[PATCH] D26955: Fix bitwidth for x87 extended-precision floating-point type

[Dominic Chen via Phabricator via cfe-commits]

ddcc added inline comments.


================
Comment at: lib/Basic/TargetInfo.cpp:229
   switch (BitWidth) {
-  case 96:
+  case 80:
     if (&getLongDoubleFormat() == &llvm::APFloat::x87DoubleExtended)
----------------
bruno wrote:
> The change makes sense but I believe there's some historical reason why this is 96 instead of 80? What problem have you found in practice? Do you have a testcase or unittest that exercise the issue (and that could be added to the patch)?
I'd be curious why it was historically set to 96; I dug up rL190044 as the original commit, but it doesn't mention 80 vs 96 for this at all.

I've been implementing an alternative symbolic constraint solver backend for the static analyzer, including floating-point support, which performs some type conversion and needs to reason about bitwidth. I'm still working on those patches, since they touch a lot of code and currently break some tests. I can write up a testcase for this issue, though I've only written IR testcases before and I'm not sure how I'd directly call a clang internal function?


https://reviews.llvm.org/D26955