Add a pass to lower unaligned loads and stores (#2078)

This replaces the wasm2js code that lowered them to pessimistic (1-byte aligned) loads and stores. The new pass will do the optimal thing, keeping 2-byte alignment where possible.

This is also nicer as a standalone pass, which has the simple property that after it runs all loads and stores are aligned, instead of some code scattered inside wasm2js.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index 7cfb21dfe..e4fbc5343 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -69,6 +69,9 @@ std::string PassRegistry::getPassDescription(std::string name) {
 void PassRegistry::registerPasses() {
   registerPass(
     "dae", "removes arguments to calls in an lto-like manner", createDAEPass);
+  registerPass("alignment-lowering",
+               "lower unaligned loads and stores to smaller aligned ones",
+               createAlignmentLoweringPass);
   registerPass("dae-optimizing",
                "removes arguments to calls in an lto-like manner, and "
                "optimizes where we removed",