[LLVMdev] Exception Tables in latest LLVM

[Yiannis Tsiouris]

On 09/02/2011 05:58 PM, Duncan Sands wrote:
> Hi Yiannis,
>
>> I have been using llvm 2.8 (i know ancient history!) for a backend that i was
>> implementing. I have been trying to port my patches to latest llvm (svn build)
>> lately but i have one problem as far as the Exception Handling mechanism is
>> concerned. It seems that there are no Exception Tables generated any more such
>> as the one below:
>
> got some example bitcode for which you see this (or, rather, don't see this
> since the problem is that you are not seeing exception tables)?
>
> Ciao, Duncan.
>
>>
>> .section    .gcc_except_table,"a", at progbits
>>       .align    4
>> GCC_except_table0:
>> .Lexception0:
>>       .byte    255                     # @LPStart Encoding = omit
>>       .byte    3                       # @TType Encoding = udata4
>>       .uleb128    41              # @TType base offset
>>       .byte    3                       # Call site Encoding = udata4
>>       .uleb128    39              # Call site table length
>> .Lset0 = .Leh_func_begin0-.Leh_func_begin0 # Region start
>>       .long    .Lset0
>> .Lset1 = .Ltmp0-.Leh_func_begin0        # Region length
>>       .long    .Lset1
>>       .long    0                       # Landing pad
>>       .uleb128    0               # Action
>> .Lset2 = .Ltmp0-.Leh_func_begin0        # Region start
>>       .long    .Lset2
>> .Lset3 = .Ltmp1-.Ltmp0                  # Region length
>>       .long    .Lset3
>> .Lset4 = .Ltmp2-.Leh_func_begin0        # Landing pad
>>       .long    .Lset4
>>       .uleb128    0               # Action
>> .Lset5 = .Ltmp1-.Leh_func_begin0        # Region start
>>       .long    .Lset5
>> .Lset6 = .Leh_func_end0-.Ltmp1          # Region length
>>       .long    .Lset6
>>       .long    0                       # Landing pad
>>       .uleb128    0               # Action
>>       .align    4
>>
>>
>> I've searched for this  but i couldn't find some documentation about the changes
>> in the EH staff and the documentation on the website is not complete... Is there
>> any way i can force the generation of these tables in current LLVM?
>>
>> Thanks in advance,
>> Yiannis
>>
Hi Duncan,

Sorry for my omission! I attach an example (test_0.ll). I do:
      llvm-as < test_0.ll | llc
and i get output-llvm28.txt with the 2.8 versions of the tools and i 
repeat with the latest versions from the svn repo and i get 
output-llvm30.txt.

As you can see there is a:
    .section	.gcc_except_table,"a", at progbits
    ....
in the 2.8 output just below the code segment while there is no such 
section in the 3.0 case!

Thanks again,
Yiannis
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