUsableInConstantExpressions(Info.Ctx) &&
+       !AllowConstexprUnknown) ||
       ((Info.getLangOpts().CPlusPlus || Info.getLangOpts().OpenCL) &&
        !Info.getLangOpts().CPlusPlus11 && !VD->hasICEInitializer(Info.Ctx))) {
     if (Init) {
@@ -16993,18 +17004,6 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
 
     if (!Info.discardCleanups())
       llvm_unreachable("Unhandled cleanup; missing full expression marker?");
-
-    if (Value.allowConstexprUnknown()) {
-      assert(Value.isLValue() && "Expected an lvalue");
-      auto Base = Value.getLValueBase();
-      const auto *NewVD = Base.dyn_cast<const ValueDecl *>();
-      if (!NewVD)
-        NewVD = VD;
-      Info.FFDiag(getExprLoc(), diag::note_constexpr_var_init_non_constant, 1)
-          << NewVD;
-      NoteLValueLocation(Info, Base);
-      return false;
-    }
   }
 
   return CheckConstantExpression(Info, DeclLoc, DeclTy, Value,

clang/lib/CodeGen/CodeGenModule.cpp

@@ -2078,9 +2078,10 @@ StringRef CodeGenModule::getMangledName(GlobalDecl GD) {
   // Prior work:
   // https://discourse.llvm.org/t/rfc-clang-diagnostic-for-demangling-failures/82835/8
   // https://github.com/llvm/llvm-project/issues/111345
-  // assert((MangledName.startswith("_Z") || MangledName.startswith("?")) &&
-  //        !GD->hasAttr<AsmLabelAttr>() &&
-  //        llvm::demangle(MangledName) != MangledName &&
+  // assert(!((StringRef(MangledName).starts_with("_Z") ||
+  //           StringRef(MangledName).starts_with("?")) &&
+  //          !GD.getDecl()->hasAttr<AsmLabelAttr>() &&
+  //          llvm::demangle(MangledName) == MangledName) &&
   //        "LLVM demangler must demangle clang-generated names");
 
   auto Result = Manglings.insert(std::make_pair(MangledName, GD));

clang/lib/Parse/ParseExprCXX.cpp

@@ -2203,8 +2203,16 @@ Parser::ParseCXXCondition(StmtResult *InitStmt, SourceLocation Loc,
       return ParseCXXCondition(nullptr, Loc, CK, MissingOK);
     }
 
-    // Parse the expression.
-    ExprResult Expr = ParseExpression(); // expression
+    ExprResult Expr = [&] {
+      EnterExpressionEvaluationContext Eval(
+          Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated,
+          /*LambdaContextDecl=*/nullptr,
+          /*ExprContext=*/Sema::ExpressionEvaluationContextRecord::EK_Other,
+          /*ShouldEnter=*/CK == Sema::ConditionKind::ConstexprIf);
+      // Parse the expression.
+      return ParseExpression(); // expression
+    }();
+
     if (Expr.isInvalid())
       return Sema::ConditionError();
 

clang/test/CodeGenCXX/cxx23-p2280r4.cpp

@@ -4,7 +4,7 @@
 
 extern int& s;
 
-// CHECK: @_Z4testv()
+// CHECK-LABEL: @_Z4testv()
 // CHECK-NEXT: entry:
 // CHECK-NEXT: [[I:%.*]] = alloca ptr, align {{.*}}
 // CHECK-NEXT: [[X:%.*]] = load ptr, ptr @s, align {{.*}}
@@ -13,3 +13,16 @@ int& test() {
   auto &i = s;
   return i;
 }
+
+// CHECK-LABEL: @_Z1fv(
+// CHECK: [[X1:%.*]] = load ptr, ptr @x, align 8
+// CHECK-NEXT: store ptr [[X1]]
+// CHECK: [[X2:%.*]] = load ptr, ptr @x, align 8
+// CHECK-NEXT: store ptr [[X2]]
+// CHECK: [[X3:%.*]] = load ptr, ptr @x, align 8
+// CHECK-NEXT: store ptr [[X3]]
+int &ff();
+int &x = ff();
+struct A { int& x; };
+struct B { A x[20]; };
+B f() { return {x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x}; }

