Add StubUnsupportedJSOps to remove operations that JS does not support (#3024)

This doesn't lower them - it just replaces the unsupported operation
with a drop. This will be useful for fuzzing, where to compare JS to the
correct semantics we must avoid operations where JS is not always
accurate.

Also fully document the i64 -> f32 conversion issue in JS.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index d94e454c3..5a0dedf37 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -340,6 +340,9 @@ void PassRegistry::registerPasses() {
   registerPass("spill-pointers",
                "spill pointers to the C stack (useful for Boehm-style GC)",
                createSpillPointersPass);
+  registerPass("stub-unsupported-js",
+               "stub out unsupported JS operations",
+               createStubUnsupportedJSOpsPass);
   registerPass("ssa",
                "ssa-ify variables so that they have a single assignment",
                createSSAifyPass);