llvm dev - Jul 2018 - Syntax for FileCheck numeric variables and expressions

Hi all,

I've written a patch to extend FileCheck to support matching
arithmetic expressions involving variable [1] (eg. to match REG+1
where REG is a variable with a numeric value). It was suggested to me
in the review to introduce the concept of numeric variable and to
allow for specifying the base the value are written in.

[1] https://reviews.llvm.org/D49084

I think the syntax should satisfy the below requirements:

* based off the [[]] construct since anything else might overload an
existing valid syntax (eg. $$ is supposed to match literally now)
* consistent with syntax for expressions using @LINE
* consistent with using ':' to define regular variable
* allows to specify base of the number a numeric variable is being set to
* allows to specify base of the result of the numeric expression

I've come up with the following syntax for which I'd like feedback:

Numeric variable definition: [[#X<base:]] (eg. [[#ADDR<16:]]) where X
is the numeric variable being defined and <base is optional in which
case base defaults to 10
Numeric variable use: [[#X>base]] (eg. [[#ADDR]]>2) where <base is
optional in which case base defaults 10
Numeric expression: [[exp>base]] (eg. [[#ADDR+2>16]] where expression
must contain at least one numeric variable


I'm not a big fan of the > for the output base being inside the
expression but [[exp]]>base would match >base literally.

Any suggestions / opinions?

Best regards,

Thomas

Hi Thomas,

In general, I think this is a good proposal. However, I don't think that
using ">" or "<" to specify base (at least alone) is a
good idea, as it
might clash with future ideas to do comparisons etc. I also think it would
be nice to have the syntax consistent between definition and use. My first
thought on a reasonable alternative was to use commas to separate the two
parts, so something like:

[[# VAR, 16:]] to capture a hexadecimal number (where the spaces are
optional). [[# VAR, 16]] to use a variable, converted to a hexadecimal
string. In both cases, the base component is optional, and defaults to
decimal.

This led me to thing that it might be better to use something similar to
printf style for the latter half, so to capture a hexadecimal number with a
leading "0x" would be: "0x[[# VAR, %x:]]" and to use it
would be "0x[[#
VAR, %x]]". Indeed, that would allow straightforward conversions between
formats, so say you defined it by capturing a decimal integer and using it
to match a hexadecimal in upper case, with leading 0x and 8 digits
following the 0x:

CHECK: [[# VAR, %d:]] # Defines
CHECK: 0x[[# VAR + 1, %8X]] # Uses

Of course, if we go down that route, it would probably make more sense to
reverse the two sides (e.g. to become "[[# %d, VAR:]]" to capture a
decimal
and "[[# %8X, VAR + 1]]" to use it).

Regards,

James

On 12 July 2018 at 15:34, Thomas Preudhomme via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
>
> I've written a patch to extend FileCheck to support matching
> arithmetic expressions involving variable [1] (eg. to match REG+1
> where REG is a variable with a numeric value). It was suggested to me
> in the review to introduce the concept of numeric variable and to
> allow for specifying the base the value are written in.
>
> [1] https://reviews.llvm.org/D49084
>
> I think the syntax should satisfy the below requirements:
>
> * based off the [[]] construct since anything else might overload an
> existing valid syntax (eg. $$ is supposed to match literally now)
> * consistent with syntax for expressions using @LINE
> * consistent with using ':' to define regular variable
> * allows to specify base of the number a numeric variable is being set to
> * allows to specify base of the result of the numeric expression
>
> I've come up with the following syntax for which I'd like feedback:
>
> Numeric variable definition: [[#X<base:]] (eg. [[#ADDR<16:]]) where X
> is the numeric variable being defined and <base is optional in which
> case base defaults to 10
> Numeric variable use: [[#X>base]] (eg. [[#ADDR]]>2) where <base is
> optional in which case base defaults 10
> Numeric expression: [[exp>base]] (eg. [[#ADDR+2>16]] where expression
> must contain at least one numeric variable
>
>
> I'm not a big fan of the > for the output base being inside the
> expression but [[exp]]>base would match >base literally.
>
> Any suggestions / opinions?
>
> Best regards,
>
> Thomas
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Hi James,

I like that suggestion very much but I think keeping the order of the
two sides as initially proposed makes more sense. In printf/scanf the
string is first because the primary use of these functions is to do
I/O and so you first specify what you are going to output/input and
then where to capture variables. The primary objective of FileCheck
variables and expressions is to capture/print them, the specifier is
an addon to allow some conversion. Does it make sense?

In the interest of speeding things up I plan to start implementing
this proposal starting tomorrow unless someone gives some more
feedback.

Best regards,

Thomas

On Fri, 13 Jul 2018 at 15:51, James Henderson
<jh7370.2008 at my.bristol.ac.uk> wrote:
>
> Hi Thomas,
>
> In general, I think this is a good proposal. However, I don't think
that using ">" or "<" to specify base (at least alone)
is a good idea, as it might clash with future ideas to do comparisons etc. I
also think it would be nice to have the syntax consistent between definition and
use. My first thought on a reasonable alternative was to use commas to separate
the two parts, so something like:
>
> [[# VAR, 16:]] to capture a hexadecimal number (where the spaces are
optional). [[# VAR, 16]] to use a variable, converted to a hexadecimal string.
In both cases, the base component is optional, and defaults to decimal.
>
> This led me to thing that it might be better to use something similar to
printf style for the latter half, so to capture a hexadecimal number with a
leading "0x" would be: "0x[[# VAR, %x:]]" and to use it
would be "0x[[# VAR, %x]]". Indeed, that would allow straightforward
conversions between formats, so say you defined it by capturing a decimal
integer and using it to match a hexadecimal in upper case, with leading 0x and 8
digits following the 0x:
>
> CHECK: [[# VAR, %d:]] # Defines
> CHECK: 0x[[# VAR + 1, %8X]] # Uses
>
> Of course, if we go down that route, it would probably make more sense to
reverse the two sides (e.g. to become "[[# %d, VAR:]]" to capture a
decimal and "[[# %8X, VAR + 1]]" to use it).
>
> Regards,
>
> James
>
> On 12 July 2018 at 15:34, Thomas Preudhomme via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>> Hi all,
>>
>> I've written a patch to extend FileCheck to support matching
>> arithmetic expressions involving variable [1] (eg. to match REG+1
>> where REG is a variable with a numeric value). It was suggested to me
>> in the review to introduce the concept of numeric variable and to
>> allow for specifying the base the value are written in.
>>
>> [1] https://reviews.llvm.org/D49084
>>
>> I think the syntax should satisfy the below requirements:
>>
>> * based off the [[]] construct since anything else might overload an
>> existing valid syntax (eg. $$ is supposed to match literally now)
>> * consistent with syntax for expressions using @LINE
>> * consistent with using ':' to define regular variable
>> * allows to specify base of the number a numeric variable is being set
to
>> * allows to specify base of the result of the numeric expression
>>
>> I've come up with the following syntax for which I'd like
feedback:
>>
>> Numeric variable definition: [[#X<base:]] (eg. [[#ADDR<16:]])
where X
>> is the numeric variable being defined and <base is optional in which
>> case base defaults to 10
>> Numeric variable use: [[#X>base]] (eg. [[#ADDR]]>2) where
<base is
>> optional in which case base defaults 10
>> Numeric expression: [[exp>base]] (eg. [[#ADDR+2>16]] where
expression
>> must contain at least one numeric variable
>>
>>
>> I'm not a big fan of the > for the output base being inside the
>> expression but [[exp]]>base would match >base literally.
>>
>> Any suggestions / opinions?
>>
>> Best regards,
>>
>> Thomas
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>