[compiler-rt] [llvm] [X86][BF16] Add libcall for F80 -> BF16 (PR #109116)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `bolt-x86_64-ubuntu-clang` running on `bolt-worker` while building `compiler-rt,llvm` at step 6 "test-build-clang-bolt-stage2-clang-bolt".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/113/builds/2862

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-clang-bolt-stage2-clang-bolt) failure: test (failure)
...
0.234 [164/18/137] Building ASM object CMakeFiles/clang_rt.builtins-i386.dir/i386/floatdixf.S.o
0.235 [163/18/138] Building C object CMakeFiles/clang_rt.builtins-x86_64.dir/absvdi2.c.o
0.235 [162/18/139] Building C object CMakeFiles/clang_rt.builtins-i386.dir/extendbfsf2.c.o
0.236 [161/18/140] Building C object CMakeFiles/clang_rt.builtins-x86_64.dir/apple_versioning.c.o
0.236 [160/18/141] Building C object CMakeFiles/clang_rt.builtins-i386.dir/mulxc3.c.o
0.237 [159/18/142] Building C object CMakeFiles/clang_rt.builtins-x86_64.dir/absvsi2.c.o
0.240 [158/18/143] Building C object CMakeFiles/clang_rt.builtins-x86_64.dir/absvti2.c.o
0.240 [157/18/144] Building C object CMakeFiles/clang_rt.builtins-x86_64.dir/addvdi3.c.o
0.241 [156/18/145] Building C object CMakeFiles/clang_rt.builtins-x86_64.dir/addvsi3.c.o
0.244 [155/18/146] Building C object CMakeFiles/clang_rt.builtins-i386.dir/truncxfbf2.c.o
FAILED: CMakeFiles/clang_rt.builtins-i386.dir/truncxfbf2.c.o 
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/build/./bin/clang --target=x86_64-unknown-linux-gnu -DVISIBILITY_HIDDEN  -O3 -DNDEBUG -m32 -fno-lto -std=c11 -fPIC -fno-builtin -fvisibility=hidden -fomit-frame-pointer -DCOMPILER_RT_HAS_FLOAT16 -MD -MT CMakeFiles/clang_rt.builtins-i386.dir/truncxfbf2.c.o -MF CMakeFiles/clang_rt.builtins-i386.dir/truncxfbf2.c.o.d -o CMakeFiles/clang_rt.builtins-i386.dir/truncxfbf2.c.o -c /home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/truncxfbf2.c
In file included from /home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/truncxfbf2.c:11:
In file included from /home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc_impl.inc:39:
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:49:2: error: Source should be double precision or quad precision!
   49 | #error Source should be double precision or quad precision!
      |  ^
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:114:15: error: unknown type name 'src_rep_t'; did you mean 'dst_rep_t'?
  114 | static inline src_rep_t extract_sign_from_src(src_rep_t x) {
      |               ^~~~~~~~~
      |               dst_rep_t
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:99:18: note: 'dst_rep_t' declared here
   99 | typedef uint16_t dst_rep_t;
      |                  ^
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:114:47: error: unknown type name 'src_rep_t'; did you mean 'dst_rep_t'?
  114 | static inline src_rep_t extract_sign_from_src(src_rep_t x) {
      |                                               ^~~~~~~~~
      |                                               dst_rep_t
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:99:18: note: 'dst_rep_t' declared here
   99 | typedef uint16_t dst_rep_t;
      |                  ^
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:115:9: error: unknown type name 'src_rep_t'; did you mean 'dst_rep_t'?
  115 |   const src_rep_t srcSignMask = SRC_REP_C(1) << (srcBits - 1);
      |         ^~~~~~~~~
      |         dst_rep_t
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:99:18: note: 'dst_rep_t' declared here
   99 | typedef uint16_t dst_rep_t;
      |                  ^
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:115:33: error: call to undeclared function 'SRC_REP_C'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  115 |   const src_rep_t srcSignMask = SRC_REP_C(1) << (srcBits - 1);
      |                                 ^
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:115:50: error: use of undeclared identifier 'srcBits'; did you mean 'dstBits'?
  115 |   const src_rep_t srcSignMask = SRC_REP_C(1) << (srcBits - 1);
      |                                                  ^~~~~~~
      |                                                  dstBits
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:101:18: note: 'dstBits' declared here
  101 | static const int dstBits = sizeof(dst_t) * CHAR_BIT;
      |                  ^
/home/worker/bolt-worker2/bolt-x86_64-ubuntu-clang/llvm-project/compiler-rt/lib/builtins/fp_trunc.h:116:32: error: use of undeclared identifier 'srcBits'; did you mean 'dstBits'?

```

</details>

https://github.com/llvm/llvm-project/pull/109116