Label alignments in shorten_branches

[Christian BRUEL]

I had the same problem a while ago, asm_insn_count function just count 
the number of line separators and assumes the default lengths.

I added a TARGET_ASM_COUNT macro. Here is in attachement for an 
implementation for SH that also accounts some of space or align 
directives. But it is difficult to go further since assembly macros 
could be more complicated. Anyway, that is already better and should fix 
your problem. Should be quite target independant.
Here I assume the instructions lengths were correctly set before 
computing the insn_current_address.

Would it be useful to submit it (well, here it is.) ?

Best Regards

Christian

2009-01-20  Christian Bruel  <christian.bruel@st.com>

	* final.c (TARGET_ASM_COUNT): Use.
	* config/sh/sh-protos.h (sh_asm_count): Declared.
	* config/sh/sh.h (TARGET_ASM_COUNT): Declared.
	* config/sh/sh.c (sh_asm_count): Defined.

Richard Guenther wrote:
> On Mon, Mar 30, 2009 at 4:53 PM, Bernd Schmidt <bernds_cb1@t-online.de> wrote:
>> Revision 18357, in 1998, introduced a mechanism to keep track of label
>> alignments during shorten branches.  It tries to determine the known
>> alignment at every point in the function, and compute the amount of padding
>> needed at every label.
>>
>> The problem is, to do this, we need to know the exact length of every
>> instruction.  The Blackfin has a few patterns where the length attribute
>> gives a maximum rather than an exact value, but even if the machine
>> description is 100% accurate, there is in general no way of knowing the
>> exact length of an asm statement.
>>
>> I have a testcase where the compiler produces an assembly file that has an
>> out-of-range jump, because it thought the label at the start of a jump table
>> (which has an alignment of 4) needs no padding, when in fact it needs 2
>> bytes of padding.
>>
>> Can anyone think of a way to make this code work, or should I just post a
>> patch to mostly revert 18357?
> 
> Add a target macro TARGET_LIES_WITH_INSN_LENGTH and
> disable 18357 based on that?
> 
> Richard.
>