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* [gcc r13-6422] c++: more mce_false folding from cp_fully_fold_init [PR108243]
@ 2023-03-02 19:05 Patrick Palka
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From: Patrick Palka @ 2023-03-02 19:05 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:5425159d176a7a92afc932cbb22d8822667099c4
commit r13-6422-g5425159d176a7a92afc932cbb22d8822667099c4
Author: Patrick Palka <ppalka@redhat.com>
Date: Thu Mar 2 14:04:50 2023 -0500
c++: more mce_false folding from cp_fully_fold_init [PR108243]
We should also fold the overall initializer passed to cp_fully_fold_init
with mce_false, which allows 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.
PR c++/108243
PR c++/97553
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.
Diff:
---
gcc/cp/cp-gimplify.cc | 19 ++++++++++++++-----
gcc/testsuite/g++.dg/opt/is_constant_evaluated3.C | 23 +++++++++++++++++++++++
2 files changed, 37 insertions(+), 5 deletions(-)
diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 921b0e4b120..b995b4f81a5 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -2449,8 +2449,8 @@ 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;
@@ -2458,7 +2458,7 @@ 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)
@@ -2468,7 +2468,16 @@ cp_fully_fold (tree x)
&& TREE_TYPE (TREE_OPERAND (x, 0)) == TREE_TYPE (x))
x = TREE_OPERAND (x, 0);
}
- return cp_fold_rvalue (x);
+ fold_flags_t flags = ff_none;
+ if (manifestly_const_eval == mce_false)
+ flags |= ff_mce_false;
+ return cp_fold_rvalue (x, flags);
+}
+
+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
@@ -2479,7 +2488,7 @@ 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 *-*-* } } }
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