From 4370b93cf307fa099973341c481e7c2d50eee572 Mon Sep 17 00:00:00 2001
From: Dominic Symes <dominic.symes@arm.com>
Date: Wed, 30 Nov 2022 14:25:20 +0000
Subject: Clarify the type of condition tensors

Condition tensors used by the control
flow operations must contain a single
element.

Change-Id: Ie3cb8f0b4a4149cee1b3aacbfa720dd4cad02fbc
Signed-off-by: Dominic Symes <dominic.symes@arm.com>
---
 chapters/control_flow.adoc | 15 ++++++++++-----
 tosa.xml                   |  4 ++--
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/chapters/control_flow.adoc b/chapters/control_flow.adoc
index 49fab74..e43ef51 100644
--- a/chapters/control_flow.adoc
+++ b/chapters/control_flow.adoc
@@ -23,8 +23,9 @@ ERROR_IF(tensor_list_shape(input_list) != tosa_input_shape(then_graph));
 ERROR_IF(tensor_list_shape(input_list) != tosa_input_shape(else_graph));
 ERROR_IF(tensor_list_shape(output_list) != tosa_output_shape(then_graph));
 ERROR_IF(tensor_list_shape(output_list) != tosa_output_shape(else_graph));
+ERROR_IF(tensor_size(shape) != 1);
 
-if (condition) {
+if (condition[0]) {
     tosa_execute_graph(then_graph, input_list, output_list);
 } else {
     tosa_execute_graph(else_graph, input_list, output_list);
@@ -43,17 +44,21 @@ ERROR_IF(tensor_list_shape(input_list) != tosa_list_shape(output_list));
 ERROR_IF(tensor_list_shape(input_list) != tosa_input_shape(cond_graph));
 ERROR_IF(tensor_list_shape(input_list) != tosa_input_shape(body_graph));
 ERROR_IF(tensor_list_shape(input_list) != tosa_output_shape(body_graph));
-ERROR_IF(tosa_output_shape(cond_graph) != tosa_list_shape([bool_t]));
+// Condition graph output must be a single element tensor with a single bool value
+ERROR_IF(tensor_size(tosa_output_shape(cond_graph)) != 1);
+ERROR_IF(tosa_output_type(cond_graph) != bool_t);
 
 // The iteration number 'i' is included to give unique names to variables
 // in each iteration of the loop and is not required by implementations
 int32_t i=0;             // iteration number
+tensor_list_t list[];    // array of tensor lists indexed by iteration
+bool_t *condition[];     // array of condition tensors indexed by iteration
 list[i] = input_list;    // copy input data as list[0]
-tosa_execute_graph(cond_graph, list[i], [condition[i]]);   // initial condition
-while (condition[i]) {
+tosa_execute_graph(cond_graph, list[i], [ condition[i] ]);   // initial condition
+while (condition[i][0]) {
     tosa_execute_graph(body_graph, list[i], list[i+1]);
     i = i+1;
-    tosa_execute_graph(cond_graph, list[i], [condition[i]]);
+    tosa_execute_graph(cond_graph, list[i], [ condition[i] ]);
 }
 output_list = list[i];
 ----
diff --git a/tosa.xml b/tosa.xml
index 5a04023..fcd3597 100644
--- a/tosa.xml
+++ b/tosa.xml
@@ -2244,8 +2244,8 @@ used.</description>
           <argument category="input" name="input_list" type="tensor_list_t" shape="-">
             <description>List of input tensors</description>
           </argument>
-          <argument category="input" name="condition" type="bool_t" shape="-">
-            <description>Input condition as rank-0 tensor</description>
+          <argument category="input" name="condition" type="bool_t*" shape="shape">
+            <description>Input condition as a size 1 tensor</description>
           </argument>
           <argument category="attribute" name="then_graph" type="tosa_graph_t" shape="-">
             <description>TOSA graph to execute if condition is true</description>
-- 
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