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Add description of most alu ext operations
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Andreas Traber
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\chapter{PULP ALU Extensions}
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\label{chap:aluext}
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\rvcore supports advanced ALU operations that allow to perform multiple
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instructions that are specified in the base instruction set in one single
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instruction and thus increases efficiency of the core.
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For example those instructions include zero-/sign-extension instructions for
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8-bit and 16-bit operands, simple bit manipulation/counting instructions and
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min/max/avg instructions.
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\section{Instructions}
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\subsection{p.avg rD, rs1, rs2}
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Performs an arithmetic right shift after the addition of rs1 and rs2.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 000 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = (rs1 + rs2) >> 1}
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\subsection{p.avgu rD, rs1, rs2}
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Performs a logical right shift after the addition of rs1 and rs2.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 001 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = (rs1 + rs2) >> 1}
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\subsection{p.slet rD, rs1, rs2}
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Performs an signed smaller than or equal comparison between rs1 and rs2.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 010 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = (rs1 <= rs2) ? -1 : 0}
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\subsection{p.sletu rD, rs1, rs2}
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Performs an unsigned smaller than or equal comparison between rs1 and rs2.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 011 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = (rs1 <= rs2) ? -1 : 0}
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\subsection{p.min rD, rs1, rs2}
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Sets rD to the minimum of rs1 and rs2, assuming both are signed 32-bit values.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 100 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = rs1 < rs2 ? rs1 : rs2}
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\subsection{p.minu rD, rs1, rs2}
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Sets rD to the minimum of rs1 and rs2, assuming both are unsigned 32-bit
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values.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 101 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = rs1 < rs2 ? rs1 : rs2}
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\subsection{p.max rD, rs1, rs2}
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Sets rD to the maximum of rs1 and rs2, assuming both are signed 32-bit values.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 110 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = rs1 > rs2 ? rs1 : rs2}
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\subsection{p.maxu rD, rs1, rs2}
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Sets rD to the maximum of rs1 and rs2, assuming both are unsigned 32-bit
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values.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0010}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 111 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = rs1 > rs2 ? rs1 : rs2}
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\subsection{p.abs rD, rs1}
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Computes the absolute value of the signed 32-bit operand rs1.
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ 00000 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 1010}
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\bitbox[]{5}{ 00000 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 000 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = rs1 < 0 ? -rs1 : rs1}
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\subsection{p.ror rD, rs1, rs2}
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\begin{center}
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\begin{bytefield}[endianness=big,bitwidth=1.3em]{32}
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\bitheader{31,25,24,20,19,15,14,12,11,7,6,0} \\
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\bitbox{7}{ funct7 }
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\bitbox{5}{ rs2 }
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\bitbox{5}{ rs1 }
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\bitbox{3}{ funct3 }
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\bitbox{5}{ rd }
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\bitbox{7}{ opcode } \\
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\bitbox[]{7}{ 000 0100}
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\bitbox[]{5}{ src2 }
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\bitbox[]{5}{ src1 }
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\bitbox[]{3}{ 101 }
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\bitbox[]{5}{ dest }
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\bitbox[]{7}{ 011 0011 }
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\end{bytefield}
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\end{center}
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\textbf{Operation:} \texttt{rD = RotateRight(rs1, rs2)}
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