llvm: convert @divFloor and @mod to forms llvm will recognize
#22540
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On x86_64, the `@divFloor` change is a strict improvement, and the
`@mod` change adds one zero latency instruction. In return, once we
upgrade to LLVM 20, when the optimizer discovers one of these operations
has a power-of-two constant rhs, it will be able to optimize the entire
operation into an `ashr` or `and`, respectively.
#I CPL CPT
old `@divFloor` | 8 | 15 | .143 |
new `@divFloor` | 7 | 15 | .148 |
old `@mod` | 9 | 17 | .134 | (rip llvm
new `@mod` | 10 | 17 | .138 | scheduler)
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On x86_64, the
@divFloorchange is a strict improvement, and the@modchange adds one zero latency instruction. In return, once we upgrade to LLVM 20, when the optimizer discovers one of these operations has a power-of-two constant rhs, it will be able to optimize the entire operation into anashrorand, respectively.