[PATCH] [DOC] LangRef: Clarify when index of temporaries begin at 0

[Mikael Lyngvig]

So what if I add this exact sentence after the place where the LR states
that temporaries begin at %0:

    If a function entry block does not have an explicit label, it will be
assigned label “%0”, then the first unnamed temporary in that block will be
“%1”, etc.

If you accept this, there's a patch for it attached to this message:

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index 18d2c9c..5db1a14 100644
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -128,7 +128,9 @@ lexical features of LLVM:
 #. Unnamed temporaries are created when the result of a computation is
    not assigned to a named value.
 #. Unnamed temporaries are numbered sequentially (using a per-function
-   incrementing counter, starting with 0).
+   incrementing counter, starting with 0). If a function entry block does
+   not have an explicit label, it will be assigned label "%0", then the
+   first unnamed temporary in that block will be "%1", etc.

 It also shows a convention that we follow in this document. When
 demonstrating instructions, we will follow an instruction with a comment


-- Mikael



2013/11/27 Sean Silva <silvas at purdue.edu>

>
>
>
> On Tue, Nov 26, 2013 at 10:01 PM, Mikael Lyngvig <mikael at lyngvig.org>wrote:
>
>> You're absolutely right (from the LR, I just searched):
>>
>>   For example, if a function entry block does not have an explicit label,
>> it will be assigned label “%0”, then the first unnamed temporary in that
>> block will be “%1”, etc.
>>
>> This is under Functions.  I guess anybody should get that far, but I
>> personally feel that the clarification I've submitted doesn't harm.
>>
>> Your current patch is inaccurate. If you want to duplicate what is
> mentioned elsewhere about the numbering to make it more likely that someone
> will see it, that would be OK.
>
> -- Sean Silva
>
>
>>
>> -- Mikael
>>
>>
>> 2013/11/27 Sean Silva <silvas at purdue.edu>
>>
>>> It is correct as written. Unnamed BB's are "unnamed temporaries" from a
>>> counting perspective. If the first BB is unlabeled, then it becomes %0. The
>>> first instruction then becomes %1, etc.
>>>
>>> I swear we mention that somewhere in LangRef (I seem to recall reviewing
>>> a patch mentioning that), but if not, a patch mentioning that would be fine.
>>>
>>> -- Sean Silva
>>>
>>>
>>> On Tue, Nov 26, 2013 at 8:50 PM, Mikael Lyngvig <mikael at lyngvig.org>wrote:
>>>
>>>> This patch adds the following sentence to the LR after it states that
>>>> temporaries begin at index 0:
>>>>
>>>>    If you do not specify a label for the entry block, the temporaries
>>>> start at index 1 as index
>>>>    0 is then used for an implicit label generated by LLVM.
>>>>
>>>> This because LLC complains when you use %0 as a temporary and there is
>>>> no entry point label in the function.  Then you get an error message, which
>>>> can be quite difficult to figure out why.
>>>>
>>>> If this patch is rejected, somebody should probably phrase the above
>>>> appropriately and submit a new patch.
>>>>
>>>>
>>>> -- Mikael
>>>>
>>>>
>>>> _______________________________________________
>>>> llvm-commits mailing list
>>>> llvm-commits at cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>
>>>>
>>>
>>
>
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