Hi!
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.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-03-24 Jakub Jelinek <ja...@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.
--- gcc/fold-const.cc.jj 2022-03-18 18:32:36.175078948 +0100
+++ gcc/fold-const.cc 2022-03-23 13:40:49.893266570 +0100
@@ -3357,8 +3357,11 @@ operand_compare::operand_equal_p (const_
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))
--- gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C.jj 2022-03-23
13:47:36.041577821 +0100
+++ gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C 2022-03-23
13:46:54.820155190 +0100
@@ -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" }
+ ;
+}
Jakub
