https://bugs.llvm.org/show_bug.cgi?id=46949
Bug ID: 46949
Summary: Opportunity to remove null pointer checks (IPO)
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Interprocedural Optimizations
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: llvm-bugs@lists.llvm.org
void clean(void);
__attribute__((noinline))
static void check(void *p)
{
if (!p)
clean();
}
void foo(void *p, void *q)
{
if (p)
check(p);
if (q)
check(q);
}
void bar(void *p, void *q)
{
check(p);
check(q);
}
foo(void*, void*): # @foo(void*, void*)
push rbx
mov rbx, rsi
test rdi, rdi
je .LBB0_2
call check(void*)
.LBB0_2:
test rbx, rbx
je .LBB0_3
mov rdi, rbx
pop rbx
jmp check(void*) # TAILCALL
.LBB0_3:
pop rbx
ret
check(void*): # @check(void*)
test rdi, rdi
je .LBB1_2
ret
.LBB1_2:
jmp clean() # TAILCALL
bar(void*, void*): # @bar(void*, void*)
push rbx
mov rbx, rsi
call check(void*)
mov rdi, rbx
pop rbx
jmp check(void*) # TAILCALL
There is a missed opportunity to remove null pointer checks (optimize "foo" to
"bar").
https://godbolt.org/z/or9oW5
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