Shivam Gupta 796b218edd
[LegalizeTypes] Expand UDIV/UREM by constant via chunk summation (#146238)
This patch improves the lowering of 128-bit unsigned division and
remainder by constants (UDIV/UREM) by avoiding a fallback to libcall
(__udivti3/uremti3) for specific divisors.

When a divisor D satisfies the condition (1 << ChunkWidth) % D == 1, the
128-bit value is split into fixed-width chunks (e.g., 30-bit) and summed
before applying a smaller UDIV/UREM. This transformation is based on the
"remainder by summing digits" trick described in Hacker’s Delight.

This fixes #137514 for some constants.
2026-03-19 17:58:54 +05:30
..
2025-05-22 15:42:22 +01:00