[llvm-bugs] [Bug 27858] New: mldst-motion miscompile with call to exit()

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27858

            Bug ID: 27858
           Summary: mldst-motion miscompile with call to exit()
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: eli.friedman at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Testcase:

#include <stdlib.h>
void f() { exit(1); }
void (*ff)() = f;
int r, s;
void g(int a, int*restrict p) {
  if (a) {ff(); r = p[1]; } 
  else { s = p[1]; } 
}
void (*gg)(int, int*restrict) = g;
int main() {
  gg(1, 0);
}

Works with gcc or clang -O0, crashes with clang -O2.

Testcase:

#include <stdlib.h>
#include <stdio.h>
void f() { throw 1; }
void (*ff)() = f;
void f2() {}
void (*ff2)() = f2;
int r, s;
void g(int a, int*__restrict p) {
  if (a) { ff2(); p[1] = 2; ff(); } 
  else { p[1] = 2; } 
}
void (*gg)(int, int*restrict) = g;
int main() {
  int a[2] = {0};
  try {
    gg(1, a);
  } catch (...) {}
  if (a[1] != 2) abort();
}

Works with gcc or clang -O0, aborts with clang -O2.

I think the problem is
MergedLoadStoreMotion::isLoadHoistBarrierInRange/isStoreSinkBarrierInRange; you
can't use alias analysis to prove that a pointer is valid.

(Artificial testcases.)

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