[PATCH] D89130: [WIP][Sparc] Fix long double on 32-bit Solaris/SPARC

[Rainer Orth via Phabricator via llvm-commits]

ro created this revision.
ro added reviewers: efriedma, brad.
Herald added subscribers: Sanitizers, s.egerton, dexonsmith, jrtc27, simoncook, fedor.sergeev, hiraditya, mgorny, jyknight.
Herald added projects: clang, Sanitizers, LLVM.
ro requested review of this revision.

The SysVr4 SPARC psABI prescribes 128-bit `long double` on 32-bit Sparc, and Solaris follows that as do some other OSes.  However, `clang` doesn't support that.

**This is not yet complete, but I need guidance in some points and believe it's easier to do so here than in the corresponding Bug 42493**

There are several noteworthy issues:

- `long double` is 128-bit IEEEquad format, but with 64-bit alignment unlike SPARC V9 which uses 128-bit alignment.
- `long double` is passed and returned by reference, just like structures and unions.
- `long double _Complex`, a Sun extension not in the psABI, is always returned in registers.
- `compiler-rt` uses `__uint128_t` for `long double` support which isn't available for 32-bit compilations by default.  It's currently enabled with `-fforce-enable-int128` which `gcc` doesn't support.

Right now the basic `long double` support seems to work (need to double-check with GCC's `gcc.dg/compat` testsuite), but compiling `compiler-rt/lib/builtins/divtc3.c` fails:

  Assertion failed: isRegLoc(), file /vol/llvm/src/llvm-project/local/llvm/include/llvm/CodeGen/CallingConvLower.h, line 150
  
  11 libc.so.1 0xffffffff7edfb158 _assert + 104
  12 clang-12  0x00000001038fdf90 llvm::SparcTargetLowering::LowerCall_32(llvm::TargetLowering::CallLoweringInfo&, llvm::SmallVectorImpl<llvm::SDValue>&) const + 11888
  13 clang-12  0x00000001038f9010 llvm::SparcTargetLowering::LowerCall(llvm::TargetLowering::CallLoweringInfo&, llvm::SmallVectorImpl<llvm::SDValue>&) const + 60
  14 clang-12  0x0000000106062f54 llvm::TargetLowering::LowerCallTo(llvm::TargetLowering::CallLoweringInfo&) const + 7724
  15 clang-12  0x0000000106039704 (anonymous namespace)::SelectionDAGLegalize::ExpandLibCall(llvm::RTLIB::Libcall, llvm::SDNode*, bool) + 1896

Besides, something will have to be done about the `__uint128_t` requirement on 32-bit targets, probably using a union with `uint64_t` members.

I'm currently lost here and will need some guidance how to proceed.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D89130

Files:
  clang/lib/Basic/Targets/Sparc.h
  clang/lib/CodeGen/TargetInfo.cpp
  compiler-rt/lib/builtins/CMakeLists.txt
  compiler-rt/lib/builtins/int_types.h
  compiler-rt/test/builtins/CMakeLists.txt
  compiler-rt/test/builtins/Unit/divtc3_test.c
  llvm/lib/Target/Sparc/SparcCallingConv.td
  llvm/lib/Target/Sparc/SparcISelLowering.cpp

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