clang/test/SemaCXX/constant-expression-cxx11.cpp

@@ -1472,8 +1472,8 @@ namespace ConvertedConstantExpr {
   enum class E {
     em = m,
     en = n, // expected-error {{enumerator value is not a constant expression}} cxx11_20-note {{initializer of 'n' is unknown}}
-    eo = (m + // pre-cxx23-error {{not a constant expression}}
-          n // cxx11_20-note {{initializer of 'n' is unknown}} cxx23-error {{not a constant expression}}
+    eo = (m + // expected-error {{not a constant expression}}
+          n // cxx11_20-note {{initializer of 'n' is unknown}}
           ),
     eq = reinterpret_cast<long>((int*)0) // expected-error {{not a constant expression}} expected-note {{reinterpret_cast}}
   };

clang/test/SemaCXX/constant-expression-p2280r4.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++23 -verify %s
+// RUN: %clang_cc1 -std=c++23 -verify=expected,nointerpreter %s
 // RUN: %clang_cc1 -std=c++23 -verify %s -fexperimental-new-constant-interpreter
 
 using size_t = decltype(sizeof(0));
@@ -39,8 +39,8 @@ void splash(Swim& swam) {
   static_assert(swam.phelps() == 28);     // ok
   static_assert((&swam)->phelps() == 28); // ok
   Swim* pswam = &swam;                    // expected-note {{declared here}}
-  static_assert(pswam->phelps() == 28);   // expected-error {{static assertion expression is not an integral constant expression}}
-                                          // expected-note@-1 {{read of non-constexpr variable 'pswam' is not allowed in a constant expression}}
+  static_assert(pswam->phelps() == 28);   // expected-error {{static assertion expression is not an integral constant expression}} \
+                                          // expected-note {{read of non-constexpr variable 'pswam' is not allowed in a constant expression}}
   static_assert(how_many(swam) == 28);    // ok
   static_assert(Swim().lochte() == 12);   // ok
   static_assert(swam.lochte() == 12);     // expected-error {{static assertion expression is not an integral constant expression}}
@@ -154,3 +154,26 @@ int g() {
     static_assert(f(arr) == 5);
 }
 }
+
+namespace GH128409 {
+  int &ff();
+  int &x = ff(); // nointerpreter-note {{declared here}}
+  constinit int &z = x; // expected-error {{variable does not have a constant initializer}} \
+                        // expected-note {{required by 'constinit' specifier here}} \
+                        // nointerpreter-note {{initializer of 'x' is not a constant expression}}
+}
+
+namespace GH129845 {
+  int &ff();
+  int &x = ff(); // nointerpreter-note {{declared here}}
+  struct A { int& x; };
+  constexpr A g = {x}; // expected-error {{constexpr variable 'g' must be initialized by a constant expression}} \
+                       // nointerpreter-note {{initializer of 'x' is not a constant expression}}
+  const A* gg = &g;
+}
+
+namespace extern_reference_used_as_unknown {
+  extern int &x;
+  int y;
+  constinit int& g = (x,y); // expected-warning {{left operand of comma operator has no effect}}
+}

clang/test/SemaCXX/constexpr-if.cpp

@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -std=c++20 -verify=cxx20,expected %s
+// RUN: %clang_cc1 -std=c++23 -verify=cxx23,expected %s
+// RUN: %clang_cc1 -std=c++26 -verify=cxx26,expected %s
+
+// expected-no-diagnostics
+
+namespace GH123524 {
+consteval void fn1() {}
+void fn2() {
+  if constexpr (&fn1 != nullptr) { }
+}
+}