Clarification on `--strict-whitespace`

[alexarice]

I'm unsure what upstream LLVM does here and can't find any documentation so thought I would just ask for clarification.

In xdsl, some tests are failing with the latest release (see xdslproject/xdsl#6411). Some of these are #48, which I'm happy to change to CHECK-EMPTY, but some seem to be to do with --strict-whitespace.

It seems that the rule for checking the amount of whitespace is strange here, because:

• It seems 0 whitespace is counted as 0. i.e. // CHECK:builtin.module { validates builtin.module {
• 1 whitespace is actually 0. i.e. // CHECK: builtin.module { validates builtin.module {
• more generally n+1 is actually n in the same way, so that the first space of the pattern seems to be ignored.

I can change the tests, but wanted to make sure that this was the intentional behaviour first. TBH it would make more sense to me to say that there always must be a space after the colon, because then at least its consistent.

[alexarice]

Just to add, xdsl contains some tests that are // CHECK: pattern and they used to match pattern and now no longer do.

[alexarice]

Behaviour is caused by the \s? in

filecheck/filecheck/parser.py

Line 35 in 7299980

+ r"(-(DAG|COUNT-\d+|NOT|EMPTY|NEXT|SAME|LABEL))?(\{LITERAL})?:\s?([^\n]*)\n?"

[AntonLydike]

I am looking into how llvm filecheck does it, one sec. Might have been a bug introduced recently.

[AntonLydike]

It appears that llvm filecheck strips whitespace around the check string, even with strict whitespace mode (but not in match full line mode). Working on a patch.

[AntonLydike]

That meas that CHECK: test and CHECK: test are equivalent checks unless full line matching is used

[alexarice]

Oh, I meant with --match-full-line and --strict-whitespace on. I think --strict-whitespace is a no-op without --match-full-line?

[AntonLydike]

So the full interaction here is:

• default mode (no flags): one or more whitespaces in a pattern match one or more whitespaces in the text. Leading/trailing whitespace is stripped from the pattern
• --strict-whitespace: Each whitespace in a pattern matches exactly one whitespace in the text BUT leading and trailing whitespaces are still stripped
• adding --match-full-lines: Leading/trailing whitespace is no longer stripped

[alexarice]

Right, and --match-full-lines without --strict-whitespace trims the start and end of the pattern and line.

This still doesn't answer if CHECK: test and CHECK:test are identical

[AntonLydike]

They are identical, unless full lines and strict whitespace are present. Every other mode will strip whitespace from the pattern before applying it, hence both result in the same pattern matching the same stuff

[alexarice]

Ok 👍