Zfb also contains FLI.{H, S, D, Q}

1 files changed, 91 insertions, 0 deletions

diff --git a/src/zfb.tex b/src/zfb.tex
index 9c801a0..a79c52f 100644
--- a/src/zfb.tex
+++ b/src/zfb.tex
@@ -154,3 +154,94 @@ registers into a floating-point register.  Integer registers {\em rs1} and
 floating-point register {\em rd}.
 FMVP.Q.X is encoded in the OP-FP major opcode with {\em funct3}=0
 and {\em funct7}=1011011.
+
+
+\section{Load-Immediate Instructions}
+
+The FLI.S instruction loads a 5-bit immediate value that represents
+a single-precision floating-point number, encoded in the {\em rs1} field, into
+floating-point register {\em rd}.
+The correspondence of {\em rs1} field values and single-precision
+floating-point values is shown in Table~\ref{tab:flis}.
+FLI.S is encoded like FMV.W.X, but with {\em rs2}=1.
+
+\begin{table}[h]
+\center
+\begin{tabular}{|r|r|c|c|c|}
+\hline
+{\em rs1}   & Value                            & Sign    & Exponent       & Significand     \\
+\hline
+ 0          & $-1.0$                           & {\tt 1} & {\tt 01111111} & {\tt 000...000} \\
+ 1          & {\em Minimum positive normal}    & {\tt 0} & {\tt 00000001} & {\tt 000...000} \\
+ 2          & $1.0 \times 2^{-16}$             & {\tt 0} & {\tt 01101111} & {\tt 000...000} \\
+ 3          & $1.0 \times 2^{-15}$             & {\tt 0} & {\tt 01110000} & {\tt 000...000} \\
+ 4          & $1.0 \times 2^{-8}$              & {\tt 0} & {\tt 01110111} & {\tt 000...000} \\
+ 5          & $1.0 \times 2^{-7}$              & {\tt 0} & {\tt 01111000} & {\tt 000...000} \\
+ 6          & $1.0 \times 2^{-4}$              & {\tt 0} & {\tt 01111011} & {\tt 000...000} \\
+ 7          & $1.0 \times 2^{-3}$              & {\tt 0} & {\tt 01111100} & {\tt 000...000} \\
+ 8          & $1.0 \times 2^{-2}$              & {\tt 0} & {\tt 01111101} & {\tt 000...000} \\
+ 9          & $1.25 \times 2^{-2}$             & {\tt 0} & {\tt 01111101} & {\tt 010...000} \\
+10          & $1.5 \times 2^{-2}$              & {\tt 0} & {\tt 01111101} & {\tt 100...000} \\
+11          & $1.75 \times 2^{-2}$             & {\tt 0} & {\tt 01111101} & {\tt 110...000} \\
+12          & $1.0 \times 2^{-1}$              & {\tt 0} & {\tt 01111110} & {\tt 000...000} \\
+13          & $1.25 \times 2^{-1}$             & {\tt 0} & {\tt 01111110} & {\tt 010...000} \\
+14          & $1.5 \times 2^{-1}$              & {\tt 0} & {\tt 01111110} & {\tt 100...000} \\
+15          & $1.75 \times 2^{-1}$             & {\tt 0} & {\tt 01111110} & {\tt 110...000} \\
+16          & 1.0                              & {\tt 0} & {\tt 01111111} & {\tt 000...000} \\
+17          & 1.25                             & {\tt 0} & {\tt 01111111} & {\tt 010...000} \\
+18          & 1.5                              & {\tt 0} & {\tt 01111111} & {\tt 100...000} \\
+19          & 1.75                             & {\tt 0} & {\tt 01111111} & {\tt 110...000} \\
+20          & 2.0                              & {\tt 0} & {\tt 10000000} & {\tt 000...000} \\
+21          & 2.5                              & {\tt 0} & {\tt 10000000} & {\tt 010...000} \\
+22          & 3                                & {\tt 0} & {\tt 10000000} & {\tt 100...000} \\
+23          & 4                                & {\tt 0} & {\tt 10000001} & {\tt 000...000} \\
+24          & 8                                & {\tt 0} & {\tt 10000010} & {\tt 000...000} \\
+25          & $2^7$                            & {\tt 0} & {\tt 10000110} & {\tt 000...000} \\
+26          & $2^8$                            & {\tt 0} & {\tt 10000111} & {\tt 000...000} \\
+27          & $2^{15}$                         & {\tt 0} & {\tt 10001110} & {\tt 000...000} \\
+28          & $2^{16}$                         & {\tt 0} & {\tt 10001111} & {\tt 000...000} \\
+29          & {\em Maximum positive normal}    & {\tt 0} & {\tt 11111110} & {\tt 111...111} \\
+30          & $+\infty$                        & {\tt 0} & {\tt 11111111} & {\tt 000...000} \\
+31          & {\em Canonical NaN}              & {\tt 0} & {\tt 11111111} & {\tt 100...000} \\
+\hline
+\end{tabular}
+\caption{Immediate values loaded by the FLI.S instruction.}
+\label{tab:flis}
+\end{table}
+
+\begin{commentary}
+The set of 32 constants was chosen by examining floating-point libraries,
+including the C standard math library, and to optimize fixed-point to
+floating-point conversion.
+
+Entries 8--22 follow a regular encoding pattern.
+\end{commentary}
+
+If the D extension is implemented, FLI.D performs the analogous operation,
+but loads a double-precision value into floating-point register {\em rd}.
+Note that entries 1 and 29 (corresponding to the minimum and maximum
+normal values) have numerically different values for double-precision than
+for single-precision.
+FLI.D is encoded like FLI.S, but with {\em fmt}=D.
+
+If the Q extension is implemented, FLI.Q performs the analogous operation,
+but loads a quad-precision value into floating-point register {\em rd}.
+Note that entries 1 and 29 (corresponding to the minimum and maximum
+normal values) have numerically different values for quad-precision.
+FLI.Q is encoded like FLI.S, but with {\em fmt}=Q.
+
+If the Zfh or Zvfh extension is implemented, FLI.H performs the analogous
+operation, but loads a half-precision floating-point value into register
+{\em rd}.
+Note that entries 1 and 29 (corresponding to the minimum and maximum normal
+values) have numerically different values for half-precision.  Furthermore,
+since $2^{16}$ is not representable in half-precision floating-point, entry 28
+in the table instead loads the maximum positive normal value---i.e., it is
+redundant with entry 29.  FLI.H is encoded like FLI.S, but with {\em fmt}=H.
+
+\begin{commentary}
+Additionally, since $2^{-16}$ is a subnormal in half-precision, entry 1 is numerically
+greater than entry 2 for FLI.H.
+\end{commentary}
+
+The FLI.{\em fmt} instructions never set any floating-point exception flags.