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diff --git a/openpower/sv/vector_swizzle.mdwn b/openpower/sv/vector_swizzle.mdwn
index dd92009197587feca2242b86c180f87b92b9cdfc..c04c8644a01b3024c785cf01a2d0914d387be80e 100644 (file)
--- a/openpower/sv/vector_swizzle.mdwn
+++ b/openpower/sv/vector_swizzle.mdwn
@@ -14,3 +14,25 @@ The reason for the dramatic increase is that the reordering of each element in v
 
 There is also benefit to encoding some useful immediates into src operands, on a per sub-element basis: being able to specify for example that the Z element of a vec4 is to be 1.0 saves a complex LD-immediate merging operation for that lane.
 
+# Options
+
+## Predication plus indices
+
+* 4 bits for predication
+* 2 bits per element
+
+## SUBVL plus indices
+
+* SUBVL specifies the length (vec2/3/4)
+* However index selection is 2 bits per element
+* Therefore the src SUBVL must be separate and distinct from the dest SUBVL
+
+# Predication mixed with immediates and indices
+
+* Three bits per element.
+* One encoding (0b000) indicates "mask"
+* Four encodings (0b1NN) indicate vec4 selection
+* Three remaining indices indicate constants
+  - 0 (or 0.0)
+  - 1 (or 1.0)
+  - -1 (or -1.0) or some other option?