[PowerPC] fix bug affecting float to int32 conversion on LE PowerPC

[DanilaZhebryakov]

when moving fcti results from float registers to normal registers through memory, even though MPI was adjusted to account for endianness, FIPtr was always adjusted for big-endian, which caused loads of wrong half of a value in little-endian mode.

[github-actions]

Thank you for submitting a Pull Request (PR) to the LLVM Project!

This PR will be automatically labeled and the relevant teams will be notified.

If you wish to, you can add reviewers by using the "Reviewers" section on this page.

If this is not working for you, it is probably because you do not have write permissions for the repository. In which case you can instead tag reviewers by name in a comment by using @ followed by their GitHub username.

If you have received no comments on your PR for a week, you can request a review by "ping"ing the PR by adding a comment “Ping”. The common courtesy "ping" rate is once a week. Please remember that you are asking for valuable time from other developers.

If you have further questions, they may be answered by the LLVM GitHub User Guide.

You can also ask questions in a comment on this PR, on the LLVM Discord or on the forums.

[llvmbot]

@llvm/pr-subscribers-backend-powerpc

Author: None (DanilaZhebryakov)

Changes

when moving fcti results from float registers to normal registers through memory, even though MPI was adjusted to account for endianness, FIPtr was always adjusted for big-endian, which caused loads of wrong half of a value in little-endian mode.

---

Full diff: https://github.com/llvm/llvm-project/pull/150194.diff

1 Files Affected:

• (modified) llvm/lib/Target/PowerPC/PPCISelLowering.cpp (+2-2)

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 459525ed4ee9a..3974d726620b7 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -8457,10 +8457,10 @@ void PPCTargetLowering::LowerFP_TO_INTForReuse(SDValue Op, ReuseLoadInfo &RLI,
 
   // Result is a load from the stack slot.  If loading 4 bytes, make sure to
   // add in a bias on big endian.
-  if (Op.getValueType() == MVT::i32 && !i32Stack) {
+  if (Op.getValueType() == MVT::i32 && !i32Stack && !Subtarget.isLittleEndian()) {
     FIPtr = DAG.getNode(ISD::ADD, dl, FIPtr.getValueType(), FIPtr,
                         DAG.getConstant(4, dl, FIPtr.getValueType()));
-    MPI = MPI.getWithOffset(Subtarget.isLittleEndian() ? 0 : 4);
+    MPI = MPI.getWithOffset(4);
   }
 
   RLI.Chain = Chain;

[vit9696]

cc @hfinkel, @nemanjai, @diggerlin, @lei137 et al, could you review this please 🙏?