Don't break bs_match sequences by mixing registers (again)

See erlang#6623 for a fix to a similar bug reported in erlang#6613. Closes erlang#6755
josevalim · Jan 30, 2023 · f3e0f6b · f3e0f6b
1 parent 9a4ac73
commit f3e0f6b
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diff --git a/lib/compiler/src/beam_ssa_codegen.erl b/lib/compiler/src/beam_ssa_codegen.erl
@@ -489,7 +489,8 @@ prefer_xregs_is([#cg_set{op=Op}=I|Is], St, Copies0, Acc)
   when Op =:= bs_checked_get;
        Op =:= bs_checked_skip;
        Op =:= bs_checked_get_tail;
-       Op =:= bs_ensure ->
+       Op =:= bs_ensure;
+       Op =:= bs_match_string ->
     Copies = prefer_xregs_prune(I, Copies0, St),
     prefer_xregs_is(Is, St, Copies, [I|Acc]);
 prefer_xregs_is([#cg_set{args=Args0}=I0|Is], St, Copies0, Acc) ->

diff --git a/lib/compiler/test/bs_match_SUITE.erl b/lib/compiler/test/bs_match_SUITE.erl
@@ -2690,6 +2690,8 @@ bs_match(_Config) ->
     <<"abc">> = do_bs_match_gh_6660(id(<<"abc">>)),
     {'EXIT', {{try_clause,abc},_}} = catch do_bs_match_gh_6660(id(abc)),
 
+    {'EXIT',{{case_clause,_},_}} = catch do_bs_match_gh_6755(id(<<"1000">>)),
+
     ok.
 
 do_bs_match_1(_, X) ->
@@ -2749,6 +2751,18 @@ do_bs_match_gh_6660(X) ->
         ok
     end.
 
+do_bs_match_gh_6755(B) ->
+    C = case B of
+            <<"1000">> -> test;
+            <<"1001">> -> test2
+        end,
+
+    _ = atom_to_list(C),
+
+    case B of
+        <<"b">> -> b
+    end.
+
 %% GH-6348/OTP-18297: Allow aliases for binaries.
 -record(ba_foo, {a,b,c}).