[libre-riscv-dev] [Bug 280] POWER spec parser needs to support fall-through cases

[bugzilla-daemon@libre-riscv.org]

http://bugs.libre-riscv.org/show_bug.cgi?id=280

--- Comment #7 from Luke Kenneth Casson Leighton <lkcl@lkcl.net> ---
blegh.  does the job.

+    """add annoying "silent keyword" (fallthrough)
+
+    this which tricks the parser into taking the (silent) case statement
+    as a "small expression".  it can then be spotted and used to indicate
+    "fall through" to the next case (in the parser)
+
+    bugs: any function that starts with the letters "case" or "default"
+    will be detected erroneously.  fixing that involves doing a token
+    lexer which spots the fact that "case" and "default" are words,
+    separating them from space, colon, bracket etc.
+    """
+    res = []
+    prev_spc_count = None
+    for l in code.split("\n"):
+        spc_count = count_spaces(l)
+        nwhite = l[spc_count:]
+        if nwhite.startswith("case") or nwhite.startswith("default"):
+            #print ("case/default", nwhite, spc_count, prev_spc_count)
+            if (prev_spc_count is not None and
+                prev_spc_count == spc_count and
+                (res[-1].endswith(":") or res[-1].endswith(": fallthrough"))):
+                res[-1] += " fallthrough" # add to previous line
+            prev_spc_count = spc_count
+        else:
+            #print ("notstarts", spc_count, nwhite)
+            prev_spc_count = None
+        res.append(l)
+    return '\n'.join(res)
+

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