51 lines
1.6 KiB
TeX
51 lines
1.6 KiB
TeX
\section{A frontend model for the Cortex A72}
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\begin{frame}{The Cortex A72}
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\begin{itemize}
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\item{} Low-power ARM CPU
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\item{} CPU of the Raspberry Pi 4: easily available
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\item{} Aarch64, NEON SIMD
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\medskip{}
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\item{} ARM CPUs not usually modeled!
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\item{} Backend modeled by \palmed{}
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\end{itemize}
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\end{frame}
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\begin{frame}
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\centering
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\includegraphics[width=0.9\textwidth]{A72_pipeline_diagram.svg}
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\end{frame}
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\begin{frame}{Manual model}
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\begin{itemize}
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\item Goal: manually craft a frontend model
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\item Try to follow methods that can be automated
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\item Propose a parametric model for future works, leaving question
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marks on some sections
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\end{itemize}
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\end{frame}
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\begin{frame}{Counting \uops{}}
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For an instruction $i$, denote \alert{$\mucount{i}$} its number of \uops{}.
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\begin{itemize}
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\item{} For $k \in \nat$, construct (if possible) $\kerK_k$ a kernel:
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\begin{itemize}
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\item instruction $i$ + $k$ ``simple'' instructions (one \uop)
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\item frontend-bound:
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\[
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\cyc{\kerK_k} = \dfrac{k + \mucount{i}}{3}
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\]
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\end{itemize}
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\item{} For well-chosen $k_0$, we should have
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\[
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\cyc{\kerK_{k_0}} + \sfrac{1}{3} = \cyc{\kerK_{k_0+1}}
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\]
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\item{} Measure to verify
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\bigskip
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\item{} If so, \textbf{\[
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\mucount{i} = 3 \cyc{\kerK_{k_0}} - k
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\]}
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\end{itemize}
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\end{frame}
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