From add16a8da9ccd07eabda2dffd0d32188f07da09c Mon Sep 17 00:00:00 2001 From: Eric Fiselier Date: Wed, 24 Apr 2019 02:23:30 +0000 Subject: [Builtins] Implement __builtin_is_constant_evaluated for use in C++2a Summary: This patch implements `__builtin_is_constant_evaluated` as specifier by [P0595R2](https://wg21.link/p0595r2). It is built on the back of Bill Wendling's work for `__builtin_constant_p()`. More tests to come, but early feedback is appreciated. I plan to implement warnings for common mis-usages like those belowe in a following patch: ``` void foo(int x) { if constexpr (std::is_constant_evaluated())) { // condition is always `true`. Should use plain `if` instead. foo_constexpr(x); } else { foo_runtime(x); } } ``` Reviewers: rsmith, MaskRay, bruno, void Reviewed By: rsmith Subscribers: dexonsmith, zoecarver, fdeazeve, kristina, cfe-commits Differential Revision: https://reviews.llvm.org/D55500 llvm-svn: 359067 --- clang/lib/CodeGen/CGDecl.cpp | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'clang/lib/CodeGen/CGDecl.cpp') diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp index aea99dbbafd..a5c02246d04 100644 --- a/clang/lib/CodeGen/CGDecl.cpp +++ b/clang/lib/CodeGen/CGDecl.cpp @@ -1783,7 +1783,8 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) { } llvm::Constant *constant = nullptr; - if (emission.IsConstantAggregate || D.isConstexpr()) { + if (emission.IsConstantAggregate || D.isConstexpr() || + D.isUsableInConstantExpressions(getContext())) { assert(!capturedByInit && "constant init contains a capturing block?"); constant = ConstantEmitter(*this).tryEmitAbstractForInitializer(D); if (constant && trivialAutoVarInit != -- cgit v1.2.3