[Bug tree-optimization/126720] New: [15/16/17 Regression] wrong code with -O3

[xxs_chy at outlook dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126720

            Bug ID: 126720
           Summary: [15/16/17 Regression] wrong code with -O3
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xxs_chy at outlook dot com
  Target Milestone: ---

Reproducer: https://godbolt.org/z/qMx8M31Pa
Testcase:
#include <stdint.h>
#define BITCAST(DST_TYPE, SRC_TYPE, VALUE)                                    
\
    (((union {                                                                
\
         SRC_TYPE src;                                                        
\
         DST_TYPE dst                                                         
\
     })VALUE)                                                                 
\
         .dst)
typedef int16_t v2i16 __attribute__((vector_size(4)));
typedef uint16_t v2u16 __attribute__((vector_size(4)));
typedef uint32_t v2u32;
v2u32 g17;
uint8_t g29;
_Bool f6_a2;
int main()
{
    uint16_t v9;
    v2u16 bc16;
    uint16_t v17 = 0;
lbl_cont8:
    v9 = ~v17;
    bc16 = (v2u16)0;
    v17 = v9;
    v9 = bc16[g29];
    bc16 = BITCAST(v2u16, uint32_t, (uint32_t)v17);
    bc16 = (v2i16)bc16 < 0;
    v17 = 29834 >> v9;
    bc16 = __builtin_shufflevector(bc16, bc16, 3, 1);
    bc16 = ~bc16;
lbl_sw25:
    bc16 = ~bc16;
lbl_bf33:
    bc16 = ~bc16;
    bc16[1] = ~v17;
lbl_br46:
    switch (~BITCAST(uint32_t, v2u16, bc16))
    {
        case 1955201024: goto lbl_sw_def57;
        case 4033962: goto lbl_sw53;
        default: __builtin_unreachable();
    }
lbl_sw53:
    if (f6_a2) goto lbl_sw25;
    goto lbl_cont8;
lbl_sw_def57:
    bc16 = bc16 >= 0;
    if (v9 == 3) return 0;
    g17 = g17 > (v2u32){};
    if (g29) goto lbl_br46;
}

This case triggers SIGSEGV at -O3.