On 09/29/2015 12:41 AM, Senthil Kumar Selvaraj wrote:
On Mon, Sep 28, 2015 at 01:38:18PM -0600, Jeff Law wrote:
On 09/28/2015 02:15 AM, Senthil Kumar Selvaraj wrote:
Hi,
The below patch skips gcc.dg/addr_equal-1.c if the target keeps null
pointer checks.
The test fails for such targets (avr, in my case) because the address
comparison in the below code does not resolve to a constant, causing
builtin_constant_p to return false and fail the test.
/* Variables and functions do not share same memory locations otherwise. */
if (!__builtin_constant_p ((void *)undef_fn0 == (void *)&undef_var0))
abort ();
For targets that delete null pointer checks, the equality comparison
expression
is optimized away to 0, as the code in match.pd knows they can only be
equal if they are both NULL, which cannot be true since
flag-delete-null-pointer-checks is on.
For targets that keep null pointer checks, 0 is a valid address and the
comparison expression is left as is, and that causes a later pass to
fold the builtin_constant_p to a false value, resulting in the test
failure.
This sounds like a failing in the compiler itself, not a testsuite issue.
Even on a target where objects can be at address 0, you can't have a
variable and a function at the same address.
Hmm, symtab_node::equal_address_to, which is where the address equality
check happens, has a comment that contradicts
your statement, and the function variable overlap check is done after the
NULL possibility check. The current code looks like this
/* If both symbols may resolve to NULL, we can not really prove them
different. */
if (!nonzero_address () && !s2->nonzero_address ())
return 2;
/* Except for NULL, functions and variables never overlap. */
if (TREE_CODE (decl) != TREE_CODE (s2->decl))
return 0;
Does anyone know why?
The only case I could think of would be weak symbols.
jeff
