[clang] [Clang] Treat constexpr-unknown value as invalid in `evaluateValue` (PR #128409)
Yingwei Zheng via cfe-commits
cfe-commits at lists.llvm.org
Wed Feb 26 08:08:02 PST 2025
https://github.com/dtcxzyw updated https://github.com/llvm/llvm-project/pull/128409
>From 83248eb164ff53442ad6d0c9d1be20027519bac1 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Tue, 18 Feb 2025 01:26:26 +0800
Subject: [PATCH 1/5] [Clang][CodeGen] Bail out on constexpr unknown values in
ConstantEmitter
---
clang/lib/CodeGen/CGExprConstant.cpp | 6 ++++--
clang/test/CodeGenCXX/cxx23-p2280r4.cpp | 13 +++++++++++++
2 files changed, 17 insertions(+), 2 deletions(-)
create mode 100644 clang/test/CodeGenCXX/cxx23-p2280r4.cpp
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index ee5874b26f534..075f3f435ad74 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1883,8 +1883,10 @@ llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
// Try to emit the initializer. Note that this can allow some things that
// are not allowed by tryEmitPrivateForMemory alone.
- if (APValue *value = D.evaluateValue())
- return tryEmitPrivateForMemory(*value, destType);
+ if (APValue *value = D.evaluateValue()) {
+ if (!value->allowConstexprUnknown())
+ return tryEmitPrivateForMemory(*value, destType);
+ }
return nullptr;
}
diff --git a/clang/test/CodeGenCXX/cxx23-p2280r4.cpp b/clang/test/CodeGenCXX/cxx23-p2280r4.cpp
new file mode 100644
index 0000000000000..bb9a90ba18ece
--- /dev/null
+++ b/clang/test/CodeGenCXX/cxx23-p2280r4.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++23 %s -emit-llvm -o - | FileCheck %s
+
+extern int& s;
+
+// CHECK: @_Z4testv()
+// CHECK-NEXT: entry:
+// CHECK-NEXT: [[I:%.*]] = alloca ptr, align {{.*}}
+// CHECK-NEXT: [[X:%.*]] = load ptr, ptr @s, align {{.*}}
+// CHECK-NEXT: store ptr [[X]], ptr [[I]], align {{.*}}
+int& test() {
+ auto &i = s;
+ return i;
+}
>From ac2bd210ffed3d882be2569a415d7c4bbcbba3e9 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Tue, 18 Feb 2025 19:20:39 +0800
Subject: [PATCH 2/5] Address review comments. NFC.
---
clang/test/CodeGenCXX/cxx23-p2280r4.cpp | 2 ++
1 file changed, 2 insertions(+)
diff --git a/clang/test/CodeGenCXX/cxx23-p2280r4.cpp b/clang/test/CodeGenCXX/cxx23-p2280r4.cpp
index bb9a90ba18ece..d5409be451df0 100644
--- a/clang/test/CodeGenCXX/cxx23-p2280r4.cpp
+++ b/clang/test/CodeGenCXX/cxx23-p2280r4.cpp
@@ -1,4 +1,6 @@
// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++23 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++17 %s -emit-llvm -o - | FileCheck %s
extern int& s;
>From 1cea7d422c31b5065c76d9fb4a251955b2bea8e6 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Fri, 21 Feb 2025 12:15:29 +0800
Subject: [PATCH 3/5] [Clang][CodeGen] Address review comments. NFC.
---
clang/lib/CodeGen/CGExprConstant.cpp | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 075f3f435ad74..7d44a9f583eca 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1883,10 +1883,10 @@ llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
// Try to emit the initializer. Note that this can allow some things that
// are not allowed by tryEmitPrivateForMemory alone.
- if (APValue *value = D.evaluateValue()) {
- if (!value->allowConstexprUnknown())
- return tryEmitPrivateForMemory(*value, destType);
- }
+ // Bail out on constexpr-unknown values since they are invalid in CodeGen.
+ if (APValue *value = D.evaluateValue();
+ value && !value->allowConstexprUnknown())
+ return tryEmitPrivateForMemory(*value, destType);
return nullptr;
}
>From bc24bde52b664ca4b3bcbbbdd48a5a14be37a278 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 23 Feb 2025 17:04:03 +0800
Subject: [PATCH 4/5] [Clang] Treat constexpr-unknown value as invalid in
`evaluateValue`
---
clang/lib/AST/Decl.cpp | 3 +++
clang/lib/AST/ExprConstant.cpp | 2 --
clang/lib/CodeGen/CGExprConstant.cpp | 6 ++++--
clang/test/SemaCXX/constant-expression-cxx11.cpp | 4 ++--
4 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 5a3be1690f335..f6cf75ed96aca 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2587,6 +2587,9 @@ APValue *VarDecl::evaluateValueImpl(SmallVectorImpl<PartialDiagnosticAt> &Notes,
!Notes.empty())
Result = false;
+ if (Eval->Evaluated.allowConstexprUnknown())
+ Result = false;
+
// Ensure the computed APValue is cleaned up later if evaluation succeeded,
// or that it's empty (so that there's nothing to clean up) if evaluation
// failed.
