RuntimeLibcalls: Account for Triple default exception handling

[arsenm]

Previously we were taking the raw TargetOptions exception mode.
This only works correctly for the TargetLowering usage, when
the -exception-model flag is explicitly used.

The interface isn't great, and interprets none to both mean use
target default and unsupported, such that it's not possible to
opt-out of exceptions on targets that report a non-none default.

We also still get the wrong mode in the linker usecase of
RuntimeLibcalls since it doesn't have the TargetMachine. But at
least wrongly being the default is an improvement over being unset.

I'm not really sure how to write a test for this.

[arsenm]

• ARM: Move sjlj libcall configuration to RuntimeLibcalls #147227
• ARM: Remove subtarget field tracking SjLj #147226
• Triple: Record default exception handling type #147225
• RuntimeLibcalls: Account for Triple default exception handling #147224 👈 (View in Graphite)
• main

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[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: Matt Arsenault (arsenm)

Changes

Previously we were taking the raw TargetOptions exception mode.
This only works correctly for the TargetLowering usage, when
the -exception-model flag is explicitly used.

The interface isn't great, and interprets none to both mean use
target default and unsupported, such that it's not possible to
opt-out of exceptions on targets that report a non-none default.

We also still get the wrong mode in the linker usecase of
RuntimeLibcalls since it doesn't have the TargetMachine. But at
least wrongly being the default is an improvement over being unset.

I'm not really sure how to write a test for this.

---

Full diff: https://github.com/llvm/llvm-project/pull/147224.diff

1 Files Affected:

• (modified) llvm/include/llvm/IR/RuntimeLibcalls.h (+8)

diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.h b/llvm/include/llvm/IR/RuntimeLibcalls.h
index 50b9791111ce2..9470d22bcad31 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.h
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.h
@@ -53,6 +53,14 @@ struct RuntimeLibcallsInfo {
       EABI EABIVersion = EABI::Default, StringRef ABIName = "") {
     initSoftFloatCmpLibcallPredicates();
     initDefaultLibCallImpls();
+
+    // FIXME: The ExceptionModel parameter is to handle the field in
+    // TargetOptions. This interface fails to distinguish the forced disable
+    // case for targets which support exceptions by default. This should
+    // probably be a module flag and removed from TargetOptions.
+    if (ExceptionModel == ExceptionHandling::None)
+      ExceptionModel = TT.getDefaultExceptionHandling();
+
     initLibcalls(TT, ExceptionModel, FloatABI, EABIVersion, ABIName);
   }
 

[DanielKristofKiss]

reasonable, anyway the right solution is to derive it from the module attributes or such.

[arsenm]

I somehow submitted these in the wrong order, #147225 should be first

[dpaoliello]

LGTM

[dpaoliello]

If you don't already have plans to fix this, could you please file an issue?

[arsenm]

If you don't already have plans to fix this, could you please file an issue?

That's at least 3 steps away. First need to split the lowering decisions from the set of libcalls, and then turn RuntimeLibcalls into an analysis, then replace the TargetOptions field with a module flag

[llvm-ci]

LLVM Buildbot has detected a new failure on builder llvm-clang-x86_64-expensive-checks-debian running on gribozavr4 while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/16/builds/22256

Here is the relevant piece of the build log for the reference

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: TableGen/RuntimeLibcallEmitter-conflict-warning.td' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/llvm-tblgen -gen-runtime-libcalls -I /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/../../include /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter-conflict-warning.td 2> /b/1/llvm-clang-x86_64-expensive-checks-debian/build/test/TableGen/Output/RuntimeLibcallEmitter-conflict-warning.td.tmp.err | /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/FileCheck /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter-conflict-warning.td # RUN: at line 1
+ /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/llvm-tblgen -gen-runtime-libcalls -I /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/../../include /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter-conflict-warning.td
+ /b/1/llvm-clang-x86_64-expensive-checks-debian/build/bin/FileCheck /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter-conflict-warning.td
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter-conflict-warning.td:29:16: error: CHECK-NEXT: is not on the line after the previous match
// CHECK-NEXT: {RTLIB::SOME_FUNC, RTLIB::func_b}, // func_b
               ^
<stdin>:98:2: note: 'next' match was here
 {RTLIB::SOME_FUNC, RTLIB::func_b}, // func_b
 ^
<stdin>:72:49: note: previous match ended here
 static const LibcallImplPair LibraryCalls[] = {
                                                ^
<stdin>:73:1: note: non-matching line after previous match is here
 {RTLIB::SOME_FUNC, RTLIB::func_a}, // func_a
^

Input file: <stdin>
Check file: /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/test/TableGen/RuntimeLibcallEmitter-conflict-warning.td

-dump-input=help explains the following input dump.

Input was:
<<<<<<
         .
         .
         .
        93:  
        94:  if (isTargetArchC()) { 
        95:  static const LibcallImplPair LibraryCalls[] = { 
        96:  {RTLIB::ANOTHER_DUP, RTLIB::dup0}, // dup0 
        97:  {RTLIB::OTHER_FUNC, RTLIB::other_func}, // other_func 
        98:  {RTLIB::SOME_FUNC, RTLIB::func_b}, // func_b 
next:29      !~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  error: match on wrong line
        99:  }; 
       100:  
       101:  for (const auto [Func, Impl] : LibraryCalls) { 
       102:  setLibcallImpl(Func, Impl); 
       103:  } 
         .
         .
         .
>>>>>>

--

...