llvm dev - Sep 2009 - [LLVMdev] tblgen bug in handling case , switch_on

Hi,

On Sat, Sep 5, 2009 at 9:12 PM, Sanjiv Gupta<sanjiv.gupta at
microchip.com> wrote:
> Is the patch below ok?
>
> Index: LLVMCConfigurationEmitter.cpp
> ==================================================================> ---
LLVMCConfigurationEmitter.cpp    (revision 80668)
> +++ LLVMCConfigurationEmitter.cpp    (working copy)
> @@ -1141,6 +1141,7 @@
>                               Callback, EmitElseIf, OptDescs, O);
>    }
>    else {
> +      EmitElseIf = true;
>      Callback(arg, (std::string(IndentLevel) + Indent1).c_str(), O);
>    }
>    O << IndentLevel << "}\n";
No, this is not OK - EmitCaseConstructHandler is supposed to be able
to generate both 'if (...) ... if (...) ... if (...) ...' and 'if
(...) ... else if (...) ... else ...' forms. That's what the
EmitElseIf argument controls.

BTW, the example in the documentation generates the 'if (...) ... else
if (...) ... else ...'  form since the 'case' there is assumed to be
inside the 'cmd_line' property.

Can you provide a small TableGen code example of what you're trying to
do which is not working?

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Mikhail Glushenkov wrote:
> Hi,
>
> On Sat, Sep 5, 2009 at 9:12 PM, Sanjiv Gupta<sanjiv.gupta at
microchip.com> wrote:
>   
>> Is the patch below ok?
>>
>> Index: LLVMCConfigurationEmitter.cpp
>>
==================================================================>> ---
LLVMCConfigurationEmitter.cpp    (revision 80668)
>> +++ LLVMCConfigurationEmitter.cpp    (working copy)
>> @@ -1141,6 +1141,7 @@
>>                               Callback, EmitElseIf, OptDescs, O);
>>    }
>>    else {
>> +      EmitElseIf = true;
>>      Callback(arg, (std::string(IndentLevel) + Indent1).c_str(), O);
>>    }
>>    O << IndentLevel << "}\n";
>>     
>
> No, this is not OK - EmitCaseConstructHandler is supposed to be able
> to generate both 'if (...) ... if (...) ... if (...) ...' and
'if
> (...) ... else if (...) ... else ...' forms. That's what the
> EmitElseIf argument controls.
>
> BTW, the example in the documentation generates the 'if (...) ... else
> if (...) ... else ...'  form since the 'case' there is assumed
to be
> inside the 'cmd_line' property.
>
> Can you provide a small TableGen code example of what you're trying to
> do which is not working?
>   
I wanted to be able to specify -O0, -O1, -O2 on the mcc16 command line.
And -O2 should be default(if none of -O0 or -O1 is specified). So I made 
following changes to PIC16Base.td, but that didn't work.


def optimizer : Tool<[
 (in_language "llvm-bitcode"),
 (out_language "llvm-bitcode"),
 (output_suffix "bc"),
 (cmd_line "$CALL(GetBinDir)opt $INFILE -o $OUTFILE"),
 (actions (case
          (switch_on "O0"), (append_cmd "-disable-opt"),
          (switch_on "O1"), (append_cmd "-constmerge -globaldce 
-globalopt -ipsccp -jump-threading -simplifycfg -gvn -scalarrepl"),
          (switch_on "O2"), (append_cmd "-constmerge -globaldce 
-globalopt -ipsccp -jump-threading -simplifycfg -gvn -instcombine 
-scalarrepl"),
          (default), (append_cmd "-constmerge -globaldce -globalopt 
-ipsccp -jump-threading -simplifycfg -gvn -instcombine -scalarrepl")))
]>;

Hi Sanjiv,

On Sun, Sep 6, 2009 at 8:07 PM, Mikhail
Glushenkov<the.dead.shall.rise at gmail.com>
wrote:
> [...]
[Sorry, the formatting was a bit off]
> The following snippet gives the expected behaviour (not tested, but
> you should get the idea):
(case
    (switch_on "O0"),
        (append_cmd "-disable-opt"),

    (or (and (switch_on "O1")
             (not (switch_on "O0"))),
        (not (switch_on "O0"))),
    (append_cmd "-constmerge -globaldce -globalopt -ipsccp
-jump-threading -simplifycfg -gvn -scalarrepl"),

    (or (and (switch_on "O2"),
             (not (switch_on "O0"))),
        (not (switch_on "O0"))),
    (append_cmd "-instcombine"))

> -O2 is the default, but -O0 overrides both -O2 and -O1; -O2 overrides -O1.

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Hi Sanjiv,

On Sun, Sep 6, 2009 at 8:13 PM, Mikhail
Glushenkov<the.dead.shall.rise at gmail.com>
wrote:
> Hi Sanjiv,
>
> On Sun, Sep 6, 2009 at 8:07 PM, Mikhail
> Glushenkov<the.dead.shall.rise at gmail.com> wrote:
>> [...]
>
> [Sorry, the formatting was a bit off]
>
>> The following snippet gives the expected behaviour (not tested, but
>> you should get the idea):
BTW, your mail has got me thinking about the semantics of 'case',
which is currently somewhat ambiguous (since it depends on context).
Probably 'case' should be modified to always mean 'if ... else if
...
else if ... [...] else ...' and the 'if (...) ... if (...) ... if
(...) ... [...]' form should be called something like 'match'. That
would be backwards-incompatible, though.

What do you think?

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