llvm dev - Dec 2015 - TableGen - cryptic error messages (~feature request)

Hello.
     I started implementing a back end in LLVM (and I'm writing some hints I
consider
useful at https://sites.google.com/site/alexsusu/home/backend-llvm ).
     Unfortunately, I hit quite a few times very cryptic error messages when
compiling
with TableGen, which required a few good hours of debugging the TableGen
program.

     The most cryptic error message was when compiling with TableGen, with the
option
-gen-asm-matcher . Here I got the following error message:
llvm-tblgen: ~/llvm/lib/TableGen/StringMatcher.cpp:52: bool 
llvm::StringMatcher::EmitStringMatcherForChar(const std::vector<const 
std::pair<std::basic_string<char>, std::basic_string<char>
>*>&, unsigned int, unsigned
int) const: Assertion `Matches.size() == 1 && "Had duplicate keys
to match on"' failed.
[...]
Stack dump:
0.      Program arguments: ~/llvm/build3/bin/llvm-tblgen -gen-asm-matcher -I 
~/llvm/include Connex.td
./run_tblgen.sh: line 13: 27011 Aborted                 (core dumped) 
~/llvm/build3/bin/llvm-tblgen -gen-asm-matcher -I ~/llvm/include Connex.td > 
ConnexGenAsmMatcher.inc

     It took me quite a few hours to find the source of the error, namely the
fact I had
defined two registers with the SAME ASM name (string) - so the disassembly (ASM
matcher)
info had conflicts. I actually sped up my debugging by editing the file 
~/llvm/lib/TableGen/StringMatcher.cpp and adding in StringMatcher::
EmitStringMatcherForChar() some printing that explained more clearly why the
error happens.

     Therefore I have this IMPORTANT question: would you feel it is useful to
make
TableGen give more detailed error messages? I personally recommend this.


   Thank you,
     Alex

On Tue, Dec 29, 2015 at 2:54 PM, RCU via llvm-dev <llvm-dev at
lists.llvm.org>
wrote:
>   Hello.
>     I started implementing a back end in LLVM (and I'm writing some
hints
> I consider useful at
> https://sites.google.com/site/alexsusu/home/backend-llvm ).
>     Unfortunately, I hit quite a few times very cryptic error messages
> when compiling with TableGen, which required a few good hours of debugging
> the TableGen program.
>
>     The most cryptic error message was when compiling with TableGen, with
> the option -gen-asm-matcher . Here I got the following error message:
> llvm-tblgen: ~/llvm/lib/TableGen/StringMatcher.cpp:52: bool
> llvm::StringMatcher::EmitStringMatcherForChar(const std::vector<const
> std::pair<std::basic_string<char>, std::basic_string<char>
>*>&, unsigned
> int, unsigned int) const: Assertion `Matches.size() == 1 &&
"Had duplicate
> keys to match on"' failed.
> [...]
> Stack dump:
> 0.      Program arguments: ~/llvm/build3/bin/llvm-tblgen -gen-asm-matcher
> -I ~/llvm/include Connex.td
> ./run_tblgen.sh: line 13: 27011 Aborted                 (core dumped)
> ~/llvm/build3/bin/llvm-tblgen -gen-asm-matcher -I ~/llvm/include Connex.td
> > ConnexGenAsmMatcher.inc
>
>     It took me quite a few hours to find the source of the error, namely
> the fact I had defined two registers with the SAME ASM name (string) - so
> the disassembly (ASM matcher) info had conflicts. I actually sped up my
> debugging by editing the file ~/llvm/lib/TableGen/StringMatcher.cpp and
> adding in StringMatcher::
> EmitStringMatcherForChar() some printing that explained more clearly why
> the error happens.
>
>     Therefore I have this IMPORTANT question: would you feel it is useful
> to make TableGen give more detailed error messages? I personally recommend
> this.
>
Seems reasonable to add some extra text to the assertion (and possibly use
better error handling - not sure if tblgen aspires to be assertion-free on
unbounded table inputs, but it probably should be... ). Perhaps you could
send a patch to llvm-commits to discuss the specifics there?

- Dave

>
>
>   Thank you,
>     Alex
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20160107/bd0196c2/attachment.html>

> On Jan 7, 2016, at 9:50 AM, David Blaikie via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> 
> 
> On Tue, Dec 29, 2015 at 2:54 PM, RCU via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>   Hello.
>     I started implementing a back end in LLVM (and I'm writing some
hints I consider useful at
https://sites.google.com/site/alexsusu/home/backend-llvm
<https://sites.google.com/site/alexsusu/home/backend-llvm> ).
>     Unfortunately, I hit quite a few times very cryptic error messages when
compiling with TableGen, which required a few good hours of debugging the
TableGen program.
> 
>     The most cryptic error message was when compiling with TableGen, with
the option -gen-asm-matcher . Here I got the following error message:
> llvm-tblgen: ~/llvm/lib/TableGen/StringMatcher.cpp:52: bool
llvm::StringMatcher::EmitStringMatcherForChar(const std::vector<const
std::pair<std::basic_string<char>, std::basic_string<char>
>*>&, unsigned int, unsigned int) const: Assertion `Matches.size() ==
1 && "Had duplicate keys to match on"' failed.
> [...]
> Stack dump:
> 0.      Program arguments: ~/llvm/build3/bin/llvm-tblgen -gen-asm-matcher
-I ~/llvm/include Connex.td
> ./run_tblgen.sh: line 13: 27011 Aborted                 (core dumped)
~/llvm/build3/bin/llvm-tblgen -gen-asm-matcher -I ~/llvm/include Connex.td >
ConnexGenAsmMatcher.inc
> 
>     It took me quite a few hours to find the source of the error, namely
the fact I had defined two registers with the SAME ASM name (string) - so the
disassembly (ASM matcher) info had conflicts. I actually sped up my debugging by
editing the file ~/llvm/lib/TableGen/StringMatcher.cpp and adding in
StringMatcher::
> EmitStringMatcherForChar() some printing that explained more clearly why
the error happens.
> 
>     Therefore I have this IMPORTANT question: would you feel it is useful
to make TableGen give more detailed error messages? I personally recommend this.
> 
> Seems reasonable to add some extra text to the assertion (and possibly use
better error handling - not sure if tblgen aspires to be assertion-free on
unbounded table inputs, but it probably should be... ). Perhaps you could send a
patch to llvm-commits to discuss the specifics there?
It definitely aspires to, yeah. An assert() for a user error is not a great
experience. Patches making that aspiration a bit closer to the reality are very
welcome.

-jim
> 
> - Dave
>  
> 
> 
>   Thank you,
>     Alex
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20160107/f2c6d379/attachment.html>