https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110414
Bug ID: 110414 Summary: [14 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: theodort at inf dot ethz.ch Target Milestone: --- https://godbolt.org/z/5E795dPvY Given the following code: void foo(void); static int a, b, e, l, m, n; static int *c = &a, *j; static int **d = &c; static int ***f; void __assert_fail(char *, char *, int, char *) __attribute__((__noreturn__)); static void g(char) { if (c == &b || c == &a) ; else __assert_fail("", "", 3, __PRETTY_FUNCTION__); } static void h(); static int *i(); static short k() { j = i(); h(); **f = &e; if (c == &b || c == &a || c == 0) __assert_fail("", "", 6, __PRETTY_FUNCTION__); return 0; } static void h() { if (l) { for (; l; l = l - 8) *d = &m; if (c == &a) ; else __assert_fail("", "", 9, __PRETTY_FUNCTION__); } if (c == &b || c == &a || c == 0) ; else { foo(); __assert_fail("", "", 8, __PRETTY_FUNCTION__); } } static int *i() { if (c == &b || c == &a) ; else { __builtin_unreachable(); __assert_fail("", "", 6, __PRETTY_FUNCTION__); } return &n; } int main() { g(a && k()); } gcc-trunk -Os does not eliminate the call to foo: main: pushq %rcx cmpl $0, a(%rip) je .L2 movl l(%rip), %edx testl %edx, %edx je .L3 movl %edx, %eax movl $__PRETTY_FUNCTION__.1, %ecx movq $m, c(%rip) shrl $3, %eax imull $-8, %eax, %eax addl %edx, %eax movl $9, %edx movl %eax, l(%rip) jmp .L7 .L3: movq c(%rip), %rax cmpq $a, %rax sete %dl cmpq $b, %rax sete %cl orb %cl, %dl jne .L4 testq %rax, %rax je .L4 call foo movl $__PRETTY_FUNCTION__.1, %ecx movl $8, %edx .L7: movl $.LC0, %esi movq %rsi, %rdi call __assert_fail .L4: movl $__PRETTY_FUNCTION__.2, %ecx movl $6, %edx jmp .L7 .L2: movq c(%rip), %rax cmpq $a, %rax je .L5 cmpq $b, %rax je .L5 movl $__PRETTY_FUNCTION__.0, %ecx movl $3, %edx jmp .L7 .L5: xorl %eax, %eax popq %rdx ret gcc-13.1.0 -Os eliminates the call to foo: main: pushq %rcx movq c(%rip), %rdx cmpq $a, %rdx sete %al cmpq $b, %rdx sete %dl orl %edx, %eax cmpl $0, a(%rip) je .L2 movl l(%rip), %edx testl %edx, %edx je .L3 movl %edx, %eax movl $__PRETTY_FUNCTION__.1, %ecx movq $m, c(%rip) shrl $3, %eax imull $-8, %eax, %eax addl %edx, %eax movl $9, %edx movl %eax, l(%rip) jmp .L7 .L2: testb %al, %al jne .L5 movl $__PRETTY_FUNCTION__.0, %ecx movl $3, %edx .L7: movl $.LC0, %esi movq %rsi, %rdi call __assert_fail .L3: movl $__PRETTY_FUNCTION__.2, %ecx movl $6, %edx jmp .L7 .L5: xorl %eax, %eax popq %rdx ret Bisects to r14-1127-g9e2017ae6ac