[M68k] implement large code model

[TechnoElf]

Fixes #106208.

[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-m68k

Author: Janis Heims (TechnoElf)

Changes

Fixes #106208.

---

Full diff: https://github.com/llvm/llvm-project/pull/106381.diff

2 Files Affected:

• (modified) llvm/lib/Target/M68k/M68kSubtarget.cpp (+31)
• (modified) llvm/lib/Target/M68k/M68kTargetMachine.cpp (-2)

diff --git a/llvm/lib/Target/M68k/M68kSubtarget.cpp b/llvm/lib/Target/M68k/M68kSubtarget.cpp
index cacdbf559faa2d..00b20966924277 100644
--- a/llvm/lib/Target/M68k/M68kSubtarget.cpp
+++ b/llvm/lib/Target/M68k/M68kSubtarget.cpp
@@ -127,6 +127,24 @@ M68kSubtarget &M68kSubtarget::initializeSubtargetDependencies(
 //  ---------------------+------------+------------+------------+-------------
 //      data global big* |   pc-rel   |  @GOTPCREL |  absolute  |  @GOTPCREL
 //  ---------------------+------------+------------+------------+-------------
+//                       |          Large          |
+//                       +-------------------------+
+//                       |   Static   |    PIC     |
+//  ---------------------+------------+------------+
+//                branch |   pc-rel   |   pc-rel   |
+//  ---------------------+------------+------------+
+//           call global |    @PLT    |    @PLT    |
+//  ---------------------+------------+------------+
+//         call internal |   pc-rel   |   pc-rel   |
+//  ---------------------+------------+------------+
+//            data local |  absolute  |  @GOTOFF   |
+//  ---------------------+------------+------------+
+//       data local big* |  absolute  |  @GOTOFF   |
+//  ---------------------+------------+------------+
+//           data global |  absolute  |  @GOTPCREL |
+//  ---------------------+------------+------------+
+//      data global big* |  absolute  |  @GOTPCREL |
+//  ---------------------+------------+------------+
 //
 // * Big data potentially cannot be reached within 16 bit offset and requires
 //   special handling for old(x00 and x10) CPUs. Normally these symbols go into
@@ -171,6 +189,13 @@ M68kSubtarget::classifyLocalReference(const GlobalValue *GV) const {
       return M68kII::MO_ABSOLUTE_ADDRESS;
     }
   }
+  case CodeModel::Large: {
+    if (isPositionIndependent()) {
+      return M68kII::MO_GOTOFF;
+    } else {
+      return M68kII::MO_ABSOLUTE_ADDRESS;
+    }
+  }
   }
 }
 
@@ -212,6 +237,12 @@ unsigned char M68kSubtarget::classifyGlobalReference(const GlobalValue *GV,
 
     return M68kII::MO_ABSOLUTE_ADDRESS;
   }
+  case CodeModel::Large: {
+    if (isPositionIndependent())
+      return M68kII::MO_GOTPCREL;
+
+    return M68kII::MO_ABSOLUTE_ADDRESS;
+  }
   }
 }
 
diff --git a/llvm/lib/Target/M68k/M68kTargetMachine.cpp b/llvm/lib/Target/M68k/M68kTargetMachine.cpp
index b65de5e177b53e..2248837e6ca61b 100644
--- a/llvm/lib/Target/M68k/M68kTargetMachine.cpp
+++ b/llvm/lib/Target/M68k/M68kTargetMachine.cpp
@@ -87,8 +87,6 @@ CodeModel::Model getEffectiveCodeModel(std::optional<CodeModel::Model> CM,
                                        bool JIT) {
   if (!CM) {
     return CodeModel::Small;
-  } else if (CM == CodeModel::Large) {
-    llvm_unreachable("Large code model is not supported");
   } else if (CM == CodeModel::Kernel) {
     llvm_unreachable("Kernel code model is not implemented yet");
   }

[mshockwave]

Thanks for the patch! could you add some tests?

[TechnoElf]

Done.

[TechnoElf]

The pipeline is failing due to a timeout in an LLDB test: lldb-api :: functionalities/fork/concurrent_vfork/TestConcurrentVFork.py. I don't really understand how that's related to the change though...

Edit: Apparently this is a known issue with the test.

[TechnoElf]

ping @mshockwave @0x59616e

[mshockwave]

LGTM. Thanks!

[knickish]

Are there any blockers to getting this in? Would be very helpful

[github-actions]

@TechnoElf Congratulations on having your first Pull Request (PR) merged into the LLVM Project!

Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR.

Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues.

How to do this, and the rest of the post-merge process, is covered in detail here.

If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again.

If you don't get any reports, no action is required from you. Your changes are working as expected, well done!