Problem with ARM longcalls

[Bernd Schmidt]

On 03/24/2011 03:24 PM, Richard Earnshaw wrote:
> 
> On Wed, 2011-03-23 at 16:46 +0100, Bernd Schmidt wrote:
>> I've discovered a problem with -mlong-calls on ARM. The bug was first
>> reported against a new target, but I'd copied the relevant code from the
>> ARM backend.
>>
>> We use current_function_section in arm_is_long_call_p to decide whether
>> we're calling something that goes into the same section. The problem
>> with this is that current_function_section can only be used during
>> final, since it relies on the global variable in_cold_section_p which is
>> set up only in assemble_start_function. On ARM, this problem manifests
>> as short-calls when a long-call would be required; in the other port it
>> was an "insn doesn't satisfy its constraints" error.
>>
>> The following patch is against 4.5, since the problem appears hidden in
>> mainline (the initialization of first_function_block_is_cold has
>> changed). Ok for trunk and branches after arm-linux tests complete?
>>
>>
>> Bernd
> 
> The ARM port currently doesn't support hot/cold partitioning of code
> (and can't until the constant pool code is rewritten to deal with it),
> so how is this a problem?

Different functions can still go into different sections. When we start
expanding a function, in_cold_section_p still contains the value that
was correct for the previous one. It will change at the start of final,
which means that current_function_section can return different values
while compiling a function. See the included testcase.


Bernd