[LLVMdev] something better than .align for branch targets (original) (raw)
Steve King steve at metrokings.com
Wed Jul 1 10:37:35 PDT 2015
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Hello LLVM, For some processors, the all or nothing behavior of the .align directive is not optimal for improving fetch efficiency of branches. For example, take an instruction fetch width of 16 bytes and a branch target just 1 byte offset into a fetch block. Align injects 15 bytes of padding rather than leaving well enough alone. Efficiency is unlikely to improve for lack of 1 byte out of 16, and performance may be hurt by all the padding not to mention code size.
Is there an existing way for a target to express a "near enough" semantic for code alignment?
Regards, -steve
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