https://gcc.gnu.org/g:842f786e4cdaf199dc66b74f662e32aaa8723d14
commit r15-11542-g842f786e4cdaf199dc66b74f662e32aaa8723d14 Author: Patrick Palka <[email protected]> Date: Fri Aug 14 15:53:10 2026 -0400 c++: testsuite: Add some opt/is_constant_evaluated3.C variants r13-6422 added opt/is_constant_evaluated3.C to verify that we constant fold copy-init such as a1. (Later, r14-6506 enabled constant folding of the a2-a5 inits.) r13-6422 turns out to trigger a latent bug and causes PR c++/126483, premature folding of is_constant_evaluated in copy-init inside a lambda scope. This patch adds a couple extra variants of this test, one where the containing function is constexpr (3a) and one where it's a lambda (3b). The new 3a.C demonstrates however that we still don't constant fold a1's copy-init when inside a constexpr function scope. 3b.C demonstrates that we do fold it when inside a (maybe-constexpr) lambda scope. gcc/testsuite/ChangeLog: * g++.dg/opt/is_constant_evaluated3a.C: New test. * g++.dg/opt/is_constant_evaluated3b.C: New test. Reviewed-by: Jason Merrill <[email protected]> (cherry picked from commit 9b0341a7a6a38912e667982003bcbfebdfb86335) Diff: --- gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C | 24 ++++++++++++++++++++++ gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C | 24 ++++++++++++++++++++++ 2 files changed, 48 insertions(+) diff --git a/gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C new file mode 100644 index 000000000000..4ec3ecdf7b5d --- /dev/null +++ b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3a.C @@ -0,0 +1,24 @@ +// A version of is_constant_evaluated3.C where the containing function is +// constexpr. +// { dg-do compile { target c++14 } } +// { dg-additional-options "-O -fdump-tree-original" } + +struct A { + constexpr A(int n) : n(n), m(__builtin_is_constant_evaluated()) { } + constexpr A() : A(42) { } + int n, m; +}; + +constexpr void f() { + A a1 = {42}; + A a2{42}; + A a3(42); + A a4; + A a5{}; +} + +// { dg-final { scan-tree-dump "a1 = {\\.n=42, \\.m=0}" "original" { xfail *-*-* } } } +// { dg-final { scan-tree-dump "a2 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a3 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a4 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a5 = {\\.n=42, \\.m=0}" "original" } } diff --git a/gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C new file mode 100644 index 000000000000..ff708e23832b --- /dev/null +++ b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3b.C @@ -0,0 +1,24 @@ +// A version of is_constant_evaluated3.C where the containing function is +// a (maybe-constexpr) lambda. +// { dg-do compile { target c++17 } } +// { dg-additional-options "-O -fdump-tree-original" } + +struct A { + constexpr A(int n) : n(n), m(__builtin_is_constant_evaluated()) { } + constexpr A() : A(42) { } + int n, m; +}; + +auto f = [] { + A a1 = {42}; + A a2{42}; + A a3(42); + A a4; + A a5{}; +}; + +// { dg-final { scan-tree-dump "a1 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a2 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a3 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a4 = {\\.n=42, \\.m=0}" "original" } } +// { dg-final { scan-tree-dump "a5 = {\\.n=42, \\.m=0}" "original" } }
