[llvm-commits] patch: target option to disable tail calls

[Chad Rosier]

On Jan 18, 2012, at 5:17 PM, Nick Lewycky wrote:

> 
> 
> On 18 January 2012 17:15, Chad Rosier <mcrosier at apple.com> wrote:
> Hi Nick,
> 
> From the test case:
> 
> ;CALL: test1:
> ;CALL-NOT: ret
> ;CALL: callq helper
> ;CALL: ret
> 
> Shouldn't it be:
> ; CALL-NOT: jmp
> 
> The call-not is there to ensure that we don't run past the end of the function and match a call from a later test instead. Presumably if we emit a jmp instead of a call, we'll fail to match the "callq helper".

Sounds good, please commit.

> Also, we generally put a space between the semi-colon and the first letter of the check prefix (i.e., "; CALL-NOT").
> 
> Good call, will do!
> 
> Nick
> 
> Same comments for test2.
> 
> LGTM, otherwise.
> 
>  Chad
> 
> On Jan 18, 2012, at 4:02 PM, Nick Lewycky wrote:
> 
>> On 18 January 2012 15:19, Chad Rosier <mcrosier at apple.com> wrote:
>> Hi Nick,
>> Why not something more like disable-tail-calls?  Most of the options begin with verbs such as Enable, Disable, Emit, Trap, etc.
>> 
>> Sounds good, replaced all over. Updated patch attached!
>> 
>> Nick
>>  
>> 
>>  Chad
>> 
>> On Jan 18, 2012, at 3:10 PM, Nick Lewycky wrote:
>> 
>> > The attached patch adds a new "-no-tail-calls" flag to llc, and implements it in the x86 backend only. The intent is to support gcc's -fno-optimize-sibling-calls in clang, which as far as I can tell just disables tail calls period. The goal is to help ASAN produce correct stack traces, which requires disabling all tail calls.
>> >
>> > As an aside, there is a good reason to do this in the backend and not at the IR-level. The "tail" marker is used to indicate things that are useful to the optimizers themselves; for example alias analysis interprets the presence of a tail marker as proof that the callee can't access any alloca's in the caller, whether the pointer has been captured or not.
>> >
>> > Please review!
>> >
>> > Nick
>> >
>> > <no-tail-calls-1.patch>_______________________________________________
>> > llvm-commits mailing list
>> > llvm-commits at cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>> 
>> 
>> <no-tail-calls-2.patch>
> 
> 

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