Rollup merge of #143477 - folkertdev:use-is-multiple-of, r=joshtriplett

use `is_multiple_of` and `div_ceil`

In tricky logic, these functions are much more informative than the manual implementations. They also catch subtle bugs:

- the manual `is_multiple_of` often does not handle division by zero
- manual `div_ceil` often does not consider overflow

The transformation is free for `is_multiple_of` if the divisor is compile-time known to be non-zero. For `div_ceil` there is a small cost to considering overflow. Here is some assembly https://godbolt.org/z/5zP8KaE1d.

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 4b07c8aef91..009e7e2487b 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -146,7 +146,7 @@ impl LlvmType for CastTarget {
                 "total size {:?} cannot be divided into units of zero size",
                 self.rest.total
             );
-            if self.rest.total.bytes() % self.rest.unit.size.bytes() != 0 {
+            if !self.rest.total.bytes().is_multiple_of(self.rest.unit.size.bytes()) {
                 assert_eq!(self.rest.unit.kind, RegKind::Integer, "only int regs can be split");
             }
             self.rest.total.bytes().div_ceil(self.rest.unit.size.bytes())