[gcc/devel/autopar_devel] c++: ICE with -Wall and constexpr if [PR94937]

[gcc/devel/autopar_devel] c++: ICE with -Wall and constexpr if [PR94937]

[Giuliano Belinassi]

https://gcc.gnu.org/g:f04f784a3f182bc68c66caf2b5bae6cdd748d83d

commit f04f784a3f182bc68c66caf2b5bae6cdd748d83d
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed May 6 19:24:58 2020 -0400

    c++: ICE with -Wall and constexpr if [PR94937]
    
    An ICE arises here because we call cp_get_callee_fndecl_nofold in a
    template, and we've got a CALL_EXPR whose CALL_EXPR_FN is a BASELINK.
    This tickles the INDIRECT_TYPE_P assert in cp_get_fndecl_from_callee.
    
    Fixed by turning the assert into a condition and returning NULL_TREE
    in that case.
    
            PR c++/94937
            * cvt.c (cp_get_fndecl_from_callee): Return NULL_TREE if the function
            type is not INDIRECT_TYPE_P.
            * decl.c (omp_declare_variant_finalize_one): Call
            cp_get_callee_fndecl_nofold instead of looking for the function decl
            manually.
    
            * g++.dg/cpp1z/constexpr-if34.C: New test.
            * g++.dg/cpp2a/is-constant-evaluated10.C: New test.

Diff:
---
 gcc/cp/ChangeLog                                   |  9 +++++++
 gcc/cp/cvt.c                                       |  3 +--
 gcc/cp/decl.c                                      | 12 +--------
 gcc/testsuite/ChangeLog                            |  6 +++++
 gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C        | 15 +++++++++++
 .../g++.dg/cpp2a/is-constant-evaluated10.C         | 30 ++++++++++++++++++++++
 6 files changed, 62 insertions(+), 13 deletions(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d8ad1d63bd4..605cdf33ae4 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,12 @@
+2020-05-18  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/94937
+	* cvt.c (cp_get_fndecl_from_callee): Return NULL_TREE if the function
+	type is not INDIRECT_TYPE_P.
+	* decl.c (omp_declare_variant_finalize_one): Call
+	cp_get_callee_fndecl_nofold instead of looking for the function decl
+	manually.
+
 2020-05-18  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/90915
diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 656e7fd3ec0..371002833d0 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -995,9 +995,8 @@ cp_get_fndecl_from_callee (tree fn, bool fold /* = true */)
   if (TREE_CODE (fn) == FUNCTION_DECL)
     return fn;
   tree type = TREE_TYPE (fn);
-  if (type == unknown_type_node)
+  if (type == NULL_TREE || !INDIRECT_TYPE_P (type))
     return NULL_TREE;
-  gcc_assert (INDIRECT_TYPE_P (type));
   if (fold)
     fn = maybe_constant_init (fn);
   STRIP_NOPS (fn);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 7c7ca1ff1c0..6469850e2dc 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7295,17 +7295,7 @@ omp_declare_variant_finalize_one (tree decl, tree attr)
   if (variant == error_mark_node && !processing_template_decl)
     return true;
 
-  variant = cp_get_callee (variant);
-  if (variant)
-    {
-      if (TREE_CODE (variant) == FUNCTION_DECL)
-	;
-      else if (TREE_TYPE (variant) && INDIRECT_TYPE_P (TREE_TYPE (variant)))
-	variant = cp_get_fndecl_from_callee (variant, false);
-      else
-	variant = NULL_TREE;
-    }
-
+  variant = cp_get_callee_fndecl_nofold (variant);
   input_location = save_loc;
 
   if (variant)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 40e9d666f00..67f2c550ff0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-05-18  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/94937
+	* g++.dg/cpp1z/constexpr-if34.C: New test.
+	* g++.dg/cpp2a/is-constant-evaluated10.C: New test.
+
 2020-05-18  Martin Sebor  <msebor@redhat.com>
 
 	PR middle-end/92815
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C
new file mode 100644
index 00000000000..6e0b2597a53
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if34.C
@@ -0,0 +1,15 @@
+// PR c++/94937 - ICE with -Wall and constexpr if.
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wall" }
+
+struct B {
+  static constexpr bool foo() { return false; }
+};
+
+template<typename T>
+struct C {
+  static void bar ()
+  {
+    if constexpr (B::foo()) ;
+  }
+};
diff --git a/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C
new file mode 100644
index 00000000000..7b2e345f448
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated10.C
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++2a } }
+// { dg-options "-Wtautological-compare" }
+
+namespace std {
+  constexpr inline bool
+  is_constant_evaluated () noexcept
+  {
+    return __builtin_is_constant_evaluated ();
+  }
+}
+
+template<typename>
+constexpr int
+foo(int i)
+{
+  if constexpr (std::is_constant_evaluated ()) // { dg-warning ".std::is_constant_evaluated. always evaluates to true in .if constexpr." }
+    return 42;
+  else
+    return i;
+}
+
+template<typename>
+constexpr int
+foo2(int i)
+{
+  if constexpr (__builtin_is_constant_evaluated ()) // { dg-warning ".std::is_constant_evaluated. always evaluates to true in .if constexpr." }
+    return 42;
+  else
+    return i;
+}