CmmSink: Be more aggressive in removing no-op assignments.

No-op assignments like R1 = R1 are not only wasteful. They can also
inhibit other optimizations like inlining assignments that read from
R1.

We now check for assignments being a no-op before and after we
simplify the RHS in Cmm sink which should eliminate most of these
no-ops.

1 files changed, 20 insertions, 3 deletions

diff --git a/testsuite/driver/testlib.py b/testsuite/driver/testlib.py
index efeaa94b89..d4c8fc38f7 100644
--- a/testsuite/driver/testlib.py
+++ b/testsuite/driver/testlib.py
@@ -800,9 +800,26 @@ def check_errmsg(needle):
             return "%s not contained in -ddump-simpl\n" % needle
     return normalise_errmsg_fun(norm)
 
-def grep_errmsg(needle):
-    def norm(str):
-        return "".join(filter(lambda l: re.search(needle, l), str.splitlines(True)))
+# grep_errmsg(regex,[match_only])
+# If match_only = True we only check the part of the error
+# that matches the regex.
+def grep_errmsg(needle:str, match_only = False):
+
+    def get_match(str:str):
+        m = re.search(needle,str)
+        if m:
+            return m.group(0)
+        else:
+            return None
+
+    def norm(str) -> str:
+        if not match_only:
+            return "".join( filter(lambda l: re.search(needle,l),
+                                   str.splitlines(True)))
+        else:
+            matches = [get_match(x) for x in str.splitlines(True)]
+            res = "\n".join([x for x in matches if x])
+            return res
     return normalise_errmsg_fun(norm)
 
 def multiline_grep_errmsg(needle):