Support chime_complex encoding of 4+4-bit integers

Project.toml

@@ -1,7 +1,7 @@
 name = "IndexSpaces"
 uuid = "3ceaaf38-e7b4-4193-a23a-303dd231a83a"
 authors = ["Erik Schnetter <[email protected]>"]
-version = "1.6.0"
+version = "1.7.0"
 
 [deps]
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"

src/IndexSpaces.jl

@@ -1415,13 +1415,27 @@ function int4x8_to_2int8x4_unshifted_withoffset(a::Int4x8)
     return (Int8x4(a_lo), Int8x4(a_hi))::NTuple{2,Int8x4}
 end
 
+# Convert `Int4x8` to `NTuple{2,Int8x4}`, but swap the high and low nibbles and remove the offset encoding.
+function int4x8_to_2int8x4_swapped_withoffset(a::Int4x8)
+    a1 = a.val                         # a + 8, implicit in the offset encoding
+    a2_lo = a1 & 0x0f0f0f0f            # extract low part
+    a3_lo = a2_lo + 0x78787878         # a + 128
+    a4_lo = a3_lo ⊻ 0x80808080         # a
+    a2_hi = (a1 >>> 0x04) & 0x0f0f0f0f # extract high part
+    a3_hi = a2_hi + 0x78787878         # a + 128
+    a4_hi = a3_hi ⊻ 0x80808080         # a
+    a5_lo, a5_hi = a4_hi, a4_lo        # Swap low and high parts
+    return (Int8x4(a5_lo), Int8x4(a5_hi))::NTuple{2,Int8x4}
+end
+
 export widen!
 function widen!(
     emitter::Emitter,
     res::Symbol,
     var::Symbol,
     simd_register::Pair{SIMD,Register};
     newtype::Union{Nothing,Type}=nothing,
+    swapped_withoffset::Bool=false,
     unshifted_withoffset::Bool=false,
 )
     simd, register = simd_register
@@ -1471,7 +1485,10 @@ function widen!(
         end
         if indextag(var_value) == indextag(res_value) == IntValueTag
             if var_value.length == 4 && res_value.length == 8
-                if unshifted_withoffset
+                @assert !(swapped_withoffset && unshifted_withoffset)
+                if swapped_withoffset
+                    stmt = :(($(res_names...),) = IndexSpaces.int4x8_to_2int8x4_swapped_withoffset($var_name))
+                elseif unshifted_withoffset
                     stmt = :(($(res_names...),) = IndexSpaces.int4x8_to_2int8x4_unshifted_withoffset($var_name))
                 else
                     stmt = :(($(res_names...),) = convert(NTuple{2,Int8x4}, $var_name))