From 986fcfb7ab62e8a0eab9280bd09b821a36563344 Mon Sep 17 00:00:00 2001
From: lkcl <lkcl@web>
Date: Sun, 6 Oct 2019 11:35:54 +0100
Subject: [PATCH]

---
 simple_v_extension/specification/mv.x.rst | 108 ++++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/simple_v_extension/specification/mv.x.rst b/simple_v_extension/specification/mv.x.rst
index dc468fb92..a90ba33ce 100644
--- a/simple_v_extension/specification/mv.x.rst
+++ b/simple_v_extension/specification/mv.x.rst
@@ -213,3 +213,111 @@ Matrix 4x4 Vector mul
     pfscaleadd,0 F2, F1, F13, F2
 
 pfscale is a 4 vec mv.shuffle followed by a fmul. pfscaleadd is a 4 vec mv.shuffle followed by a fmac.
+
+Pseudocode
+==========
+
+Swizzle:
+
+::
+
+pub trait SwizzleConstants: Copy + 'static {
+    const CONSTANTS: &'static [Self; 4];
+}
+
+impl SwizzleConstants for u8 {
+    const CONSTANTS: &'static [Self; 4] = &[0, 1, 0xFF, 0x7F];
+}
+
+impl SwizzleConstants for u16 {
+    const CONSTANTS: &'static [Self; 4] = &[0, 1, 0xFFFF, 0x7FFF];
+}
+
+impl SwizzleConstants for f32 {
+    const CONSTANTS: &'static [Self; 4] = &[0.0, 1.0, -1.0, 0.5];
+}
+
+// impl for other types too...
+
+pub fn swizzle<Elm, Selector>(
+    rd: &mut [Elm],
+    rs1: &[Elm],
+    rs2: &[Selector],
+    vl: usize,
+    destsubvl: usize,
+    srcsubvl: usize)
+where
+    Elm: SwizzleConstants,
+    // Selector is a copyable type that can be converted into u64
+    Selector: Copy + Into<u64>,
+{
+    const FIELD_SIZE: usize = 3;
+    const FIELD_MASK: u64 = 0b111;
+    for vindex in 0..vl {
+        let selector = rs2[vindex].into();
+        // selector's type is u64
+        if selector >> (FIELD_SIZE * destsubvl) != 0 {
+            // handle illegal instruction trap
+        }
+        for i in 0..destsubvl {
+            let mut sel_field = selector >> (FIELD_SIZE * i);
+            sel_field &= FIELD_MASK;
+            let src = if (sel_field & 0b100) == 0 {
+                &rs1[(vindex * srcsubvl)..]
+            } else {
+                SwizzleConstants::CONSTANTS
+            };
+            sel_field &= 0b11;
+            if sel_field as usize >= srcsubvl {
+                // handle illegal instruction trap
+            }
+            let value = src[sel_field as usize];
+            rd[vindex * destsubvl + i] = value;
+        }
+    }
+}
+
+Swizzle2:
+
+::
+
+fn swizzle2<Elm, Selector>(
+    rd: &mut [Elm],
+    rs1: &[Elm],
+    rs2: &[Selector],
+    rs3: &[Elm],
+    vl: usize,
+    destsubvl: usize,
+    srcsubvl: usize)
+where
+    // Elm is a copyable type
+    Elm: Copy,
+    // Selector is a copyable type that can be converted into u64
+    Selector: Copy + Into<u64>,
+{
+    const FIELD_SIZE: usize = 3;
+    const FIELD_MASK: u64 = 0b111;
+    for vindex in 0..vl {
+        let selector = rs2[vindex].into();
+        // selector's type is u64
+        if selector >> (FIELD_SIZE * destsubvl) != 0 {
+            // handle illegal instruction trap
+        }
+        for i in 0..destsubvl {
+            let mut sel_field = selector >> (FIELD_SIZE * i);
+            sel_field &= FIELD_MASK;
+            let src = if (sel_field & 0b100) != 0 {
+                rs1
+            } else {
+                rs3
+            };
+            sel_field &= 0b11;
+            if sel_field as usize >= srcsubvl {
+                // handle illegal instruction trap
+            }
+            let value = src[vindex * srcsubvl + (sel_field as usize)];
+            rd[vindex * destsubvl + i] = value;
+        }
+    }
+}
+
-- 
2.30.2