[gcc r15-2756] c++: fold calls to std::forward_like [PR96780]

[Patrick Palka via Gcc-cvs]

https://gcc.gnu.org/g:180625ae72b3f733813a360fae4f0d6ce79eccdc

commit r15-2756-g180625ae72b3f733813a360fae4f0d6ce79eccdc
Author: Patrick Palka <ppa...@redhat.com>
Date:   Tue Aug 6 11:51:45 2024 -0400

    c++: fold calls to std::forward_like [PR96780]
    
    This extends our folding of cast-like standard library functions
    to also include C++23's std::forward_like.
    
            PR c++/96780
    
    gcc/cp/ChangeLog:
    
            * cp-gimplify.cc (cp_fold) <case CALL_EXPR>: Fold calls
            to std::forward_like as well.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/opt/pr96780.C: Also test std::forward_like folding.
    
    Reviewed-by: Marek Polacek <mpola...@redhat.com>
    Reviewed-by: Jason Merrill <ja...@redhat.com>

Diff:
---
 gcc/cp/cp-gimplify.cc              | 1 +
 gcc/testsuite/g++.dg/opt/pr96780.C | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index b88c3b7f370b..0c589eeaaec4 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -3313,6 +3313,7 @@ cp_fold (tree x, fold_flags_t flags)
            && DECL_NAME (callee) != NULL_TREE
            && (id_equal (DECL_NAME (callee), "move")
                || id_equal (DECL_NAME (callee), "forward")
+               || id_equal (DECL_NAME (callee), "forward_like")
                || id_equal (DECL_NAME (callee), "addressof")
                /* This addressof equivalent is used heavily in libstdc++.  */
                || id_equal (DECL_NAME (callee), "__addressof")
diff --git a/gcc/testsuite/g++.dg/opt/pr96780.C 
b/gcc/testsuite/g++.dg/opt/pr96780.C
index 61e11855eeb3..a29cda8b836e 100644
--- a/gcc/testsuite/g++.dg/opt/pr96780.C
+++ b/gcc/testsuite/g++.dg/opt/pr96780.C
@@ -29,6 +29,10 @@ void f() {
   auto&& x11 = std::as_const(a);
   auto&& x12 = std::as_const(ca);
 #endif
+#if __cpp_lib_forward_like
+  auto&& x13 = std::forward_like<int&&>(a);
+  auto&& x14 = std::forward_like<int&&>(ca);
+#endif
 }
 
 // { dg-final { scan-tree-dump-not "= std::move" "gimple" } }
@@ -36,3 +40,4 @@ void f() {
 // { dg-final { scan-tree-dump-not "= std::addressof" "gimple" } }
 // { dg-final { scan-tree-dump-not "= std::__addressof" "gimple" } }
 // { dg-final { scan-tree-dump-not "= std::as_const" "gimple" } }
+// { dg-final { scan-tree-dump-not "= std::forward_like" "gimple" } }