[PATCH] D41338: [CodeGen] lower math intrinsics to finite version of libcalls when possible (PR35672)

[Hal Finkel via Phabricator via llvm-commits]

hfinkel added a comment.

In https://reviews.llvm.org/D41338#958611, @efriedma wrote:

> > Do the finite calls need the double-leading underscores? I saw an existing test with __sqrt_finite, so I assume we want those, but I'm not sure if/how the regular calls acquire the underscores.
>
> That's just how they're named; the names come from the glibc headers.
>
> > Does this make sense for ISD::STRICT_FEXP (the strict version of the node)?
>
> I would guess strict and fast math don't really mix...


I agree.

> 
> 
>> Does the mathlib actually support the long double variants?
> 
> long double variants should exist, as far as I know... at least for the "long double" which is native for the platform.

Correct.



================
Comment at: lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:4049
   case ISD::STRICT_FEXP:
-    Results.push_back(ExpandFPLibCall(Node, RTLIB::EXP_F32, RTLIB::EXP_F64,
-                                      RTLIB::EXP_F80, RTLIB::EXP_F128,
-                                      RTLIB::EXP_PPCF128));
+    if (CanUseFiniteLibCall && DAG.getLibInfo().has(LibFunc_exp_finite))
+      Results.push_back(ExpandFPLibCall(Node, RTLIB::EXP_FINITE_F32,
----------------
efriedma wrote:
> "getLibInfo().has(LibFunc_exp_finite)" probably isn't the right check.  There are three __exp*_finite variants; each of them may or may not be legal, and you need to check that the long double variant actually accepts the input float type.
> 
> Also, it looks like TargetLibraryInfo doesn't contain the appropriate checks to disable them (it assumes any non-Windows platform has __exp_finite, which is clearly false).
> and you need to check that the long double variant actually accepts the input float type.

How would we check this?

> (it assumes any non-Windows platform has __exp_finite, which is clearly false).

Hrmm. We could start with disabling them for any non-GNU triple.


https://reviews.llvm.org/D41338