Fix incorrect bit-order in packed struct output of external registers. #111

src/peakrdl_regblock/hwif/generators.py

@@ -110,27 +110,27 @@ class InputStructGenerator_Hier(HWIFStructGenerator):
             # External reg is 1 sub-word. Add a packed struct to represent it
             type_name = self.get_typdef_name(node, "__fields")
             self.push_struct(type_name, "rd_data", packed=True)
-            current_bit = 0
-            for field in node.fields():
+            current_bit = width - 1
+            for field in reversed(list(node.fields())):
                 if not field.is_sw_readable:
                     continue
-                if field.low > current_bit:
+                if field.high < current_bit:
                     # Add padding
                     self.add_member(
-                        f"_reserved_{field.low - 1}_{current_bit}",
-                        field.low - current_bit
+                        f"_reserved_{current_bit}_{field.high + 1}",
+                        current_bit - field.high
                     )
                 self.add_member(
                     kwf(field.inst_name),
                     field.width
                 )
-                current_bit = field.high + 1
+                current_bit = field.low - 1
 
             # Add end padding if needed
-            if current_bit != width:
+            if current_bit != -1:
                 self.add_member(
-                    f"_reserved_{width - 1}_{current_bit}",
-                    width - current_bit
+                    f"_reserved_{current_bit}_0",
+                    current_bit + 1
                 )
             self.pop_struct()
         else:
@@ -237,27 +237,27 @@ class OutputStructGenerator_Hier(HWIFStructGenerator):
             # External reg is 1 sub-word. Add a packed struct to represent it
             type_name = self.get_typdef_name(node, "__fields")
             self.push_struct(type_name, name, packed=True)
-            current_bit = 0
-            for field in node.fields():
+            current_bit = width - 1
+            for field in reversed(list(node.fields())):
                 if not field.is_sw_writable:
                     continue
-                if field.low > current_bit:
+                if field.high < current_bit:
                     # Add padding
                     self.add_member(
-                        f"_reserved_{field.low - 1}_{current_bit}",
-                        field.low - current_bit
+                        f"_reserved_{current_bit}_{field.high + 1}",
+                        current_bit - field.high
                     )
                 self.add_member(
                     kwf(field.inst_name),
                     field.width
                 )
-                current_bit = field.high + 1
+                current_bit = field.low - 1
 
             # Add end padding if needed
-            if current_bit != width:
+            if current_bit != -1:
                 self.add_member(
-                    f"_reserved_{width - 1}_{current_bit}",
-                    width - current_bit
+                    f"_reserved_{current_bit}_0",
+                    current_bit + 1
                 )
             self.pop_struct()
         else:

tests/lib/simulators/questa.py

@@ -29,6 +29,9 @@ class Questa(Simulator):
 
             # Ignore noisy warning about vopt-time checking of always_comb/always_latch
             "-suppress", "2583",
+
+            # Suppress "error" about use of the `line directive
+            "-suppress", "13465",
         ]
 
         # Add source files

tests/run.sh

@@ -2,30 +2,26 @@
 
 set -e
 
-this_dir="$( cd "$(dirname "$0")" ; pwd -P )"
+cd "$(dirname "$0")"
 
 # Initialize venv
-venv_bin=$this_dir/.venv/bin
-python3 -m venv $this_dir/.venv
-source $this_dir/.venv/bin/activate
+python3 -m venv .venv
+source .venv/bin/activate
 
 # Install test dependencies
-pip install -U pip setuptools wheel
-pip install -r $this_dir/requirements.txt
+pip install -r requirements.txt
 
 # Install dut
-cd $this_dir/../
-pip install -U .
-cd $this_dir
+pip install -U ..
 
 # Run unit tests
 pytest --workers auto --cov=peakrdl_regblock --synth-tool skip
 
 # Generate coverage report
-coverage html -i -d $this_dir/htmlcov
+coverage html -i -d htmlcov
 
 # Run lint
-pylint --rcfile $this_dir/pylint.rc ../src/peakrdl_regblock
+pylint --rcfile pylint.rc ../src/peakrdl_regblock
 
 # Run static type checking
-mypy $this_dir/../src/peakrdl_regblock
+mypy ../src/peakrdl_regblock

tests/test_external/tb_template.sv

@@ -294,4 +294,18 @@
     end
     wait fork;
 
+    // Check register struct bit-order
+    repeat(32) begin
+        regblock_pkg::top__my_reg_alt__external__fields__in_t fields_in;
+        regblock_pkg::top__my_reg_alt__external__fields__out_t fields_out;
+        fields_in = $urandom();
+        fields_out = $urandom();
+
+        assert(fields_in.whatever_a == fields_in[3:2]);
+        assert(fields_in.whatever_c == fields_in[15:8]);
+
+        assert(fields_out.whatever_b == fields_out[4]);
+        assert(fields_out.whatever_c == fields_out[15:8]);
+    end
+
 {% endblock %}