8 files changed, 139 insertions, 6 deletions
diff --git a/src/passes/CoalesceLocals.cpp b/src/passes/CoalesceLocals.cpp
index 39c480107..c36371ec0 100644
--- a/src/passes/CoalesceLocals.cpp
+++ b/src/passes/CoalesceLocals.cpp
@@ -183,7 +183,7 @@ struct CoalesceLocals : public WalkerPass<CFGWalker<CoalesceLocals, Visitor<Coal
 
   void calculateInterferences();
 
-  void calculateInterferences(LocalSet& locals);
+  void calculateInterferences(const LocalSet& locals);
 
   // merge starts of a list of blocks, adding new interferences as necessary. return
   // whether anything changed vs an old state (which indicates further processing is necessary).
@@ -282,8 +282,6 @@ void CoalesceLocals::flowLiveness() {
       queue.insert(in);
     }
   }
-  // live locals at the entry block include params, obviously, but also
-  // vars, in which case the 0-init value is actually used.
 #ifdef CFG_DEBUG
   std::hash<std::vector<bool>> hasher;
   std::cout << getFunction()->name << ": interference hash: " << hasher(*(std::vector<bool>*)&interferences) << "\n";
@@ -347,9 +345,17 @@ void CoalesceLocals::calculateInterferences() {
       }
     }
   }
+  // Params have a value on entry, so mark them as live, as variables
+  // live at the entry expect their zero-init value.
+  LocalSet start = entry->contents.start;
+  auto numParams = getFunction()->getNumParams();
+  for (Index i = 0; i < numParams; i++) {
+    start.insert(i);
+  }
+  calculateInterferences(start);
 }
 
-void CoalesceLocals::calculateInterferences(LocalSet& locals) {
+void CoalesceLocals::calculateInterferences(const LocalSet& locals) {
   size_t size = locals.size();
   for (size_t i = 0; i < size; i++) {
     for (size_t j = i + 1; j < size; j++) {
diff --git a/test/passes/coalesce-locals-learning.txt b/test/passes/coalesce-locals-learning.txt
index 14091cb98..aa3c8c9c0 100644
--- a/test/passes/coalesce-locals-learning.txt
+++ b/test/passes/coalesce-locals-learning.txt
@@ -318,9 +318,10 @@
   (func $params (param $0 i32) (param $1 f32)
     (local $2 i32)
     (local $3 i32)
-    (get_local $0)
+    (local $4 i32)
     (get_local $2)
     (get_local $3)
+    (get_local $4)
   )
   (func $interfere-in-dead
     (local $0 i32)
diff --git a/test/passes/coalesce-locals.txt b/test/passes/coalesce-locals.txt
index 3c1632f68..d0edbd71d 100644
--- a/test/passes/coalesce-locals.txt
+++ b/test/passes/coalesce-locals.txt
@@ -318,9 +318,10 @@
   (func $params (param $0 i32) (param $1 f32)
     (local $2 i32)
     (local $3 i32)
-    (get_local $0)
+    (local $4 i32)
     (get_local $2)
     (get_local $3)
+    (get_local $4)
   )
   (func $interfere-in-dead
     (local $0 i32)
diff --git a/test/unit.asm.js b/test/unit.asm.js
index 5b958a111..2f307e085 100644
--- a/test/unit.asm.js
+++ b/test/unit.asm.js
@@ -234,6 +234,19 @@ function asm(global, env, buffer) {
     -3.14159;
   }
 
+  function zeroInit(x) {
+    x = x | 0;
+    var y = 0; // reusing this with x is dangerous - x has a value, and y needs to start at 0!
+    if (lb(0) | 0) {
+      if (lb(1) | 0) y = 3;
+    } else {
+      y = 3;
+    }
+    if ((y | 0) == 3) {
+      lb(2) | 0;
+    }
+  }
+
   function z() {
   }
   function w() {
diff --git a/test/unit.fromasm b/test/unit.fromasm
index 7ee15cd05..3fb76981d 100644
--- a/test/unit.fromasm
+++ b/test/unit.fromasm
@@ -425,4 +425,32 @@
     )
     (i32.const 0)
   )
+  (func $zeroInit (param $0 i32)
+    (local $1 i32)
+    (if
+      (call $lb
+        (i32.const 0)
+      )
+      (if
+        (call $lb
+          (i32.const 1)
+        )
+        (set_local $1
+          (i32.const 3)
+        )
+      )
+      (set_local $1
+        (i32.const 3)
+      )
+    )
+    (if
+      (i32.eq
+        (get_local $1)
+        (i32.const 3)
+      )
+      (call $lb
+        (i32.const 2)
+      )
+    )
+  )
 )
diff --git a/test/unit.fromasm.imprecise b/test/unit.fromasm.imprecise
index 293fc490a..a4716941d 100644
--- a/test/unit.fromasm.imprecise
+++ b/test/unit.fromasm.imprecise
@@ -417,4 +417,32 @@
     )
     (i32.const 0)
   )
+  (func $zeroInit (param $0 i32)
+    (local $1 i32)
+    (if
+      (call $lb
+        (i32.const 0)
+      )
+      (if
+        (call $lb
+          (i32.const 1)
+        )
+        (set_local $1
+          (i32.const 3)
+        )
+      )
+      (set_local $1
+        (i32.const 3)
+      )
+    )
+    (if
+      (i32.eq
+        (get_local $1)
+        (i32.const 3)
+      )
+      (call $lb
+        (i32.const 2)
+      )
+    )
+  )
 )
diff --git a/test/unit.fromasm.imprecise.no-opts b/test/unit.fromasm.imprecise.no-opts
index 2f7665622..c3da01359 100644
--- a/test/unit.fromasm.imprecise.no-opts
+++ b/test/unit.fromasm.imprecise.no-opts
@@ -693,6 +693,34 @@
   (func $exportMe
     (f64.const -3.14159)
   )
+  (func $zeroInit (param $x i32)
+    (local $y i32)
+    (if
+      (call $lb
+        (i32.const 0)
+      )
+      (if
+        (call $lb
+          (i32.const 1)
+        )
+        (set_local $y
+          (i32.const 3)
+        )
+      )
+      (set_local $y
+        (i32.const 3)
+      )
+    )
+    (if
+      (i32.eq
+        (get_local $y)
+        (i32.const 3)
+      )
+      (call $lb
+        (i32.const 2)
+      )
+    )
+  )
   (func $z
     (nop)
   )
diff --git a/test/unit.fromasm.no-opts b/test/unit.fromasm.no-opts
index 19c13f29f..92d2d2add 100644
--- a/test/unit.fromasm.no-opts
+++ b/test/unit.fromasm.no-opts
@@ -697,6 +697,34 @@
   (func $exportMe
     (f64.const -3.14159)
   )
+  (func $zeroInit (param $x i32)
+    (local $y i32)
+    (if
+      (call $lb
+        (i32.const 0)
+      )
+      (if
+        (call $lb
+          (i32.const 1)
+        )
+        (set_local $y
+          (i32.const 3)
+        )
+      )
+      (set_local $y
+        (i32.const 3)
+      )
+    )
+    (if
+      (i32.eq
+        (get_local $y)
+        (i32.const 3)
+      )
+      (call $lb
+        (i32.const 2)
+      )
+    )
+  )
   (func $z
     (nop)
   )