On Fri, Apr 24, 2026 at 06:54:05AM -0500, Segher Boessenkool wrote:
Hi!
On Fri, Apr 24, 2026 at 11:17:40AM +0530, Mukesh Kumar Chaurasiya (IBM) wrote:
The core crate currently depends on these two functions for i64/u64/ i128/u128/core::time::Duration formatting, but we shouldn’t use that in the kernel so let’s panic if they are ever called.
This doesn’t yet fix drm_panic_qr.rs, which also uses __udivdi3 when CONFIG_CC_OPTIMIZE_FOR_SIZE=y, but at least makes the rest of the kernel build on PPC32.
GCC uses calls to functions like even __addsi3 whenever the (sub-)target does not implement some RTL, doesn't have a define_insn and the like for it. When you write a new port you only *have* to implement a very few things, the rest is done in libgcc (you might still have to write some of that for your target, no free lunch etc.)
32-bit PowerPC has no instructions for 64-bit divisions, nor instructions that help implementing it in software. It still very often helps to hand-write machine code for it, it very easily can usually be more than twice as fast for example (for example if the divisor is less than half a word big, the common case -- it can be made tens of times faster then).
There can be many reasons why a GCC backend decides to call a libgcc routine. For __udivdi3 on -m32 rs6000 you'll be good AFAICS :-) (but poisoning functions like you do is a terrible idea in general!)
Whoopsie, I forgot to mention:
Approved for trunk.
Segher