pan/bi: Add unused instruction mechanism

Certain instructions are highly unlikely to ever be used in the Bifrost
compiler, due to differences in the Mesa stack versus the Arm compiler,
as well as hardware features added speculatively and that never became
API visible. It doesn't make sense to include these instructions in the
IR, so let's disable them, while retaining complete disassembly.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8213>

src/panfrost/bifrost/gen_disasm.py

@@ -25,7 +25,7 @@ import itertools
 from isa_parse import parse_instructions, opname_to_c, expand_states
 from mako.template import Template
 
-instructions = parse_instructions(sys.argv[1])
+instructions = parse_instructions(sys.argv[1], include_unused = True)
 
 # Constructs a reserved mask for a derived to cull impossible encodings
 

src/panfrost/bifrost/isa_parse.py

@@ -96,7 +96,8 @@ def parse_instruction(ins):
             'immediates': [],
             'swaps': [],
             'derived': [],
-            'staging': ins.attrib.get('staging', '')
+            'staging': ins.attrib.get('staging', ''),
+            'unused': ins.attrib.get('unused', False),
     }
 
     if 'exact' in ins.attrib:
@@ -146,12 +147,19 @@ def parse_instruction(ins):
 
     return variants
 
-def parse_instructions(xml):
+def parse_instructions(xml, include_unused = False):
     final = {}
     instructions = ET.parse(xml).getroot().findall('ins')
 
     for ins in instructions:
-        final[ins.attrib['name']] = parse_instruction(ins)
+        parsed = parse_instruction(ins)
+
+        # Some instructions are for useful disassembly only and can be stripped
+        # out of the compiler, particularly useful for release builds
+        if parsed[0][1]["unused"] and not include_unused:
+            continue
+
+        final[ins.attrib['name']] = parsed
 
     return final