From 7077f78538be1364df24477fc713dfe480e63558 Mon Sep 17 00:00:00 2001
From: Alon Zakai <alonzakai@gmail.com>
Date: Thu, 13 Oct 2016 12:22:50 -0700
Subject: when simplify-locals give br_if a value, the br_if also returns it,
 so it must be dropped

---
 src/passes/SimplifyLocals.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

(limited to 'src/passes/SimplifyLocals.cpp')

diff --git a/src/passes/SimplifyLocals.cpp b/src/passes/SimplifyLocals.cpp
index acc6860be..17206af89 100644
--- a/src/passes/SimplifyLocals.cpp
+++ b/src/passes/SimplifyLocals.cpp
@@ -93,7 +93,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
   // sinkables. For the final exit from a block (falling off)
   // exitter is null.
   struct BlockBreak {
-    Break* br;
+    Expression** brp;
     Sinkables sinkables;
   };
 
@@ -128,7 +128,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
         // value means the block already has a return value
         self->unoptimizableBlocks.insert(br->name);
       } else {
-        self->blockBreaks[br->name].push_back({ br, std::move(self->sinkables) });
+        self->blockBreaks[br->name].push_back({ currp, std::move(self->sinkables) });
       }
     } else if (curr->is<Block>()) {
       return; // handled in visitBlock
@@ -290,7 +290,7 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
     auto breaks = std::move(blockBreaks[block->name]);
     blockBreaks.erase(block->name);
     if (breaks.size() == 0) return; // block has no branches TODO we might optimize trivial stuff here too
-    assert(!breaks[0].br->value); // block does not already have a return value (if one break has one, they all do)
+    assert(!(*breaks[0].brp)->cast<Break>()->value); // block does not already have a return value (if one break has one, they all do)
     // look for a set_local that is present in them all
     bool found = false;
     Index sharedIndex = -1;
@@ -328,7 +328,8 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
     for (size_t j = 0; j < breaks.size(); j++) {
       // move break set_local's value to the break
       auto* breakSetLocalPointer = breaks[j].sinkables.at(sharedIndex).item;
-      auto* br = breaks[j].br;
+      auto* brp = breaks[j].brp;
+      auto* br = (*brp)->cast<Break>();
       assert(!br->value);
       // if the break is conditional, then we must set the value here - if the break is not taken, we must still have the new value in the local
       auto* set = (*breakSetLocalPointer)->cast<SetLocal>();
@@ -336,6 +337,9 @@ struct SimplifyLocals : public WalkerPass<LinearExecutionWalker<SimplifyLocals,
         br->value = set;
         set->setTee(true);
         *breakSetLocalPointer = getModule()->allocator.alloc<Nop>();
+        // in addition, as this is a conditional br that now has a value, it now returns a value, so it must be dropped
+        br->finalize();
+        *brp = Builder(*getModule()).makeDrop(br);
       } else {
         br->value = set->value;
         ExpressionManipulator::nop(set);
-- 
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