On Fri, 1 Nov 2024, Jan Hubicka wrote:
> > I have a vague memory that one of the tests in SPEC has a loop that > > tries to malloc, doubling the size each time, until it fails. Would > > the patch change the behavior of such a loop? > > If the resulting allocation is unused except for NULL check we will make > it always "succeed" and thus the loop will likely loop forever. I > wonder what this loop computes on systems, like linux, that overcommits > memory. Even with overcommit, malloc is going to return NULL as soon as you pass a half or more of the address space as the requested allocation size. Since the patch eliminates malloc with unknown size, I think this transform is incorrect (wasn't correct for the same reason in LLVM either). I'm pretty sure it's going to break some Glibc tests that verify that malloc(SIZE_MAX / 2 + 1) does not succeed. Please reconsider? Why to we need to match LLVM here? Alexander
