Add EH support for EffectAnalyzer (#2631)

This adds EH support to `EffectAnalyzer`. Before `throw` and `rethrow`
conservatively set property. Now `EffectAnalyzer` has a new property
`throws` to represent an expression that can throw, and expression that
can throw sets `throws` correctly.

When EH is enabled, any calls can throw too, so we cannot reorder them
with another expression with any side effects, meaning all calls should
be treated in the same way as branches when evaluating `invalidate`.
This prevents many reorderings, so this patch sets `throws` for calls
only when the exception handling features is enabled. This is also why I
passed `--disable-exception-handling` to `wasm2js` tests. Most of code
changes outside of `EffectAnalyzer` class was made in order to pass
`FeatureSet` to it.

`throws` isn't always set whenever an expression contains a throwable
instruction. When an throwable instruction is within an inner try, it
will be caught by the corresponding inner catch, so it does not set
`throws`.

1 files changed, 12 insertions, 6 deletions

diff --git a/src/passes/LocalCSE.cpp b/src/passes/LocalCSE.cpp
index b49c92310..f7c1cda26 100644
--- a/src/passes/LocalCSE.cpp
+++ b/src/passes/LocalCSE.cpp
@@ -60,8 +60,11 @@ struct LocalCSE : public WalkerPass<LinearExecutionWalker<LocalCSE>> {
     Index index; // the local we are assigned to, local.get that to reuse us
     EffectAnalyzer effects;
 
-    UsableInfo(Expression* value, Index index, PassOptions& passOptions)
-      : value(value), index(index), effects(passOptions, value) {}
+    UsableInfo(Expression* value,
+               Index index,
+               PassOptions& passOptions,
+               FeatureSet features)
+      : value(value), index(index), effects(passOptions, features, value) {}
   };
 
   // a list of usables in a linear execution trace
@@ -136,7 +139,7 @@ struct LocalCSE : public WalkerPass<LinearExecutionWalker<LocalCSE>> {
     // pre operations
     Expression* curr = *currp;
 
-    EffectAnalyzer effects(self->getPassOptions());
+    EffectAnalyzer effects(self->getPassOptions(), self->getModule()->features);
     if (effects.checkPre(curr)) {
       self->checkInvalidations(effects);
     }
@@ -152,7 +155,7 @@ struct LocalCSE : public WalkerPass<LinearExecutionWalker<LocalCSE>> {
 
     // post operations
 
-    EffectAnalyzer effects(self->getPassOptions());
+    EffectAnalyzer effects(self->getPassOptions(), self->getModule()->features);
     if (effects.checkPost(curr)) {
       self->checkInvalidations(effects, curr);
     }
@@ -194,7 +197,9 @@ struct LocalCSE : public WalkerPass<LinearExecutionWalker<LocalCSE>> {
         } else {
           // not in table, add this, maybe we can help others later
           usables.emplace(std::make_pair(
-            hashed, UsableInfo(value, set->index, getPassOptions())));
+            hashed,
+            UsableInfo(
+              value, set->index, getPassOptions(), getModule()->features)));
         }
       }
     } else if (auto* get = curr->dynCast<LocalGet>()) {
@@ -215,7 +220,8 @@ struct LocalCSE : public WalkerPass<LinearExecutionWalker<LocalCSE>> {
     if (!value->type.isConcrete()) {
       return false; // don't bother with unreachable etc.
     }
-    if (EffectAnalyzer(getPassOptions(), value).hasSideEffects()) {
+    if (EffectAnalyzer(getPassOptions(), getModule()->features, value)
+          .hasSideEffects()) {
       return false; // we can't combine things with side effects
     }
     auto& options = getPassRunner()->options;