Disable the memory64 feature in Memory64Lowering.cpp (#5679)

* Disable sign extension in SignExtLowering.cpp

The sign extension lowering pass would previously lower away the sign extension
instructions, but it wouldn't disable the sign extension feature, so follow-on
passes such as optimize-instructions could reintroduce sign extension
instructions.

Fix the pass to disable the sign extension feature to prevent sign extension
instructions from being reintroduced later.

* update pass description

* Disable the memory64 feature in Memory64Lowering.cpp

For consistency with other feature lowering passes, disable memory64 in addition
to lowering its use away. Although no other passes would introduce new uses of
memory64 at the moment, this makes the lowering pass more robust against a
future where memory64 might accidentally be reintroduced after being lowered away.

* Update test/lit/passes/memory64-lowering-features.wast

Co-authored-by: Alon Zakai <azakai@google.com>

---------

Co-authored-by: Alon Zakai <azakai@google.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/test/lit/passes/memory64-lowering-features.wast b/test/lit/passes/memory64-lowering-features.wast
new file mode 100644
index 000000000..4c5c1c207
--- /dev/null
+++ b/test/lit/passes/memory64-lowering-features.wast
@@ -0,0 +1,9 @@
+;; RUN: wasm-opt %s --enable-memory64 --print-features --print --memory64-lowering --print-features | filecheck %s
+
+;; Check that the --memory64-lowering pass disables the signext feature.
+
+;; CHECK: --enable-memory64
+;; CHECK: (module
+;; CHECK-NOT: --enable-memory64
+
+(module)