Fix unsafe bit syntax matching optimization

As part of sys_core_fold, variables involved in bit syntax
matching would be annotated when it would be safe for a later
pass to do the delayed sub-binary creation optimization.

An implicit assumption regarding the annotation was that the
code must not be further optimized. That assumption was broken
in 05130e48555891, which introduced a fixpoint iteration
(applying the optimizations until there were no more changes).
That means that a variable could be annotated as safe for
reusing the match context in one iteration, but a later iteration
could rewrite the code in a way that would make the optimization
unsafe.

One way to fix this would be to clear all reuse_for_context
annotations before each iteration. But that would be wasteful.

Instead I chose to fix the problem by moving out the annotation
code to a separate pass (sys_core_bsm) that is run later after
all major optimizations of Core Erlang has been done.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 7c27750556..77e4234c70 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -529,7 +529,7 @@ bin_opt_info(Config) when is_list(Config) ->
 	    Code,
 	    [bin_opt_info],
 	    {warnings,
-	     [{4,sys_core_fold,orig_bin_var_used_in_guard},
+	     [{4,sys_core_bsm,orig_bin_var_used_in_guard},
 	      {5,beam_bsm,{no_bin_opt,{{t1,1},no_suitable_bs_start_match}}},
 	      {9,beam_bsm,{no_bin_opt,
 			   {binary_used_in,{extfunc,erlang,split_binary,2}}}} ]}}],