[llvm-dev] byval vs. explicitly coded copy (original) (raw)
Friedman, Eli via llvm-dev llvm-dev at lists.llvm.org
Fri Nov 3 15:44:58 PDT 2017
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On 11/3/2017 2:57 PM, Rodney M. Bates via llvm-dev wrote:
Is there any disadvantage to inserting explicit llvm code in a prolog to copy a parameter, rather than putting the 'byval' attribute on the formal or indirect call?
I have an IR that, without some significant work, does not make enough information available at an indirect call site to know whether a copy is needed. (The original source language knows, it just gets lost at an indirect call.)
It's fine; actually, you'll probably get better code in many cases by avoiding byval. (If you're calling code which uses the C calling convention, you might need to use "byval" to match the calling convention.)
-Eli
-- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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