2 files changed, 42 insertions, 26 deletions

diff --git a/js/src/jit/BacktrackingAllocator.cpp b/js/src/jit/BacktrackingAllocator.cpp
index 741ed1592..645aefc4f 100644
--- a/js/src/jit/BacktrackingAllocator.cpp
+++ b/js/src/jit/BacktrackingAllocator.cpp
@@ -1736,6 +1736,18 @@ BacktrackingAllocator::deadRange(LiveRange* range)
 }
 
 bool
+BacktrackingAllocator::moveAtEdge(LBlock* predecessor, LBlock* successor, LiveRange* from,
+                                  LiveRange* to, LDefinition::Type type)
+{
+    if (successor->mir()->numPredecessors() > 1) {
+        MOZ_ASSERT(predecessor->mir()->numSuccessors() == 1);
+        return moveAtExit(predecessor, from, to, type);
+    }
+
+    return moveAtEntry(successor, from, to, type);
+}
+
+bool
 BacktrackingAllocator::resolveControlFlow()
 {
     // Add moves to handle changing assignments for vregs over their lifetime.
@@ -1846,15 +1858,11 @@ BacktrackingAllocator::resolveControlFlow()
                 if (!alloc().ensureBallast()) {
                     return false;
                 }
-                if (mSuccessor->numPredecessors() > 1) {
-                    MOZ_ASSERT(predecessor->mir()->numSuccessors() == 1);
-                    if (!moveAtExit(predecessor, from, to, def->type())) {
-                        return false;
-                    }
-                } else {
-                    if (!moveAtEntry(successor, from, to, def->type())) {
-                        return false;
-                    }
+
+                // Note: we have to use moveAtEdge both here and below (for edge
+                // resolution) to avoid conflicting moves. See bug 1493900.
+                if (!moveAtEdge(predecessor, successor, from, to, def->type())) {
+                    return false;
                 }
             }
         }
@@ -1884,16 +1892,12 @@ BacktrackingAllocator::resolveControlFlow()
                     if (targetRange->covers(exitOf(predecessor)))
                         continue;
 
-                    if (!alloc().ensureBallast())
+                    if (!alloc().ensureBallast()) {
                         return false;
+                    }
                     LiveRange* from = reg.rangeFor(exitOf(predecessor), true);
-                    if (successor->mir()->numPredecessors() > 1) {
-                        MOZ_ASSERT(predecessor->mir()->numSuccessors() == 1);
-                        if (!moveAtExit(predecessor, from, targetRange, reg.type()))
-                            return false;
-                    } else {
-                        if (!moveAtEntry(successor, from, targetRange, reg.type()))
-                            return false;
+                    if (!moveAtEdge(predecessor, successor, from, targetRange, reg.type())) {
+                        return false;
                     }
                 }
             }
diff --git a/js/src/jit/BacktrackingAllocator.h b/js/src/jit/BacktrackingAllocator.h
index 9910498fb..c6cf26695 100644
--- a/js/src/jit/BacktrackingAllocator.h
+++ b/js/src/jit/BacktrackingAllocator.h
@@ -108,8 +108,9 @@ class Requirement
         }
 
         MOZ_ASSERT(newRequirement.kind() == Requirement::REGISTER);
-        if (kind() == Requirement::FIXED)
+        if (kind() == Requirement::FIXED) {
             return allocation().isRegister();
+        }
 
         *this = newRequirement;
         return true;
@@ -353,10 +354,12 @@ class LiveRange : public TempObject
     // Comparator for use in range splay trees.
     static int compare(LiveRange* v0, LiveRange* v1) {
         // LiveRange includes 'from' but excludes 'to'.
-        if (v0->to() <= v1->from())
+        if (v0->to() <= v1->from()) {
             return -1;
-        if (v0->from() >= v1->to())
+        }
+        if (v0->from() >= v1->to()) {
             return 1;
+        }
         return 0;
     }
 };
@@ -642,10 +645,12 @@ class BacktrackingAllocator : protected RegisterAllocator
 
         // Comparator for use in splay tree.
         static int compare(CallRange* v0, CallRange* v1) {
-            if (v0->range.to <= v1->range.from)
+            if (v0->range.to <= v1->range.from) {
                 return -1;
-            if (v0->range.from >= v1->range.to)
+            }
+            if (v0->range.from >= v1->range.to) {
                 return 1;
+            }
             return 0;
         }
     };
@@ -744,36 +749,43 @@ class BacktrackingAllocator : protected RegisterAllocator
 
     MOZ_MUST_USE bool moveInput(LInstruction* ins, LiveRange* from, LiveRange* to,
                                 LDefinition::Type type) {
-        if (from->bundle()->allocation() == to->bundle()->allocation())
+        if (from->bundle()->allocation() == to->bundle()->allocation()) {
             return true;
+        }
         LMoveGroup* moves = getInputMoveGroup(ins);
         return addMove(moves, from, to, type);
     }
 
     MOZ_MUST_USE bool moveAfter(LInstruction* ins, LiveRange* from, LiveRange* to,
                                 LDefinition::Type type) {
-        if (from->bundle()->allocation() == to->bundle()->allocation())
+        if (from->bundle()->allocation() == to->bundle()->allocation()) {
             return true;
+        }
         LMoveGroup* moves = getMoveGroupAfter(ins);
         return addMove(moves, from, to, type);
     }
 
     MOZ_MUST_USE bool moveAtExit(LBlock* block, LiveRange* from, LiveRange* to,
                                  LDefinition::Type type) {
-        if (from->bundle()->allocation() == to->bundle()->allocation())
+        if (from->bundle()->allocation() == to->bundle()->allocation()) {
             return true;
+        }
         LMoveGroup* moves = block->getExitMoveGroup(alloc());
         return addMove(moves, from, to, type);
     }
 
     MOZ_MUST_USE bool moveAtEntry(LBlock* block, LiveRange* from, LiveRange* to,
                                   LDefinition::Type type) {
-        if (from->bundle()->allocation() == to->bundle()->allocation())
+        if (from->bundle()->allocation() == to->bundle()->allocation()) {
             return true;
+        }
         LMoveGroup* moves = block->getEntryMoveGroup(alloc());
         return addMove(moves, from, to, type);
     }
 
+    MOZ_MUST_USE bool moveAtEdge(LBlock* predecessor, LBlock* successor, LiveRange* from,
+                                 LiveRange* to, LDefinition::Type type);
+
     // Debugging methods.
     void dumpAllocations();