[llvm-bugs] [Bug 37664] New: opt miscompiles with "opt -O3 -newgvn -structurizecfg"

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Sat Jun 2 13:31:08 PDT 2018


            Bug ID: 37664
           Summary: opt miscompiles with "opt -O3 -newgvn -structurizecfg"
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: Vsevolod.Livinskij at frtk.ru
                CC: llvm-bugs at lists.llvm.org

Created attachment 20385
  --> https://bugs.llvm.org/attachment.cgi?id=20385&action=edit

Opt produces incorrect code with -O3 -newgvn -structurizecfg
opt-bisect-limit points to Machine Common Subexpression Elimination on function
Testcase looks weird, but I can't reduce it further.

>$ cat func.cpp
#include "init.h"
void tf_3_foo() {
  bool a(var_3);
  var_2 = (tf_3_var_38 && struct_obj.member_1_3) ||
                  (a && arr_3[0]) || !a || !ptr;
>$ cat driver.cpp
#include "init.h"
#include <vector>
void a(long) {}
std::vector<int> b;
struct_1 struct_2::member_2;
bool var_1, var_2;
const bool tf_3_var_38 = false;
unsigned short var_3 = 3;
tf_3_struct_1 struct_obj;
std::array<unsigned short, 10> arr_2;
std::valarray<bool> arr_3{false};
unsigned short *ptr = &arr_2[0];
void tf_3_foo();
int main() {
  printf("%d\n", (int)var_2);
>$ cat init.h
#include <valarray>
struct struct_1 {
  int member_1 : 13;
struct struct_2 {
  static struct_1 member_2;
extern const bool tf_3_var_38;
extern unsigned short var_3;
struct tf_3_struct_1 {
  bool member_1_3 : 3;
} extern struct_obj;
extern std::valarray<bool> arr_3;
extern bool var_2;
extern unsigned short *ptr;

>$ clang++ driver.cpp func.cpp
>$ ./a.out
>$ clang++ -O3 -Xclang -disable-llvm-optzns -emit-llvm -c -o func.bc func.cpp
>$ opt -O3 -o func.ll func.bc -newgvn -structurizecfg
>$ clang++ -O3 -c -o func.o func.ll
>$ clang++ driver.cpp func.o
>$ ./a.out

LLVM version:
clang version 7.0.0 (trunk 333377)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /llvm/bin-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64

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