On 9/27/23 17:21, Vineet Gupta wrote:
On 9/27/23 13:14, Jeff Law wrote:
It would help to describe how these patterns were under specified so
that folks don't continue to make the same mistake as new tests get
added.
dg-final scan-assembler, scan-assembler-not, and scan-assembler-times
use a tcl regular expression (often referred to abbreviated as RE), as
described in https://www.tcl.tk/man/tcl8.4/TclCmd/re_syntax.html .
If your RE is not specific enough, it can match LTO information that the
compiler places into its assembly output when the relevant options are
provided, which is common when running tests where the test harness
iterates over a number of optimization option combinations.
Note that '.' is an atom that can match any character. If you want to
match a dot specifically, you have to escape it with a backslash: '\.' .
When you are matching an instruction mnemonic, an effective way to
avoid matching in LTO information is to enforce matching of word start
(\m) and/or word end (\M) .
Note also that the backslash has to be quoted. If the RE is enclosed in
'"' quotes, extra backslashes are needed. That is not necessary when it
is enclosed in curly braces.
For example, "ld.w" will be matched in:
.ascii "h\227\022\212ld@w\251jr\254'\320\255vwj\252\026\016\364"
If you write {\mld\.w\M} instead, you avoid this problem.
OK. So that naturally leads to the question, why aren't others seeing
this, both in the RISC-V world and more generally. I'm not aware of
any case where I've run the testsuite and tripped over this issue, nor
am I aware of anyone else tripping over it.
Actually I did run into it. See commit ecfa870ff29d979bd2c ("RISC-V:
optim const DF +0.0 store to mem [PR/110748]") where a false failure was
triggered due to these random LTO strings and needed adjusting.
Ah! Good (I suppose).
-/* { dg-final { scan-assembler-not "sw" } } */
-/* { dg-final { scan-assembler-not "fld" } } */
-/* { dg-final { scan-assembler-not "fsd" } } */
-/* { dg-final { scan-assembler-not "lw" } } */
+/* { dg-final { scan-assembler-not "\tsw\t" } } */
+/* { dg-final { scan-assembler-not "\tfld\t" } } */
+/* { dg-final { scan-assembler-not "\tfsd\t" } } */
+/* { dg-final { scan-assembler-not "\tlw\t" } } */
The downside of this approach (which I nearly suggested to Joern) is
that it relies on tabs before/after the mnemonic. That would also imply
a review policy to ensure we always use tabs -- and there's going to be
cases where spotting a tab vs space is going to be tough in a patch
review, particularly after the mnemonic.
We could instead match a regexp that allows spaces or tabs, but at that
point I doubt it's simpler than Joern's approach.
So I recommend we go forward with Joern's approach (so consider that an
ACK for the trunk). Joern can you post a follow-up manual twiddle so
that other ports can follow your example and avoid this problem?
THanks,
jeff
