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, 0 deletions

diff --git a/lib/compiler/test/compile_SUITE.erl b/lib/compiler/test/compile_SUITE.erl
index 4e2753ba5f..f647a4030d 100644
--- a/lib/compiler/test/compile_SUITE.erl
+++ b/lib/compiler/test/compile_SUITE.erl
@@ -371,6 +371,7 @@ do_file_listings(DataDir, PrivDir, [File|Files]) ->
     do_listing(Simple, TargetDir, dinline, ".inline"),
     do_listing(Simple, TargetDir, dcore, ".core"),
     do_listing(Simple, TargetDir, dcopt, ".copt"),
+    do_listing(Simple, TargetDir, dcbsm, ".core_bsm"),
     do_listing(Simple, TargetDir, dsetel, ".dsetel"),
     do_listing(Simple, TargetDir, dkern, ".kernel"),
     do_listing(Simple, TargetDir, dlife, ".life"),