Fix bool conversion bug in Vulkan code generator (halide#8067)

* Fix bug in Vulkan code generator that was incorrectly passing the
address of a byte vector, instead of its contents to
builder.declare_constant()

* Add bool_predicate_cast correctness test to verify bool conversion for
Vulkan codegen works as expected

---------

Co-authored-by: Derek Gerstmann <[email protected]>

src/CodeGen_Vulkan_Dev.cpp

@@ -548,6 +548,9 @@ void fill_bytes_with_value(uint8_t *bytes, int count, int value) {
 }
 
 SpvId CodeGen_Vulkan_Dev::SPIRV_Emitter::convert_to_bool(Type target_type, Type value_type, SpvId value_id) {
+    debug(2) << "CodeGen_Vulkan_Dev::SPIRV_Emitter::convert_to_bool(): casting from value type '"
+             << value_type << "' to target type '" << target_type << "' for value id '" << value_id << "' !\n";
+
     if (!value_type.is_bool()) {
         value_id = cast_type(Bool(), value_type, value_id);
     }
@@ -590,8 +593,8 @@ SpvId CodeGen_Vulkan_Dev::SPIRV_Emitter::convert_to_bool(Type target_type, Type
 
     SpvId result_id = builder.reserve_id(SpvResultId);
     SpvId target_type_id = builder.declare_type(target_type);
-    SpvId true_value_id = builder.declare_constant(target_type, &true_data);
-    SpvId false_value_id = builder.declare_constant(target_type, &false_data);
+    SpvId true_value_id = builder.declare_constant(target_type, &true_data[0]);
+    SpvId false_value_id = builder.declare_constant(target_type, &false_data[0]);
     builder.append(SpvFactory::select(target_type_id, result_id, value_id, true_value_id, false_value_id));
     return result_id;
 }

test/correctness/CMakeLists.txt

@@ -14,6 +14,7 @@ tests(GROUPS correctness
       bit_counting.cpp
       bitwise_ops.cpp
       bool_compute_root_vectorize.cpp
+      bool_predicate_cast.cpp
       bound.cpp
       bound_small_allocations.cpp
       bound_storage.cpp

test/correctness/bool_predicate_cast.cpp

@@ -0,0 +1,39 @@
+#include "Halide.h"
+#include <stdio.h>
+
+using namespace Halide;
+
+int main(int argc, char **argv) {
+
+    // Test explicit casting of a predicate to an integer as part of a reduction
+    // NOTE: triggers a convert_to_bool in Vulkan for a SelectOp
+    Target target = get_jit_target_from_environment();
+    Var x("x"), y("y");
+
+    Func input("input");
+    input(x, y) = cast<uint8_t>(x + y);
+
+    Func test("test");
+    test(x, y) = cast(UInt(8), input(x, y) >= 32);
+
+    if (target.has_gpu_feature()) {
+        Var xi("xi"), yi("yi");
+        test.gpu_tile(x, y, xi, yi, 8, 8);
+    }
+
+    Realization result = test.realize({96, 96});
+    Buffer<uint8_t> a = result[0];
+    for (int y = 0; y < a.height(); y++) {
+        for (int x = 0; x < a.width(); x++) {
+            uint8_t correct_a = ((x + y) >= 32) ? 1 : 0;
+            if (a(x, y) != correct_a) {
+                printf("result(%d, %d) = (%d) instead of (%d)\n",
+                       x, y, a(x, y), correct_a);
+                return 1;
+            }
+        }
+    }
+
+    printf("Success!\n");
+    return 0;
+}