LGTM for libc/src/string/memory_utils/elements.h

Cool, thanks for the change. I like the approach, only have minor comments.

Add more proposals for representing the range data.

Forgot to add test file.

Thanks @nikic !

Retiring this in favor of D99022.

fix conjugation.

Thi sis similar to

use switch as suggested

Rebase on test base to show diff.

In D97854#2617097, @scanon wrote:

Is there a mechanism to instruct the sanitizer to ignore a specific expression or function? From a cursory reading, I am mildly concerned about a deluge of false positives from primitives that compute exact (or approximate) residuals; these are acting to eliminate or precisely control floating-point errors, but tend to show up as "unstable" in a naive analysis that isn't aware of them.

When bootstrapping LLVM with nsan, there are only a few issues.

Nice, thanks. I tried that a couple years back but had ARM buildbot errors that maintainers were not able to expain. Let's hope it goes better this time !

Only cosmetic comments.

Thanks for the patch. Apparently both gcc and clang are fine if the attribute is placed before the definition: https://godbolt.org/z/5aTrcb, so we could do without the ifdefs.
(Though gcc does not know about the attribute, but that's also the case with the current version)

Improve commit message.

Thanks for the comments.

...and add a side-effecting instruction at the top.

Make the test more robust to future optimizations as suggested by James.

Simplify the test as suggested by James.

Update comment.

Thanks for the repro. I think a better fix is D92375 (missing split).

Thanks, comments addressed.

Add to release notes.

Thanks, could you please add a unit test for this ?

LGTM for llvm-exegesis

This was eventually landed as rG8383fddc4fa9b4e61954e5ac93b00719a39d2291

In D90742#2389801, @anna wrote:

hi @courbet,
our internal buildbots at Azul has failed because of an older assembler. We’ve taken in all commits/reverts/relands w.r.t this change upto Nov 4th.

The specific failure is:
/tmp/cc2lBtEi.s: Assembler messages:
/tmp/cc2lBtEi.s:541: Error: no such instruction: `fxsave64 16(%rax)'
/tmp/cc2lBtEi.s:566: Error: no such instruction: `fxrstor64 16(%rdi)'
/tmp/cc2lBtEi.s:592: Error: no such instruction: `fxrstor64 16(%rdi)'
make[2]: *** [tools/llvm-exegesis/lib/X86/CMakeFiles/LLVMExegesisX86.dir/Target.cpp.o] Error 1

Any suggestions to fix this apart from an upgrade (which seems to be a very invasive change on our machines)?

In D90742#2373442, @courbet wrote:

In D90742#2373438, @thakis wrote:

Looks like this doesn't build on windows: http://45.33.8.238/win/27220/step_4.txt

Thanks, I missed this bot. I'll send a fix.

In D90742#2373438, @thakis wrote:

Looks like this doesn't build on windows: http://45.33.8.238/win/27220/step_4.txt

Address review comments

Thanks, PTAL.

This looks good for the llvm-exegesis part. I'm not familiar enough with the PowerPC target to review the rest.