add slids

[libreriscv.git] / simple_v_extension / simple_v_chennai_2018.tex

diff --git a/simple_v_extension/simple_v_chennai_2018.tex b/simple_v_extension/simple_v_chennai_2018.tex
index 14e593c435fe139abec15cf85de504baa461bdee..902f7cc22a4ca9583b362fa488bdd1fff3d17c54 100644 (file)
--- a/simple_v_extension/simple_v_chennai_2018.tex
+++ b/simple_v_extension/simple_v_chennai_2018.tex
@@ -50,7 +50,7 @@
    https://sigarch.org/simd-instructions-considered-harmful
    \item Setup and corner-cases alone are extremely complex.\\
             Hardware is easy, but software is hell.
-   \item O($N^{6}$) ISA opcode proliferation!\\
+   \item O($N^{6}$) ISA opcode proliferation (1000s of instructions)\\
             opcode, elwidth, veclen, src1-src2-dest hi/lo
   \end{itemize}
 }
@@ -59,6 +59,8 @@
 
  \begin{itemize}
    \item Effectively a variant of SIMD / SIMT (arbitrary length)\vspace{4pt}
+   \item Fascinatingly, despite being a SIMD-variant, RVV only has
+         O(N) opcode proliferation! (extremely well designed)
    \item Extremely powerful (extensible to 256 registers)\vspace{4pt}
    \item Supports polymorphism, several datatypes (inc. FP16)\vspace{4pt}
    \item Requires a separate Register File (32 w/ext to 256)\vspace{4pt}
@@ -66,11 +68,9 @@
   \end{itemize}
   However...
    \begin{itemize}
-   \item 98 percent opcode duplication with rest of RV (CLIP)
+   \item 98 percent opcode duplication with rest of RV
    \item Extending RVV requires customisation not just of h/w:\\
             gcc, binutils also need customisation (and maintenance)
-   \item Fascinatingly, despite being a SIMD-variant, RVV only has
-         O(N) opcode proliferation! (extremely well designed)
   \end{itemize}
 }
 
@@ -150,7 +150,7 @@
    \item Standard and future and custom opcodes now parallel\\
          (crucially: with NO extra instructions needing to be added)
   \end{itemize}
-  Note: EVERYTHING is parallelised:
+  Note: EVERY scalar op now paralleliseable
    \begin{itemize}
    \item All LOAD/STORE (inc. Compressed, Int/FP versions)
    \item All ALU ops (Int, FP, SIMD, DSP, everything)
@@ -370,9 +370,9 @@ for (i = 0; i < 16; i++) // 16 CSRs?
 \begin{semiverbatim}
 def get\_pred\_val(bool is\_fp\_op, int reg):
    tb = int\_pred if is\_fp\_op else fp\_pred
-   if (!tb[reg].enabled):
-      return ~0x0              // all ops enabled
-   predidx = tb[reg].predidx   // redirection occurs HERE
+   if (!tb[reg].enabled): return ~0x0 // all ops enabled
+   predidx  = tb[reg].predidx  // redirection occurs HERE
+   predidx += tb[reg].bank << 5 // 0 (1=rsvd)
    predicate = intreg[predidx] // actual predicate HERE
    if (tb[reg].inv):
       predicate = ~predicate   // invert ALL bits