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 6ccb6e23f8d2f..5e69b44c20e9c 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -3628,8 +3628,6 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
if (AllowConstexprUnknown) {
if (!Result)
Result = &Info.CurrentCall->createConstexprUnknownAPValues(VD, Base);
- else
- Result->setConstexprUnknown();
}
return true;
}
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 7d44a9f583eca..0295f703b9061 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1884,9 +1884,11 @@ llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
// Try to emit the initializer. Note that this can allow some things that
// are not allowed by tryEmitPrivateForMemory alone.
// Bail out on constexpr-unknown values since they are invalid in CodeGen.
- if (APValue *value = D.evaluateValue();
- value && !value->allowConstexprUnknown())
+ if (APValue *value = D.evaluateValue()) {
+ assert(!value->allowConstexprUnknown() &&
+ "Constexpr unknown values are not allowed in CodeGen");
return tryEmitPrivateForMemory(*value, destType);
+ }
return nullptr;
}
diff --git a/clang/test/SemaCXX/constant-expression-cxx11.cpp b/clang/test/SemaCXX/constant-expression-cxx11.cpp
index 76e2f81947051..0702673144bd5 100644
--- a/clang/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx11.cpp
@@ -122,9 +122,9 @@ namespace CaseStatements {
}
extern int &Recurse1;
-int &Recurse2 = Recurse1; // expected-note {{declared here}}
+int &Recurse2 = Recurse1; // pre-cxx23-note {{declared here}}
int &Recurse1 = Recurse2;
-constexpr int &Recurse3 = Recurse2; // expected-error {{must be initialized by a constant expression}} expected-note {{initializer of 'Recurse2' is not a constant expression}}
+constexpr int &Recurse3 = Recurse2; // expected-error {{must be initialized by a constant expression}} pre-cxx23-note {{initializer of 'Recurse2' is not a constant expression}}
extern const int RecurseA;
const int RecurseB = RecurseA; // expected-note {{declared here}}
>From 52c81598da38532c119db9c06fcc3d7f9c332a8e Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Thu, 27 Feb 2025 00:07:22 +0800
Subject: [PATCH 5/5] [Clang][AST] Fix diag regression
---
clang/lib/AST/Decl.cpp | 3 ---
clang/lib/AST/ExprConstant.cpp | 12 ++++++++++++
clang/test/SemaCXX/constant-expression-cxx11.cpp | 4 ++--
3 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index f6cf75ed96aca..5a3be1690f335 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2587,9 +2587,6 @@ APValue *VarDecl::evaluateValueImpl(SmallVectorImpl<PartialDiagnosticAt> &Notes,
!Notes.empty())
Result = false;
- if (Eval->Evaluated.allowConstexprUnknown())
- Result = false;
-
// Ensure the computed APValue is cleaned up later if evaluation succeeded,
// or that it's empty (so that there's nothing to clean up) if evaluation
// failed.
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 5e69b44c20e9c..42801dc4e18fa 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -16998,6 +16998,18 @@ 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,
diff --git a/clang/test/SemaCXX/constant-expression-cxx11.cpp b/clang/test/SemaCXX/constant-expression-cxx11.cpp
index 0702673144bd5..76e2f81947051 100644
--- a/clang/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx11.cpp
@@ -122,9 +122,9 @@ namespace CaseStatements {
}
extern int &Recurse1;
-int &Recurse2 = Recurse1; // pre-cxx23-note {{declared here}}
+int &Recurse2 = Recurse1; // expected-note {{declared here}}
int &Recurse1 = Recurse2;
-constexpr int &Recurse3 = Recurse2; // expected-error {{must be initialized by a constant expression}} pre-cxx23-note {{initializer of 'Recurse2' is not a constant expression}}
+constexpr int &Recurse3 = Recurse2; // expected-error {{must be initialized by a constant expression}} expected-note {{initializer of 'Recurse2' is not a constant expression}}
extern const int RecurseA;
const int RecurseB = RecurseA; // expected-note {{declared here}}
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