llvm-cbe generates missing LLVMMul_uov from .ll ouput from clang++-10 (plzip-1.9 dec_stdout.c)

[makise-homura]

Say, we have LLVM 10.0.0, and just have built llvm-cbe in current directory.

Trying to build dec_stdout.cc from plzip-1.9 with lzlib-1.12:

wget -q http://download.savannah.gnu.org/releases/lzip/lzlib/lzlib-1.12.tar.gz
wget -q http://download.savannah.gnu.org/releases/lzip/plzip/plzip-1.9.tar.gz
tar xf plzip-1.9.tar.gz
tar xf lzlib-1.12.tar.gz
clang++-10 -S -emit-llvm -g -Iplzip-1.9 -Ilzlib-1.12 -o dec_stdout.ll plzip-1.9/dec_stdout.cc
./llvm-cbe dec_stdout.ll
gcc-10 -Wno-builtin-declaration-mismatch -Wno-address-of-packed-member -c -o dec_stdout.o dec_stdout.cbe.c

I have the following output (among the messages caused by #132) then:

dec_stdout.cbe.c: In function ‘llvm_OC_umul_OC_with_OC_overflow_OC_i64’:
dec_stdout.cbe.c:735:14: warning: implicit declaration of function ‘LLVMMul_uov’ [-Wimplicit-function-declaration]
  735 |   r.field1 = LLVMMul_uov(8 * sizeof(a), &a, &b, &r.field0);
      |              ^~~~~~~~~~~

If we grep dec_stdout.cbe.c for LLVMMul_uov, we'll find out that this function is used, but not declared:

  r.field1 = LLVMMul_uov(8 * sizeof(a), &a, &b, &r.field0);

Quick reproducer for this (newint.cc):

int main() { int a, *b = new int[a]; }

Reproduction:

clang++-10 -S -emit-llvm -g -o newint.ll newint.cc
./llvm-cbe newint.ll
gcc-10 newint.cbe.c -o newint

Clang and gcc versions:

clang version 10.0.0-4ubuntu1 Target: x86_64-pc-linux-gnu Thread model: posix
gcc-10 (Ubuntu 10.2.0-5ubuntu1~20.04) 10.2.0