clang 15 fails to compile program using `smmintrin.h` on ppc64el

[madscientist159]

Updating Clang to version 15 yields new compilation errors on an existing program that includes the smmintrin.h compatibility header. These errors originate from within Clang's own internal header files, not from the application itself.

/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:71:25: error: use of undeclared identifier '__builtin_mffs'
    __fpscr_save.__fr = __builtin_mffs();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:74:5: error: use of undeclared identifier '__builtin_mtfsf'
    __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:86:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:89:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
    __builtin_set_fpscr_rn(0b00);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:105:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
    __builtin_set_fpscr_rn(__fpscr_save.__fpscr);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:131:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:133:5: error: use of undeclared identifier '__builtin_mtfsf'
    __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:162:25: error: use of undeclared identifier '__builtin_mffs'
    __fpscr_save.__fr = __builtin_mffs();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:165:5: error: use of undeclared identifier '__builtin_mtfsf'
    __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:177:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:180:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
    __builtin_set_fpscr_rn(0b00);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:196:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
    __builtin_set_fpscr_rn(__fpscr_save.__fpscr);
    ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:222:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
    __fpscr_save.__fr = __builtin_mffsl();
                        ^
/usr/lib/llvm-15/lib/clang/15.0.7/include/ppc_wrappers/smmintrin.h:224:5: error: use of undeclared identifier '__builtin_mtfsf'
    __builtin_mtfsf(0b00000011, __fpscr_save.__fr);

This issue may have been introduced in this patch series:
https://reviews.llvm.org/D119407

[llvmbot]

@llvm/issue-subscribers-backend-powerpc

[EugeneZelenko]

Could you please try 17 or main branch? https://godbolt.org should be helpful.

[madscientist159]

I can try in a few days, the application is quite large so would need to ensure the rest of it builds enough with 17 to get to the same point.

That said, I highly doubt 17 or main are fixed, since the builtins are not present in clang/include/clang/Basic/BuiltinsPPC.def and the offending calls are still present in clang/lib/Headers/ppc_wrappers/smmintrin.h

[nemanjai]

I can confirm that this is NOT fixed in trunk. It "works" with C, but not with C++. Namely, it compiles in C files as long as one does not use the builtins that haven't been implemented. Presumably a call to a function such as _mm_round_pd will emit calls to bogus functions such as __builtin_mffs on CPU's prior to Power9.

The frustrating thing is that I think we have previously had a similar issue where these wrappers don't work on C++ and we've clearly either not fixed them all or we've introduced new ones. We need to add C++ test cases for all of these wrappers on top of the C tests that we have (and we should test with -mcpu=pwr9/-mcpu=pwr8).

A simple test case that shows the offending builtins just in this file:

#include <smmintrin.h>

int main(int argc, const char **argv) {
  return 3;
}

Compilation:

$ clang++ -S t.cpp -DNO_WARN_X86_INTRINSICS
In file included from t.cpp:1:
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:71:25: error: use of undeclared identifier '__builtin_mffs'
   71 |     __fpscr_save.__fr = __builtin_mffs();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:74:5: error: use of undeclared identifier '__builtin_mtfsf'
   74 |     __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:86:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
   86 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:89:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
   89 |     __builtin_set_fpscr_rn(0b00);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:105:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
  105 |     __builtin_set_fpscr_rn(__fpscr_save.__fpscr);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:131:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
  131 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
   86 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:133:5: error: use of undeclared identifier '__builtin_mtfsf'
  133 |     __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:162:25: error: use of undeclared identifier '__builtin_mffs'
  162 |     __fpscr_save.__fr = __builtin_mffs();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:165:5: error: use of undeclared identifier '__builtin_mtfsf'
  165 |     __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:177:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
  177 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
   86 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:180:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
  180 |     __builtin_set_fpscr_rn(0b00);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:196:5: error: use of undeclared identifier '__builtin_set_fpscr_rn'
  196 |     __builtin_set_fpscr_rn(__fpscr_save.__fpscr);
      |     ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:222:25: error: use of undeclared identifier '__builtin_mffsl'; did you mean '__builtin_infl'?
  222 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:86:25: note: '__builtin_infl' declared here
   86 |     __fpscr_save.__fr = __builtin_mffsl();
      |                         ^
/home/ubuntu/nemanjai/llvm/trunk1/build/lib/clang/18/include/ppc_wrappers/smmintrin.h:224:5: error: use of undeclared identifier '__builtin_mtfsf'
  224 |     __builtin_mtfsf(0b00000011, __fpscr_save.__fr);
      |     ^
14 errors generated.

[ecnelises]

https://reviews.llvm.org/D158066