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| Paper: dividing by seven johnl@taugh.com (John R Levine) (2026-04-10) |
| Re: Paper: dividing by seven anton@mips.complang.tuwien.ac.at (2026-04-13) |
| Re: Paper: dividing by seven robin51@dodo.com.au (2026-04-19) |
| Re: Paper: dividing by seven anton@mips.complang.tuwien.ac.at (2026-04-19) |
| From: | John R Levine <johnl@taugh.com> |
| Newsgroups: | comp.compilers |
| Date: | Fri, 10 Apr 2026 12:04:13 -0400 |
| Organization: | Compilers Central |
| Injection-Info: | gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="59820"; mail-complaints-to="abuse@iecc.com" |
| Keywords: | code, optimize, paper |
| Posted-Date: | 10 Apr 2026 12:26:05 EDT |
Optimization of 32-bit Unsigned Division by Constants on 64-bit Targets
Shigeo Mitsunari, Takashi Hoshino
Granlund and Montgomery proposed an optimization method for unsigned
integer division by constants [3]. Their method (called the GM method in
this paper) was further improved in part by works such as [1] and [7], and
is now adopted by major compilers including GCC, Clang, Microsoft
Compiler, and Apple Clang. However, for example, for x/7, the generated
code is designed for 32-bit CPUs and therefore does not fully exploit
64-bit capabilities. This paper proposes an optimization method for 32-bit
unsigned division by constants targeting 64-bit CPUs. We implemented
patches for LLVM/GCC and achieved speedups of 1.67x on Intel Xeon w9-3495X
(Sapphire Rapids) and 1.98x on Apple M4 (Apple M-series SoC) in the
microbenchmark described later. The LLVM patch has already been merged
into llvm:main [6], demonstrating the practical applicability of the
proposed method.
https://arxiv.org/abs/2604.07902
Regards,
John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly
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