[llvm-bugs] [Bug 49206] New: compile-time explosion with assumes at -O3 in clang-8.0 upwards versions

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49206

            Bug ID: 49206
           Summary: compile-time explosion with assumes at -O3 in
                    clang-8.0 upwards versions
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: haoxintu at gmail.com
                CC: llvm-bugs at lists.llvm.org

Hi, all.

This code makes Clang-8.0 to clang-trunk versions hung on with -O3 at compile
time.

$cat s.c
#include <stdint.h>
int a;
int64_t b;
void c(int d) {
  int e;
  uint64_t f;
  int16_t g;
  int8_t i = a;
  for (;;) {
    int16_t k = i;
    uint64_t *j = d;
    for (; k; k++)
      for (; e;) {
        uint64_t *m = &f;
        if ((e += g) <= 0) {
          *m &= 4;
          if (b || *j) {
          l:
            *j *= b;
            goto l;
          }
        }
      }
  }
}

$clang -c -w -O3 s.c
//endless compiling

$clang -v
clang version 13.0.0 (https://github.com/llvm/llvm-project
22f00f61dd5483a9fdaed3b7592d392c23b3646a)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir:
/home/haoxin/haoxin-data/dut-research/compilers/llvm-project/build-20210216/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Candidate multilib: .;@m64
Selected multilib: .;@m64


Thanks,
Haoxin

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