We should also fold the overall initializer passed to cp_fully_fold_init with mce_false, which enables folding of the copy-initialization of 'a1' in the below testcase (the initializer here is an AGGR_INIT_EXPR).
Unfortunately this doesn't help with direct- or default-initialization because we don't call cp_fully_fold_init in that case, and even if we did the initializer in that case is expressed as a bare CALL_EXPR instead of an AGGR_INIT_EXPR, which cp_fully_fold_init can't really fold. Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? PR c++/108243 gcc/cp/ChangeLog: * cp-gimplify.cc (cp_fully_fold): Add an internal overload that additionally takes and propagate an mce_value parameter, and define the existing public overload in terms of it. (cp_fully_fold_init): Pass mce_false to cp_fully_fold. gcc/testsuite/ChangeLog: * g++.dg/opt/is_constant_evaluated3.C: New test. --- gcc/cp/cp-gimplify.cc | 14 +++++++---- .../g++.dg/opt/is_constant_evaluated3.C | 23 +++++++++++++++++++ 2 files changed, 33 insertions(+), 4 deletions(-) create mode 100644 gcc/testsuite/g++.dg/opt/is_constant_evaluated3.C diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc index 32fe53521cc..5d5c6efb856 100644 --- a/gcc/cp/cp-gimplify.cc +++ b/gcc/cp/cp-gimplify.cc @@ -2447,8 +2447,8 @@ cp_fold_rvalue (tree x) /* Perform folding on expression X. */ -tree -cp_fully_fold (tree x) +static tree +cp_fully_fold (tree x, mce_value manifestly_const_eval) { if (processing_template_decl) return x; @@ -2456,7 +2456,7 @@ cp_fully_fold (tree x) have to call both. */ if (cxx_dialect >= cxx11) { - x = maybe_constant_value (x); + x = maybe_constant_value (x, /*decl=*/NULL_TREE, manifestly_const_eval); /* Sometimes we are given a CONSTRUCTOR but the call above wraps it into a TARGET_EXPR; undo that here. */ if (TREE_CODE (x) == TARGET_EXPR) @@ -2469,6 +2469,12 @@ cp_fully_fold (tree x) return cp_fold_rvalue (x); } +tree +cp_fully_fold (tree x) +{ + return cp_fully_fold (x, mce_unknown); +} + /* Likewise, but also fold recursively, which cp_fully_fold doesn't perform in some cases. */ @@ -2477,7 +2483,7 @@ cp_fully_fold_init (tree x) { if (processing_template_decl) return x; - x = cp_fully_fold (x); + x = cp_fully_fold (x, mce_false); cp_fold_data data (ff_mce_false); cp_walk_tree (&x, cp_fold_r, &data, NULL); return x; diff --git a/gcc/testsuite/g++.dg/opt/is_constant_evaluated3.C b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3.C new file mode 100644 index 00000000000..0a1e46e5638 --- /dev/null +++ b/gcc/testsuite/g++.dg/opt/is_constant_evaluated3.C @@ -0,0 +1,23 @@ +// PR c++/108243 +// { dg-do compile { target c++11 } } +// { 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; +}; + +int main() { + 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" { xfail *-*-* } } } +// { dg-final { scan-tree-dump "a3 = {\\.n=42, \\.m=0}" "original" { xfail *-*-* } } } +// { dg-final { scan-tree-dump "a4 = {\\.n=42, \\.m=0}" "original" { xfail *-*-* } } } +// { dg-final { scan-tree-dump "a5 = {\\.n=42, \\.m=0}" "original" { xfail *-*-* } } } -- 2.39.2.501.gd9d677b2d8