On 2/21/23 14:10, Patrick Palka wrote:
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?
OK.
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
*-*-* } } }
