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* [gcc r12-7797] fold-const: Handle C++ dependent COMPONENT_REFs in operand_equal_p [PR105035]
@ 2022-03-24 11:24 Jakub Jelinek
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From: Jakub Jelinek @ 2022-03-24 11:24 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:8698ff67cdff4364c8adad2921ed532359a155ec
commit r12-7797-g8698ff67cdff4364c8adad2921ed532359a155ec
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Mar 24 12:23:51 2022 +0100
fold-const: Handle C++ dependent COMPONENT_REFs in operand_equal_p [PR105035]
As mentioned in the PR, operand_equal_p already contains some hacks so that
it can be called already on pre-instantiation C++ trees from templates,
but the recent change to compare DECL_FIELD_OFFSET in the COMPONENT_REF
case broke this. Many such COMPONENT_REFs are already punted on earlier
because they have NULL TREE_TYPE, but in this case the code knows what
type they have but still uses an IDENTIFIER_NODE as second operand
of COMPONENT_REF (I think SCOPE_REF is something that could be used too).
The following patch looks at those DECL_FIELD_*OFFSET fields only if
both field[01] args are FIELD_DECLs and otherwise keeps it to the
earlier OP_SAME (1) check that guards this whole block.
2022-03-24 Jakub Jelinek <jakub@redhat.com>
PR c++/105035
* fold-const.cc (operand_equal_p) <case COMPONENT_REF>: If either
field0 or field1 is not a FIELD_DECL, return false.
* g++.dg/warn/Wduplicated-cond2.C: New test.
Diff:
---
gcc/fold-const.cc | 7 +++++--
gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C | 29 +++++++++++++++++++++++++++
2 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 39a5a52958d..b647e5305aa 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -3357,8 +3357,11 @@ operand_compare::operand_equal_p (const_tree arg0, const_tree arg1,
tree field0 = TREE_OPERAND (arg0, 1);
tree field1 = TREE_OPERAND (arg1, 1);
- if (!operand_equal_p (DECL_FIELD_OFFSET (field0),
- DECL_FIELD_OFFSET (field1), flags)
+ /* Non-FIELD_DECL operands can appear in C++ templates. */
+ if (TREE_CODE (field0) != FIELD_DECL
+ || TREE_CODE (field1) != FIELD_DECL
+ || !operand_equal_p (DECL_FIELD_OFFSET (field0),
+ DECL_FIELD_OFFSET (field1), flags)
|| !operand_equal_p (DECL_FIELD_BIT_OFFSET (field0),
DECL_FIELD_BIT_OFFSET (field1),
flags))
diff --git a/gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C b/gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C
new file mode 100644
index 00000000000..c977389a2e4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C
@@ -0,0 +1,29 @@
+// PR c++/105035
+// { dg-do compile }
+// { dg-options "-Wduplicated-cond" }
+
+class A {
+ struct B { int c; int f; } e;
+ template <typename> void foo ();
+ void bar ();
+};
+
+template <typename> void
+A::foo ()
+{
+ int g;
+ if (&g == &e.c)
+ ;
+ else if (&g == &e.f)
+ ;
+}
+
+void
+A::bar ()
+{
+ int g;
+ if (&g == &e.c) // { dg-message "previously used here" }
+ ;
+ else if (&g == &e.c) // { dg-warning "duplicated 'if' condition" }
+ ;
+}
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