__noop not marked as constexpr #102064
#105983
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@llvm/pr-subscribers-clang Author: ofAlpaca (ofAlpaca) ChangesResolves #102064 llvm-project/clang/lib/Sema/SemaDecl.cpp Line 14402 in b6603e1 By adding a BI__noop case in bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp) should fix the problem.Correct me if there is anything I misunderstood. Full diff: https://github.com/llvm/llvm-project/pull/105983.diff 4 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 971df672b6ca1e..e60407061ccd3b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -861,6 +861,8 @@ Bug Fixes to Compiler Builtins
- Clang now allows pointee types of atomic builtin arguments to be complete template types
that was not instantiated elsewhere.
+- Fix ``__noop`` not marked as constexpr. (#GH102064)
+
Bug Fixes to Attribute Support
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index f5b15cf90d1f83..b42f7ea1d9de68 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -2516,7 +2516,7 @@ def IsoVolatileStore : MSLangBuiltin, Int8_16_32_64Template {
def Noop : MSLangBuiltin {
let Spellings = ["__noop"];
- let Attributes = [NoThrow];
+ let Attributes = [NoThrow, Constexpr];
let Prototype = "int(...)";
}
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 5af712dd7257b1..d505346bccd9b3 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -12586,6 +12586,10 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
return false;
}
+ case Builtin::BI__noop:
+ // __noop always evaluates successfully
+ return true;
+
case Builtin::BI__builtin_is_constant_evaluated: {
const auto *Callee = Info.CurrentCall->getCallee();
if (Info.InConstantContext && !Info.CheckingPotentialConstantExpression &&
diff --git a/clang/test/SemaCXX/GH102064.cpp b/clang/test/SemaCXX/GH102064.cpp
new file mode 100644
index 00000000000000..0ed930439e3d75
--- /dev/null
+++ b/clang/test/SemaCXX/GH102064.cpp
@@ -0,0 +1,3 @@
+// RUN: %clang_cc1 -std=c++20 -fms-extensions %s
+// expected-no-diagnostics
+constexpr int x = []{ __noop; return 0; }();
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@DanielJump It looks like the problem is about Windows's backslash. |
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An off-topic concern: |
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I am sorry, I couldn't make much headway in the last weeks because I was
still understanding the codebase. Please feel free to reassign. I will
attempt to take on issues in the future when I am much more prepared.
…On Tue, 27 Aug, 2024, 7:38 am Younan Zhang, ***@***.***> wrote:
An off-topic concern:
The issue was initially assigned to @AdiSin123
<https://github.com/AdiSin123> three weeks ago. Did you talk to @AdiSin123
<https://github.com/AdiSin123> to ensure that @AdiSin123
<https://github.com/AdiSin123> gives up the fix? It would be polite to
ask first in the issue before you start working on this.
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@zyn0217 |
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@cor3ntin |
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You have to resolve the conflict in |
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Resolves #102064
I think the problem is that the function
bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp)return defaultfalsedirectly when visiting expression of__noop.Thus,
__noopcannot be evaluated as constant initializer in here.llvm-project/clang/lib/Sema/SemaDecl.cpp
Line 14402 in b6603e1
By adding a
BI__noopcase inbool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp)should fix the problem.Correct me if there is anything I misunderstood.