[gcc/devel/fortran_unsigned] c++: consteval propagation and templates [PR115986]

[Thomas Kﾃｶnig via Gcc-cvs]

https://gcc.gnu.org/g:25ace453ff530251978bac22af2c0932aa5da5ad

commit 25ace453ff530251978bac22af2c0932aa5da5ad
Author: Jason Merrill <ja...@redhat.com>
Date:   Fri Jul 26 17:20:18 2024 -0400

    c++: consteval propagation and templates [PR115986]
    
    Here the call to e() makes us decide to check d() for escalation at EOF, but
    while checking it we try to fold_immediate 0_c, and get confused by the
    template trees.  Let's not mess with escalation for function templates.
    
            PR c++/115986
    
    gcc/cp/ChangeLog:
    
            * cp-gimplify.cc (remember_escalating_expr): Skip function
            templates.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/consteval-prop21.C: New test.

Diff:
---
 gcc/cp/cp-gimplify.cc                         |  4 ++++
 gcc/testsuite/g++.dg/cpp2a/consteval-prop21.C | 17 +++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index e6629dea5fdc..6a5e4cf62ca1 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -53,6 +53,10 @@ static GTY(()) hash_set<tree> *deferred_escalating_exprs;
 static void
 remember_escalating_expr (tree t)
 {
+  if (uses_template_parms (t))
+    /* Templates don't escalate, and cp_fold_immediate can get confused by
+       other template trees in the function body (c++/115986).  */
+    return;
   if (!deferred_escalating_exprs)
     deferred_escalating_exprs = hash_set<tree>::create_ggc (37);
   deferred_escalating_exprs->add (t);
diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval-prop21.C 
b/gcc/testsuite/g++.dg/cpp2a/consteval-prop21.C
new file mode 100644
index 000000000000..debbda4f4259
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/consteval-prop21.C
@@ -0,0 +1,17 @@
+// PR c++/115986
+// { dg-do compile { target c++20 } }
+
+template <typename T>
+constexpr int b(T) {
+  return 0;
+}
+consteval __uint128_t operator"" _c(const char*) { return 0; }
+constexpr char e() {
+  long f = true ? 0 : b(long(1));
+  return b(f);
+}
+template <typename>
+void d() {
+  0_c;
+  static_assert(e());
+}